Pioneering superior efficiency in Methylene blue and Rhodamine b dye degradation under solar light irradiation using CeO2/Co3O4/g-C3N4 ternary photocatalysts

In this research work, we have successfully synthesized the CeO2/Co3O4/g-C3N4 ternary nanocomposite for hydrothermal method for photocatalytic applications. The synthesized nanocomposites were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy TEM, Photoluminescent spectra (PL), X-ray photoelectron spectroscopy (XPS), Brunauer- Emmett-Teller (BET) and Ultraviolet diffuse reflectance spectroscopy (UV-DRS) technique. As per the optical spectroscopic investigations CeO2/Co3O4/g-C3N4 ternary nanocomposite exhibited the high optical absorption range and its band gap is reduced from 2.95 eV to1.83 eV. The PL spectra showed the lowered emission peak intensity of ternary nanocomposite which is revealed that the better charge separation and slow recombination of electron hole pairs. The highest photocatalytic degradation efficiency of CeO2/Co3O4/g-C3N4 ternary nanocomposite showed 93 % and 86 % towards the pollutant methylene blue and Rhodamine B. Moreover, photodegradation of the pollutants followed pseudo-first order kinetics with a very high-rate constant of 0.02211 min-1 and 0.017756 min-1. Additionally, the ternary nano catalyst was delivered the remarkable stability performance even after five cycles. This research may provide a low-cost approach for synthesized visible light responsive catalysts for use in environmental remediation applications.

Organic Donor-Acceptor Thermally Activated Delayed Fluorescence Photocatalysts in the Photoinduced Dehalogenation of Aryl Halides

We report a family of donor-acceptor thermally activated delayed fluorescent (TADF) compounds based on derivatives of DMAC-TRZ, that are strongly photoreducing. Both Eox and thus E*ox could be tuned via substitution of the DMAC donor with a Hammett series of p-substituted phenyl moieties while Ered remained effectively constant. These compounds were assessed in the photoinduced dehalogenation of aryl halides, and analogues bearing electron withdrawing groups were found to produce the highest yields. Substrates of up to Ered = -2.72 V could be dehalogenated at low PC loading (1 mol%) and under air, conditions much milder than previously reported for this reaction. Spectroscopic and chemical studies demonstrate that all PCs, including literature reference PCs, photodegrade, and that it is these photodegradation products that are responsible for the reactivity.

Counterion influence on near-infrared-II heptamethine cyanine salts for photothermal therapy

Photothermal therapy (PTT) has attracted extensive attention in cancer treatment. Heptamethine cyanine dyes with near-infrared (NIR) absorption performance have been investigated for PTT. However, they are often accompanied by poor photostability, suboptimal photothermal conversion and limited therapeutic efficacy. The photophysical properties of fluorescent organic salts can be tuned through counterion pairing. However, whether the counterion can influence the photostability and photothermal properties of heptamethine cyanine salts has not been clarified. In this work, we investigated the effects of eleven counter anions on the physical and photothermal properties of NIR-II heptamethine cyanine salts with the same heptamethine cyanine cation. The anions have great impacts on the physiochemical properties of dyes in solution including aggregation, photostability and photothermal conversion efficiency. The physical tuning enables the control over the cytotoxicity and phototoxicity of the dyes. The selected salts have been demonstrated to significantly suppress 4T1 breast tumor growth with low toxicity. The findings that the counterion has great effects on the photothermal properties of cationic NIR-II heptamethine cyanine dyes will provide a reference for the preparation of improved photothermal agents through counterion pairing with possible translation to humans.

A Dual-Function Hemicyanine Material with Highly Efficient Photothermal and Photodynamic Effect Used for Tumor Therapy

Small molecular organic optical agents with synergistic effects of photothermal therapy (PTT) and photodynamic therapy (PDT), hold credible promise for anti-tumor therapy by overcoming individual drawbacks and enhancing photon utilization efficiency. However, developing effective dual-function PTT-PDT photosensitizers (PSs) for efficient synergistic phototherapy remains challenging. Here, a benz[c,d]indolium-substituted hemicyanine named Rh-BI, which possesses a high photothermal conversion efficiency of 41.67% by exhaustively suppressing fluorescence emission, is presented. Meanwhile, the rotating phenyl group at meso-site induces charge recombination to enhance the molar extinction coefficient up to 13.58 × 104 M-1cm-1, thereby potentiating the photodynamic effect. Under 808 nm irradiation, Rh-BI exhibits significant phototoxicity in several cancer cell types in vitro with IC50 values as low as ≈0.5 µM. Moreover, treatment of 4T1 tumor-bearing mice with Rh-BI under laser irradiation successfully inhibits tumor growth. In a word, an effective strategy is developed to build PTT-PDT dual-functional optical materials based on hemicyanine backbone for tumor therapy by modulating conjugation system interaction to adjust the energy consumption pathway.

Visible-light Excited and Highly Photostable Organic Fluorophore with dual-state Emission

Organic fluorophores with dual-state emission (DSE) are rare or difficult to observe because most of them display either aggregation-induced emission (AIE) or aggregation-caused quenching (ACQ). Amazing works have been accomplished, yet most of the DSE compounds were excited by UV light which limits their wide application in bioimaging. In this work, we achieved a visible-light excited DSE fluorophore and realized its imaging in SKOV-3 cells and zebrafish. The naphtho[2',3':4,5]imidazo[1,2-a]pyridine (NIP) core ensures its emission in dilute solution. Meanwhile, the twisted phenyl ring blocks fluorescence quenching induced by the π-π stacking and leads to the emission of the solid. The fluorescence intensity is steady even after 6 h of continuous intense sunlight. More importantly, photostability of NIP in cells is much better than commercial dye (mitochondrial green).

Exchangeable Self-Assembled Lanthanide Antennas for PLIM Microscopy

Lanthanides have unique photoluminescence (PL) emission properties, including very long PL lifetimes. This makes them ideal for biological imaging applications, especially using PL lifetime imaging microscopy (PLIM). PLIM is an inherently multidimensional technique with exceptional advantages for quantitative biological imaging. Unfortunately, due to the required prolonged acquisitions times, photobleaching of lanthanide PL emission currently constitutes one of the main drawbacks of PLIM. In this study, we report a small aqueous-soluble, lanthanide antenna, 8-methoxy-2-oxo-1,2,4,5-tetrahydrocyclopenta[de]quinoline-3-phosphonic acid, PAnt, specifically designed to dynamically interact with lanthanide ions, serving as exchangeable dye aimed at mitigating photobleaching in PLIM microscopy in cellulo. Thus, self-assembled lanthanide complexes that may be photobleached during image acquisition are continuously replenished by intact lanthanide antennas from a large reservoir. Remarkably, our self-assembled lanthanide complex clearly demonstrated a significant reduction of PL photobleaching when compared to well-established lanthanide cryptates, used for bioimaging. This concept of exchangeable lanthanide antennas opens new possibilities for quantitative PLIM bioimaging.

Localization Study of Photostable Alexa 488 at Single Molecule Level

Understanding the relationships between molecular organization and dynamics of a complex system is very important to understand the photophysical properties of such system. This paper focuses on a novel strategy based on single molecule spectroscopy and single molecule localization microscopy to elucidate the photostability and localization of a fluorophore molecule on a 2D biomembrane. Improvement of in-plane resolution of a signal in a nano-dimension within the diffraction limit has been discussed in a new way. And, how this better in-plane resolution information can be used for precise localization of a single molecule on a 2D system has also been discussed.

Thiolation for Enhancing Photostability of Fluorophores at the Single-Molecule Level

Fluorescent probes are essential for single-molecule imaging. However, their application in biological systems is often limited by the short photobleaching lifetime. To overcome this, we developed a novel thiolation strategy for squaraine dyes. By introducing thiolation of the central cyclobutene of squaraine (thio-squaraine), we observed a ≈5-fold increase in photobleaching lifetime. Our single-molecule data analysis attributes this improvement to improved photostability resulting from thiolation. Interestingly, bulk measurements show rapid oxidation of thio-squaraine to its oxo-analogue under irradiation, giving the perception of inferior photostability. This discrepancy between bulk and single-molecule environments can be ascribed to the factors in the latter, including larger intermolecular distances and restricted mobility, which reduce the interactions between a fluorophore and reactive oxygen species produced by other fluorophores, ultimately impacting photobleaching and photoconversion rate. We demonstrate the remarkable performance of thio-squaraine probes in various imaging buffers, such as glucose oxidase with catalase (GLOX) and GLOX+trolox. We successfully employed these photostable probes for single-molecule tracking of CD56 membrane protein and monitoring mitochondria movements in live neurons. CD56 tracking revealed distinct motion states and the corresponding protein fractions. This investigation is expected to propel the development of single-molecule imaging probes, particularly in scenarios where bulk measurements show suboptimal performance.

Photostable and high-brightness aggregation-induced emission of iridium luminogen achieving reliable and sensitive continuous luminescent quantification of molecular oxygen

Online continuous luminescent oxygen quantification requires both high-brightness luminescence and superior photobleaching resistance of luminogens to afford the requisite level of sensitivity and operational stability, which remains a challenge. Herein, a fluorine-free design strategy of incremental rotors for preparing iridium luminogens with excellent photobleaching resistance and high-brightness aggregation-induced emission (AIE) is presented. The incremental rotors gradually improve the rotational activity of substituents, efficaciously activating the AIE with synchronously improved aggregation-state luminescence efficiency, which is theoretically confirmed by the variations of dipole moments and experimentally verified by the luminescent lifetimes. Moreover, the introduction of triphenylamine significantly improves the photobleaching resistance of iridium luminogens. Subsequently, by optimizing the loading capacity of the iridium luminogen, the improvement of high-brightness AIE on the oxygen sensitivity of ethocel films is successfully observed. Thickness attenuation of ethocel films dramatically shortens the quenching/recovery response to 4.7 s. Importantly, owing to the exceptional photobleaching resistance of the iridium luminogen, distinguished photo-fatigue resistance with operational stability is exhibited by the ethocel film with no luminescence attenuation during 8000 s continuous oxygen quantification.

Self-assembled low molecular weight chitosan-based cationic micelle for improved water solubility, stability and sustained release of α-tocopherol

New amphiphilic low molecular weight chitosan-graft-nicotinic acid bearing decyl groups (LCND) was synthesized by two-step reaction and spontaneously assembled into cationic micelle by ultra-sonication method to improve water solubility and photostability properties of α-tocopherol. The chemical structure of LCND was characterized and physical properties of cationic micelle were evaluated. Results displayed that cationic micelle exhibited strong self-assemble ability with nanoscale spherical morphology and showed best loading ability with loading content of 18.50% when the feeding ratio of LCND to α-tocopherol reached 10:3. Meanwhile, the greatly enhanced water solubility, photostability and sustained release behavior of α-tocopherol in cationic micelle were observed. The cumulative release of α-tocopherol in cationic micelle reached up 82.18% within 96 h while free α-tocopherol was completely released within 10 h. Additionally, release kinetics models were also fitted. The LCND cationic micelle could be promising nanocarrier for improving the physicochemical properties of α-tocopherol in food fields.

Backbone 1H, 15N and 13C resonance assignments of the 27kDa fluorescent protein mCherry

mCherry is one of the most successfully applied monomeric red fluorescent proteins (RFPs) for in vivo and in vitro imaging. However, questions pertaining to the photostability of the RFPs remain and rational further engineering of their photostability requires information about the fluorescence quenching mechanism in solution. To this end, NMR spectroscopic investigations might be helpful, and we present the near-complete backbone NMR chemical shift assignment to aid in this pursuit.

Ultrabright organic fluorescent probe for quantifying the dynamics of cytosolic/nuclear lipid droplets

Lipid droplets (LDs) are extremely active organelles that play a crucial role in energy metabolism, membrane formation, and the production of lipid-derived signaling molecules by regulating lipid storage and release. Nevertheless, directly limited by the lack of superior fluorescent probes, studies of LDs dynamic motion velocity have been rarely reported, especially for nuclear LDs. Herein, a novel organic fluorescent probe Lipi-Bright has been rationally developed based on bridged cyclization of distyrylbenzene. The fully ring-fused molecule structure endows the probe with high photostability. Moreover, this new fluorescent probe displays the features of excellent LDs staining specificity as well as ultrahigh fluorescence brightness. Lipi-Bright labeled LDs was dozens of times brighter than representative probes BODIPY 493/503 or Nile Red. Consequently, by in-situ time-lapse fluorescence imaging, the dynamics of LDs have been quantitatively studied. For instance, the velocities of cytosolic LDs (37 ± 15 nm/s) are found to be obviously faster than those of nuclear LDs (24 ± 4 nm/s), and both the cytosolic LDs and the nuclear LDs would be moved faster or slower depend on the various stimulations. Overall, this work providing plentiful information on LDs dynamics will greatly facilitate the in-depth investigation of lipid metabolism.

Novel Foscan®-derived ring-fused chlorins for photodynamic therapy of cancer

Photodynamic therapy (PDT) is an established anticancer treatment that combines the use of a photosensitiser (PS) and a light source of a specific wavelength for the generation of reactive oxygen species (ROS) that are toxic to the tumour cells. Foscan® (mTHPC) is a clinically-approved chlorin used for the PDT treatment of advanced head and neck, prostate and pancreatic cancers but is characterized by being photochemically unstable and associated with prolonged skin photosensitivity. Herein, we report the synthesis of new 4,5,6,7-tetrahydropyrazolo[1,5-a]pyridine-fused chlorins, having the meso-tetra(3-hydroxyphenyl)macrocycle core of mTHPC, by exploring the [8π + 2π] cycloaddition of a meso-tetra(3-hydroxyphenyl)porphyrin derivative with diazafulvenium methides. These chlorins have photochemical properties similar to Foscan® but are much more photostable. Among the novel compounds, two chlorins with a hydroxymethyl group and its azide derivative present in the 4,5,6,7-tetrahydropyrazolo[1,5-a]pyridine-fused system, are promising photodynamic agents with activity in the 100 nM range against triple-negative breast cancer cells and, in the case of azidomethyl chlorin, a safer phototherapeutic index compared to Foscan®.

Photodegradation of free base and zinc porphyrins in the presence and absence of oxygen

Comparison of photostability in degassed and aerated toluene solutions is reported for 5,10,15,20-tetraphenylporphyrin, 5,10,15-tri(p-tolyl)porphyrin, and their zinc analogues. After degassing, quantum yields of photodegradation are higher, but the photodecomposition rates decrease. Lower stability in deoxygenated solutions is due to much longer triplet lifetimes: 200-300 microseconds, compared to 200-360 ns in non-degassed toluene. For the zinc porphyrins, the LC-MS results show that the initial photoproduct contains two oxygen atoms. Based on electronic absorption and calculations, it is assigned to dehydrated zinc biladienone structure, relatively stable in toluene, but readily demetallated in dichloromethane. A similar species is formed also in the case of free bases, but it then undergoes hydration due to traces of water present in the solvent. Zinc derivatives were found to form biladienones even in degassed solutions. To explain this observation, we postulate formation of a complex with remaining oxygen or oxygen-containing species which is not removed by freeze-thaw procedure. This hypothesis is confirmed by MS results and by the analysis of photodegradation products obtained when zinc porphyrin is complexed with dimethylsulfoxide (DMSO). Under these circumstances, changes in absorption are the same as in the absence of DMSO when non-degassed toluene is used, but irradiation of deoxygenated solutions leads to a different photoproduct. For both degassed and non-degassed solvents, complexation with DMSO results in the enhancement of photostability.

Effect of atmosphere and relative humidity on photodegradation of clopidogrel under artificial solar and indoor light irradiation

Knowledge of the chemical stability of active pharmaceutical ingredients (APIs) is an important issue in the drug development process. This work describes a methodical approach and a comprehensive protocol for forced photodegradation studies of solid clopidogrel hydrogen sulfate (Clp) under artificial sunlight and indoor irradiation at different relative humidities (RHs) and atmospheres. The results showed that, at low RHs (up to 21%), this API was relatively resistant to simulated sunlight as well as indoor light. However, at higher RHs (between 52% and 100%), more degradation products were formed, and the degradation rate increased with rising RH. The influence of oxygen on the degradation was relatively low, and most degradation reactions proceeded even in humid argon atmosphere. The photodegradation products (DP) were analyzed with two different HPLC systems (LC-UV, LC-UV-MS) and selected impurities were separated by a semi-preparative HPLC and identified by high resolution mass spectrometry (ESI-TOF-MS) and 1H NMR techniques. Based on the obtained results, a light induced degradation pathway could be proposed for Clp in solid state.

Fabrication of carboxymethyl chitosan films for cheese packaging containing gliadin-carboxymethyl chitosan nanoparticles co-encapsulating natamycin and theaflavins

In this study, gliadin-carboxymethyl chitosan composite nanoparticles (GC NPs) co-encapsulated natamycin (Nata) and theaflavins (TFs) were constructed and added as an antioxidant, antifungal, and structural enhancer to carboxymethyl chitosan (CMCS) films. The stabilized GC NPs with a particle size of 160.7 ± 2.8 nm, a zeta potential of -29.0 ± 0.9 mV, and a protein content in the supernatant of 96 ± 1 % could be fabricated. Tests of pH and salt ions showed that the stability of NPs dispersion was based on electrostatic repulsion. Co-encapsulation of TFs enhanced the photostability of Nata and the antioxidant activity of the NPs dispersion. The interactions between gliadin with Nata and TFs were studied by molecular simulations. As a functional additive, the addition of Nata/TFs-GC NPs could improve the optical properties, mechanical properties, water-blocking capability, and antifungal and antioxidant activities of the CMCS films. The in-vivo test showed that the functional film could be used to inhibit the growth of Aspergillus niger on cheese.

Biomineralization: A new tool for developing eco-sustainable Ti-doped hydroxyapatite-based hybrid UV filters

It is well known that the prolonged exposure to UV radiation from sunlight can compromise human health and is particularly damaging to the skin, leading to sunburn, photo-aging and skin cancer. Sunscreen formulations containing UV-filters present a barrier against solar UV and help to mitigate the harmful effects however, concern about their safety for both human and environmental health is still a much-debated topic. EC regulations classify UV-filters depending on their chemical nature, particle size, and mechanism of action. Furthermore, it regulates their use in cosmetic products with specific limitations in terms of concentration (organic UV filters) and particle size and surface modification to reduce their photo-activity (mineral UV filters). The regulations have prompted researchers to identify new materials that show promise for use in sunscreens. In this work, biomimetic hybrid materials composed of titanium-doped hydroxyapatite (TiHA) grown on two different organic templates, derived from animal (gelatin - from pig skin) and vegetable (alginate - from algae) sources. These novel materials were developed and characterized to obtain sustainable UV-filters as a safer alternative for both human and ecosystem health. This 'biomineralization' process yielded TiHA nanoparticles that demonstrated high UV reflectance, low photoactivity, good biocompatibility and an aggregate morphology which prevents dermal penetration. The materials are safe for topical application and for the marine environment; moreover, they can protect organic sunscreen components from photodegradation and yield long-lasting protection.

Mitochondria-targeting fluorescent sensor with high photostability and permeability for visualizing viscosity in mitochondrial malfunction, inflammation, and AD models

Viscosity changes in mitochondria are closely associated with numerous cellular processes and diseases. Currently available fluorescence probes used in mitochondrial viscosity imaging are not very photostable or sufficiently permeable. Herein, a highly photostable and permeable mitochondria-targeting red fluorescent probe (Mito-DDP) was designed and synthesized for viscosity sensing. Viscosity was imaged in living cells using a confocal laser scanning microscope, and the results suggested that Mito-DDP penetrated the membrane and stained the living cells. Importantly, practical applications of Mito-DDP were demonstrated: viscosity visualization was realized for mitochondrial malfunction, cellular and zebrafish inflammation, and Drosophila Alzheimer's disease models, i.e., for subcellular organelles, cells, and organisms. The excellent analytical and bioimaging performance of Mito-DDP in vivo makes it an effective tool for exploring the physiological and pathological effects of viscosity.

Tuning the Photophysical Properties and Photostability of Bis(naphthobipyrrolylmethene) derived BODIPY via Functionalization

A series of NIR absorbing and emitting, naphthobipyrrole derived BODIPY dyes are reported. These dyes possess different functional groups viz. -CHO, -CN, -NO2, -Br and Ph at its α,α'-positions. All the derivatives were characterized thoroughly via various spectroscopic means as well as single-crystal X-ray structural analyses. Impacts of functionalization on its photophysical properties as well as photostability were evaluated. For instance, incorporation of the phenyl moieties at the α, α'-positions by Suzuki coupling of the dibromo-derivative 4 with phenyl boronic acid led to substantial bathochromic shift in absorption (762 vs 727 nm) and emission (778 vs 744 nm) relative to the unsubstituted parent dye VI. Theoretical calculations have been performed by ground state optimization to evaluate the electronic transitions which supports experimental observation.

Color-variable dual-dyed photodynamic antimicrobial polyethylene terephthalate (PET)/cotton blended fabrics

The urgent demand for scalable, potent, color variable, and comfortable antimicrobial textiles as personal protection equipment (PPE) to help reduce infection transmission in hospitals and healthcare facilities has significantly increased since the start of the COVID-19 pandemic. Here, we explored photodynamic antimicrobial polyethylene terephthalate/cotton (TC) blended fabrics comprised of photosensitizer-conjugated cotton fibers and polyethylene terephthalate (PET) fibers dyed with disperse dyes. A small library of TC blended fabrics was constructed wherein the PET fibers were embedded with traditional disperse dyes dominating the fabric color, thereby enabling variable color expression, while the cotton fibers were covalently coupled with the photosensitizer thionine acetate as the microbicidal agent. Physical (SEM, CLSM, TGA, XPS and mechanical strength) and colorimetric (K/S and CIELab values) characterization methods were employed to investigate the resultant fabrics, and photooxidation studies with DPBF demonstrated the ability of these materials to generate reactive oxygen species (i.e., singlet oxygen) upon visible light illumination. The best results demonstrated a photodynamic inactivation of 99.985% (~ 3.82 log unit reduction, P = 0.0021) against Gram-positive S. aureus, and detection limit inactivation (99.99%, 4 log unit reduction, P ≤ 0.0001) against Gram-negative E. coli upon illumination with visible light (60 min; ~ 300 mW/cm²; λ ≥ 420 nm). Enveloped human coronavirus 229E showed a photodynamic susceptibility of ~ 99.99% inactivation after 60 min illumination (400-700 nm, 65 ± 5 mW/cm²). The presence of the disperse dyes on the fabrics showed no significant effects on the aPDI results, and furthermore, appeared to provide the photosensitizer with some measure of protection from photobleaching, thus improving the photostability of the dual-dyed fabrics. Taken together, these results suggest the feasibility of low cost, scalable and color variable thionine-conjugated TC blended fabrics as potent self-disinfecting textiles.

Breaking the bottleneck of organic light conversion agents: Preparation, performance evaluation and intrinsic mechanism

Poor photostability has become a major obstacle of organic fluorescent dyes (OFD) used as light conversion agent. To explore the intrinsic mechanisms of photodegradation and highly efficient means to enhance photostability, here, three s-triazine dyes and two 1,3,5-triphenylbenzene luminescent agents were designed and synthesized. Further, the relationships of photostability, intramolecular charge transfer effect, energy gap between singlet and triplet, and active oxygen generating capacity are analyzed and discussed. AIE activity, solid-state fluorescence emission, light conversion quality, and photostability combined with thermostability show TPT-DB (2,4,6-tris(4-(3,6-ditertbutyl-9H-carbazol-9-yl)phenyl)-1,3,5-triazine) is the best light conversion agent among of the dyes, whose photosynthetic photon flux density at 400-500 nm and 600-700 nm in doping film increased successively to 6.20% and 25.78% of the blank film, emission intensity can maintain 93.4% of the initial value after intensified UV radiation of 20 h (365 nm, 40 w), and has good thermal stability, Td up to 374 °C. Furthermore, oxygen-free environment was confirmed to be the most effective measure to enhance the photostability of OFD, thereby a simple and efficient method is adopted to block the diffusion of oxygen and significantly enhance the photostability of OFD by amphiphilic ethylene-vinyl alcohol copolymer. The work not only provides an excellent light conversion agent, but also clears the obstacles for the large-scale application of OFD as light conversion agents.

In-situ synthesis of novel dual S-scheme AgI/Ag6Mo7O24/g-C3N4 heterojunctions with tandem structure for photocatalytic degradation of organic pollutants

The controllable design of multivariate heterojunction with sequential structures is of significant relevance for breaking the performance limit of binary composite photocatalysts. In this work, the novel dual S-scheme ternary-component AgI/Ag₆Mo₇O₂₄/exfoliated g-C₃N₄ (ECN) composite was prepared by a two-step in-situ synthetic strategy. The energy band bending at the heterointerface and the formation of dual built-in electric field could be observed due to distinct work functions of different components in the ternary composite. Benefiting from the sequential heterojunction structure, the AgI/Ag₆Mo₇O₂₄/ECN composite achieved 98.7% removal efficiency of 2-nitrophenol (2-NP) within 70 min under visible light irradiation, and AgI/Ag₆Mo₇O₂₄/ECN also showed higher degradation efficiency for a variety of organic pollutants such as methylene blue (MB), rhodamine B (RhB), methyl orange (MO), 4-nitrophenol (4-NP), 2-sec-butyl-4,6-dinitrophenol (DNBP) and tetracycline (TC). Notably, •OH and •O₂^- played dominant roles in the AgI/Ag₆Mo₇O₂₄/ECN set up, which was consistent with the dual S-scheme charge transfer mechanism. In-depth insights for the photodegradation of 2-NP were presented based on a combined DFT study and GC-MS analysis. Additionally, the photoreduction of Ag⁺ in AgI/Ag₆Mo₇O₂₄/ECN was also evaded by the fast transfer of photogenerated electrons through the dual S-scheme pathway, achieving the effect of killing two birds with one stone.

A visual bi-layer sensor based on Agar/TiO2/butterfly bean flower anthocyanin/κ-carrageenan with photostability for monitoring Penaeus chinensis freshness

Visual indicator bi-layer films were manufactured incorporating κ-carrageenan, butterfly pea flower anthocyanin, varying Nano‑titanium dioxide (TiO₂) content and agar for Penaeus chinensis (Chinese white shrimp) freshness detection. The κ-carrageenan-anthocyanin (CA) layer served as indicator, while the TiO₂-agar (TA) layer functioned as the protective layer to improve the photostability of film. The bi-layer structure was characterized by scanning electron microscopy (SEM). The TA2-CA film had the best tensile strength with a value of 17.8 MPa and the lowest water vapor permeability (WVP) value of bi-layer films was 2.98 × 10^-7 g.m^-1.h^-1.pa^-1. The bi-layer film protected anthocyanin against exudation when immersed in aqueous solution of varying pH. The TiO₂ particles filled the pores of the protective layer, increasing the opacity from 1.61 up to 4.49 significantly improving the photostability with a consequent slight color change under illumination of UV/visible light. Under UV irradiation, the TA2-CA film had no significant color change with a ΔE value of 4.23. Finally, the TA2-CA films showed an obvious color change from blue to yellow green in the early stages of Penaeus chinensis putrefaction (≤48 h) then the color change and Penaeus chinensis freshness were well correlated (R² = 0.8739).

Effects of PFOS at ng/L levels on photostability of extracellular polymeric substances under solar irradiation by fluorescence and infrared spectroscopy

The ubiquitous EPS (extracellular polymeric substances), as a type of dissolved organic carbon, plays a key role in carbon cycling in water environment. When EPS meet the omnipresent PFOS (perfluorooctane sulfonate), they must interact with each other and exert profound effect on behavior and fate of both, which is still not well known. We hypothesized that the highly persistent PFOS at real environmental levels may significantly influence behavior of EPS under solar irradiation which may retard carbon turnover. In this study, 3D-EEM fluorescence spectroscopy and FTIR spectroscopy were used to probe responses of composition and structure of EPS under solar irradiation in the absence and presence of PFOS (5-500 ng/L). The experimental results showed that PFOS at ng/L levels significantly affected responses of EPS to sunlight irradiation and the effects were dependent on the components in EPS. Photostability of humic-like substances was significantly increased in the presence of PFOS; Degradation and unfolding of proteins induced by solar light were reduced by PFOS. In addition, degradation of both hydrophilic and hydrophobic functional groups by sunlight was inhibited by PFOS. The novel findings provide new insights for assessing the environmental behavior of EPS and PFOS and understanding the effect of PFOS on carbon cycling in water environments.

Bright and Photostable Fluorescent Metal Nanocluster Supraparticles from Invert Emulsions

Fluorescent supraparticles of gold, silver and copper nanoclusters are synthesized by simply drying of invert emulsions, resulting in a dozen-fold increase in photoluminescence quantum yield (up to ≈80 %) and a significant improvement in photostability. The inhibition of the ligand twisting during the intramolecular charge transfer is found to be responsible for the enhancement, especially for the gold nanocluster supraparticles. This research provides a general, flexible, and easy method for producing highly luminescent and photostable metal nanocluster-based materials that promise practical applications in white-light-emitting diodes.

Mesoporous silica size, charge, and hydrophobicity affect the loading and releasing performance of lambda-cyhalothrin

Nanopesticides are attracting increasing attention as a promising technology in agriculture to improve insecticidal efficacy, decrease pesticides uses, and reduce potential environmental impacts. We synthesized mesoporous silica nanoparticles, i.e., Mobil Composition of Matter No.48 (MCM-48), with different sizes (63-130 nm), charges (-22 to 12 mV), and hydrophobicity (water contact angle 29-103°) to assess their loading amount and release of a typical poorly soluble halogenated pyrethroid (i.e., lambda-cyhalothrin particles, LCNS). The smallest MCM-48 displayed relatively higher loading amount of LCNS (~16%) compared to the larger MCM-48 nanoparticles, likely because of its higher pore volume (1.46 cm³ g^-1) and pore size (3.56 nm). LCNS loading amount was further improved to ~26% and ~36% after -NH₂ (positively charged) and -CH₃ (hydrophobic) functionalization, respectively, probably due to hydrogen bonding, electrostatic, and hydrophobic interactions with LCNS. Loading LCNS in MCM-48 nanoparticles also significantly improved its dispersion in water and ultraviolet (UV) light stability, with a 3-7 times longer half-life than that of free LCNS. Although the -NH₂ and -CH₃ modifications of MCM-48 slightly decreased the UV stability of LCNS, they significantly decreased the release efficiency of LCNS, possibly because of their stronger interactions with LCNS. In addition, the insecticidal effects of LCNS-loaded MCM-48 were more efficient and longer than those of free LCNS. The findings clarify the relationships between physicochemical properties and performance of mesoporous silica nanoparticles, and will inform the rational design of materials for controlled release of pesticides and sustainable control of pests.

In vitro safety evaluation of sunscreen formulation from nanostructured lipid carriers using human cells and skin model

There is a risk of toxicological reactions due to systemic absorption and photo-instability of sunscreens. The study aimed to investigate the safety profile (cytotoxicity, phototoxicity, photostability, UV filter release profile, and skin irritation properties) of sunscreen (NLC-TRF sunscreen) produced from nanostructured lipid carriers (NLCs) and tocotrienol-rich fraction (TRF). The cytotoxicity and phototoxicity of the sunscreen were evaluated on normal human dermal fibroblast (NHDF) and skin irritation properties was tested on skin model. Besides, the photoprotection in pre- and post-UV irradiation were analysed to determine the photostability. Additionally, the release profile for UV filters (diethylamino hydroxybenzoyl hexyl benzoate (DHHB) and ethylhexyl triazone (EHT)) were evaluated. The NLC-TRF sunscreen demonstrated no cytotoxicity and skin irritation to cause cell death. It showed no phototoxic effect and high photostability up to 10 Minimal Erythema Dose (MED) to ensure high SPF value above 50 and broad-spectrum of UV absorption. The NLC-TRF sunscreen implies its safety for topical application with sustainable release profile for UV filter (cumulative release of 28% for DHHB and 40% for EHT after 8 h) due to the application of NLCs. The results suggest that the NLC-TRF sunscreen is an advanced formulation with improved stability and is safe for topical delivery.

Evaluation of chemotherapeutic response in living cells using subcellular Organelle‒Selective amphipathic carbon dots

Monitoring of structural changes in subcellular organelles is critical to evaluate the chemotherapeutic response of cells. However, commercial organelle selective fluorophores are easily photobleached, and thus are unsuitable for real-time and long-term observation. We have developed photostable carbon-dot liposomes (CDsomes)-based fluorophores for organellar and suborganellar imaging to circumvent these issues. The CDs synthesized through a mild pyrolysis/hydrolysis process exhibit amphipathic nature and underwent self-assembly to form liposome-like structures (CDsomes). The controlled hydrophilicity or hydrophobicity-guided preparation of CDsomes are used to selectively and rapidly (<1 min) stain nucleolus, cytoplasm, and membrane. In addition, the CDsomes offer universal high-contrast staining not only in fixed cells but also in living cells, allowing real-time observation and morphological identification in the specimen. The as-prepared CDsomes exhibit excitation-dependent fluorescence, and are much more stable under photoirradiation (e.g., ultraviolet light) than traditional subcellular dyes. Interestingly, the CDsomes can be transferred to daughter cells by diluting the particles, enabling multigenerational tracking of suborganelle for up to six generations, without interrupting the staining pattern. Therefore, we believe that the ultra-photostable CDsomes with high biocompatibility, and long-term suborganellar imaging capabilities, hold a great potential for screening and evaluating therapeutic performance of various chemotherapeutic drugs.

Squaraine Dyes Derived from Indolenine and Benzo[e]indole as Potential Fluorescent Probes for HSA Detection and Antifungal Agents

Four squaraine dyes derived from 2,3,3-trimethylindolenine and 1,1,2-trimethyl-1H-benzo[e]indole with different combinations of barbituric groups attach to the central ring, having ester groups and alkyl chains in the nitrogen atoms of heterocyclic rings were synthesized. These dyes were fully characterized and their photophysical behavior was studied in ethanol and phosphate-buffered saline solution. Absorption and emission bands between 631 and 712 nm were detected, with the formation of aggregates in aqueous media, which is typical of this class of dyes. Tests carried out with 1,3-diphenylisobenzofuran allowed us to verify the ability of the dyes to produce singlet oxygen. The interaction of synthesized dyes with human serum albumin (HSA) was also evaluated, being demonstrated a linear correlation between fluorescence intensity and protein concentration. The antifungal potential of the dyes against the yeast Saccharomyces cerevisiae was evaluated using a broth microdilution assay. In order to test the photosensitizing capacity of the synthesized dyes, tests were carried out in the dark and with irradiation, using a custom-built light-emitting diode that emits close to the absorption wavelength of the studied dyes. The results showed that the interaction of dyes with HSA and the antifungal activity depends on the different structural modifications of the dyes.

The role of nitro group on the excited-state relaxation mechanism of P-Z base pair

DNAs' photostability is significant to the normal function of organisms. P-Z is a hydrogen bonded artificial DNA base pair, where P and Z represent 2-amino-imidazo[1,2-a]-1,3,5-triazin-4(8H)one and 6-amino-5nitro-2(1H)-pyridone, respectively. The excited-state relaxation mechanism of P-Z pair is investigated using static TDDFT calculations combined with the non-adiabatic dynamic simulations at TDDFT level. The roles of nitro rotation, nitro out-of-plane deformation, and single proton transfer (SPT) along hydrogen bond are revealed. The results of potential energy profile calculations demonstrate that the SPT processes along the hydrogen bonds are unfavorable to occur statically, which is in great contrast to the natural base pair. The non-adiabatic dynamic simulations show that the excited-state nitro rotation and nitro out-of-plane deformation are the two important relaxation channels which lead to the fast internal conversion to S₀ state. The SPT from Z to P is also observed, followed by distortion on P, inducing the fast internal conversion to S₀ state. However, this channel (decay via SPT process) plays minor roles on the excited-state relaxation mechanism statistically. This work shows the great differences of the excited-state relaxation mechanism between the natural base pairs and artificial base pair, also sheds new light into the role of hydrogen bond and nitro group in P-Z base pair.

Fabrication of Pt doped TiO2-ZnO@ZIF-8 core@shell photocatalyst with enhanced activity for phenol degradation

Phenol's presence in aqueous solution due to the pollution from chemical and agricultural industries (e.g., coking tobacco leaves) causes severe environmental problems. As a result, many scientists and engineers search for catalysts to remove phenol from water by photodegradation. Thus, we synthesized Pt-doped TiO₂-ZnO@ZIF-8 core@shell particles (Pt/TiO₂-ZnO@ZIF-8) by a simple method involving crystallization, absorption, pyrolysis and growth steps. The resulting materials were analyzed by the powder X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM, respectively), surface area measurements and UV-vis absorption spectroscopy. The photocatalytic activities of our materials were evaluated by phenol degradation in aqueous solutions. Pt-doped TiO₂-ZnO particles possessed a polyhedral structure and exhibited broad absorption above 400 nm. Coating with ZIF-8 increased the specific surface area of the Pt-doped TiO₂-ZnO particles. Both Pt doping and ZIF-8 coating significantly enhanced the photocatalytic performance of TiO₂-ZnO. Pt/TiO₂-ZnO@ZIF-8 decomposed 99.7 % of phenol after the corresponding solution was exposed to UV light for 24 min. This performance was significantly better than the phenol decomposition ability of TiO₂-ZnO, Pt/TiO₂-ZnO and TiO₂, which degraded 76.1 %, 95.2 % and 86.9 % of phenol, respectively. Pt/TiO₂-ZnO@ZIF-8 also demonstrated excellent recycling stability. All these properties, including photostability, made our novel Pt/TiO₂-ZnO@ZIF-8 catalyst a promising material for practical applications in environmental remediation.

Spectroscopic Behavior and Photophysical Parameters of 2-(Acetoxymethyl)-6-(1,2,4-triazinylaminodihydroquinazolinyl)tetrahydropyran Derivative in Different Solid Hosts

Optical and photophysical properties of 6-substituted-1,2,4-Triazine fluorescent derivative dye doped in silicate based sol-gel, homopolymer of methyl methacrylate (PMMA), and copolymer (MMA/diethylene glycol dimethacrylate) (DEGDMA) were investigated. The pores of different hosts and caging of the dye were found to effect on the parameters such as molar absorptivity, cross sections of singlet-singlet electronic absorption and emission spectra, excited state lifetime, quantum yield of fluorescence. The dipole moment of electronic transition, the length of attenuation and oscillator strength of electronic transition from So → S1 have been calculated. The dye was pumped with different powers using 3^rd harmonic Nd: YAG laser of 355 nm and pulse duration 8 ns, with repetition rate 10 Hz. Good photo stability for dye was attained. After 55,000 pumping pulses of (10 mJ/pulse), the photo-stabilities were decreased to 53%, 48%, and 45% of the initial ASE of dye in sol gel, PMMA, and Co-polymer respectively. The dye in sol-gel matrix showed improvement of photo stability compared with those in organic polymeric matrices.

Modelling Photoionisation in Isocytosine: Potential Formation of Longer-Lived Excited State Cations in its Keto Form

Studying the effects of UV and VUV radiation on non-canonical DNA/RNA nucleobases allows us to compare how they release excess energy following absorption with respect to their canonical counterparts. This has attracted much research attention in recent years because of its likely influence on the origin of our genetic lexicon in prebiotic times. Here we present a CASSCF and XMS-CASPT2 theoretical study of the photoionisation of non-canonical pyrimidine nucleobase isocytosine in both its keto and enol tautomeric forms. We analyse their lowest energy cationic excited states including 2 π + , 2 n O + and 2 n N + and compare these to the corresponding electronic states in cytosine. Investigating lower-energy decay pathways we find - unexpectedly - that keto-isocytosine+ presents a sizeable energy barrier potentially inhibiting decay to its cationic ground state, whereas enol-isocytosine+ features a barrierless and consequently ultrafast pathway analogous to the one previously found for the canonical (keto) form of cytosine+ . Dynamic electron correlation reduces the energy barrier in the keto form substantially (by ∼1 eV) but it is nevertheless still present. We additionally compute the UV/Vis absorption signals of the structures encountered along these decay channels to provide spectroscopic fingerprints to assist future experiments in monitoring these intricate photo-processes.

Curauá-derived carbon dots: Fluorescent probes for effective Fe(III) ion detection, cellular labeling and bioimaging

This study reports the generation of curauá-derived carbon dots (C-dots) and their suitability for Fe(III) detection, bioimaging and FACS analysis. C-dots were generated from curauá (Ananas erectifolius) fibers by a facile one-step hydrothermal approach. They exhibited graphite-like structure with a mean diameter of 2.4 nm, high water solubility, high levels of carboxyl and hydroxyl functional groups, excitation-dependent multicolor fluorescence emission (in the range 450 nm - 560 nm) and superior photostability. C-dots were highly selective and effective for the detection of ferric Fe(III) ion in an aqueous medium with a detection limit of 0.77 μM in the linear range of 0-30 μM, a value much lower than the guideline limits proposed by the World Health Organization (WHO). In biological cell systems, C-dots were very well tolerated by B16F1 mouse melanoma and J774.A1 mouse macrophages cell lines, both of which effectively internalized C-dots in their cytoplasmic compartment. Finally, C-dots were effective probes for long-term live cell imaging experiments and multi-channel flow cytometry analysis. Collectively, our findings demonstrate that curauá-derived C-dots serve as versatile and effective natural products for Fe(III) ion sensing, labeling and bioimaging of various cell types. This study adds novel C-dots to the library of carbon-based probes and paves the way towards a sustainable conversion of a most abundant biomass waste into value-added products.

Photostability enhancement of silica-coated gold nanostars for photoacoustic imaging guided photothermal therapy

Gold nanostars (GNSs) are promising contrast agents for simultaneous photothermal therapy and photoacoustic imaging (PAI) owing to their excellent photothermal conversion efficiency. However, GNSs are easily reshaped under transient high-intensity laser pulses, which can cause a rapid shift in the light absorption peak, resulting in a decrease in both therapeutic and monitoring effects. In this work, we synthesized GNSs without toxic surfactants and coated them with a silica shell to retain their shape, thus maintaining their photostability. The excellent performance of these silica-coated GNSs was verified through both in vitro and in vivo PAI experiments. The silica-coated GNSs exhibited a threefold improvement in photoacoustic stability, as compared with the non-coated GNSs. The proposed silica coating method for GNSs was found to improve the photostability of GNSs, making them efficient, safe, and reliable nanoparticles for PAI.

Photochemical stability of warfarin potassium in powdered pharmaceutical tablets

BACKGROUND

Warfarin potassium (Wf) commercial tablets originally formulated for adults are ground before administration to pediatric patients and elderly patients with dysphagia.

OBJECTIVE

The present study investigated the effect of tablet grinding on the photostability of four types of commercial Wf tablets and predicted the photostability of the tablet powders by chemometric analysis.

METHODS

The photodegradation of Wf content was evaluated by reversed-phase column high-performance liquid chromatography with ultraviolet (HPLC-UV).

RESULTS

The bulk Wf powder was relatively photostable, whereas ground Wf tablets underwent substantial photodegradation. The photostability of the ground powders of a brand-name Wf commercial tablet and three generic Wf commercial tablets was quantitatively assessed and compared. In certain cases, the Wf in all the three ground generic tablets was less photostable than in the ground brand-name tablets. After 28 days of light irradiation, the Wf content decreased to 69.79% in the brand-name tablets, while it was 31.90% in some generic tablets. To clarify the factors influencing the relative photostability in various Wf formulations, we analyzed the intermolecular interactions between the active ingredient and the excipients by partial least-squares regression analysis based on photostability screening for each additive.

CONCLUSION

The results suggested that the additives light anhydrous silicic acid and povidone adversely affect the stability of Wf tablets. In addition, the light stability of ground tablets was affected considerably by their formulation.

Laser performance and investigation of the optimal density functional and the dependence of the basis sets for (E, E)-2,5-bis (3,4-dimethoxystyryl) pyrazine (BDP) molecule

This manuscript includes some photophysical parameters and some optical properties such as absorption and emission spectra of the (E, E)-2,5-bis (3,4-dimethoxystyryl) pyrazine (BDP) by applying sol–gel and copolymer matrices. The BDP molecular structure is incorporated in sol–gel matrix and copolymer of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA). In case of sol–gel matrix, the BDP molecular structure has higher quantum yield in addition to photostability maxima. The laser behavior of this molecular structure containing sol–gel matrix is good senior compared to copolymer one via using diode laser (450 nm) as pumping laser of power 160 mW. Also, the fluorescence profile of the BDP molecular structure is sensitized via using cadmium sulfide (CdS) quantum dots (QDs) by applying sol–gel host. The optimized structure of the BDP molecule is obtained via applying B3LYP/6-31G(d) level of theory. The electronic absorption and emission spectra of the BDP molecular structure in ethanol solvent were calculated using time-dependent density functional theory (TDDFT) at CAM-B3LYP/6-31G +  + (d, p) level. The obtained theoretical results were compared to experimental ones.

Spectral Behavior and Photophysical Parameters of Dihydrophenanthro[9,10-e][1,2,4]Triazine Derivative Dyes in Sol-Gel and Methyl Methacrylate Polymer Matrices

This paper deals with the optical and photophysical properties of dihydrophenanthro[9,10-e][1,2,4]triazine fluorescent dyes doped in Silicate based sol-gel and homo-poly methyl methacrylate (PMMA). Solid hosts were found to effect on the optical and photophysical parameters such as molar absorptivity, cross sections of singlet-singlet electronic absorption and emission spectra, excited state lifetime, quantum yield of fluorescence. The dipole moment of electronic transition, the length of attenuation and oscillator strength of electronic transition from S_o → S₁ have been calculated. The dyes were pumped with different powers using 3^rd harmonic Nd:YAG laser of 355 nm and pulse duration 8 ns, with a repetition rate at (10 Hz). Good photostability for compounds 1 and 2 were attained. It was decreased to 49% & 54% and 46% & 40% of the initial ASE of dyes in sol gel and PMMA, respectively, after 55,000 pumping pulses at (10 mJ/pulse). The dyes in sol-gel showed improved photostability compared with those in organic polymeric matrices.

The dark side of white hair? Artificial light irradiation reduces cortisol concentrations in white but not black hairs of cattle and pigs

Analysing hair cortisol concentrations (HCCs) is a minimally invasive way to retrospectively assess long-term stress, and its application in studies of animal welfare and stress has attracted considerable interest. However, not only stress-related effects but also hair-specific characteristics and external influences can affect HCCs and interfere with the interpretation of results. Thus, it was the aim of this study to investigate the impact of daylight and UV irradiation on cortisol concentrations in the hairs of pigs and cattle. We also examined whether a potential irradiation effect on HCCs depended on the colour of the hair. For this purpose, black and white hair samples from 18 Saddleback pigs and 18 Holstein Friesian cattle were exposed to artificial light (both visible and UV) and compared with control hair samples from the same animals kept in the dark. Exposure to artificial light significantly decreased HCCs in both pigs (P < 0.05) and cattle (P < 0.001), and hair colour had an influence on HCCs, with black hair showing higher cortisol levels than white hair (cattle: P < 0.001, pigs: P = 0.07). The interaction between light exposure and hair colour was significant in both pigs (P < 0.01) and cattle (P < 0.001), so light exposure reduced HCCs in porcine white hair but not black hair. In cattle, light-exposed white hair exhibited lower hair cortisol levels than control white hair or black hair. These results demonstrate that artificial light irradiation degrades hair cortisol or favours its elimination by structural changes of the hair matrix. However, this effect was only detectable in white hair, indicating that the melanin pigments in black hair absorbed radiation, thereby reducing the effects of photodegradation. Compared with other known influencing factors on HCCs, such as age and body region, the influence of light irradiation was relatively low in this in vitro experiment. However, further studies should investigate this influence under real-life animal conditions, such as outdoor and indoor housing.

Photostability of l-tryptophan in aqueous solution: Effect of atmosphere and antioxidants addition

l-Tryptophan (l-Trp) is an amino acid important in nutrition, and mainly provided by food supplements. However, it is known to be unstable under light irradiation, which is an issue for the nutrition and feed industry. In the present study, the photostability of l-Trp was studied in acidic aqueous solutions under air and under an inert atmosphere, N₂. The photodegradation was followed using UV-visible and fluorescence spectroscopy after photolysis. Moreover, molecular orbitals and bond dissociation energies calculations, and electron spin resonance spectroscopy were performed. From all these results, a photodegradation occurring through a free radical pathway was suggested. Interestingly, several antioxidants were tested to improve the photostability of l-Trp, especially during irradiation under air, since the l-Trp was evidenced to be much less stable under air than under N₂. The results showed that sodium benzoate or EDTA were not efficient, but antioxidants such as chlorogenic acid, ascorbic acid or potassium sorbate improved significantly the photostability of l-Trp in acidic solutions.

Photostability studies of GarKS peptides for topical formulation development

There is a growing interest in the use of antimicrobial peptides (AMPs) as potent alternatives for conventional antibiotics, especially in chronic infected wounds. The development of a suitable topical formulation requires a thorough assessment of the photostability profiles of AMPs. In this study, we sought to investigate the photostability of novel Garvicin KS (GarKS; composed of three peptides GakA, GakB, and GakC) peptides either as an individual peptide or in combinations. The photostability of the aqueous peptide solution was determined using Suntest (indoor and outdoor conditions). Furthermore, the antimicrobial efficacy of the peptides was evaluated following UVA irradiations. Photodegradation of the peptides under indoor and outdoor conditions followed first-order kinetics. Individual peptides (GakA, GakB, and GakC) were more prone to photodegradation as compared to combination peptides (GakA+GakB, GakB+GakC, and GakA+GakC) both under indoor and outdoor conditions where the GakA+GakB combination was the most photostable. A combination of GakA+GakB+GakC enhanced photostability under indoor conditions but was reduced under outdoor conditions. A combination of three peptides with an antioxidant (glutathione) or superoxide/hydrogen peroxide scavenger (trehalose) enhanced the photostability of peptides with the highest stability achieved at a peptide:photostabilizer molar ratio of 1:0.8 for glutathione. A nominal increase in the MIC value for the peptide combinations as opposed to a larger increase for individual peptides further supports the photostability effects of combination peptides following UVA irradiations. These results suggest that the GakA+GakB or GakA+GakB+GakC combinations exhibited the highest photostability with excellent antimicrobial efficacy deemed suitable for the development of a potent AMP formulation for topical applications.

A novel photoacoustic-fluorescent contrast agent for quantitative imaging of lymphatic drainage

In vivo near-infrared (NIR) photoacoustic imaging (PAI) studies using novel contrast agents require validation, often via fluorescence imaging. Bioconjugation of NIR dyes to proteins is a versatile platform to obtain contrast agents for specific biomedical applications. Nonfluorescent NIR dyes with higher photostability present advantages for quantitative PAI, compared to most fluorescent NIR dyes. However, they don't provide a fluorescence signal required for fluorescence imaging. Here, we designed a hybrid PA-fluorescent contrast agent by conjugating albumin with a NIR nonfluorescent dye (QC-1) and a visible spectrum fluorescent dye, a BODIPY derivative. The new hybrid tracer QC-1/BSA/BODIPY (QBB) had a low minimum detectable concentration (2.5μM), a steep linear range (2.4-54.4 μM; slope 3.39 E -5), and high photostability. Tracer signal was measured in vivo using PAI to quantify its drainage from eye to the neck and its localization in the neck lymph node was validated with postmortem fluorescence imaging.

Novel cryogenic dual-emission mechanism of lead-free double perovskite Cs2AgInCl6 and using SiO2 to enhance their photoluminescence and photostability

Lead halide perovskite have attracted world-wide attention regarding their serious hazards on ecological environment and human health. To improve both the emission intensity and stability of Cs₂AgInCl₆, this study explores using SiO₂ to structurally adjust Cs₂AgInCl₆. Note that including SiO₂ changed the growth style and crystal morphology of Cs₂AgInCl₆ from an octahedron to a truncated octahedron. After structural adjustment, the unit cells scattered, and the absorption limit broke. Moreover, SiO₂ was demonstrated to passivate the material's surface to form an anti-oxidation protective layer. Consequently, the photoluminescence emission intensity increased by 181.5% and the stability of Cs₂AgInCl₆ improved by 83.11%. This work provides a methodology and reference for future improvements to the luminescence of Cs₂AgInCl₆. Furthermore, a novel double-emission phenomenon (λ_ex = 365 nm: λ_em ≈ 580 nm; λ_ex = 325 nm: λ_em ≈ 505 nm) of Cs₂AgInCl₆ at cryogenic temperatures (20 K) was discovered; this phenomenon explains the shoulder emission problem of 400-450 nm at room temperature and clarifies the luminescence mechanism of Cs₂AgInCl₆.

Photostability of Semiconductor Quantum Dots in Response to UV Exposure

The interest in quantum dots (QDs) and their popularity in life science applications stems from their high photostability and unique optical properties such as superior light absorption. Photostability of semiconductor QDs is reportedly higher than that of organic dyes, but QDs may also be affected by light exposure. The outcome of such exposure may depend on many experimental factors, can lead to either an increase or decrease in the photoluminescent efficiency of QDs and is difficult to predict. QDs may therefore require experimental testing for their photostability especially prior to quantitative applications. A simple QD testing procedure described here showed a substantial degree of photobleaching when exposed to UV; nevertheless, the rate of change was noticeably lower than that measured for traditional organic dyes, as expected. The procedure reported is also applicable to traditional organic dyes and allows for quantitative comparisons to be conducted.

Ester derivatives of phyllohydroquinone effectively deliver the active form of vitamin K1 topically, owing to their non-photosensitivity

Topical application of phylloquinone (PK) is beneficial to the skin; however, its topical use is limited in Europe owing to its photosensitive properties such as photodegradation and phototoxicity. We evaluated the suitability of ester derivatives of phyllohydroquinone (PKH), the active form of PK, for topical application to overcome the abovementioned problems of PK. We used the PKH derivatives PKH-1,4-bis-N,N-dimethylglycinate hydrochloride (PKH-DMG) and PKH-1,4-bis-hemisuccinate (PKH-SUC) for our studies. Photostability was determined by measuring the residual concentration after irradiation with artificial sunlight and multi-wavelength light. Phototoxicity after ultraviolet A (UVA) irradiation was assessed by measuring drug-induced singlet oxygen and intracellular reactive oxygen species (ROS) generation, and cell viability of a human epidermal keratinocyte cell line (HaCaT). Delivery of PKH into HaCaT cells was assessed by measuring PK epoxide (PKO) levels. The PKH derivatives showed higher photostability than PK. After UVA irradiation, PK induced high singlet oxygen levels and intracellular ROS generation, and reduced cell viability, whereas the PKH derivatives showed no effects. The PKH derivatives increased intracellular PKO levels. AUC_{PKO(0-72 h)} values after PKH-DMG and PKH-SUC treatments were 0.741- and 22.9-fold higher than that after PK treatment, respectively. In conclusion, PKH derivatives act as PKH prodrugs and are suitable for topical application without the need for special protection from light.

Nanoscale integration of porphyrin in GroEL protein cage: Photophysical and photochemical investigation

In this paper, we introduce a new type of functional, supramolecular porphyrin conjugate created using the bacterial GroEL protein cage based on non-specific hydrophobic interaction. The synthesis, structure and property of the porphyrin conjugate were characterized by dynamic light scattering, UV-vis spectroscopy and fluorescence spectroscopy. We observed that the model zinc-tetraphenylporphyrin (Zn-TPP) with high hydrophobicity can be well-dispersed in aqueous solutions with the aid of GroEL open chamber, which is known to be a favorable nanocompartment for aggregation-prone molecules. The maximal encapsulation efficiency of Zn-TPP in GroEL was determined to be ~98%. It is further seen that the constructed double Zn-TPP-GroEL complex exhibited good photocatalytic activity in the model reactions of the production of singlet oxygen and the reduction of methyl viologen under illumination with visible light. Moreover, we found that GroEL can significantly improve the photostability of Zn-TPP molecules as a result of nanoscale assembly within its hydrophobic chamber. Hence enhanced water solubility and photostability of Zn-TPP, which are considered as the first two hurdles for the wide usage of porphyrins, were achieved simultaneously by the development of GroEL cage as a building block. Supramolecular nanostructures formed from porphyrins (or related molecules) and GroEL for photocatalysis would greatly simplify applications of such structures.

Surface functionalized red fluorescent dual-metallic Au/Ag nanoclusters for endoplasmic reticulum imaging

An efficient method is reported to prepare endoplasmic reticulum-targetable dual-metallic gold-silver nanoclusters, denoted as ER-Au/Ag nanoclusters (NCs), by virtue of a rationally designed molecular ligand. The prepared ER-Au/Ag NCs possesses red-emitting fluorescence with a strong emission at 622 nm and a high fluorescence quantum yield of 5.1%, which could avoid the influence of biological auto-fluorescence. Further investigation results showed that ER-Au/Ag NCs exhibited superior photostability, minimal cytotoxicity, and ER-targeting capability. Enabled by these meritorious features, ER-Au/Ag NCs have been successfully employed for long-term bioimaging of ER in living cells.Graphical abstract A sensitive non-enzymatic fluorescent glucose probe-based ZnO nanorod decorated with Au nanoparticles.

Green Synthesis of Sodium Alginate Capped -CuInS2 Quantum Dots with Improved Fluorescence Properties

CuInS₂ (CIS) quantum dots (QDs) are known to be ideal fluorophores based on their low toxicity and tunable emission. However, due to low quantum yield (QY) and photostability, the surface is usually passivated by a higher bandgap shell (e.g. ZnS). This always resulted in a blue-shifted emission position which is not usually favourable for biological imaging. To address this problem, we herein report the passivation of green synthesized near infra-red emitting glutathione (GSH) capped CuInS₂ QDs using different concentration of sodium alginate (SA) at different temperatures. The as-synthesized QDs are small (~ 3.2 nm), highly crystalline and emitted in the near infra-red region. The optical results showed a 36% increase in photostability and a 2-fold increase in quantum yield at ratio 1:8 (SA: CIS) which is suitable for prolonged biological imaging applications. Transmission electron microscope and X-ray diffraction (XRD) analyses showed that the materials are highly crystalline without any change in shape and size after passivation with the biopolymer. Graphical Abstract.

Infusion of trans-resveratrol in micron-scale grape skin powder for enhanced stability and bioaccessibility

A novel delivery system using micron-scale grape skin powder (GSP) was developed that enhanced loading, stability and bioaccessibility of trans-resveratrol (trans-Res). Vacuum assisted infusion of GSP results in a high yield (~1 mg/g) of trans-Res and improved photostability of infused trans-Res in GSP exposed to UV-A light. The release of trans-Res from GSP was ~ 45% during gastric digestion and the total release in the intestinal phase during sequential digestion processes using low and high bile salts was ~ 70% and ~ 90%, respectively. Moreover, the release of endogenous polyphenols in GSP during simulated gastrointestinal digestion was similar to the release profile of infused resveratrol, suggesting strong interactions of infused resveratrol with the GSP matrix. In summary, this research illustrates a novel approach to utilize food by-products to enhance stability and bioaccessibility of bioactive compounds.

Spectroscopic and photostability study of water-soluble hypericin encapsulated with polyvinylpyrrolidone

Hypericin has gained great attention as a powerful photosensitizing and fluorescent agent for photodynamic therapy (PDT) and fluorescence diagnosis (FD) of cancer. However, native hypericin is hydrophobic and nearly insoluble in aqueous media which hinders its photobiological activity. Herein, we demonstrate the encapsulation of hypericin and polyvinylpyrrolidone (hypericin@PVP) as an attractive class of water-soluble formula of hypericin with improved absorption and emission characteristics in water. The absorption and fluorescence properties of the water-soluble hypericin@PVP were studied at room temperature. Also, the photostability of the prepared hypericin@PVP was studied under visible light irradiation. The absorbance and emission measurements confirm the association and binding of hypericin and PVP with a binding constant (K_b) of 1.2 × 10⁵ M^-1. The interaction between hypericin and PVP in water could lead to the dissociation of aggregated hypericin into their monomeric state which is crucial for effective photobiological implementation in PDT and FD. Upon encapsulation with PVP, hypericin showed a significant increase in the fluorescence properties with an enhanced emission intensity of 300% at a PVP concentration of 1 × 10^-4 M. Moreover, water-soluble hypericin@PVP demonstrated high photostability under visible light irradiation with an irradiance of 15 mW/cm² and exposure time up to 150 min. This enhancement in the absorption, emission, and photostability of hypericin in water is related to the effects of encapsulation with PVP and the unique spectroscopic properties of the formulated hypericin@PVP.