Optical characterization and dispersion analyses of plasma polymerized methyl acrylate thin films

This work reports the structural characteristics, surface morphology, linear and nonlinear optical properties of 110 to 225 nm thick plasma polymerized methyl acrylate (PPMA) thin films. X-ray diffraction analyses confirm the amorphous nature of the films. Field emission scanning electron micrographs of the films display cluster-based surface morphology. Attenuated total reflectance Fourier transform infrared spectroscopy confirms the chemical structural changes in the films. The optical properties were studied based on the absorbance, transmittance, and reflectance spectra measured by an ultraviolet-visible spectrophotometer within the wavelength ranges from 200 to 800 nm. The direct optical band gap and Urbach values are increased from 3.66 to 3.83 eV and 0.28 to 0.45 eV, respectively with increasing film thickness. The extinction coefficient and refractive index were evaluated, and discussed a correlation between the refractive index and the optical bandgap. The real and imaginary dielectric constants, volume/surface energy loss functions and skin depth were deduced. The oscillator energies and parameters were analyzed using the concept of Wemple-DiDomenico and Sellmeier models, respectively for a single oscillator. Static linear refractive index for the studied films exhibits normal dispersion behavior with film thicknesses and satisfied Moss, Ravindra-Gupta, and Herve-Vandamme rules. The linear susceptibility, third-order nonlinear susceptibility and the non-linear refractive index are considerably reduced from 0.20, 29.5 × 10-14 esu, and 5.89 × 10-12 esu with increasing optical band gap energies. The outcomes from the analyses of PPMA demonstrated their potential for usage in electronic, optoelectronic, and non-linear device applications.

Holotomography and atomic force microscopy: a powerful combination to enhance cancer, microbiology and nanotoxicology research

Modern imaging strategies are paramount to studying living systems such as cells, bacteria, and fungi and their response to pathogens, toxicants, and nanomaterials (NMs) as modulated by exposure and environmental factors. The need to understand the processes and mechanisms of damage, healing, and cell survivability of living systems continues to motivate the development of alternative imaging strategies. Of particular interest is the use of label-free techniques (microscopy procedures that do not require sample staining) that minimize interference of biological processes by foreign marking substances and reduce intense light exposure and potential photo-toxicity effects. This review focuses on the synergic capabilities of atomic force microscopy (AFM) as a well-developed and robust imaging strategy with demonstrated applications to unravel intimate details in biomedical applications, with the label-free, fast, and enduring Holotomographic Microscopy (HTM) strategy. HTM is a technique that combines holography and tomography using a low intensity continuous illumination laser to investigate (quantitatively and non-invasively) cells, microorganisms, and thin tissue by generating three-dimensional (3D) images and monitoring in real-time inner morphological changes. We first review the operating principles that form the basis for the complementary details provided by these techniques regarding the surface and internal information provided by HTM and AFM, which are essential and complimentary for the development of several biomedical areas studying the interaction mechanisms of NMs with living organisms. First, AFM can provide superb resolution on surface morphology and biomechanical characterization. Second, the quantitative phase capabilities of HTM enable superb modeling and quantification of the volume, surface area, protein content, and mass density of the main components of cells and microorganisms, including the morphology of cells in microbiological systems. These capabilities result from directly quantifying refractive index changes without requiring fluorescent markers or chemicals. As such, HTM is ideal for long-term monitoring of living organisms in conditions close to their natural settings. We present a case-based review of the principal uses of both techniques and their essential contributions to nanomedicine and nanotoxicology (study of the harmful effects of NMs in living organisms), emphasizing cancer and infectious disease control. The synergic impact of the sequential use of these complementary strategies provides a clear drive for adopting these techniques as interdependent fundamental tools.

Refractive index adjustable intraocular lens design to achieve diopter control for improving the treatment of ametropia after cataract surgery

Intraocular lens (IOL) implantation is currently the most effective clinical treatment for cataracts. Nevertheless, due to the growth of the eye axis in patients with congenital cataracts during the process of growth and development, the progressive incapacity of an IOL with a fixed focus does not meet the demands of practical usage, leading to the occurrence of ametropia. This work describes an innovative class of an IOL bulk material that offers good biosafety and light-controlled refractive index adjustment. Acrylate materials were synthesized for the preparation of IOLs by free radical polymerization of ethylene glycol phenyl ether methacrylate (EGPEMA), hydrophilic monomer 2-(2-ethoxyethoxy) ethyl acrylate (EA), and functional monomer hydroxymethyl coumarin methacrylate (CMA). Under 365/254 nm ultraviolet (UV) irradiation, the coumarin group could adjust the polymer material's refractive index through reversible photoinduced dimerization/depolymerization. Meanwhile, the potential for the IOL use is enabled by its satisfactory biosafety. Such a light-induced diopter adjustable IOL will be more appropriate for implantation during cataract surgery since it will not require the correction needed for ametropia and will offer more accurate and humane treatment. STATEMENT OF SIGNIFICANCE.

The Effect of Lens Shape, Zonular Insertion and Finite Element Model on Simulated Shape Change of the Eye Lens

The process of lens shape change in the eye to alter focussing (accommodation) is still not fully understood. Modelling approaches have been used to complement experimental findings in order to determine how constituents in the accommodative process influence the shape change of the lens. An unexplored factor in modelling is the role of the modelling software on the results of simulated shape change. Finite element models were constructed in both Abaqus and Ansys software using biological parameters from measurements of shape and refractive index of two 35-year-old lenses. The effect of zonular insertion on simulated shape change was tested on both 35-year-old lens models and with both types of software. Comparative analysis of shape change, optical power, and stress distributions showed that lens shape and zonular insertion positions affect the results of simulated shape change and that Abaqus and Ansys show differences in their respective models. The effect of the software package used needs to be taken into account when constructing finite element models and deriving conclusions.

Ni doping induced property enhancement in laser ablated BaSnO3 films suitable for optoelectronic applications

Pulsed laser deposition is a straightforward approach for preparing films with superconducting to dielectric properties with atomic layer precision. The deep-seated mechanisms involved in the particle transport from target to substrate and subsequent film formation still need to be fully comprehended. This manuscript reports the property enhancement observed in laser ablated perovskite BaSnO3 films with Ni doping. Films' crystallinity improvement is observed, and an intensity enhancement of 1150% is observed on 3 mol% Ni-doping. The optimum Ni-doping concentration in BaSnO3 is found to be 3 mol%. Herein, Ni-doped BaSnO3 films deposited by PLD showed an unusual increase in film thickness (i.e., from 615 nm in the pure film to 1317 nm in the film with 7 mol% Ni-doping as revealed by lateral SEM analysis and spectroscopic ellipsometry). We propose an "Induced Magnetic field-assisted Particle Convergence (IMPC)" effect for this superficial growth enhancement. The film's optical properties are modified with an increased nickel doping level, and the bandgap energy shows renormalization. All the films show excellent transmittance (80-90%) in the Vis.-NIR region. Hall-effect measurement reveals the increased carrier concentration by three orders (2.98 × 1011 to 3.50 × 1014 cm-3). In addition, the enhancement in mobility from 3.13 to 20.93 cm2V-1s-1 and a decrease in electrical resistivity by six orders (i.e., from 4.05 × 109 to 1.13 × 103 Ω cm) are observed on 7 mol% Ni doping. XPS measurements reveals that the Ba, Sn and Ni ions are at 2+, 4+ and 2+ oxidation states. Using spectroscopic ellipsometric method, we estimated the optical constants of the films, the refractive index, dielectric constant, and extinction coefficient show a normal dispersion behavior. The high crystallinity, high transmittance, suitable surface topography, and improved electrical performances of the Ni-doped BaSnO3 films make them excellent candidates for optoelectronic devices and solar cells.

Leaving trusted paths: Estimating corneal keratometric index in cataract surgery eyes with zero-power implants

PURPOSE

This study aimed to estimate the corneal keratometric index in the eyes of cataract surgery patients who received zero-power intraocular lenses (IOLs).

METHODOLOGY

This retrospective study analyzed postoperative equivalent spherical refraction and axial length, mean anterior curvature radius and aqueous humor refractive index to calculate the theoretical corneal keratometric index value (nk). Data was collected from 2 centers located in France and Germany.

RESULTS

Thirty-six eyes were analyzed. The results revealed a mean corneal keratometric index of 1.329 ± 0.005 for traditional axial length (AL) and 1.331 ± 0.005 for Cooke modified axial length (CMAL). Results ranged from minimum values of 1.318/1.320 to maximum values of 1.340/1.340.

CONCLUSION

The corneal keratometric index is a crucial parameter for ophthalmic procedures and calculations, particularly for IOL power calculation. Notably, the estimated corneal keratometric index value of 1.329/1.331 in this study is lower than the commonly used 1.3375 index. These findings align with recent research demonstrating that the theoretical corneal keratometric index should be approximately 1.329 using traditional AL and 1.331 using CMAL, based on the ratio between the mean anterior and posterior corneal curvature radii (1.22).

Influence of Synthesis Temperature on the Structural, Morphological and Optical Properties of MoO3 Nanorods

Molybdenum trioxide nanomaterials have attained notable attention in the recent past and are used in various optoelectronic and biomedical applications. Here blue and purple blue light emitting MoO3 nanophosphors were synthesized using the simple hydrothermal method at three different temperatures 100ºC, 150°C, and 200°C. Structural characterization using XRD along with Raman spectroscopy confirms the formation of a highly stable orthorhombic phase. Micro strain effects have been analyzed by employing the Williamson-Hall method using a uniform deformation model. Nanorod like morphology was obtained from FESEM. Optical analysis, using Tauc plot shows a decreasing trend in bandgap value with increasing temperature. Emission peaks in the photoluminescence spectrum are associated with the transition between the sub-bands of the Mo5+ defect state. From CIE coordinates it is confirmed that the characteristic light from the samples is blue and purple-blue. Being an excellent blue and purple blue light emitting phosphor, MoO3 is a suitable material for future LED and fluorescence imaging applications.

Two-in-one sensor of refractive index and Raman scattering using hollow-core microstructured optical waveguides for colloid characterization

Hollow-core microstructured optical waveguides (HC-MOW) have recently emerged in sensing technologies, including the gas and liquid detection for industrial as well as clinical applications. Antiresonant HC-MOW provide capabilities for applications in refractive index (RI) sensing, while the long optical path for analyte-light interaction in HC-MOW leads to increased sensitivity of sensor based on Raman scattering signal measurements. In this study, we developed a two-in-one sensor device using HC-MOW for RI and Raman scattering detection. The performance of the sensor was evaluated by characterizing protein-copolymer multicomponent colloids, specifically, bovine serum albumin (BSA) and poly(N - vinyl-2 -pyrrolidone-co-acrylic acid) P(VP-AA) nano-sized complexes and microbubbles of the corresponding shell. Monocomponent solutions showed linear dependencies of RI and characteristic Raman peak intensities on mass concentration. Multicomponent Raman sensing of BSA@P(VP-AA) complexes and microbubbles revealed that changes in P(VP-AA) characteristic peak intensities can describe interactions between components needed to produce colloid systems. RI sensing of multicomponent colloids demonstrated linear dependence on total mass concentrations for BSA@P(VP-AA) complexes, while corresponding BSA@P(VP-AA) microbubbles can be detected with concentrations as high as 4.0 × 108 MB/mL. Therefore, the developed two-in-one sensor of RI and Raman scattering can be used the robust characterization of albumin-based colloids designed for therapeutic and diagnostic needs.

Smart colloidal photonic crystal sensors

Smart colloidal photonic crystals (PCs) with stimuli-responsive periodic micro/nano-structures, photonic bandgaps, and structural colors have shown unique advantages (high sensitivity, visual readout, wireless characteristics, etc.) in sensing by outputting diverse structural colors and reflection signals. In this review, smart PC sensors are summarized according to their fabrications, structures, sensing mechanisms, and applications. The fabrications of colloidal PCs are mainly by self-assembling the well-defined nanoparticles into the periodical structure (supersaturation-, polymerization-, evaporation-, shear-, interaction-, and field-induced self-assembly process). Their structures can be divided into two groups: closely packed and non-closely packed nano-structures. The sensing mechanisms can be explained by Bragg's law, including the change in the effective refractive index, lattice constant, and the order degree. The sensing applications are detailly introduced according to the analytes of the target, including solvents, vapors, humidity, mechanical force, temperature, electrical field, magnetic field, pH, ions/molecules, and so on. Finally, the corresponding challenges and the future potential prospects of artificial smart colloidal PCs in the sensing field are discussed.

Investigation of structural, mechanical, electronic and optical responses of Ga doped aluminum arsenide for optoelectronic applications: By first principles

Owing to the rapidly increasing performance of ternary semiconductors; Aluminium Gallium Arsenide (Al1-xGaxAs; x = 0, 0.25, 0.50, 0.75) has been studied by first-principles calculations in Cambridge Serial Total Energy Package (CASTEP-Code). Density functional theory in the frame of full potential linear augmented plane wave (FP-LAPW) is used. The structural, electronic, and optical behavior of the Zinc Blend (ZB) structure of AlAs with Ga impurity was computed by using generalized gradient approximation (GGA) as exchange potential and Perdew-Burke-Ernzerhof (PBE) as functional. Changes in lattice parameters (a), bulk modulus (66.07-76.85), hardness (5.79-8.91) and machinability (1.36-1.46), band gap energy (Eg), and optical properties are computed and discussed in this work. Lattice parameters and elastic constants showed excellent agreement with the reported data whereas some properties were found to excel much more than the theoretical reports. Remarkable bandgap reduction from 1.7eV to 0.28eV is very encouraging in its low-energy applications in UV and visible ranges. Real (Re) and Imaginary (Img) parts of the dielectric function and refractive index shifts towards lower energy values show good agreement with those of theoretical and experimental works. We contribute to the knowledge and characterization of Al1-xGaxAs facilitating its integration into various technological advancements such as photovoltaic, laser, diodes, and high-frequency transistors.

Comparative investigations of electronic, mechanical and optical responses of Ra-doping in Barium Titanate for optoelectronic applications: A computational insight

This unique study examined the theoretical pure BaTiO3 and doped Ra (Ba1-xRaxTiO3) impact on electronic, mechanical and optical responses were using Heydscuseria-Ernzerhof screened hybrid functional (HSE06) and generalized gradient approximation (GGA-PBE) with norm-converging pseudopotential approaches in the density functional theory. Computed the lattice constant and bond lengths for pure (BaTiO3) and doped atoms as well as explored the changes of consequences of electronic, mechanical and optical responses. The calculated values indicate the BaTiO3 is an indirect characteristic and an optically inactive nature. The low energy state and also conduction band of the crystal structure to transform to the direction of low energy and narrows the electronic band gap. The bandgap of pure BaTiO3 is continually reduced which shifts the Fermi energy level Eg. When increasing the doping impurities (x) of (Ra) in BaTiO3, the band gap shifts from indirect (X-G) to direct (X-X) nature and become optically active. The elastic and mechanical responses are essential for suitable (Ra) doped material ensuring structural integrity and predicting a ductile behavior. Kleinman coefficient (ξ ) , it is clear that (Ra)-doped materials shows slightly large resistance to bond bending and bond angle distortion as compare to pure BaTiO3. Optical characteristics of the both pure and doped (Ra) materials in the core level spectra are thoroughly investigated. Optical coefficients are obtained in the energy scale start from 0 to 20 eV. Moreover, the results of optical properties show excellent influence of doping so that this material can be employed as UV filter in the UV region and in optoelectronics devices.

High Quantum Yield Amino Acid Carbon Quantum Dots with Unparalleled Refractive Index

Carbon quantum dots (CQDs) are one of the most promising types of fluorescent nanomaterials due to their exceptional water solubility, excellent optical properties, biocompatibility, chemical inertness, excellent refractive index, and photostability. Nitrogen-containing CQDs, which include amino acid based CQDs, are especially attractive due to their high quantum yield, thermal stability, and potential biomedical applications. Recent studies have attempted to improve the preparation of amino acid based CQDs. However, the highest quantum yield obtained for these dots was only 44%. Furthermore, the refractive indices of amino acid derived CQDs were not determined. Here, we systematically explored the performance of CQDs prepared from all 20 coded amino acids using modified hydrothermal techniques allowing more passivation layers on the surface of the dots to optimize their performance. Intriguingly, we obtained the highest refractive indices ever reported for any CQDs. The values differed among the amino acids, with the highest refractive indices found for positively charged amino acids including arginine-CQDs (∼2.1), histidine-CQDs (∼2.0), and lysine-CQDs (∼1.8). Furthermore, the arginine-CQDs reported here showed a nearly 2-fold increase in the quantum yield (∼86%) and a longer decay time (∼8.0 ns) compared to previous reports. In addition, we also demonstrated that all amino acid based CQD materials displayed excitation-dependent emission profiles (from UV to visible) and were photostable, water-soluble, noncytotoxic, and excellent for high contrast live cell imaging or bioimaging. These results indicate that amino acid based CQD materials are high-refractive-index materials applicable for optoelectronic devices, bioimaging, biosensing, and studying cellular organelles in vivo. This extraordinary RI may be highly useful for exploring cellular elements with different densities.

Frequency-dependent nonlinear optical response and refractive index investigation of lactone-derived thermochromic compounds

Nonlinear optical (NLO) switchable materials play a crucial role in the fields of electronics and optoelectronics. The selection of an appropriate switching approach is vital in designing such materials to enhance their NLO response. Among various approaches, thermos-switching materials have shown a 4-fold increase in NLO response compared to other photo-switching materials. In this study, we computationally investigated the geometric, electronic, and nonlinear optical properties of reversible lactone-based thermochromic compounds using the ωB97XD/6-311+G (d,p) level of theory. Molecular orbital studies are employed to analyze the electronic properties of the close and open isomers of these compounds, while time-dependent density functional theory (TD-DFT) analysis is utilized to evaluate their molecular absorption. Our findings reveal that the π-electronic conjugation-induced delocalization significantly influences the ON-OFF switchable nonlinear optical response of the lactone-based thermochromic compounds. Notably, among all compounds, the open isomer of lactone 2 exhibits the highest hyperpolarizability value (6596.69 au). Furthermore, we extended our analysis to investigate the frequency-dependent second and third-order hyperpolarizabilities. The most pronounced frequency-dependent NLO response is observed at 532 nm. Additionally, we calculated the refractive index of these thermochromic compounds to further assess their nonlinear optical response. The open isomer of lactone 1 demonstrates the highest refractive index value (3.99 × 10-14 cm2/W). Overall, our study highlights the excellent potential of reversible thermochromic compounds as NLO molecular thermos-switches for future applications.

Starting with an Integral Membrane Protein Project for Structural Biology: Production, Purification, Detergent Quantification, and Buffer Optimization-Case Study of the Exporter CntI from Pseudomonas aeruginosa

Production, extraction, purification, and stabilization of integral membrane proteins are key steps for successful structural biology studies, in particular for X-ray crystallography or single particle microscopy. Here, we present the purification protocol of CntI from Pseudomonas aeruginosa, a new metallophore exporter of the Drug Metabolite Transporter (DMT) family involved in pseudopaline secretion. Subsequent to CntI purification, we optimized the buffer pH, salts, and additives by differential scanning fluorimetry (DSF), also known as Thermofluor Assay (TFA) or fluorescent thermal stability assay (FTSA), with the use of dye 1-AnilinoNaphthalene-8-Sulfonic acid (ANS), a fluorescent molecule compatible with detergents. After the buffer optimization, the purified CntI was analyzed by Size Exclusion Chromatography coupled with Multi-Angle Laser Light Scattering (SEC-MALLS), UV absorbance, and Refractive Index detectors, in order to determine the absolute molar mass of the protein-detergent complex, the detergent amount bound to the protein and the amount of protein-free detergent micelles. Altogether, these biophysical techniques give preliminary and mandatory information about the suitability of the purified membrane protein for further biophysical or structural investigations.

Optimization of Flow Imaging Microscopy Setting Using Spherical Beads with Optical Properties Similar to Those of Biopharmaceuticals

Flow imaging microscopy (FIM) is widely used to characterize biopharmaceutical subvisible particles (SVPs). The segmentation threshold, which defines the boundary between the particle and the background based on pixel intensity, should be properly set for accurate SVP quantification. However, segmentation thresholds are often subjectively and empirically set, potentially leading to variations in measurements across instruments and operators. In the present study, we developed an objective method to optimize the FIM segmentation threshold using poly(methyl methacrylate) (PMMA) beads with a refractive index similar to that of biomolecules. Among several candidate particles that were evaluated, 2.5-µm PMMA beads were the most reliable in size and number, suggesting that the PMMA bead size analyzed by FIM could objectively be used to determine the segmentation threshold for SVP measurements. The PMMA bead concentrations measured by FIM were highly consistent with the indicative concentrations, whereas the PMMA bead size analyzed by FIM decreased with increasing segmentation threshold. The optimal segmentation threshold where the analyzed size was closest to the indicative size differed between an instrument with a black-and-white camera and that with a color camera. Inter-instrument differences in SVP concentrations in acid-stressed recombinant adeno-associated virus (AAV) and protein aggregates were successfully minimized by setting an optimized segmentation threshold specific to the instrument. These results reveal that PMMA beads can aid in determining a more appropriate segmentation threshold to evaluate biopharmaceutical SVPs using FIM.

An innovative detection technique for capillary electrophoresis: Localized terahertz emission-time domain spectroscopy

Terahertz (THz) time-domain spectroscopy (TDS) is a recently emerging analysis method which can provide unique information on molecular vibration and rotation induced by inter/intra-molecular interactions. Although the application of THz-TDS to high-performance microscale separation methods like capillary electrophoresis (CE) has been anticipated, it has been hindered due to the diffraction limit of THz wave (typically, hundreds µm). In order to realize CE-THz-TDS, in this study, we placed a narrow open-tubular capillary on the surface of a GaAs semiconductor substrate as a "localized" THz-emitter. By focusing femtosecond pulsed laser beams at the surface of a gallium arsenide (GaAs) substrate closest to the capillary, THz waves were locally generated to pass through the capillary, so that THz absorbance spectra were obtained from the capillary which has narrower inner diameter than the diffraction limit. As a typical result from acetic acid analysis in the CE-THz-TDS platform, information on the refractive index and extinction coefficient was obtained, which showed non-linear and linear concentration dependence, respectively, similar to conventional THz-TDS using large liquid cells. Finally, CE-THz-TDS analysis of several carboxylic acids was demonstrated. Two acids were successfully separated and detected with THz-TDS, where their electrophoretic mobility values were estimated as close to those obtained with conventional contactless conductivity detection. Our proposed CE-THz-TDS showed the potential for the systematic analysis of inter/intra-molecular weak interactions like hydrogen bonds, which are unable to obtain with conventional detectors.

Quantitative phase imaging for characterization of single cell growth dynamics

Quantitative phase imaging (QPI) has emerged as an indispensable tool in the field of biomedicine, offering the ability to obtain quantitative maps of phase changes due to optical path length delays without the need for contrast agents. These maps provide valuable information about cellular morphology and dynamics, unperturbed by the introduction of exogenous substances. In this review, a summary of recent studies that have focused on elucidating the growth dynamics of individual cells using QPI is presented. Specifically, investigations into cellular changes occurring during mitosis, the differentiation of cellular organelles, the assessment of distinct cell death processes (i.e., apoptosis, necrosis, and oncosis) and the precise measurement of live cell temperature are explored. Furthermore, the captivating applications of QPI in theragnostics, where its potential for transformative impact is prominently showcased, are highlighted. Finally, the challenges that need to be overcome for its wider adoption and successful integration into biomedical research are outlined.

Screening techniques for monitoring the sub-visible particle formation of free fatty acids in biopharmaceuticals

Free fatty acid (FFA) particles that originate from the enzymatic hydrolysis of polysorbate (PS) via co-purified host cell proteins generally appear abruptly in drug products during real-time (long-term) storage. Efforts were taken to understand the kinetics of FFA particle formation, aiming for a mitigation strategy. However, it is rather challenging particularly in the sub-visible particle (SVP) range, due to either the insufficient sensitivity of the analytical techniques used or the interference of the formulation matrices of proteinaceous drug products. In this study, we examined the feasibility of Raman microscopy, backgrounded membrane imaging (BMI) and total holographic characterization (THC) on the detection of FFA sub-visible particles (SVPs). The results indicate that THC is the most sensitive technique to track their occurrence during the course of PS hydrolysis. Moreover, with this technique we are able to distinguish different stages of FFA particle formation in the medium. In addition, a real time stability study of a biopharmaceutical was analyzed, demonstrating the viability of THC to monitor SVPs in a real sample and correlate it to the visible particles (VPs) occurrence.

Chromatic dispersion of soft contact lens materials

PURPOSE

To investigate and evaluate the chromatic dispersion of various hydrogel and silicon hydrogel contact lens materials.

METHODS

Eighteen different soft contact lens materials with high and low water content in lens power of -1.00 DS were measured by one operator at temperature of 20 °C ± 0.5° soaked in ISO standard phosphate-buffered saline (PBS) and in their respective packaging solutions (PS). An analogue Abbe refractometer (Model Zuzi 320, AUXILAB, S.L., Navarra, Spain) was used for refractive index (RI) measurements at 5 different wavelengths. All contact lenses were presented in a random and masked order to the operator. The Bland-Altman method with 95 % limits of agreement (LoA) and coefficient of repeatability (CoR) was used to characterise the repeatability of refractive index measurements. The Abbe numbers for each material were calculated by entering the measured and interpolated refractive indices into the Abbe number equation. One-way ANOVA analysis was used to test if there were significant differences between the 5 different wavelengths (470 nm-680 nm) within each material. An unpaired t-test was used to determine if there were differences in refractive index or dispersion between packaging solution and PBS results.

RESULTS

Nelfilcon A (Dailies Aqua Comfort Plus) soaked in PS showed the best repeatability of all 18 examined soft contact lenses across all wavelengths with an average refractive index of 1.3848 for all 6 contact lenses with a standard deviation of 0.00064. The 95 % limits of agreement were between 1.3835 and 1.3860. The mean coefficient of repeatability for nelfilcon A was 0.00125. For contact lenses soaked in ISO Standard PBS comfilcon A (Biofinity) had the best repeatability. The average refractive index of all 6 contact lenses was 1.4041 with a standard deviation of 0.00031 and a coefficient of repeatability of 0.00060. The 95 % limits of agreement were between 1.4035 and 1.4047. The analysis with One-way ANOVA with multiple comparisons involving Holm-Sidak post-hoc, showed that there are significant differences (p < 0.001, Fratio = 376.2 between wavelengths and Fratio = 1559 between different refractive indices) in the refractive index of most common lens materials across the visible wavelength range. Based on unpaired t-test, there is no significant difference (p > 0.05) in the Abbe numbers of the tested lens materials whether they have been placed in the packaging solution or in standard PBS (p > 0.05, 95 % CI = -4.8070 to 5.8680, t = 0.2054). The Abbe numbers for the calculated contact lenses soaked in PS ranged between 43.7 and 89.9. For contact lenses stored in PBS the range was between 46.3 and 81.6.

CONCLUSION

There is a good repeatability between repeated RI measurements taken from the same lens and from the same material. The significant differences between the refractive indices across the 5 different wavelengths showed the presence of chromatic dispersion in the 18 evaluated soft contact lens materials. Furthermore, it could be shown that there is no significant difference in dispersion whether the contact lenses are soaked in standard PBS or in their respective packaging solutions. With no other published data available as a reference, absolute accuracy of the calculated Abbe numbers remains to be confirmed, however, this study did confirm that significant chromatic dispersion exists in soft contact lens materials.

First-principle calculations to investigate structural, electronic, mechanical, optical, and thermodynamic features of promising (La, In)-doped AlSb for optoelectronic applications

CONTEXT

A remarkable change in lattice parameters and bulk modulus is achieved by the suitable addition of Al (Al_1-x La_x Sb) and In (Al_1-x In_x Sb) atoms in the AlSb compound. Electronic responses like band structure, the total partial density of states, and the elemental density of states are thoroughly investigated. The computed values indicate that the binary compound AlSb is an indirect band gap and an optically inactive response. After increasing the doping concentrations (0.25, 0.5, 0.75) of La and In in AlSb, the band gap changes from indirect to direct nature. Hence, Al_1-0.75 La_0.25 Sb, Al_1-0.50 La_0.50 Sb, Al_1-0.75 In_0.25Sb, and Al_1-0.50 In_0.50Sb become optically active. The illustrious roles of Al-3p and In-4d states on the band gap and nonlinear responses of these compounds are extensively explored by the comparison between the computed results of ultra-soft and norm converging pseudopotentials. The excess specific heat (C_V), enthalpy of mixing (Hm), and phonon dispersion curves resulting from the concentrations "x" are estimated in order to investigate the thermodynamic stability responses of the pristine and doped AlSb. The obtained C_V and thermal coefficient statistics for Al_1-x La_x Sb and Al_1-x In_x Sb may be useful for a good mapping of experimental results and examining these compounds' enharmonic responses. There is a valuable change in optical characteristics like dielectric functional, absorption, conductivity, and refractive index due to the addition of (La, In) impurities in AlSb. It is further observed that Al_1-0.75 La_0.25 Sb, Al_1-0.50 La_0.50 Sb, Al_1-0.75 In_0.25Sb, and Al_1-0.50 In_0.50Sb are significantly mechanically stable compared to pristine AlSb. The above results suggest that Al_1-x La_x Sb and Al_1-x In_x Sb are high-performance optical materials and can be promising potential candidates for optoelectronic applications.

METHODS

The structural, electronic, mechanical, vibrational, and optical responses of the pure and doped Al_1-0.75 La_0.25 Sb, Al_1-0.50 La_0.50 Sb, Al_1-0.75 In_0.25Sb, and Al_1-0.50 In_0.50Sb are investigated, using Heydscuseria-Ernzerhof screened hybrid functional (HSEO6) and generalized gradient approximation (GGA) with norm-converging and ultra-soft pseudopotential techniques in the density functional theory.

Time-domain Brillouin imaging of sound velocity and refractive index using automated angle scanning

We present a picosecond optoacoustic technique for mapping both the longitudinal sound velocity v and the refractive index n in solids by automated measurement at multiple probe incidence angles in time-domain Brillouin scattering. Using a fused silica sample with a deposited titanium film as an optoacoustic transducer, we map v and n in the depth direction. Applications include the imaging of sound velocity and refractive index distributions in three dimensions in inhomogeneous samples such as biological cells.

Progress in theoretical study of lead-free halide double perovskite Na2AgSbX6 (X = F, Cl, Br, and I) thermoelectric materials

CONTEXT

Herein, we have studied progressively novel metal lead-free halide double perovskite renewable energy materials. Due to their potential use in electronic devices, researchers have investigated these materials with a lot of interest. From the electronic structure, we have found that these are the indirect band gap semiconductors within the range between 1.273 and 3.986 eV. Optical parameters such as dielectric constant, electrical conductivity, and absorption coefficient have also been investigated, which have shown that these materials have potential use in photovoltaics. We have checked stability issues by thermodynamic parameters and phonon spectra. We have found them thermally stable; however, the phonon spectra show their dynamical instability and except for Na₂AgSbF₆ and Na₂AgSbI₆, the remaining compounds are weak in mechanical stability. For another futuristic purpose, thermoelectric parameters such as Seebeck coefficient, power factor, and figure of merit have also been calculated, which again verifies that these materials may be very useful in thermoelectric devices. Most of the parameters have been computed for the first time.

METHODS

We have performed this computational work using WIEN2k simulation code, which is based on the full-potential linearized augmented plane wave (FP-LAPW) technique. It is one of the most reliable techniques to calculate the photovoltaic properties of semiconducting perovskites. The interaction between ion-core and valence electrons was dealt with within the PAW technique as implemented in Vienna Ab initio Simulation Package (VASP).

Two-dimensional material-enhanced surface plasmon resonance for antibiotic sensing

Two-dimensional (2D) materials attract attention from the academic community due to their excellent properties, and their wide application in sensing is expected to revolutionize environmental monitoring, medical diagnostics, and food safety. In this work, we systematically evaluate the effects of 2D materials on the Au chip surface plasmon resonance (SPR) sensor. The results reveal that 2D materials cannot improve the sensitivity of intensity-modulated SPR sensors. However, there exists an optimal real part of RI of 3.5-4.0 and optimal thickness when choosing nanomaterials for sensitivity enhancement of SPR sensors in angular modulation. In addition, the smaller the imaginary part of the nanomaterial RI, the higher the sensitivity of the proposed Au SPR sensor. The 2D material's thickness needed for the highest sensitivity decreases with increasing real part and imaginary part of the RI. As a case study, we developed a 5 nm-thickness MoS₂-enhanced SPR biosensor, which exhibited a low sulfonamides (SAs) detection limit of 0.05 μg/L based on a group-targeting indirect competitive immunoassay, nearly 12-fold lower than that of the bare Au SPR system. The proposed criteria help to shed light on the 2D material-Au surface interaction, which has greatly promoted the development of novel SPR biosensing with outstanding sensitivity.

Retrieval of refractive index of ultrafine single particle using hygroscopic growth factor obtained by high sensitive surface plasmon resonance microscopy

When exposed to different relative humidities (RHs), the optical properties of atmospheric aerosols will change because of changes in the aerosol particle size and complex refractive index (RI), which will affect haze formation and global climate change. The potential contributions of ultrafine particles to the atmospheric optical characteristics and to haze spreading cannot be ignored because of their high particle number concentrations and strong diffusibility; measurement of the optical properties of wet ultrafine particles is thus highly important for environmental assessment. Therefore, a surface plasmon resonance microscopy with azimuthal rotation illumination (SPRM-ARI) system is designed to determine the RIs of single particle aerosols with diameters of less than 100 nm in the hygroscopic growth process. Measurements are taken using mixed single particles with different mass ratios. The RIs of mixed single aerosols at different RHs are retrieved by measuring the scattering light intensity using the SPRM-ARI system and almost all the RIs of the bicomponent particles with different mass ratios decrease with increasing water content under high RH conditions. Finally, for each of the bicomponent particles, the maximum standard deviations for the retrieved RI values are only 2.06×10^-3, 3.08×10^-3 and 3.83×10^-3, corresponding to the NaCl and NaNO₃ bicomponent particles with a 3:1 mass ratio at 76.0% RH, the NaCl and glucose particles with a 1:3 mass ratio at 89.0% RH, and the NaCl and OA particles with a 1:1 mass ratio at 78.0% RH, respectively; these results indicate that the high-sensitivity SPRM-ARI system can measure the RI effectively and accurately.

A unified framework for the numerical evaluation of the Q-subtractive Kramers-Kronig relations and application to the reconstruction of optical constants of quartz

The direct usage of the Kramers-Kronig (KK) relations is complicated by two factors: limited frequency range of the available spectra and experimental errors. Here, we reconsider the application of the KK relations to experimental data for the construction of a self-consistent set of optical constants over a wide spectral range: the real part of the complex optical constant, F₁, is reconstructed using the imaginary part F₂, obtained from an experiment. The focus is on multiply (Q-)subtractive KK relations, which in contrast to the standard KK transformation, exploit information about F₁ at a certain number Q of anchor frequencies. We develop a general mathematical framework of the Q-subtractive KK relations and analyze all sources of errors contributing to the inaccuracy of the reconstructed F₁. We show that for the reconstruction of F₁ only a single evaluation of the standard KK relation is needed together with a correction term given by an approximate evaluation of the error in the standard KK. It is demonstrated that in the classical form of the Q-subtractive KK relations, this correction term coincides with the Lagrange interpolation polynomial of the error with nodes at the anchor frequencies. Another correction term can also be constructed as a lower degree polynomial through a least squares fit, a particular realization of which is taking the average of Q singly subtractive KK relations. As a result, recommendations for the application of Q-subtractive KK relations are given. The accuracy of the considered approaches is illustrated on synthetic examples and experimental data of fused SiO₂.

Recognition of microplastics suspended in seawater via refractive index by Mueller matrix polarimetry

Microplastics have become the marine pollution posing a human health risk, but they are difficult to be detected and recognized for different materials, irregular shapes, and broad size distributions. Microplastics' refractive index (RI) is related to the materials and can be characterized by the Mueller matrix. In this work, the particles are suspended in water and their Mueller matrices are measured by a particulate Mueller matrix polarimetry setup. Four kinds of spherical particles including microplastics are effectively classified by their Mueller matrices. Moreover, two kinds of common microplastics with broad size distributions, irregular shapes, and random orientations are also well recognized by the Mueller matrix. These results imply that RI plays a vital role in the recognition of microplastics suspended in water. By using the Mie theory and discrete dipole approximation simulation, the discussions explain in physics origin how RI affects Mueller matrix coupling with size and structure, and give some decoupling methods. Results in this work help advance future tools to in situ recognize the microplastics in seawater.

Amendment the surface structure and optical properties of Makrofol LT by low energy oxygen ion bombardment

Ion beam bombardment is a powerful technique to improve the surface properties of polymeric materials without changing the bulk properties. Herein, Makrofol LT films were bombarded with low energy of oxygen ions at different fluences ranging from 11 × 10¹⁷ to 44 × 10¹⁷ ions/cm². X-ray diffraction, FTIR spectroscopy, surface-roughness tester, ultraviolet-visible spectroscopy, and Fluorescence spectroscopy were used to examine the change in the structure, chemical functional groups, alteration in surface roughness parameters, and photo-physical properties. The obtained results evidenced that the ordering and disordering structure of bombarded Makrofol LT films were influenced by ion beam irradiation according to the ion fluence. The FTIR spectroscopy of functional group examination revealed the possibility of the presence of sp²-carbon clusterization and amorphization. The surface roughness parameters increase as the ion fluences increase. Optical measurements exhibit a shift of absorption-edge towards the visible zone that correlated to the surface damage and the creation of CC bonds. The fluorescence spectra exhibit that the yield intensities decrease with increasing ion fluences. This refers to improvement in the radiative-recombination rate relative to non-radiative recombination. This is attributable to the growth of clusters, the increase of density states of the surface, and the increase in the surface roughness of the bombarded samples.

Numerical Simulation of Surface Plasmon Resonance Optical Fiber Biosensor Enhanced by Using Alloys for Medical Application

Tuberculosis is a very dangerous disease. Therefore, early and quick diagnosis of this disease can increase the chances of overcoming it. Studies show that people with tuberculosis have a lower blood plasma refractive index than healthy people. The performance of the fiber optic sensor based on surface plasmon resonance is investigated for the metal/oxide/graphene structure and for cases where the diameter of the fiber optic core is 300, 600, and 940 µm while blood plasma is considered as the sensing medium. The sensor characteristics such as sensitivity, detection accuracy and figure of merit are simulated for each structure using the theory of matrix method in Wolfram Mathematica software. The simulation results show that the aluminum/lutetium oxide/graphene structure has the highest quality factor when the core diameter of the optical fiber is 940 µm. In continuation of this research, the effects of using alloys with different mixture proportions to improve the quality are investigated. According to results, the structure of aluminum/copper alloy (with a ratio of 30/70)-lutetium oxide graphene is the best choice for improving the quality of the sensor.

Shrimp miR-965 transfers tumoricidal mitochondria

Background

Micro RNA of Marsupenaeus japonicas has been known to promote apoptosis of tumor cells. However, the detailed mechanisms are not well understood.

Results

Using tomographic microscope, which can detect the internal structure of cells, we observed breast tumor cells following treatment of the miRNA. Intriguingly, we found that mitochondria migrate to an adjacent tumor cells through a tunneling nanotube. To recapitulate this process, we engineered a microfluidic device through which mitochondria were transferred. We show that this mitochondrial transfer process released endonuclease G (Endo G) into tumor cells, which we referred to herein as unsealed mitochondria. Importantly, Endo G depleted mitochondria alone did not have tumoricidal effects. Moreover, unsealed mitochondria had synergistic apoptotic effects with subtoxic dose of doxorubicin thereby mitigating cardiotoxicity.

Conclusions

Together, we show that the mitochondrial transfer through microfluidics can provide potential novel strategies towards tumor cell death.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12575-022-00178-8.

Clinical and experimental study of a terahertz time-domain system for the determination of the pathological margins of laryngeal carcinoma

Objective

Laryngeal cancer is a common malignancy in otorhinolaryngological head and neck surgery, accounting for approximately one-third of all head and neck malignancies. Terahertz time-domain spectroscopy (THz-TDS) has recently been found to be useful for the detection of tumors. This study was conducted to investigate the application of THz-TDS in the diagnosis of pathological resection margins of laryngeal cancer.

Methods

Fresh laryngeal cancer tissues from 10 patients with laryngeal cancer were extracted, and after simultaneous HE staining and terahertz imaging, the tumor area, paracancerous area, and normal tissue area of each laryngeal cancer tissue sample were located under a microscope according to the pathological results of HE staining.

Results

The shape contours of the tumor region revealed by terahertz imaging maps and HE staining were similar. In the terahertz spectrum in the frequency range of 0.5–1.9 THz, both the absorption coefficient and refractive index values followed the order tumor > para cancer > normal tissue, with statistically significant differences (P < 0.01). When the terahertz frequency was 1.5 THz, the absorption coefficient of terahertz light waves by laryngeal cancer tissue and the percentage of nuclei showed an extremely high positive correlation (P < 0.01, r = 0.971). In the frequency ranges of 0.5–1.2 THz and 1.6–1.9 THz, the absorption coefficients of the highly differentiated group were higher than those of the moderately differentiated group. In the frequency range of 1.2–1.6 THz, the results were reversed, with statistically significant differences (P < 0.05). In the frequency range of 0.5–1.9 THz, the highly differentiated group had a higher refractive index than the moderately differentiated group, with a statistically significant difference (P < 0.05).

Conclusions

THz-TDS can be used to determine the pathological margins of laryngeal cancer based on the absorption coefficient and refractive index, and the magnitudes of the absorption coefficient and refractive index are related to the percentage of nuclei. The degree of differentiation of laryngeal cancer tissue can be assessed by THz-TDS. The study shows that the terahertz time-domain system is promising for applications in the diagnosis of laryngeal cancer, especially for the more accurate identification of intraoperative margins.

Parameterization of the ambient aerosol refractive index with source appointed chemical compositions

The refractive index of ambient aerosols is widely used in the climate model and remote sensing. Traditionally, the real part of the refractive index (RRI) of the ambient aerosol is calculated from the measured mass fraction of the main inorganic components with known refractive index, without full resolving the effects of variation in the RRI of organic components, which always contribute more than 50 % of the total aerosol mass. For the first time, the ambient aerosol RRI and the aerosol chemical components were measured concurrently at a suburban site Changping, in Beijing, China. Measurements results show that the ambient aerosol ranges between 1.57 and 1.71 with a mean value of 1.66. The mean mass fractions of organic aerosol (OA), nitrate, sulfate, ammonium, and chloride to total non-refractory aerosol loading are 43.1 %, 21.9 %, 21.6 %, 13.1 %, and 0.3 % respectively. Source appointment analysis of the organic aerosol show that the fossil fuel-related OA, cooking OA, biomass burning OA, less oxidized oxygenated OA and more oxidized OOA contributes 18.0 %, 11.2 %, 4.1 %, 39.9 %, 26.7 % to the total aerosol. A new parameterization scheme of the ambient aerosol RRI, which considers the source appointed OA, is proposed based on the concurrent measurements of RRI and chemical composition. The measured and parameterized RRI shows good consistency with a correlation coefficient of 0.79 and slope of 0.98. Our measurement results reveal that a significant deviation of the calculated RRI exists without considering the variation of the RRI of the aerosol organic component. The parametrization scheme is adopted and applicable in aerosol model for bettering estimating the corresponding optical and radiative effects.

A novel strategy regarding geometric product for liquids discrimination based on THz reflection spectroscopy

A novel expression of geometric product that associated with the geometric relationship from geometric algebra constructed by the vectorized refractive index and absorption coefficient in THz region is proposed, which could provide a new insight into the THz properties of materials. From the novel expression, the candidate characteristic parameters are extracted for liquids discrimination and present the abundant second order correlation information of optical parameters with the consideration of dimension rising. Three groups of liquids, containing C-reactive protein calibrators and alpha fetoprotein calibrators, were selected as examples to validate the feasibility of the proposed strategy. Comparing with the traditional THz parameters, including refractive index, absorption coefficient, and complex permittivity, the novel approach exhibits notable superiority for differentiation with the evaluation of statistical differences and effect sizes. The proposed geometric product expression could have a large potential on promoting the substance identification in some applications of THz technology.

Complex refractive index of freshly excised human breast tissue as a marker of disease

We report differences in the refractive index of healthy and tumorous freshly excised human breast tissue as determined from reflectance profile measurements at five wavelengths (432 nm, 532 nm, 633 nm, 964 nm, 1551 nm) in the visible and near-infrared using a standard prism-coupling refractometer. These refractive index differences, particularly in the near-infrared, can be used to distinguish fibroadenomas and cancerous growths not only from normal breast tissue but also from each other.

Applicability of Reddish-Orange Light Emitting Samarium (III) Complexes for Biomedical and Multifunctional Optoelectronic Devices

Six crimson samarium (III) complexes based on β-ketone carboxylic acid and ancillary ligands were synthesized by adopting the grinding technique. All synthesized complexes were investigated via elemental analysis, infrared, UV-Vis, NMR, TG/DTG and photoluminescence studies. Optical properties of these photostimulated samarium (III) complexes exhibit reddish-orange luminescence due to ⁴G_5/2 → ⁶H_7/2 electronic transition at 606 nm of samarium (III) ions. Further, energy bandgap, color purity, CIE color coordinates, CCT and quantum yield of all complexes were determined accurately. Replacement of water molecules by ancillary ligands enriched these complexes (S2-S6) with decay time, quantum yield, luminescence, energy bandgap and biological properties than parent complex (S1). Interestingly, these efficient properties of complexes may find their applications in optoelectronics and lighting systems. In addition to these, the antioxidant and antimicrobial assays were also investigated to explore the applications in biological assays.

Label-free imaging and evaluation of characteristic properties of asthma-derived eosinophils using optical diffraction tomography

Optical diffraction tomography (ODT), an emerging imaging technique that does not require fluorescent staining, can measure the three-dimensional distribution of the refractive index (RI) of organelles. In this study, we used ODT to characterize the pathological characteristics of human eosinophils derived from asthma patients presenting with eosinophilia. In addition to morphological information about organelles appearing in eosinophils, including the cytoplasm, nucleus, and vacuole, we succeeded in imaging specific granules and quantifying the RI values of the granules. Interestingly, ODT analysis showed that the RI (i.e., molecular density) of granules was significantly different between eosinophils from asthma patients and healthy individuals without eosinophilia, and that vacuoles were frequently found in the cells of asthma patients. Our results suggest that the physicochemical properties of eosinophils derived from patients with asthma can be quantitatively distinguished from those of healthy individuals. The method will provide insight into efficient evaluation of the characteristics of eosinophils at the organelle level for various diseases with eosinophilia.

Does salting-out effect nucleate nanobubbles in water: Spontaneous nucleation?

The solubility of gases in aqueous salt solution decreases with the salt concentration, often termed the "salting-out effect." The dissolution of salt in water is followed by dissociation of salt and further solvation of ions with water molecules. The solvation weakens the affinity of gaseous molecules, and thus it releases the excess dissolved gas. Now it is interesting to know that what happens to the excess gas released during salting-out? Since it is imperative to note that the transfer of the dissolved gas in the bulk liquid may often occur in the form of nanobubbles. In this work, we have answered this question by investigating the nano-entities nucleation during the salting-out effect. The solubility of gases in aqueous salt solution decreases with the salt concentration, and it is often termed as the "salting-out effects." The dissolution of salt in water undergoes dissociation of salt and further solvation of ions with water molecules. The solvation weakens the affinity of gaseous molecules, and thus it releases the excess dissolved gas. Now it is interesting to know that what happens to the excess gas released during salting-out? While it is also imperative to note that the gas transfer in the bulk liquid often occurs in the form of bubbles. With this hypothesis, we have experimentally investigated that whether the salting-out effect nucleates nanobubble or not. What is the strong scientific evidence to prove that they are nanobubbles? Does the salting-out parameter affect the number density? The answers to such questions are essential for the fundamental understanding of the origin and driving force for nanobubble generation. We have provided three distinct proofs for the nano-entities to be the nanobubbles, namely, (1) by freezing and thawing experiments, (2) by destroying the nanobubbles under ultrasound field, and (3) we also proposed a novel method for refractive index estimation of nanobubbles to differentiate them from nano drops and nanoparticles. The refractive index (RI) of nanobubbles was estimated to be 1.012 for mono- and di-valent salts and 1.305 for trivalent salt. The value of RI closer to 1 provides strong evidence of gas-filled nanobubbles. Both positive and negative charged nanobubbles nucleate during the salting-out effect depending upon the valency of salt. The nanobubbles during the salting-out effect are stable only for up to three days. This shorter stability could plausibly be due to reduced colloidal stability at a low surface charge.

Development and validation of a simple and reliable alternative method for process monitoring and final product quality control during fatty acid ethyl esters production

As the production of biofuels increase, there is an urgent need to easily analytically control their production at the plant level as well as to assess the quality of the final products. Especially method capable of determining fatty acid ethyl ester content of 96.5% is crucial for utilization in praxis. In this work, a refractive index method with required sensitivity was developed and validated by means of a standard reference gas chromatography method. Validation with a considerable set of real unique samples obtained at pilot scale was performed for both purposes - process monitoring at high conversions and final product quality control. The results confirmed a favourable degree of accuracy with a relative deviation lower than 3.5% from the reference value given by the gas chromatography. Moreover, application of the method for quality control of fresh and long-term stored samples revealed that the deterioration of final products during storage can be detected. The developed refractive index method is thus suitable for the simple and rapid evaluation of the quality of produced fatty acid ethyl esters and for analytical monitoring of their production process.

Spectroscopic ellipsometric study datasets of the fluorinated polymers: Bifunctional urethane methacrylate perfluoropolyether (PFPE) and polyvinylidene fluoride (PVDF)

The datasets in this work contain the experimentally measured (real) refractive indices, optical transmission intensity, and optical absorption spectra of bifunctional urethane methacrylate perfluoropolyether (PFPE; Fluorolink® MD700) substrate of (0.98 ± 0.13) mm thickness and polyvinylidene fluoride (PVDF; Kynar® 705) thin-film of (4.47 ± 0.29) µm thickness over a spectral range from 300 nm to 1000 nm, as measured via variable angle spectroscopic ellipsometry. The refractive indices data were determined by employing a single Cauchy optical constants function based layer using a Levenberg-Marquardt multi-iterative regression algorithm for all model minimizations. The mean-squared error (MSE) was used as the maximum likelihood estimator, with a convergence of the Levenberg-Marquardt algorithm reached when successive iterations were unable to improve the MSE. The resulting best-fit parameter values were evaluated for sensitivity (expressed as a confidence limit), and possible correlations. Furthermore, the experimentally measured optical transmission intensity and determined optical absorption of PFPE and PVDF, over a spectral range from 300 nm to 1000 nm, is also presented, as measured via ellipsometry and corrected using Fresnel equations to accommodate surface interference. Given the high transmission of (88.4 ± 0.5)% for PFPE and (95.6 ± 0.6) % for PVDF found, and the low refractive index 1.27 (λ = 589.3 nm) found for PFPE; it is thought that these datasets may be useful for optical applications, such as for photo-curable synthesis processes, or being used as a host-matrix material for photoluminescent compounds.

Evaluating the failure to bloom in dark-cutting and lactate-enhanced beef longissimus steaks

Previous studies have noted lower L* (lightness) values for both dark-cutting beef and normal-pH beef enhanced with lactate. In the current study, absorption-coefficient, scattering-coefficient, CIE L*a*b* values, refractive index of sarcoplasm, and inter-muscle bundle space were evaluated for dark-cutting beef, normal-pH beef enhanced with lactate, normal-pH beef enhanced with water, and normal-pH beef not enhanced with either water or lactate. Compared with non-enhanced loins, lactate-enhancement had lower a*, chroma, oxymyoglobin, reflectance, scattering, and inter-muscle bundle space as well as greater absorption and refractive index. Dark-cutting steaks had lower a*, chroma, oxymyoglobin values, reflectance, and scattering as well as less inter-muscle bundle space compared with lactate-enhanced steaks. Sarcoplasm refractive index values were greater in lactate-enhanced steaks than dark-cutting steaks. The results suggest that changes in muscle structure and optical properties due to either pH or lactate addition can alter muscle darkening and blooming properties.

Extremely large static and dynamic nonlinear optical response of small superalkali clusters NM3M' (M, M'=Li, Na, K)

Exploring novel nonlinear optical (NLO) materials with excess electron properties is essential for advancing the use of excess electron compounds in optics. The studied superalkali clusters NM₃M' (M, M' = Li, Na, K) are thermodynamically stable and their binding energies range from -27.10 to -53.84 kcal mol^-1. The observed significant values for VIPs suggest their electronic stabilities. Being excess electron candidate these clusters show significant β_o value (3.9 × 10⁷ au), which nicely correlates the hyperpolarizability reported by a two-level model (β_tl). Furthermore, these clusters exhibit a remarkable static second hyperpolarizability (γ_o) value of 1.1 × 10¹⁰ au for the NK₄ superalkali cluster. The hyper Rayleigh scattering (β_HRS) is also computed where the highest value of 2.9 × 10⁷ is recorded for NNa₃K superalkali. The obtained values of β_vec values (projection of hyperpolarizability on dipole moment vector) also signify the excellent nonlinearity of clusters. Besides, the calculated electro-optica pockel's effect β(-ω; ω,0) and second harmonic generation β(-2ω; ω, ω) values are much pronounced at larger dispersion frequency ω = 1064 nm. Moreover, the frequency-dependent second hyperpolarizability γ(ω) with dc-Kerr effect γ(-ω; ω,0,0) and electric field induced second harmonic generation γ(-2ω; ω,ω,0) show larger values at ω = 1064 nm. Thus the highest value of the dc-Kerr constant increases up to 1.0 × 10¹¹ au which also signifies the larger nonlinear refractive index of the studied cluster. We hope this work could open up new possibilities using superalkali clusters as NLO materials for optoelectronics, laser, second harmonic generation and as frequency doubler.

An interlaboratory study evaluating the interpretation of forensic glass evidence using refractive index measurements and elemental composition

Seventeen laboratories participated in three interlaboratory exercises to assess the performance of refractive index, micro X-ray Fluorescence Spectroscopy (μXRF), and Laser Induced Breakdown Spectroscopy (LIBS) data for the forensic comparison of glass samples. Glass fragments from automotive windshields were distributed to the participating labs as blind samples and participants were asked to compare the glass samples (known vs. questioned) and report their findings as they would in casework. For samples that originated from the same source, the overall correct association rate was greater than 92% for each of the three techniques (refractive index, μXRF, and LIBS). For samples that originated from different vehicles, an overall correct exclusion rate of 82%, 96%, and 87% was observed for refractive index, μXRF, and LIBS, respectively. Special attention was given to the reporting language used by practitioners as well as the use of verbal scales and/or databases to assign a significance to the evidence. Wide variations in the reported conclusions exist between different laboratories, demonstrating a need for the standardization of the reporting language used by practitioners. Moreover, few labs used a verbal scale and/or a database to provide a weight to the evidence. It is recommended that forensic practitioners strive to incorporate the use of a verbal scale and/or a background database, if available, to provide a measure of significance to glass forensic evidence (i.e., the strength of an association or exclusion).

Propagation of the pure-cubic optical solitons and stability analysis in the absence of chromatic dispersion

The main concentration of this article is to extract pure-cubic optical solitons in nonlinear optical fiber modeled by nonlinear Schrödinger equation (NLSE). The governing model is discussed the with the effect of third-order dispersion, Kerr law of nonlinearity and without chromatic dispersion. We extract the solutions in different forms like, Jacobi's elliptic, hyperbolic, periodic, exponential function solutions including a class of solitary wave solutions such that bright, dark, singular, kink-shape, multiple-optical soliton, and mixed complex soliton solutions. Recently developed integration tools known as Φ 6 -model expansion method, generalized exponential rational function method (GERFM) and generalized Kudryashov method are applied to analyze the governing model. The studied model is also discussed by the concept of modulation instability (MI) analysis. The constraints conditions are explicitly presented for the resulting solutions and singular periodic wave solutions are recovered. Furthermore, for explaining the solutions in physical phenomena, the three dimensional, two dimensional, and their related contours graphs are plotted under the selection of appropriate parameters. The accomplished results show that the applied computational system is direct, productive, reliable and can be carried out in more complicated phenomena. The results show that the studied equation theoretically has extremely rich pure-cubic optical structures of nonlinear fiber relevance.

Larger than expected variation range in the real part of the refractive index for ambient aerosols in China

The real part of the refractive index (RRI) of ambient aerosol, which is widely used in remote sensing and atmospheric models, is one of the key factors determining its particles' optical properties. The characteristics of ambient aerosol RRI in China have not yet been well studied owing to a lack of observations. For the first time, the properties of aerosol RRI were studied based on field measurements in China at four sites with different atmospheres. The results revealed that the measured ambient aerosol RRI varied significantly between 1.36 and 1.78, increasing with the mass ratio of organic components. The scattering coefficient and direct radiative effects of the aerosols were estimated to increase by factors of 2 and 3, respectively, when RRI increased from 1.36 to 1.78. Our results indicate that variation in ambient aerosol RRI should be considered in aerosol and climate models to achieve an accurate estimation of aerosol's radiative impacts.

Comparison of ultraviolet and refractive index detections in the HPLC analysis of sugars

Refractive index (RI) detection is the standard approach for quantitatively detecting sugars via high-performance liquid chromatography (HPLC), while ultraviolet (UV) absorbance detection is the most commonly used detection method for general HPLC analysis. We compared the two detection approaches of UV and RI in the HPLC analysis of small sugars to investigate whether UV detection could be an alternative method to RI detection. UV detection was performed using a photodiode array scanning from 190 to 400 nm. We obtained comparable limit of detection (LOD) results for RI and UV detection in the HPLC analysis of monosaccharides, while HPLC-RI provided better LOD results than HPLC-UV in disaccharide analysis. Both HPLC-RI and HPLC-UV methods were applied to analyze a real honey sample, and similar results were obtained in terms of precision and recovery. The study conclusively shows that the UV-based HPLC analysis of sugars offers a sufficient alternative to RI-based HPLC analysis.

Comprehensive Size Distribution and Composition Analysis of Adeno-Associated Virus Vector by Multiwavelength Sedimentation Velocity Analytical Ultracentrifugation

During the manufacturing of recombinant adeno-associated virus vectors, it is generally difficult to purify out vectors that lack nucleic acids (empty particles, EPs), contain incomplete nucleic acids (intermediate particles, IPs) or aggregates. These impurities may cause side effects and therefore it is essential to both quantify and reduce them; however, comprehensive identification of the size distribution and components of virus vectors have been lagging. We developed multiwavelength sedimentation velocity analytical ultracentrifugation to characterize EPs, full particles, IPs, and aggregates in adeno-associated virus vector samples. The wavelength-dependent ultraviolet (UV) absorption of capsid protein and encapsulated single-stranded DNA could be deduced from the multiwavelength detection followed by size distribution analysis and peak area integration. Subsequently, a spectral deconvolution analysis using the wavelength-dependent UV absorption data enabled the identification of the protein-nucleic acid ratio of all species. A comprehensive approach for quantifying the viral vector particles and related impurities was established.

Oxacarbon superalkali C3X3Y3 (X = O, S and Y = Li, Na, K) clusters as excess electron compounds for remarkable static and dynamic NLO response

An intriguing class of excess electron oxacarbon superalkali clusters is explored for nonlinear optical response through density functional theory (DFT) methods at CAM-B3LYP/6-311++G(d,p). These superalkali clusters shows noticeable binding energies per atom (E_b) which reveals their thermodynamic stabilities (-86.45 ∼ -119.44 kcal mol^-1). The obtained significant VIPs values also suggest the electronic stability of these clusters. The VIP values range from 2.06 eV to 3.42 eV. These clusters show remarkable electronic properties and their HOMO-LUMO gaps (E_H-L) are significantly reduced. The lowest H-L gap of 0.96 eV is obtained for C₃O₃K₃ while the highest H-L gap of 2.07 eV is calculated for C₃S₃Li₃. The obtained PDOS spectra further provide evidence for the superior electronic properties of these clusters. The clusters show excellent nonlinear optical properties as revealed from remarkable values (1.6 × 10⁶ au) of static first hyperpolarizability. The controlling factors for hyperpolarizability are also explored by using conventional two-level model. The calculated values of β_o are correlated nicely with β_tl. The crucial excitation energy is the key factor in controlling the first hyperpolarizability. In these excess electron clusters, the second hyperpolarizability (γ_o) response increases up to 4.3 × 10⁹ au. Moreover, the calculated scattering hyperpolarizability (β_HRS) values are quite significant in these clusters and the highest value of 1.3 × 10⁶ au is calculated for C₃S₃K₃. Additionally, these clusters also possess larger dynamic nonlinearities. The dynamic second hyperpolarizability with dc-Kerr effect increases up to 1.0 × 10¹¹ au. The remarkable values for refractive index (n₂) also suggest the excellent nonlinearity of these superalkali clusters.

A simple and reliable refractometric method to determine the total solids concentration of the cervico-vaginal bovine mucus samples

Cervico-vaginal mucus (CVM) is a viscoelastic substance continuously produced by secretory cells of the endocervix and the vagina of cows. Its physicochemical composition varies depending on the hormonal status of the estrous cycle. In veterinary medicine refractometry is a widely diffused technique to determine total solids (TS) content of biological samples, but there are not published data of CVM total solids from refractometric measures. Refractometric TS determination contributes to the qualitative constituents analysis of CVM, additionally it is an easier and more inexpensive technique than gravimetric TS determination. The main goal of the present paper was to validate a refractometric method to estimate TS concentration of the soluble fraction of CVM samples. Samples were collected from seventy-three Holando Argentino cows of Santa Fe province farms in Argentina. Cows were classified in three experimental groups: healthy, subclinical (SE) and clinical endometritis (CE) group. To achieve a solubilisation protocol for CVM samples, four Triton™ X-100 concentrations were tested. Refractive index (RI) and gravimetric total solid (gTS) concentration of solubilised samples were determined for the three experimental groups. A mathematical equation was determined with the experimental data from the healthy group, in order to obtain calculated total solid concentration (cTS) from refractivity (R) values. To validate the RI method for CVM samples, cTS concentrations were compared with gTS concentrations from endometritis group samples. Triton™ X-100 0.01% (V/V) improved CVM samples handling and did not change physicochemical parameters (gTS, Na⁺ and K⁺ concentration, and RI values). The linear regression equation obtained was: cTS (g/dL) = (R - 0.67)/16.2, r² = 0.91. Correlation between gTS and cTS concentration was: r = 0.97 for SE group and r = 0.97 for CE group. The homogenization protocol allowed the measurement of physicochemical parameters without altering their values. A high correlation coefficient between cTS and gTS postulates refractometry as an accurate method to determine TS concentration for solubilised CVM samples.

Effects of Viscosity and Refractive Index on the Emission and Diffusion Properties of Alexa Fluor 405 Using Fluorescence Correlation and Lifetime Spectroscopies

Fluorescence Correlation Spectroscopy (FCS) studies of the interaction of polymers or proteins in solution are strongly affected by the viscosity and refractive index of the medium, and the effects are likely to be more significant with the use of short wavelength excitation (e.g., 405 nm diode lasers). Failing to account for these issues can lead to incorrect measurement of average size, conformational changes, and dynamic behaviour of polymers and proteins. Steady-state, time-resolved, and FCS measurements of Alexa 405 in glycerol:water mixtures were performed to determine its suitability for FCS measurements with 405 nm excitation. The effects of the refractive index and viscosity on the diffusion coefficient and photophysical parameters (lifetime and relative quantum yield) of the fluorophore were determined. Alexa 405 lifetime decreased from 3.55 ns in water to 3.25 ns in a 50:50 glycerol:water mixture, while its diffusion coefficient dropped from 333 ± 16 to 44 ± 1 µm²s^- 1. Lifetime data collected from micromolar solutions of Alexa 405 did however also suggest that as solvent polarity decreased, aggregates (excimers) were formed as evidenced by the appearance of a rising edge in the decay plots. The interdependence between lifetime, refractive index, and diffusion coefficient could be accurately fitted by a simple polynomial function indicating that the probe is well behaved and predictable in the glycerol:water model system. Overall, Alexa 405 is a most promising and reliable probe for FCS measurement using violet laser diode excitation sources.

Absorption properties and forcing efficiency of light-absorbing water-soluble organic aerosols: Seasonal and spatial variability

Light-absorbing organic aerosols, also known as brown carbon (BrC), enhance the warming effect of the Earth's atmosphere. The seasonal and spatial variability of BrC absorption properties is poorly constrained and accounted for in the climate models resulting in a substantial underestimation of their radiative forcing estimates. This study reports seasonal and spatial variability of absorption properties and simple forcing efficiency of light-absorbing water-soluble organic carbon (WSOC, SFE_WSOC) by utilizing current and previous field-based measurements reported mostly from Asia along with a few observations from Europe, the USA, and the Amazon rainforest. The absorption coefficient of WSOC at 365 nm (b_abs-365) and the concentrations of carbonaceous species at Kanpur were about an order of magnitude higher during winter than in the monsoon season owing to differences in the boundary layer height, active sources and their strengths, and amount of seasonal wet precipitation. The WSOC aerosols during winter exhibited ∼1.6 times higher light absorption capacity than in the monsoon season at Kanpur site. The assessment of spatial variability of the imaginary component of the refractive index spectrum (k_λ) across South Asia has revealed that it varies from ∼1 to 2 orders of magnitude and light absorption capacity of WSOC ranges from 3 to 21 W/g. The light absorption capacity of WSOC aerosols exhibited less spatial variability across East Asia (5-13 W/g) when compared to that in the South Asia. The photochemical aging of WSOC aerosols, indicated by the enhancement in WSOC/OC ratio, was linked to degradation in their light absorption capacity, whereas the absorption Ångström exponent (AAE) remained unaffected. This study recommends the adoption of refined climate models where sampling regime specific absorption properties are calculated separately, such that these inputs can better constrain the model estimates of the global effects of BrC.

Exploring the optoelectronic and third-order nonlinear optical susceptibility of cross-shaped molecules: insights from molecule to material level

In the present investigation, we use a dual computational approach (at single molecular and solid-state levels) to explore the optoelectronic and nonlinear optical (NLO) properties of cross-shaped derivatives. The solid-state electronic band structures of the compounds 1-3 (the derivatives of tetracarboxylic acid in cross-shaped having the core of benzene (1), pyrazinoquinoxaline (2), and tetrathiafulvalene (3)) are calculated. The calculated band gaps for compounds 1-2 are found to be direct bad gaps and compound 3 to be indirect bad gap with energy gaps of 2.749, 1.765, and 0.875 eV, respectively. The important optical properties including refractive index, absorption coefficients, loss functions, and extinction coefficient of these semiconductors are calculated at bulk level to seek their potential applications as efficient optoelectronic materials. Additionally, we use the Lorentz approximation to calculate the third-order NLO susceptibilities of compounds 1-3 using the molecular hyperpolarizability and solid-state parameters. The calculated third-order NLO susceptibilities of compounds 1-3 are found to be 6.92 × 10^-12, 64.0 × 10^-12, and 26.3 × 10^-12 esu, respectively. Thus, the present study not only provides a way to connect the calculated third-order molecular NLO polarizability to NLO susceptibilities for compounds 1-3 through Lorentz approximation but also highlights the importance of central core modifications on their NLO susceptibilities.