Optical characterization and defect-induced behavior in ZnAl1.999Ho0.001O4 spinel: Unraveling novel insights into structure, morphology, and spectroscopic features

The ZnAl1.999Ho0.001O4 phosphor, prepared by the solid-state method, crystallizes in the cubic spinel structure. Morphology and chemical composition homogeneity were determined via Energy Dispersive X-ray and SEM analysis. The (Eg) optical band gap was evaluated from the UV/vis absorption spectrum, confirming direct transition behavior according to Tauc's law. The Urbach energy (Eu) in the ZnAl1.999Ho0.001O4 spinel was higher than that in the ZnAl2O4 spinel, indicating increased disorder and a higher concentration of defects due to Ho3+ ions. The penetration depth (δ(λ)), optical extinction (k(λ)), and refractive index (n(λ)) were assessed across wavelengths (λ). The room temperature absorption spectrum revealed several peaks corresponding to the 4f-4f transitions of Ho3+ ions.

Composition, Optical Resonances, and Doping of InP/InGaP Nanowires for Tandem Solar Cells: a Micro-Raman Analysis

We present a micro-Raman study of InP/InGaP tandem junction photovoltaic nanowires. These nanowires render possible InGaP compositions that cannot be made in thin films due to strain. The micro-Raman spectra acquired along the nanowires reveal the existence of compositional changes in the InGaP alloy associated with the doping sequence. The heavily Zn-doped InxGa1-xP (x is the In molar fraction) side of the tunnel diode is Ga rich, x = 0.25, with respect to the n-type and intrinsic segments of the top cell, which are close to the nominal composition of the NWs (x = 0.35). The p-type end segment is still Ga-rich. Electromagnetic resonances are observed in the tunnel diode. The Raman signal arising from the InGaP side of the tunnel diode is significantly enhanced. This enhancement permits the observation of a Raman mode that can be associated with an LO phonon plasmon coupled mode (LOPCM). This mode has not been previously reported in the literature of InGaP, and it permits the Raman characterization of the tunnel diode. The analysis of this mode and its relation to the LO phonon modes of the alloy, InP-like and GaP-like, allows to establish an apparent one-mode behavior for the phonon plasmon coupling. It indicates that hole plasma couples to the GaP-like LO mode. The LOPCMs are modeled using the Lindhard Mermin formalism for the dielectric function.

On the mechanism of piezoresistance in nanocrystalline graphite

Strain sensors are sensitive to mechanical deformations and enable the detection of strain also within integrated electronics. For flexible displays, the use of a seamlessly integrated strain sensor would be beneficial, and graphene is already in use as a transparent and flexible conductor. However, graphene intrinsically lacks a strong response, and only by engineering defects, such as grain boundaries, one can induce piezoresistivity. Nanocrystalline graphene (NCG), a derivative form of graphene, exhibits a high density of defects in the form of grain boundaries. It holds an advantage over graphene in easily achieving wafer-scale growth with controlled thickness. In this study, we explore the piezoresistivity in thin films of nanocrystalline graphite. Simultaneous measurements of sheet resistance and externally applied strain on NCG placed on polyethylene terephthalate (PET) substrates provide intriguing insights into the underlying mechanism. Raman measurements, in conjunction with strain applied to NCG grown on flexible glass, indicate that the strain is concentrated at the grain boundaries for smaller strain values. For larger strains, mechanisms such as grain rotation and the formation of nanocracks might contribute to the piezoresistive behavior in nanocrystalline graphene.

Non-Destructive and Non-Invasive Approaches for the Identification of Hydroxy Lead-Calcium Phosphate Solid Solutions ((PbxCa1-x)5(PO4)3OH) in Cultural Heritage Materials

Lead-calcium phosphates are unusual compounds sometimes found in different kinds of cultural heritage objects. Structural and physicochemical properties of this family of materials, which fall into the hydroxypyromorphite-hydroxyapatite solid solution, or (PbxCa1-x)5(PO4)3OH, have received considerable attention during the last few decades for promising applications in different fields of environmental and material sciences, but their diagnostic implications in the cultural heritage context have been poorly explored. This paper aims to provide a clearer understanding of the relationship between compositional and structural properties of the peculiar series of (PbxCa1-x)5(PO4)3OH solid solutions and to determine key markers for their proper non-destructive and non-invasive identification in cultural heritage samples and objects. For this purpose, a systematic study of powders and paint mock-ups made up of commercial and in-house synthesized (PbxCa1-x)5(PO4)3OH compounds with a different Pb2+/Ca2+ ratio was carried out via a multi-technique approach based on scanning electron microscopy, synchrotron radiation-based X-ray techniques, i.e., X-ray powder diffraction and X-ray absorption near edge structure spectroscopy at the Ca K- and P K-edges, and vibrational spectroscopy methods, i.e., micro-Raman and Fourier transform infrared spectroscopy. The spectral modifications observed in the hydroxypyromorphite-hydroxyapatite solid solution series are discussed, by assessing the advantages and disadvantages of the proposed techniques and by providing reference data and optimized approaches for future non-destructive and non-invasive applications to study cultural heritage objects and samples.

Simultaneous Application of Raman and Laser-Induced Breakdown Spectroscopy in the Gas Phase with a Single Laser and Detector

Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) are powerful tools for molecular and elemental analysis, respectively. Their combined application, however, is challenging due to the differences in the signal generation and detection characteristics. This note proposes three experimental schemes for the simultaneous application of Raman and LIBS for gas-phase diagnostics. Ring-cavity optical pulse stretchers facilitate shaping suitable pulse pairs from a Q-switched laser that enables the quasi-simultaneous detection of the Raman and LIBS signals on a single detector.

Resonant Raman Scattering Study of Strain and Defects in Chemical Vapor Deposition Grown MoS2 Monolayers

The development of bottom-up synthesis routes for semiconducting transition metal dichalcogenides (TMDs) and the assessment of their defects are of paramount importance to achieve their applications. TMD monolayers grown by chemical vapor deposition (CVD) can be subjected to significant strain and, here, Raman and photoluminescence spectroscopies are combined to characterize strain in over one hundred MoS2 monolayer samples grown by CVD. The frequency changes of phonons as a function of strain are analyzed, and used to extract the Grüneisen parameter of both zone-center and edge phonons. Additionally, the intensity of the defect-induced longitudinal acoustic (LA) and transverse acoustic (TA) Raman bands are discussed in relation to strain and electronic doping. The experimental mode-Grüneisen parameters obtained are compared with those calculated by density functional theory (DFT), to better characterize the type of strain and its resulting effects on Grüneisen parameters. The findings indicate that the use of Raman spectra to determine defect densities in 2D MoS2 must be always conducted considering strain effects. To the best of the authors' knowledge, this work constitutes the first report on double resonance Raman processes studied as a function of strain in 2D-MoS2. The new approach to obtain the Grüneisen parameter from zone-edge phonons in MoS2 can also be extended to other 2D semiconducting TMDs.

Growth, crystal structure and IR luminescence of KSrY1-xErx(BO3)2

A series of novel KSrY1-xErx(BO3)2 (x = 0-1) phosphors that emit near-infrared radiation was synthesized using solid-state methods. Pure Y and Er crystals were grown using a KF flux via the top-seeded solution growth technique. In situ high-temperature single crystal X-ray diffraction, Raman spectroscopy and DFT calculations were used for characterization. Within the series, a polymorphic phase transition from space group P21/m to R3m was discovered between 550 and 600°C. The concentration dependence of the luminescence intensity was measured for the samples. A strong emission of Er3+ electron transition 4I13/2 → 4I15/2 was detected within the 1529-1549 nm range, with the maximum observed for the KSrY0.4Er0.6(BO3)2 composition.

Unveiling the efficacy of a bulk Raman spectra-based model in predicting single cell Raman spectra of microorganisms

In a previous publication, we trained predictive models based on Raman bulk spectra of microorganisms placed on a silicon dioxide protected silver mirror slide to make predictions for new Raman spectra, unknown to the models, of microorganisms placed on a different substrate, namely stainless steel. Now we have combined large sections of this data and trained a convolutional neural network (CNN) to make predictions for single cell Raman spectra. We show that a database based on microbial bulk material is conditionally suited to make predictions for the same species in terms of single cells. Data of 13 different microorganisms (bacteria and yeasts) were used. Two of the 13 species could be identified 90% correctly and five other species 71%-88%. The six remaining species were correctly predicted by only 0%-49%. Especially stronger fluorescence in bulk material compared to single cells but also photodegradation of carotenoids are some effects that can complicate predictions for single cells based on bulk data. The results could be helpful in assessing universal Raman tools or databases.

Advanced Synthesis and Characterization of CdO/CdS/ZnO Heterostructures for Solar Energy Applications

This study introduces an innovative method for synthesizing Cadmium Oxide /Cadmium Sulfide/Zinc Oxide heterostructures (CdO/CdS/ZnO), emphasizing their potential application in solar energy. Utilizing a combination of electrochemical deposition and oxygen annealing, the research provides a thorough analysis of the heterostructures through scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) spectroscopy. The findings reveal a complex surface morphology and a composite structure with significant contributions from hexagonal CdS and cubic CdO phases. The study highlights the uniformity in the distribution of luminescent centers and the crystalline quality of the heterostructures, which is evident from the PL analysis. The redshift observed in the emission peak and the additional peaks in the excitation spectrum indicate intricate optical properties influenced by various factors, including quantum confinement and lattice strain. The research demonstrates these heterostructures' potential in enhancing solar cells' efficiency and applicability in optoelectronic devices. This comprehensive characterization and analysis pave the way for future optimization and application in efficient and sustainable solar energy solutions.

Deep learning analysis for rapid detection and classification of household plastics based on Raman spectroscopy

The overuse of plastics releases large amounts of microplastics. These tiny and complex pollutants may cause immeasurable damage to human social life. Raman spectroscopy detection technology is widely used in the detection, identification and analysis of microplastics due to its advantages of fast speed, high sensitivity and non-destructive. In this work, we first recorded the Raman spectra of eight common plastics in daily life. By adjusting parameters such as laser wavelength, laser power, and acquisition time, the Raman data under different acquisition conditions were diversified, and the corresponding Raman spectra were obtained, and a database of eight household plastics was established. Combined with deep learning algorithms, an accurate, fast and simple classification and identification method for 8 types of plastics is established. Firstly, the acquired spectral data were preprocessed for baseline correction and noise reduction, Then, four machine learning algorithms, linear discriminant analysis (LDA), decision tree, support vector machine (SVM) and one-dimensional convolutional neural network (1D-CNN), are used to classify and identify the preprocessed data. The results showed that the classification accuracy of the three machine learning models for the Raman spectra of standard plastic samples were 84%, 93% and 93% respectively. The 1D-CNN model has an accuracy rate of up to 97% for Raman spectroscopy. Our study shows that the combination of Raman spectroscopy detection techniques and deep learning algorithms is a very valuable approach for microplastic classification and identification.

Identification and Structural Characterization of Twisted Atomically Thin Bilayer Materials by Deep Learning

Two-dimensional materials are expected to play an important role in next-generation electronics and optoelectronic devices. Recently, twisted bilayer graphene and transition metal dichalcogenides have attracted significant attention due to their unique physical properties and potential applications. In this study, we describe the use of optical microscopy to collect the color space of chemical vapor deposition (CVD) of molybdenum disulfide (MoS2) and the application of a semantic segmentation convolutional neural network (CNN) to accurately and rapidly identify thicknesses of MoS2 flakes. A second CNN model is trained to provide precise predictions on the twist angle of CVD-grown bilayer flakes. This model harnessed a data set comprising over 10,000 synthetic images, encompassing geometries spanning from hexagonal to triangular shapes. Subsequent validation of the deep learning predictions on twist angles was executed through the second harmonic generation and Raman spectroscopy. Our results introduce a scalable methodology for automated inspection of twisted atomically thin CVD-grown bilayers.

Conformation of the hydrazo bond in new 2-methyl-3,5-dinitro-6-(2-phenylhydrazinyl)pyridine and its influence on the structural and optic properties - Quantum chemical DFT calculations

A new methyl-dinitro-phenylhydrazinyl-pyridine derivative [2-methyl-3,5-dinitro-6-(2-phenylhydrazinyl)pyridine] was synthesised and characterised by means of structural and spectroscopic measurements. The X-ray diffraction studies revealed that the compound crystallises in the centrosymmetric monoclinic space group P21/n, with two symmetry-independent molecules in the asymmetric unit with Z = 8. Hydrazo bridge C-NH-NH-C links two fragments composed of phenyl ring and pyridine unit substituted with methyl and nitro groups. Such a structure was confirmed by 1H and 13C NMR studies as well as IR, Raman, UV-Vis, and emission spectra. The results were analysed using the quantum-chemical DFT calculations. The paper reports the vibrational characteristics and discusses dynamical properties of this moiety. The full set of the normal modes typical of the hydrazo bridge was identified and assigned to respective IR and Raman bands. The results of structural and spectroscopic studies were used to find the dependence between the conformation of the θ-NH-NH-ϕ system and its optic properties. The experimental UV-Vis and emission spectra were discussed in terms of the calculated singlet and triplet states that allowed assigning the unique spectral pattern originating from the electrons of the hydrazo-bridge system.

Thermal Transport and Mechanical Stress Mapping of a Compression Bonded GaN/Diamond Interface for Vertical Power Devices

Bonding diamond to the back side of gallium nitride (GaN) electronics has been shown to improve thermal management in lateral devices; however, engineering challenges remain with the bonding process and characterizing the bond quality for vertical device architectures. Here, integration of these two materials is achieved by room-temperature compression bonding centimeter-scale GaN and a diamond die via an intermetallic bonding layer of Ti/Au. Recent attempts at GaN/diamond bonding have utilized a modified surface activation bonding (SAB) method, which requires Ar fast atom bombardment immediately followed by bonding within the same tool under ultrahigh vacuum (UHV) conditions. The method presented here does not require a dedicated SAB tool yet still achieves bonding via a room-temperature metal-metal compression process. Imaging of the buried interface and the total bonding area is achieved via transmission electron microscopy (TEM) and confocal acoustic scanning microscopy (C-SAM), respectively. The thermal transport quality of the bond is extracted from spatially resolved frequency-domain thermoreflectance (FDTR) with the bonded areas boasting a thermal boundary conductance of >100 MW/m2·K. Additionally, Raman maps of GaN near the GaN-diamond interface reveal a low level of compressive stress, <80 MPa, in well-bonded regions. FDTR and Raman were coutilized to map these buried interfaces and revealed some poor thermally bonded areas bordered by high-stress regions, highlighting the importance of spatial sampling for a complete picture of bond quality. Overall, this work demonstrates a novel method for thermal management in vertical GaN devices that maintains low intrinsic stresses while boasting high thermal boundary conductances.

Chlamydia psittaci infected cell studies by 4Pi Raman and atomic force microscopy

Chlamydia psittaci is an avian bacterial pathogen that can cause atypical pneumonia in humans via zoonotic transmission. It is a Gram-negative intracellular bacterium that proliferates inside membrane bound inclusions in the cytoplasm of living eukaryotic cells. The study of such cells with C. psittaci inside without destroying them poses a significant challenge. We demonstrated in this work the utility of a combined multitool approach to analyze such complex samples. Atomic force microscopy was applied to obtain high-resolution images of the surface of infected cells upon entrance of bacteria. Atomic force microscopy scans revealed the morphological changes of the cell membrane of Chlamydia infected cells such as changes in roughness of cell membrane and the presence of micro vesicles. 4Pi Raman microscopy was used to image and probe the molecular composition of intracellular bacteria inside intact cells. Information about the structure of the inclusion produced by C. psittaci was obtained and it was found to have a similar molecular fingerprint as that of an intracellular lipid droplet but with less proteins and unsaturated lipids. The presented approach demonstrates complementarity of various microscopy-based approaches and might be useful for characterization of intracellular bacteria.

Ante- and Post-Mortem Fracture Identification Protocol Based on Low- and High-Level Fusion Using Fourier Transform Infrared Spectroscopy and Raman Spectroscopy Association

In this study, the application of low-level fusion (LLF) and high-level fusion (HLF) strategies using a combination of Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy in the identification of antemortem and postmortem fracture at different postmortem intervals (PMIs) was investigated. On a technical level, the same hard tissue sample can be detected using a mix of FT-IR and Raman techniques. At the method level, two cutting-edge chemometrics approaches (LLF and HLF) combining FT-IR and Raman spectroscopic data are explored. The models were ranked in accordance with their parametric quality as follows: HLF and LLF + HLF models > LLF single model > Raman single model > FT-IR single model. The LLF model performed marginally better than the Raman model, however, when compared to other models, the HLF model performed considerably better. The HLF model achieved the best performance, with both cross-validation accuracy and test data set accuracy of 0.88. The importance of the feature wavelengths in the model construction process was subsequently evaluated by intersection fusion, and it was found that the absorbance bands of amide I, PO43- ν1 ν3, and CH2 in FT-IR and phenylalanine, CO32- ν1- PO43- ν3, and amide III in Raman have outstanding contributions to the construction of antemortem and postmortem fractures identification models. Overall, the combination of FT-IR and Raman with the HLF strategy is a novel and promising approach for developing antemortem and postmortem fracture identification models at different PMIs.

Vibrational spectroscopic detection and analysis of salicylic acid and aspirin binary cocrystal

Salicylic acid is a raw material for preparing aspirin and holds an important position in medical history. Studying the crystallization of these two drugs is of great significance in improving their dissolution rate, bioavailability, and physical stability. Although various techniques have been used for structural characterization, there is still a lack of information on the collective vibrational behavior of aspirin and salicylic acid eutectic compounds. Firstly, two starting materials (salicylic acid and aspirin) were ground in a 1:1 M ratio to prepare eutectic compounds. The eutectic composition was studied using vibrational spectroscopy techniques, such as X-ray powder diffusion (XRPD), terahertz time-domain spectroscopy (THz-TDS), and Raman spectroscopy. Additionally, the structure of the aspirin and salicylic acid eutectic was simulated and optimized using density functional theory. It was found that the eutectic type II was the most consistent with the experiment, and the corresponding vibration modes of each peak were provided. These results offer a unique method for characterizing the structural composition of eutectic crystals, which can be utilized to enhance the physical and chemical properties, as well as the pharmacological activity, of specific drugs at the molecular level.

Paper electrophoretic enrichment-assisted ultrasensitive SERS detection

To achieve sensitive detection of trace substances in fluids by surface-enhanced Raman spectroscopy (SERS), effective enrichment of molecules at subwavelength regions (hot spots) with a large enhancement is adopted. In this work, a glass fibre paper with Ag nanoparticles (AgNPs) is employed for electrodynamic enrichment of analytes in fluids by paper electrophoresis integrated with field amplification sample stacking (FASS) and capillary effects to obtain both Raman and SERS convenient and sensitive detection. With the help of electrophoretic enrichment on the glass fibre paper and surface plasmon enhancement on the AgNPs, this paper electrophoretic enrichment could improve the detection limit of Raman and SERS detection by more than an order of magnitude, even achieving a SERS detection limit of 10-17 M for Nile Blue A. Furthermore, this flexible SERS detection method can also detect trace organic contaminants at the ppt level in aquaculture and food applications.

Infrared Resonance Raman of Bilayer Graphene: Signatures of Massive Fermions and Band Structure on the 2D Peak

Few-layer graphene possesses low-energy carriers that behave as massive Fermions, exhibiting intriguing properties in both transport and light scattering experiments. Lowering the excitation energy of resonance Raman spectroscopy down to 1.17 eV, we target these massive quasiparticles in the split bands close to the K point. The low excitation energy weakens some of the Raman processes that are resonant in the visible, and induces a clearer frequency-separation of the substructures of the resonance 2D peak in bi- and trilayer samples. We follow the excitation-energy dependence of the intensity of each substructure, and comparing experimental measurements on bilayer graphene with ab initio theoretical calculations, we trace back such modifications on the joint effects of probing the electronic dispersion close to the band splitting and enhancement of electron-phonon matrix elements.

Selective CW Laser Synthesis of MoS2 and Mixture of MoS2 and MoO2 from (NH4)2MoS4 Film

Very recently, the synthesis of 2D MoS2 and WS2 through pulsed laser-directed thermolysis can achieve wafer-scale and large-area structures, in ambient conditions. In this paper, we report the synthesis of MoS2 and MoS2 oxides from (NH4)2MoS4 film using a visible continuous-wave (CW) laser at 532 nm, instead of the infrared pulsed laser for the laser-directed thermolysis. The (NH4)2MoS4 film is prepared by dissolving its crystal powder in DI water, sonicating the solution, and dip-coating onto a glass slide. We observed a laser intensity threshold for the laser synthesis of MoS2, however, it occurred in a narrow laser intensity range. Above that range, a mixture of MoS2 and MoO2 is formed, which can be used for a memristor device, as demonstrated by other research groups. We did not observe a mixture of MoS2 and MoO3 in the laser thermolysis of (NH4)2MoS4. The laser synthesis of MoS2 in a line pattern is also achieved through laser scanning. Due to of the ease of CW beam steering and the fine control of laser intensities, this study can lead toward the CW laser-directed thermolysis of (NH4)2MoS4 film for the fast, non-vacuum, patternable, and wafer-scale synthesis of 2D MoS2.

Strong Room-Temperature Ferromagnetism of MoS2 Compound Produced by Defect Generation

Ferromagnetic materials have been attracting great interest in the last two decades due to their application in spintronics devices. One of the hot research areas in magnetism is currently the two-dimensional materials, transition metal dichalcogenides (TMDCs), which have unique physical properties. The origins and mechanisms of transition metal dichalcogenides (TMDCs), especially the correlation between magnetism and defects, have been studied recently. We investigate the changes in magnetic properties with a variation in annealing temperature for the nanoscale compound MoS2. The pristine MoS2 exhibits diamagnetic properties from low-to-room temperature. However, MoS2 compounds annealed at different temperatures showed that the controllable magnetism and the strongest ferromagnetic results were obtained for the 700 °C-annealed sample. These magnetizations are attributed to the unpaired electrons of vacancy defects that are induced by annealing, which are confirmed using Raman spectroscopy and electron paramagnetic resonance spectroscopy (EPR).

Exploring the use of NIR and Raman spectroscopy for the prediction of quality traits in PDO cheeses

The aims of this proof of principle study were to compare two different chemometric approaches using a Bayesian method, Partial Least Square (PLS) and PLS-discriminant analysis (DA), for the prediction of the chemical composition and texture properties of the Grana Padano (GP) and Parmigiano Reggiano (PR) PDO cheeses by using NIR and Raman spectra and quantify their ability to distinguish between the two PDO and among their ripening periods. For each dairy chain consortium, 9 cheese samples from 3 dairy industries were collected for a total of 18 cheese samples. Three seasoning times were chosen for each dairy industry: 12, 20, and 36 months for GP and 12, 24, and 36 months for PR. A portable NIR instrument (spectral range: 950-1,650 nm) was used on 3 selected spots on the paste of each cheese sample, for a total of 54 spectra collected. An Alpha300 R confocal Raman microscope was used to collect 10 individual spectra for each cheese sample in each spot for a total of 540 Raman spectra collected. After the detection of eventual outliers, the spectra were also concatenated together (NIR + Raman). All the cheese samples were assessed in terms of chemical composition and texture properties following the official reference methods. A Bayesian approach and PLS-DA were applied to the NIR, Raman, and fused spectra to predict the PDO type and seasoning time. The PLS-DA reached the best performances, with 100% correctly identified PDO type using Raman only. The fusion of the data improved the results in 60% of the cases with the Bayesian and of 40% with the PLS-DA approach. A Bayesian approach and a PLS procedure were applied to the NIR, Raman, and fused spectra to predict the chemical composition of the cheese samples and their texture properties. In this case, the best performance in validation was reached with the Bayesian method on Raman spectra for fat (R2VAL = 0.74). The fusion of the data was not always helpful in improving the prediction accuracy. Given the limitations associated with our sample set, future studies will expand the sample size and incorporate diverse PDO cheeses.

Development of a Nuclear Fuel Dissolution Monitor Based on Raman Spectroscopy

The processing of spent nuclear fuel and other nuclear materials is a critical component of nuclear material management with implications for global security. The first step of fuel processing is dissolution, with several charges of fuel sequentially added to a batch of solvent. The incomplete dissolution of a charge precludes the addition of the next charge. As the dissolution takes place in a heated, highly corrosive and radiological vessel, direct monitoring of the process is not possible. We discuss the use of Raman spectroscopy to indirectly monitor dissolution through an analysis of the gaseous emissions from the dissolver. Challenges associated with the implementation of Raman spectroscopy include the composition and physical characteristics of the offgas stream and the impact of operating conditions. Nonetheless, we observed that NO2 concentrations serve as a reliable indicator of process activity and correlate to the amount of fuel material that remains undissolved. These results demonstrate the promise of the method for monitoring nuclear material dissolution.

Effective fully polarizable QM/MM approaches to compute Raman and Raman Optical Activity spectra in aqueous solution

Raman and Raman Optical Activity (ROA) signals are amply affected by solvent effects, especially in the presence of strongly solute-solvent interactions such as Hydrogen Bonding (HB). In this work, we extend the fully atomistic polarizable Quantum Mechanics/Molecular Mechanics approach, based on the Fluctuating Charges and Fluctuating Dipoles force field to the calculation of Raman and ROA spectra. Such an approach is able to accurately describe specific HB interactions, by also accounting for anisotropic contributions due to the inclusion of fluctuating dipoles. To highlight the potentiality of the novel approach, Raman and ROA spectra of L-Serine and L-Cysteine dissolved in aqueous solution are computed and compared both with alternative theoretical approaches and experimental measurements.

Investigation into polymorphism within ethenzamide-ethylmalonic acid cocrystal using Raman and terahertz vibrational spectroscopy

Two cocrystal polymorphs of ethenzamide (ETZ) and ethylmalonic acid (EMA) were synthesized by solvent evaporation. Crystal structure analysis revealed that the main amide - carboxyl heterosynthon in ETZ-EMA cocrystal Form I and Form II are the same, but the crystal structure of these two polymorphs are different. Terahertz (THz) and Raman vibrational spectroscopy were used to characterize ETZ, EMA, ETZ-EMA cocrystal polymorph Form I and Form II respectively. The experimental results showed that ETZ, EMA, ETZ-EMA cocrystal Form I and ETZ-EMA cocrystal Form II exhibited completely different characteristic peaks. Both THz and Raman vibrational spectroscopy can be used to distinguish ETZ-EMA cocrystal Form I from Form II. Furthermore, the investigation of phase transition induced by temperature and solid-state grinding was also performed. In the temperature phase transition experiments, when the powder sample was heated to a temperature range of 80-82 °C, the metastable ETZ-EMA cocrystal Form I transformed into the more stable ETZ-EMA cocrystal Form II. Solid-state grinding analysis revealed that the results of the ETZ-EMA cocrystal polymorph synthesis in grinding experiments depended on the polarity of the solvents used. Grinding without solvent or with high polarity solvents tended to result in the stable ETZ-EMA cocrystal Form II. Moreover, the metastable ETZ-EMA cocrystal Form I would transform into Form II after further grinding process. These results demonstrate that THz and Raman vibrational spectroscopy have high sensitivity and accuracy in the detection of both cocrystal synthesis and cocrystal polymorph phase transitions.

Cost-Effective Ultrabright Silicon Quantum Dots and Highly Efficient LEDs from Low-Carbon Hydrogen Silsesquioxane Polymers

Cost-effective methods of synthesizing bright colloidal silicon quantum dots (SiQDs) for use as heavy-metal-free QDs, which have applications as light sources in biomedicine and displays, are required. We report simple protocols for synthesizing ultrabright colloidal SiQDs and fabricating SiQD LEDs based on hydrogen silsesquioxane (HSQ) polymer synthesis. Red photoluminescence with a quantum yield (PLQY) of 60-80% and LEDs with an external quantum efficiency (EQE) of >10% were obtained at 1/3600th of the cost of existing methods. This was achieved by using HSiCl3 and a low-polarity solvent to prepare the HSQ polymer and by optimizing the LED hole-injection layer thickness. A stochastic analysis of 31 SiQD syntheses revealed that SiQDs with the highest PLQYs were obtained from a hard, low-carbon HSQ polymer precursor containing many Si-H groups and cage structures. Notably, simple FTIR measurements predicted whether a HSQ polymer would yield high-PLQY SiQDs and high-EQE LEDs. These straightforward, cost-effective protocols should lead to advances in SiQD synthesis and LED fabrication methods.

Nanoscale Infrared Spectroscopic Characterization of Extended Defects in 4H-Silicon Carbide

Extended defects in wide-bandgap semiconductors have been widely investigated using techniques providing either spectroscopic or microscopic information. Nano-Fourier transform infrared spectroscopy (nano-FTIR) is a nondestructive characterization method combining FTIR with nanoscale spatial resolution (∼20 nm) and topographic information. Here, we demonstrate the capability of nano-FTIR for the characterization of extended defects in semiconductors by investigating an in-grown stacking fault (IGSF) present in a 4H-SiC epitaxial layer. We observe a local spectral shift of the mid-infrared near-field response, consistent with the identification of the defect stacking order as 3C-SiC (cubic) from comparative simulations based on the finite dipole model (FDM). This 3C-SiC IGSF contrasts with the more typical 8H-SiC IGSFs reported previously and is exemplary in showing that nanoscale spectroscopy with nano-FTIR can provide new insights into the properties of extended defects, the understanding of which is crucial for mitigating deleterious effects of such defects in alternative semiconductor materials and devices.

High pressure study of sodium trihydride

The reactivity between NaH and H2 has been investigated through a series of high-temperature experiments up to pressures of 78 GPa in diamond anvil cells combined with first principles calculations. Powder X-ray diffraction measurements show that heating NaH in an excess of H2 to temperatures around 2000 K above 27 GPa yields sodium trihydride (NaH3), which adopts an orthorhombic structure (space group Cmcm). Raman spectroscopy measurements indicate that NaH3 hosts quasi-molecular hydrogen (H 2 δ - ) within a NaH lattice, with the H 2 δ - stretching mode downshifted compared to pure H2 (Δν ∼-120 cm-1 at 50 GPa). NaH3 is stable under room temperature compression to at least 78 GPa, and exhibits remarkable P-T stability, decomposing at pressures below 18 GPa. Contrary to previous experimental and theoretical studies, heating NaH (or NaH3) in excess H2 between 27 and 75 GPa does not promote further hydrogenation to form sodium polyhydrides other than NaH3.

Nondestructive and Rapid Screening of Aflatoxin-Contaminated Single Peanut Kernels Using Field-Portable Spectroscopy Instruments (FT-IR and Raman)

A nondestructive and rapid classification approach was developed for identifying aflatoxin-contaminated single peanut kernels using field-portable vibrational spectroscopy instruments (FT-IR and Raman). Single peanut kernels were either spiked with an aflatoxin solution (30 ppb-400 ppb) or hexane (control), and their spectra were collected via Raman and FT-IR. An uHPLC-MS/MS approach was used to verify the spiking accuracy via determining actual aflatoxin content on the surface of randomly selected peanut samples. Supervised classification using soft independent modeling of class analogies (SIMCA) showed better discrimination between aflatoxin-contaminated (30 ppb-400 ppb) and control peanuts with FT-IR compared with Raman, predicting the external validation samples with 100% accuracy. The accuracy, sensitivity, and specificity of SIMCA models generated with the portable FT-IR device outperformed the methods in other destructive studies reported in the literature, using a variety of vibrational spectroscopy benchtop systems. The discriminating power analysis showed that the bands corresponded to the C=C stretching vibrations of the ring structures of aflatoxins were most significant in explaining the variance in the model, which were also reported for Aspergillus-infected brown rice samples. Field-deployable vibrational spectroscopy devices can enable in situ identification of aflatoxin-contaminated peanuts to assure regulatory compliance as well as cost savings in the production of peanut products.

Dissociation Kinetics and Antimicrobial Activity of Ofloxacin Antibiotic in Artificial Tears Via 1H-NMR, Raman, and UV-Vis Spectroscopic Analysis

Introduction: The hydrogen-bonded networks play a significant role in influencing several physicochemical properties of ofloxacin in artificial tears (ATs), including density, pH, viscosity, and self-diffusion coefficients. The activities of the ofloxacin antibiotic with Ats mixtures are not solely determined by their concentration but are also influenced by the strength of the hydrogen bonding network which highlight the importance of considering factors such as excessive tear production and dry eye conditions when formulating appropriate dosages of ofloxacin antibiotics for eye drops. Objectives: Investigating the physicochemical properties of ofloxacin-ATs mixtures, which serve as a model for understanding the impact of hydrogen bonding on the antimicrobial activity of ofloxacin antibiotic eye drops. Determine the antimicrobial activities of the ofloxacin-Ats mixture with different concentration of ofloxacin. Methods: The ofloxacin-ATs mixtures were analyzed using 1H-NMR, Raman, and UV-Vis spectroscopies, with variation of ofloxacin concentration to study its dissociation kinetics in ATs, mimicking its behavior in human eye tears. The investigation includes comprehensive analysis of 1H-NMR spectral data, self-diffusion coefficients, Raman spectroscopy, UV-Vis spectroscopy, liquid viscosity, and acidity, providing a comprehensive assessment of the physicochemical properties. Results: Analysis of NMR chemical shifts, linewidths, and self-diffusion coefficient curves reveals distinct patterns, with peaks or minima observed around 0.6 ofloxacin mole fraction dissociated in ATs, indicating a strong correlation with the hydrogen bonding network. Additionally, the pH data exhibits a similar trend to viscosity, suggesting an influence of the hydrogen bonding network on protonic ion concentrations. Antibacterial activity of the ofloxacin-ATs mixtures is evaluated through growth rate analysis against Salmonella typhimurium, considering varying concentrations with mole fractions of 0.1, 0.4, 0.6, 0.8, and 0.9. Conclusions: The antibiotic-ATs mixture with a mole fraction of 0.6 ofloxacin exhibited lower activity compared to mixtures with mole fractions of 0.1 and 0.4, despite its lower concentration. The activities of the mixtures are not solely dependent on concentration but are also influenced by the strength of the hydrogen bonding network. These findings emphasize the importance of considering tear over-secretion and dry eye problems when designing appropriate doses of ofloxacin antibiotics for eye drop formulations.

Mechanochemical synthesis of cerium chlorapatite from a mixture of cerium chloride heptahydrate, dicalcium phosphate dihydrate, and calcium hydroxide for biomedical application

BACKGROUND

Cerium ions promote osteoclastogenesis and activate bone metabolism, while cerium oxide nanoparticles exhibit potent anti-inflammatory properties, making them promising for biomedical applications.

OBJECTIVE

The purpose of this study was to develop and evaluate a synthesis method for sustained-release cerium-ion bioceramics containing apatite. Substituted apatite was found to be an effective biomaterial.

METHODS

Cerium-containing chlorapatite was synthesized using a mechanochemical method employing dicalcium phosphate, cerium chloride heptahydrate, and calcium hydroxide as raw materials. The synthesized samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Raman spectroscopy.

RESULTS

Cerium chlorapatite was successfully synthesized in the 10.1% and 20.1% samples. However, at Ce concentrations higher than 30.2%, the samples consisted of three or more phases, indicating the instability of a single phase.

CONCLUSION

The method used in this study was found to be more efficient and cost-effective than the precipitation method for producing substituted apatite and calcium phosphate-based biomaterials. This research contributes to the development of sustained-release cerium-ion bioceramics with potential applications in the field of biomedicine.

Pilot SERS Monitoring Study of Two Natural Hypersaline Lake Waters from a Balneary Resort during Winter-Months Period

Water samples from two naturally hypersaline lakes, renowned for their balneotherapeutic properties, were investigated through a pilot SERS monitoring program. Nanotechnology-based techniques were employed to periodically measure the ultra-sensitive SERS molecular characteristics of the raw water-bearing microbial community and the inorganic content. Employing the Pearson correlation coefficient revealed a robust linear relationship between electrical conductivity and pH and Raman and SERS spectral data of water samples, highlighting the interplay complexity of Raman/SERS signals and physicochemical parameters within each lake. The SERS data obtained from raw waters with AgNPs exhibited a dominant, reproducible SERS feature resembling adsorbed β-carotene at submicromole concentration, which could be related to the cyanobacteria-AgNPs interface and supported by TEM analyses. Notably, spurious SERS sampling cases showed molecular traces attributed to additional metabolites, suggesting multiplexed SERS signatures. The conducted PCA demonstrated observable differences in the β-carotene SERS band intensities between the two lakes, signifying potential variations in picoplankton abundance and composition or environmental influences. Moreover, the study examined variations in the SERS intensity ratio I245/I1512, related to the balance between inorganic (Cl--induced AgNPs aggregation) and organic (cyanobacteria population) balance, in correlation with the electrical conductivity. These findings signify the potential of SERS data for monitoring variations in microorganism concentration, clearly dependent on ion concentration and nutrient dynamics in raw, hypersaline water bodies.

Spectromicroscopy Study of Induced Defects in Ion-Bombarded Highly Aligned Carbon Nanotubes

Highly aligned multi-wall carbon nanotubes were investigated with scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) before and after bombardment performed using noble gas ions of different masses (argon, neon and helium), in an ultra-high-vacuum (UHV) environment. Ion irradiation leads to change in morphology, deformation of the carbon (C) honeycomb lattice and different structural defects in multi-wall carbon nanotubes. One of the major effects is the production of bond distortions, as determined by micro-Raman and micro-X-ray photoelectron spectroscopy. We observe an increase in sp3 distorted bonds at higher binding energy with respect to the expected sp2 associated signal of the carbon 1s core level, and increase in dangling bonds. Furthermore, the surface damage as determined by the X-ray photoelectron spectroscopy carbon 1s core level is equivalent upon bombarding with ions of different masses, while the impact and density of defects in the lattice of the MWCNTs as determined by micro-Raman are dependent on the bombarding ion mass; heavier for helium ions, lighter for argon ions. These results on the controlled increase in sp3 distorted bonds, as created on the multi-wall carbon nanotubes, open new functionalization prospects to improve and increase atomic hydrogen uptake on ion-bombarded multi-wall carbon nanotubes.

Observation of the most H2-dense filled ice under high pressure

Hydrogen hydrates are among the basic constituents of our solar system's outer planets, some of their moons, as well Neptune-like exo-planets. The details of their high-pressure phases and their thermodynamic conditions of formation and stability are fundamental information for establishing the presence of hydrogen hydrates in the interior of those celestial bodies, for example, against the presence of the pure components (water ice and molecular hydrogen). Here, we report a synthesis path and experimental observation, by X-ray diffraction and Raman spectroscopy measurements, of the most H[Formula: see text]-dense phase of hydrogen hydrate so far reported, namely the compound 3 (or C[Formula: see text]). The detailed characterisation of this hydrogen-filled ice, based on the crystal structure of cubic ice I (ice I[Formula: see text]), is performed by comparing the experimental observations with first-principles calculations based on density functional theory and the stochastic self-consistent harmonic approximation. We observe that the extreme (up to 90 GPa and likely beyond) pressure stability of this hydrate phase is due to the close-packed geometry of the hydrogen molecules caged in the ice I[Formula: see text] skeleton.

The Enrichment of Whey Protein Isolate Hydrogels with Poly-γ-Glutamic Acid Promotes the Proliferation and Osteogenic Differentiation of Preosteoblasts

Osseous disease accounts for over half of chronic pathologies, but there is a limited supply of autografts, the gold standard; hence, there is a demand for new synthetic biomaterials. Herein, we present the use of a promising, new dairy-derived biomaterial: whey protein isolate (WPI) in the form of hydrogels, modified with the addition of different concentrations of the biotechnologically produced protein-like polymeric substance poly-γ-glutamic acid (γ-PGA) as a potential scaffold for tissue regeneration. Raman spectroscopic analysis demonstrated the successful creation of WPI-γ-PGA hydrogels. A cytotoxicity assessment using preosteoblastic cells demonstrated that the hydrogels were noncytotoxic and supported cell proliferation from day 3 to 14. All γ-PGA-containing scaffold compositions strongly promoted cell attachment and the formation of dense interconnected cell layers. Cell viability was significantly increased on γ-PGA-containing scaffolds on day 14 compared to WPI control scaffolds. Significantly, the cells showed markers of osteogenic differentiation; they synthesised increasing amounts of collagen over time, and cells showed significantly enhanced alkaline phosphatase activity at day 7 and higher levels of calcium for matrix mineralization at days 14 and 21 on the γ-PGA-containing scaffolds. These results demonstrated the potential of WPI-γ-PGA hydrogels as scaffolds for bone regeneration.

Micro-Raman for Local Strain Evaluation of GaN LEDs and Si Chips Assembled on Cu Substrates

Integrated circuits are created by interfacing different materials, semiconductors, and metals, which are appropriately deposited or grown on substrates and layers soldered together. Therefore, the characteristics of starting materials and process temperatures are of great importance, as they can induce residual strains in the final assembly. Identifying and quantifying strain becomes strategically important in optimizing processes to enhance the performance, duration, and reliability of final devices. This work analyzes the thermomechanical local strain of semiconductor materials used to realize LED modules for lighting applications. Gallium Nitride active layers grown on sapphire substrates and Si chips are assembled by soldering with eutectic AuSn on copper substrates and investigated by Raman spectroscopy in a temperature range of -50 to 180 °C. From the Raman mapping of many different samples, it is concluded that one of the leading causes of strain in the GaN layer can be attributed to the differences in the thermal expansion coefficient among the various materials and, above all, among the chip, interconnection material, and substrate. These differences are responsible for forces that slightly bend the chip, causing strain in the GaN layer, which is most compressed in the central region of the chip and slightly stretched in the outer areas.

Unveiling microplastics from zippers: Characterisation and visualisation through Raman imaging analysis

Microplastics have emerged as a global concern due to the increased plastic contamination found in a variety of sources. Herein we unveil microplastics released from plastic zippers that can generally be found in our clothes and textiles. We first employ a scanning electron microscope (SEM) to visualise the scratches developed on the zipper teeth and the derived particles. We then use Raman imaging to identify and simultaneously visualise the plastics from the chemical or molecular spectrum window. Based on hundreds to thousands of spectra, rather than a single spectrum or even a single peak that works as just a pixel in the image, imaging analysis can significantly increase the signal-to-noise ratio. Furthermore, the non-uniform distribution of components or multi-components can also be effectively imaged to avoid the possible bias from the single-spectrum analysis. The challenge to convert the hundreds to thousands of spectra of a hyperspectral matrix to an image is also discussed, and chemometrics is adopted and recommended to further improve the signal-to-noise ratio. The co-ingredient of titanium oxide in the zipper teeth/sewing lines is also effectively identified by Raman imaging. Based on the effective characterisation, we estimate that up to ~410 microplastics could be potentially released during each time of on-off zipping, although the variation can be expected and depends on several other factors. This study reminds us to be aware of the potential contamination derived from similar types of microplastic sources in our daily lives.

Nondestructive Metabolomic Fingerprinting: FTIR, NIR and Raman Spectroscopy in Food Screening

In recent years, there has been renewed interest in the maintenance of food quality and food safety on the basis of metabolomic fingerprinting using vibrational spectroscopy combined with multivariate chemometrics. Nontargeted spectroscopy techniques such as FTIR, NIR and Raman can provide fingerprint information for metabolomic constituents in agricultural products, natural products and foods in a high-throughput, cost-effective and rapid way. In the current review, we tried to explain the capabilities of FTIR, NIR and Raman spectroscopy techniques combined with multivariate analysis for metabolic fingerprinting and profiling. Previous contributions highlighted the considerable potential of these analytical techniques for the detection and quantification of key constituents, such as aromatic amino acids, peptides, aromatic acids, carotenoids, alcohols, terpenoids and flavonoids in the food matrices. Additionally, promising results were obtained for the identification and characterization of different microorganism species such as fungus, bacterial strains and yeasts using these techniques combined with supervised and unsupervised pattern recognition techniques. In conclusion, this review summarized the cutting-edge applications of FTIR, NIR and Raman spectroscopy techniques equipped with multivariate statistics for food analysis and foodomics in the context of metabolomic fingerprinting and profiling.

Molecular structure, spectral analysis and chemical activity of sabizabulin: A computational study

In this study, a detailed computational spectroscopic investigation of sabizabulin, a small molecule known as a tubulin inhibitor with potential antineoplastic, antiviral, and anti-inflammatory activities, has been presented. Our work utilizes Density Functional Theory (DFT) calculations to explore molecular optimization, thermodynamic characteristics, and the analysis of normal modes with vibrational assignments. We calculate essential properties such as standard zero-point vibrational energy, entropy, dipole moment, etc., based on data extracted from the optimized molecular structure. Additionally, we examine Mulliken charges and the Molecular Electrostatic Potential (MEP) plot to comprehend the electronic distribution and chemical activity of sabizabulin. Our findings provide valuable insights into the spectroscopic properties of sabizabulin, highlighting its potential therapeutic applications. Our work aims to explore future research directions that could expand the understanding of sabizabulin's actions and enhance its applicability in medical treatments.

Simulated gastrointestinal digestion of polylactic acid (PLA) biodegradable microplastics and their interaction with the gut microbiota

The accumulation of microplastics (MPs) in the environment as well as their presence in foods and humans highlight the urgent need for studies on the effects of these particles on humans. Polylactic acid (PLA) is the most widely used bioplastic in the food industry and medical field. Despite its biodegradability, biocompatibility, and "Generally Recognized As Safe" (GRAS) status, recent animal model studies have shown that PLA MPs can alter the intestinal microbiota; however, to date, no studies have been reported on the possible gut and health consequences of its intake by humans. This work simulates the ingestion of a realistic daily amount of PLA MPs and their pass through the gastrointestinal tract by combining the INFOGEST method and the gastrointestinal simgi® model to evaluate possible effects on the human colonic microbiota composition (16S rRNA gene sequencing analysis) and metabolic functionality (lactic acid and short-chain fatty acids (SCFA) production). Although PLA MPs did not clearly alter the microbial community homeostasis, increased Bifidobacterium levels tended to increase in presence of millimetric PLA particles. Furthermore, shifts detected at the functional level suggest an alteration of microbial metabolism, and a possible biotransformation of PLA by the human microbial colonic community. Raman spectroscopy and field emission scanning electron microscopy (FESEM) characterization revealed morphological changes on the PLA MPs after the gastric phase of the digestion, and the adhesion of organic matter as well as a microbial biofilm, with surface biodegradation, after the intestinal and colonic phases. With this evidence and the emerging use of bioplastics, understanding their impact on humans and potential biodegradation through gastrointestinal digestion and the human microbiota merits critical investigation.

SERS and machine learning based effective feature extraction for detection and identification of amphetamine analogs

Surface-enhanced Raman spectroscopy (SERS) is extensively researched in diverse disciplines due to its sensitivity and non-destructive nature. It is particularly considered a potential and promising technology for rapid on-site screening in drug detection. In this investigation, a technique was developed for fabricating nanocrystals of Ag@Au SNCs. Ag@Au SNCs, as the basic material of SERS, can detect amphetamine at concentrations as low as 1 μg/mL. The Ag@Au SNCs exhibits a strong surface plasmon resonance effect, which amplifies molecular signals. The SERS spectra of ten substances, including amphetamine and its analogs, showed a strong peak signal. To establish a qualitative distinction, we examined the Raman spectra and conducted density functional theory (DFT) calculations on the ten aforementioned species. The DFT calculation enabled us to determine the vibrational frequency and assign normal modes, thereby facilitating the qualitative differentiation of amphetamines and its analogs. Furthermore, the SERS spectrum of the ten mentioned substances was analysed using the support vector machine learning algorithm, which yielded a discrimination accuracy of 98.0 %.

An Experimental and Theoretical Insight into I2 /Br2 Oxidation of Bis(pyridin-2-yl)Diselane and Ditellane

The reactivity between bis(pyridin-2-yl)diselane o Py2 Se2 and ditellane o Py2 Te2 (L1 and L2, respectively; o Py=pyridyn-2-yl) and I2 /Br2 is discussed. Single-crystal structure analysis revealed that the reaction of L1 with I2 yielded [(HL1+ )(I- )⋅5/2I2 ]∞ (1) in which monoprotonated cations HL1+ template a self-assembled infinite pseudo-cubic polyiodide 3D-network, while the reaction with Br2 yielded the dibromide Ho PySeII Br2 (2). The oxidation of L2 with I2 and Br2 yielded the compounds Ho PyTeII I2 (3) and Ho PyTeIV Br4 (6), respectively, whose structures were elucidated by X-ray diffraction analysis. FT-Raman spectroscopy measurements are consistent with a 3c-4e description of all the X-Ch-X three-body systems (Ch=Se, Te; X=Br, I) in compounds 2, 3, Ho PyTeII Br2 (5), and 6. The structural and spectroscopic observations are supported by extensive theoretical calculations carried out at the DFT level that were employed to study the electronic structure of the investigated compounds, the thermodynamic aspects of their formation, and the role of noncovalent σ-hole halogen and chalcogen bonds in the X⋅⋅⋅X, X⋅⋅⋅Ch and Ch⋅⋅⋅Ch interactions evidenced structurally.

[Methods, applications, and future perspectives of intraoperative tissue identification]

Over the last century, there has been a steady development of new technologies for intraoperative tissue identification and differentiation. The applications are varied, with the core purpose being to identify target structures while preserving adjacent tissue and thereby follow a general paradigm of minimally invasive medicine. Particularly in oncology, a further asset of these technologies is the identification or classification of neoplastic tissue to support and improve therapy, for example, in breast cancer surgery.Many technologies under consideration make use of the different physical characteristics of treated tissues, such as induced fluorescence, optical coherence, and electrical impedance.Recent developments are focusing on moving from ex vivo to in situ and from asynchronous to real-time assistance of the clinicians, for example, by means of optical emission spectroscopy. Refinements of existing and the creation of new methods will include AI tools to make them more powerful while reducing the inter-operator variability in operative interventions. This talk addresses several aspects of the usage and suitability of these technologies for intraoperative, therapy-supporting application.

Development of Inkjet Printable Formulations Based on Polyorganosilazane and Divinylbenzene

Within this work, ink formulations based on polyorganosilazane (OPSZ) and divinylbenzene (DVB) were developed to be processed by inkjet printing. The formulations were studied regarding their rheological, structural, and thermal properties. The rheological results show that the new formulations meet the requirements of the inkjet printer by showing both low viscosity (below 20 mPa∙s at printing temperature) and Newtonian flow behavior even at high shear rates. Additionally, the inks have surface tensions in the range of 21 to 26 mN/m2. First, printing experiments of single layers were successfully conducted and show that the developed formulations can be processed by inkjet printing. The inks were crosslinked by UV light and then pyrolyzed at 1100 °C resulting in a ceramic yield between 75 and 42%, depending on the ink formulation. The crosslinking behavior was studied via FTIR spectroscopy, and the results reveal that crosslinking occurs mainly via free-radical polymerization of the vinyl group. Furthermore, the results indicate that silicon carbonitride (SiCN) was formed after the pyrolysis. The results of the electrical properties of the amorphous ceramics differ in dependence on the amount of DVB in the formulation. A maximum electrical conductivity of 1.2 S/cm-1 was observed for a UV-cured sample with a high amount of DVB pyrolyzed at 1100 °C. The generation in electrical conductivity is given by the formation of free carbon derived most likely by DVB.

Chitosan from Marine Amphipods Inhibits the Wilt Banana Pathogen Fusarium oxysporum f. sp. Cubense Tropical Race 4

In this work, we extracted chitosan from marine amphipods associated with aquaculture facilities and tested its use in crop protection. The obtained chitosan was 2.5 ± 0.3% of initial ground amphipod dry weight. The chemical nature of chitosan from amphipod extracts was confirmed via Raman scattering spectroscopy and Fourier transform infrared spectroscopy (FTIR). This chitosan showed an 85.7-84.3% deacetylation degree. Chitosan from biofouling amphipods at 1 mg·mL-1 virtually arrested conidia germination (ca. sixfold reduction from controls) of the banana wilt pathogenic fungus Fusarium oxysporum f. sp cubense Tropical Race 4 (FocTR4). This concentration reduced (ca. twofold) the conidia germination of the biocontrol fungus Pochonia chlamydosporia (Pc123). Chitosan from amphipods at low concentrations (0.01 mg·mL-1) still reduced FocTR4 germination but did not affect Pc123. This is the first time that chitosan is obtained from biofouling amphipods. This new chitosan valorizes aquaculture residues and has potential for biomanaging the diseases of food security crops such as bananas.

Calibration of Raman Bandwidths on the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) Deep Ultraviolet Raman and Fluorescence Instrument Aboard the Perseverance Rover

In this work, we derive a simple method for calibrating Raman bandwidths for the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument onboard NASA's Perseverance rover. Raman bandwidths and shapes reported by an instrument contain contributions from both the intrinsic Raman band (IRB) and instrumental artifacts. To directly correlate bandwidth to sample properties and to compare bandwidths across instruments, the IRB width needs to be separated from instrumental effects. Here, we use the ubiquitous bandwidth calibration method of modeling the observed Raman bands as a convolution of a Lorentzian IRB and a Gaussian instrument slit function. Using calibration target data, we calculate that SHERLOC has a slit function width of 34.1 cm-1. With a measure of the instrument slit function, we can deconvolve the IRB from the observed band, providing the width of the Raman band unobscured by instrumental artifact. We present the correlation between observed Raman bandwidth and intrinsic Raman bandwidth in table form for the quick estimation of SHERLOC Raman intrinsic bandwidths. We discuss the limitations of using this model to calibrate Raman bandwidth and derive a quantitative method for calculating the errors associated with the calibration. We demonstrate the utility of this method of bandwidth calibration by examining the intrinsic bandwidths of SHERLOC sulfate spectra and by modeling the SHERLOC spectrum of olivine.

Gelatin-assisted fabrication of reduced nanographene oxide for dual-modal imaging of melanoma cells

In this work we report a gelatin-based, simple two-steps approach for fabrication of reduced graphene oxide (rGO-GEL) possessing high stability and biocompatibility, as novel label-free intracellular contrast agents. Gelatin, a biopolymer that is known for its versatility, was employed not only to biocompatibilize the rGO, but also to prevent the aggregation of the GO nanosheets during the reduction process. To confirm the successful reduction process and the attachment of the gelatin to the rGO nanosheets, we employed multiple spectroscopic analyses such as FT-IR, Raman, UV-VIS and photoluminescence, while the morphology and the lateral dimensions of the resulting hybrid rGO-GEL were investigated by Scanning-Transmission Electron Microscopy (STEM). Cellular toxicity test proved that the rGO-GEL nanoflakes are nontoxic for melanoma B16-F10 cells, even at high concentrations. Finally, the intracellular tracking after 24 h of treatment was performed by non-invasive Super-resolution re-scan confocal microscopy as well as Confocal Raman imaging, thus implementing our nanoflakes as a suitable contrast agent candidate for cellular imaging of interest.

Insights into the Si─H Bonding Configuration at the Amorphous/Crystalline Silicon Interface of Silicon Heterojunction Solar Cells by Raman and FTIR Spectroscopy

In silicon heterojunction solar cell technology, thin layers of hydrogenated amorphous silicon (a-Si:H) are applied as passivating contacts to the crystalline silicon (c-Si) wafer. Thus, the properties of the a-Si:H is crucial for the performance of the solar cells. One important property of a-Si:H is its microstructure which can be characterized by the microstructure parameter R based on Si─H bond stretching vibrations. A common method to determine R is Fourier transform infrared (FTIR) absorption measurement which, however, is difficult to perform on solar cells for various reasons like the use of textured Si wafers and the presence of conducting oxide contact layers. Here, it is demonstrated that Raman spectroscopy is suitable to determine the microstructure of bulk a-Si:H layers of 10 nm or less on textured c-Si underneath indium tin oxide as conducting oxide. A detailed comparison of FTIR and Raman spectra is performed and significant differences in the microstructure parameter are obtained by both methods with decreasing a-Si:H film thickness.

An Investigation on the Use of Au@SiO2@Au Nanomatryoshkas as Gap-Enhanced Raman Tags

Gap-enhanced Raman tags are a new type of optical probe that have wide applications in sensing and detection. A gap-enhanced Raman tag is prepared by embedding Raman molecules inside a gap between two plasmonic metals such as an Au core and Au shell. Even though placing Raman molecules beneath an Au shell seems counter-intuitive, it has been shown that such systems produce a stronger surface-enhanced Raman scattering response due to the strong electric field inside the gap. While the theoretical support of the stronger electric field inside the gap was provided in the literature, a comprehensive understanding of how the electric field inside the gap compares with that of the outer surface of the particle was not readily available. We investigated Au@SiO2@Au nanoparticles with diameters ranging from 35 nm to 70 nm with varying shell (2.5-10 nm) and gap (2.5-15 nm) thicknesses and obtained both far-field and near-field spectra. The extinction spectra from these particles always have two peaks. The low-energy peak redshifts with the decreasing shell thickness. However, when the gap thickness decreases, the low-energy peaks first blueshift and then redshift, producing a C-shape in the peak position. For every system we investigated, the near-field enhancement spectra were stronger inside the gap than on the outer surface of the nanoparticle. We find that a thin shell combined with a thin gap will produce the greatest near-field enhancement inside the gap. Our work fills the knowledge gap between the exciting potential applications of gap-enhanced Raman tags and the fundamental knowledge of enhancement provided by the gap.

Neither lysigenous nor just oil: Demystifying myrtaceous secretory cavities

PREMISE

Leaf subepidermal secretory cavities are a notable trait in Myrtaceae, but their formation is still controversial because of the lack of consensus on their ontogeny among authors. Knowledge about the compounds present in these cavities has grown over the last few years, demonstrating that terpenoid-rich oils are not their unique content. These two points are the focus of this study on the ontogeny, structure, and contents of secretory cavities in neotropical Myrtaceae.

METHODS

We used histochemical tests and Raman analysis to verify the basic chemical composition of the cavity contents of nine species. We studied the ontogeny of glands in one species, comparing aldehyde-fixed tissues and fresh sections mounted in an inert medium.

RESULTS

We observed schizogenous development and appearance of the secretory cavities and found that sample processing may induce cell breakdown, which can be misinterpreted as lysigeny. The content of these cavities contains putative terpenes, resins, carbonyl groups, and flavonoids.

CONCLUSIONS

Our findings support the hypothesis that the lysigenous appearance of the oil glands is a technical artifact. These tissue distortions must be considered when interpreting the development of this type of secretory structure. Moreover, the basic analyses of chemical constituents show for the first time that the glands of neotropical Myrtaceae are potential reservoirs of some compounds such as flavonoids previously reported as novelties for a few other myrtaceous species. Because some of them are non-lipid compounds, the idea that the glands are just oil repositories is no longer applicable.

Pressure-Induced Dynamic Tuning of Interlayer Coupling in Twisted WSe2/WSe2 Homobilayers

Moiré superlattices induced by twisted van der Waals (vdW) heterostructures or homostructures have recently gained significant attention due to their potential to generate exotic strong-correlation electronic and phonon phenomena. However, the lack of dynamic tuning for interlayer coupling of moiré superlattices hinders a thorough understanding and development of the moiré correlation state. Here, we present a dynamic tuning method for twisted WSe2/WSe2 homobilayers using a diamond anvil cell (DAC). We demonstrate the powerful tuning of interlayer coupling and observe an enhanced response to pressure for interlayer breathing modes and the rapid descent of indirect excitons in twisted WSe2/WSe2 homobilayers. Our findings indicate that the introduction of a moiré superlattice for WSe2 bilayers gives rise to hybridized excitons, which lead to the different pressure-evolution exciton behaviors compared to natural WSe2 bilayers. Our results provide a novel understanding of moiré physics and offer an effective method to tune interlayer coupling of moiré superlattices.