UV-vis Absorption Spectroscopy Research Articles

Spectral Characteristics of Dissolved Organic Matter in Sediments from Yuanhe River Basin

Dissolved organic matter （DOM） plays an important role in indicating the pollution of the water environment, and sediment is the main source of endogenous pollution of the water environment. Research on the spectral characteristics of DOM in sediments was important for the interpretation of water environment pollution. In this study, UV-visible absorption spectroscopy and three-dimensional fluorescence spectroscopy combined with the parallel factor analysis （PARAFAC） were used to analyze the fluorescent components, sources, and influencing factors of DOM in sediments from the Yuanhe River Basin. The results showed that the average of ω（TN）, ω（TP）, and ω（OM） in sediments from the Yuanhe River Basin were 0.52, 0.66, and 21.22 g·kg-1, respectively. The concentrations of total nitrogen and total phosphorus increased along the flow direction. In addition, the sediment DOM from the Yuanhe River Basin mainly originated from terrestrial sources. The chromophoric DOM concentration and aromaticity of DOM from the downstream reaches were significantly higher than those from the upstream and midstream reaches. Based on PARAFAC, four fluorescent components of DOM in sediments from the Yuanhe River Basin were identified, including three humus-like components （C1, C3, and C4） and one protein-like component （C2）. The sediment DOM was dominated by humus-like materials. Moreover, the fluorescent intensity of the fluorescent components was higher in the downstream reaches. Redundancy analysis revealed that the physicochemical properties of sediments in the mainstream and downstream reaches played a more significant role in the spectral properties of DOM. Phosphorus pollution and the terrestrial humus-like substance of sediment DOM were homologous. These results indicated that the spectral properties of DOM were the indicator of water environmental pollution in the region with strong anthropogenic influence.

Temperature-Dependent Structural and Optoelectronic Properties of the Layered Perovskite 2-Thiophenemethylammonium Lead Iodide.

Improved knowledge of the influence of temperature upon layered perovskites is essential to enable perovskite-based devices to operate over a broad temperature range and to elucidate the impact of structural changes upon the optoelectronic properties. We examined the Ruddlesden-Popper layered perovskite 2-thiophenemethylammonium lead iodide (ThMA2PbI4) and observed a structural phase transition between a high- and a low-temperature phase at 220 K using temperature-dependent X-ray diffraction, UV-visible absorption, and photoluminescence (PL) spectroscopy. The structural phase transition altered the tilt pattern of the inorganic octahedra layer, modifying the absorption and PL spectra. Further, we found a narrow and intense additional PL peak in the low-temperature phase, which we assigned to radiative emission from a defect-bound exciton state. In both phases we determined the thermal expansion coefficient and found values similar to those of cubic 3D perovskites, i.e., larger than those of typical substrates such as glass. These results demonstrate that the organic spacer plays a critical role in controlling the temperature-dependent structural and optoelectronic properties of layered perovskites and suggests more widely that strain management strategies may be needed to fully utilize layered perovskites in device applications.

Spectral-Sensing System for Distinguishing CH3OH and CD3OD.

Spectrally discriminating CH3OH and CD3OD, and even detecting CH3OH contents in the CD3OD solvent, are important yet have not been achieved so far, likely owing to their very similar chemical/physical properties. Herein, dynamic transesterification reactions, which can be achieved via two-step proton transfers, can be signaled via ultraviolet UV-visible (UV/vis) absorption and fluorescence spectroscopies under mild experimental conditions. Introduction of strong electron-withdrawing groups, such as -NO2, to the aromatic ring (benzoic acid moiety or phenol moiety) of carboxylate esters to activate the esters is important for transesterification reactions and is an intriguing method for modulating the selectivity of the spectral response. The rate constant of the transesterification reaction enhanced with increasing the total number of strong electron-withdrawing groups. Furthermore, the rate constants of esters in which substituent(s) are connected to the phenol moiety are higher than those of corresponding esters in which substituent(s) are connected to the benzoic acid moiety. In transesterification systems, added aliphatic amines mainly play two roles: (i) lowering the energy barrier of the first transesterification step via the formation of intermolecular hydrogen bonding in ternary systems and (ii) deprotonating the released 4-nitrophenol in UV/vis absorption spectral systems to generate an UV/vis absorption spectral signal reporter, i.e., nitrophenolate anions. As a result of the methanol-mediated transesterification reaction, spectral-sensing systems can be established for discriminating CH3OH and CD3OD and even detecting low CH3OH contents in the CD3OD solvent, owing to the kinetic isotope effect. This is the first example of spectral recognition between CD3OD and CH3OH.

Structure-driven development of a biomimetic rare earth artificial metalloprotein

The 2011 discovery of the first rare earth-dependent enzyme in methylotrophic Methylobacterium extorquens AM1 prompted intensive research toward understanding the unique chemistry at play in these systems. This enzyme, an alcohol dehydrogenase (ADH), features a La3+ ion closely associated with redox-active coenzyme pyrroloquinoline quinone (PQQ) and is structurally homologous to the Ca2+-dependent ADH from the same organism. AM1 also produces a periplasmic PQQ-binding protein, PqqT, which we have now structurally characterized to 1.46-Å resolution by X-ray diffraction. This crystal structure reveals a Lys residue hydrogen-bonded to PQQ at the site analogously occupied by a Lewis acidic cation in ADH. Accordingly, we prepared K142A- and K142D-PqqT variants to assess the relevance of this site toward metal binding. Isothermal titration calorimetry experiments and titrations monitored by UV-Vis absorption and emission spectroscopies support that K142D-PqqT binds tightly (Kd = 0.6 ± 0.2 μM) to La3+ in the presence of bound PQQ and produces spectral signatures consistent with those of ADH enzymes. These spectral signatures are not observed for WT- or K142A-variants or upon addition of Ca2+ to PQQ ⸦ K142D-PqqT. Addition of benzyl alcohol to La3+-bound PQQ ⸦ K142D-PqqT (but not Ca2+-bound PQQ ⸦ K142D-PqqT, or La3+-bound PQQ ⸦ WT-PqqT) produces spectroscopic changes associated with PQQ reduction, and chemical trapping experiments reveal the production of benzaldehyde, supporting ADH activity. By creating a metal binding site that mimics native ADH enzymes, we present a rare earth-dependent artificial metalloenzyme primed for future mechanistic, biocatalytic, and biosensing applications.

Effects of Clay Nanosheets on the Photostability of Cationic Porphyrin.

The photodecomposition behavior of cationic porphyrin ZnTMAP4+ (zinc tetrakis-(N,N,N-trimethylanilinium-4-yl) porphyrin) in water and complexed with clay nanosheets was investigated by light irradiation to the Soret band of ZnTMAP4+. The decomposition of ZnTMAP4+ was observed by UV-visible absorption spectroscopy. While the decomposition quantum yield (ϕdec) was 3.4 × 10-4 in water, that was 9.4 × 10-7 on the exfoliated clay nanosheets. It was revealed that the photostability of ZnTMAP4+ was stabilized by the complex formation with clay. When ZnTMAP4+ was intercalated between the stacked clay nanosheets, ϕdec was further decreased to 4.9 × 10-7. The photostability increased by 361 times and 693 times for the exfoliated and stacked state, respectively. These results indicate that the flat clay surface has the potential to control intra- and intermolecular photochemical reactions.

A Polymethionine Nanoparticle Fluorescent Probe for Sensitive Detection of Naringin and Naringenin.

In this work, we demonstrated a novel, sensitive and effective fluorescent naringin (NRG) and naringenin (NRGe) detection method using polymethionine nanoparticles (PMNPs) as a fluorescent nanoprobe. The PMNPs were first synthesized by autopolymerization of methionine at 90 °C when trace copper ions existed. The as-prepared PMNPs were thoroughly characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), gel permeation chromatograph (GPC), nuclear magnetic resonance spectroscopy (NMR), transient and steady-state fluorescence and UV-Vis absorption spectroscopy. The quenching mechanism was attributed to the inner filter effect (IFE). Moreover, the developed assay was used successfully to detect NRG and NRGe in real samples of citrus fruits, illustrating that this detection method has great potential application in the field of citrus fruits analysis.

An inclusive comparison regarding aggregation of surface active ionic liquid and conventional surfactant with a cationic dye Acridine Red exposed in view of spectroscopic and theoretical study

The investigation was conducted on the interaction of acridine red (AR) with sodium dodecyl sulfate (SDS) and 1-butyl-3-methyl imidazolium octyl sulfate (BMImOS) in both premicellar and post micellar concentrations. The interaction between AR and room temperature ionic liquid (RTIL) 1-butyl-3-methyl imidazolium bromide (BMImBr) was studied to understand the effect of imidazolium cation on micellization. Spectroscopic experiments, such as UV–visible absorption spectroscopy, steady-state fluorescence spectroscopy, time-resolved fluorescence spectroscopy, and dynamic light scattering, have been introduced. Various important parameters like spectral shifts, anisotropy, and aggregation number have been determined spectroscopically. However, a fresh insight into density functional theory calculations has also been provided. The observed results have been explained in terms of the aggregation behavior of the amphiphiles. A prominent redshift accompanied by a change in intensity is observed in the presence of surfactant and SAIL. However, in the case of BMImBr, no such spectral shift has been observed; only a decrease in spectral intensity highlights the quenching ability of the imidazolium cation. Average lifetime also provides some additional information regarding the difference in the formation of aggregates by SDS and BMImOS, which is further established from particle size density obtained from DLS. The salt like role of 1-butyl-3-methyl imidazolium cation also has been logically explained by anisotropy measurement and the determination of aggregation number. Using Gauss View 5.0 and Gaussian 09 package, the energy of optimization of each set of amphiphiles along with dye has been determined to follow the interaction at the molecular level. TDDFT calculations have also been performed to determine the structure of HOMO and LUMO.

Functionalizing Thiosemicarbazones for Covalent Conjugation.

Thiosemicarbazones (TSCs) with their modular character (thiosemicarbazides + carbonyl compound) allow broad variation of up to four substituents on the main R1R2C=N(1)-NH-C(S)-N(4)R3R4 core and are thus interesting tools for the formation of conjugates or the functionalization of nanoparticles (NPs). In this work, di-2-pyridyl ketone was introduced for the coordination of metals and 9-anthraldehyde for luminescence as R1 and R2 to TSCs. R3 and R4 substituents were varied for the formation of conjugates. Amino acids were introduced at the N4 position to produce [R1R2TSC-spacer-amino acid] conjugates. Further, functions such as phosphonic acid (R-P(O)(OH)2), D-glucose, o-hydroquinone, OH, and thiol (SH) were introduced at the N4 position producing [R1R2TSC-spacer-anchor group] conjugates for direct NP anchoring. Phenyl, cyclohexyl, benzyl, ethyl and methyl were used as spacer units. Both phenyl phosphonic acid TSC derivatives were bound on TiO2 NPs as a first example of direct NP anchoring. [R1R2TSC-spacer-end group] conjugates including OH, S-Bn (Bn = benzyl), NH-Boc (Boc = tert-butyloxycarbonyl), COOtBu, C≡CH, or N3 end groups were synthesized for potential covalent binding to functional molecules or functionalized NPs through amide, ester, or triazole functions. The synthesis of the thiosemicarbazides H2NNH-C(S)-NR3R4 starting from amines, including amino acids, SCCl2 or CS2, and hydrazine and their condensation with dipyridyl ketone and anthraldehyde led to 34 new TSC derivatives. They were synthesized in up to six steps with overall yields ranging from 10 to 85% and were characterized by a combination of nuclear magnetic resonance spectroscopy and mass spectrometry. UV-vis absorption and photoluminescence spectroscopy allowed us to easily trace the dipyridyl imine and anthracene chromophores.

Solvent effect on the excited state photophysics of Imiquimod: A DFT/TD-DFT and spectroscopic study

Solvation plays an important role in chemistry and biology. The role of the solvent is crucial in any chemical processes such as tautomerization that controls the structure and function of biomolecules. The current study aims to explore how different solvent medium affects the tautomeric forms of an antitumor drug, Imiquimod (IMQ). We have used several spectroscopical methods, including UV–Vis absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy, and quantum mechanical (QM) calculations. Our results revealed that solvent, indeed, plays a significant role in the modulation of the photophysics of the drug. IMQ has three emission bands in protic and aprotic solvents and two bands in non-polar medium associated with different forms of the drug. Using time-resolved technique, and comparing with the predicted lifetimes from QM calculations, we succeed to assign these three forms as cation, tautomer and neutral of IMQ with 1.6 ns, 2.0 ns and 4.0 ns lifetime values, respectively. Since IMQ is a nucleobase analogue and one of the most effective medications for skin tumors; these findings about which specie of IMQ is present in a given medium, and beyond, how the medium alters the photophysics of the molecule may provide deeper insights into its structure and function.

Entrance channels to coproheme in coproporphyrin ferrochelatase probed by exogenous imidazole binding

Iron insertion into porphyrins is an essential step in heme biosynthesis. In the coproporphyrin-dependent pathway, specific to monoderm bacteria, this reaction is catalyzed by the monomeric enzyme coproporphyrin ferrochelatase. In addition to the mechanistic details of the metalation of the porphyrin, the identification of the substrate access channel for ferrous iron to the active site is important to fully understand this enzymatic system. In fact, whether the iron reaches the active site from the distal or the proximal porphyrin side is still under debate. In this study we have thoroughly addressed this question in Listeria monocytogenes coproporphyrin ferrochelatase by X-ray crystallography, steady-state and pre-steady-state imidazole ligand binding studies, together with a detailed spectroscopic characterization using resonance Raman and UV–vis absorption spectroscopies in solution. Analysis of the X-ray structures of coproporphyrin ferrochelatase-coproporphyrin III crystals soaked with ferrous iron shows that iron is present on both sides of the porphyrin. The kinetic and spectroscopic study of imidazole binding to coproporphyrin ferrochelatase‑iron coproporphyrin III clearly indicates the presence of two possible binding sites in this monomeric enzyme that influence each other, which is confirmed by the observed cooperativity at steady-state and a biphasic behavior in the pre-steady-state experiments. The current results are discussed in the context of the entire heme biosynthetic pathway and pave the way for future studies focusing on protein-protein interactions.

Mussel shell-derived biogenic hydroxyapatite as reinforcement on chitosan-loaded gentamicin composite for antibacterial activity and bone regeneration

In this study, hydroxyapatite (HAp) was synthesized from natural biowaste materials, specifically mussel shells, and combined with chitosan (CS) and gentamicin sulfate antibiotic (GA) using an in-situ method. The resulting composite material, designated HAp/CS-GA, has its physicochemical and structural properties characterized by Fourier transform infrared spectroscopy (FTIR) analysis. The structure was confirmed by X-ray diffraction (XRD) analysis. Additionally, field emission scanning electron microscopy (FE-SEM) equipped with the energy dispersive X-ray spectroscopic (EDX) technique was used to determine the surface topography and main components. The composite of HAp/CS-GA was analyzed using a drug release profile by UV–visible spectroscopy (UV–Vis). The fabricated composites antimicrobial behavior was examined against bone infection-causing Gram-positive and Gram-negative bacteria, showing potential activity against Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus compared to Escherichia coli, respectively. Simultaneously, the cytotoxicity of the composite was evaluated by MTT assay using an MG-63 osteoblast-like cell line that exhibited no toxicity in the prepared composite. After a 24 h incubation period, the MG-63 cells on the HAp/CS-GA composite showed good proliferation, according to Hoechst 33258 fluorescence staining results. The results suggested that the composite had excellent biocompatibility and antibacterial activity and enhanced the osteoblast cell proliferation. Therefore, the designed HAp/CS-GA composite would be a promising candidate for bone tissue engineering.

Facile one-step synthesis and characterization of MnO nanoneedles and their application in solar photocatalysis

Manganese oxide (MnO) colloidal nanoneedles have been successfully synthesized by a facile one-step method based on the alkaline reaction of the precursor manganese acetate salt and excess sodium hydroxide. X-ray diffraction and FT-IR spectroscopy confirmed the synthesized MnO nanoneedles phase and structure. The optical properties of synthesized MnO nanoneedles were studied by UV–Vis absorption spectroscopy. Optical particle size and band gap of synthesized MnO colloidal nanoneedles were calculated. HR-TEM/SEM images and EDX allow us to determined particle shape and size. The photocatalytic activity of the MnO nanoneedles was evaluated using the Congo red azo dye in an aqueous solution under solar light irradiation. The results showed that nanoneedles, compared with commercial ZnO nanoparticles, exhibited high photocatalytic activity. The photocatalytic studies also showed that various parameters such as band gap, size, shape, and rate constant velocity remarkably affected the remotion rate of Congo red azo dye.

Photopolymerization initiated by p-diethylene glycol monomethyl ether cinnamyl formamide-based disulfide under 455 nm LED with minimized volume shrinkage

This study introduces a novel p-diethylene glycol monomethyl ether cinnamyl formamide-based disulfide monomer, N,N′-(disulfanediylbis(2,1-phenylene)) bis(4-(4-(2-(2-methoxyethoxy)ethoxy) phenyl)-2-oxobut-3-enamide) (Mp-BSCF), designed to reduce the volume shrinkage of photosensitive resins and initiate monomer polymerization under 455 nm LED light irradiation. The photochemical properties and photoinitiation efficiency of Mp-BSCF are systematically investigated using UV–vis absorption spectroscopy, electron paramagnetic resonance (EPR) and real-time infrared spectroscopy. Although its weak absorption around 455 nm, Mp-BSCF can generate arylthiyl radicals under 455 nm LED irradiation, and then effectively initiate the polymerization of triethylene glycol dimethacrylate (TEGDMA)/A glycerolate dimethacrylate (Bis-GMA) system. Increasing Mp-BSCF addition enhances the final double bond conversion and maximum polymerization rate of the TEGDMA/Bis-GMA system, reaching up to 82.0 % and 2.02 % s−1, respectively. Notably, Mp-BSCF significantly reduces the volume shrinkage of the photopolymerization system, with the addition of 10 % Mp-BSCF resulting in a 50 % reduction compared to the control system. This reduction is attributed to the dynamic reversible nature of the SS bond “breaking-recovery” and the intermolecular hydrogen bond interaction. Additionally, Mp-BSCF improves the thermal stability, friction resistance, and hardness of the TEGDMA/Bis-GMA photopolymerization system.

Salinity effect on corrosion inhibition of 2-mercaptopyrimidine as an inhibitor in CO2-containing solution

In this work, the effects of Cl-, Ca2+, and Mg2+ on the corrosion inhibition performance of 2-mercaptopyrimidine (2-MP) were investigated. The analysis reveals a marked reduction in the inhibition efficiency of 2-MP, from 91.24 % to 76.29 %, as the NaCl content in the solution rises from 1 wt% to 20 wt%. UV–visible absorption spectroscopy and quartz crystal microbalance measurements indicate that the desorption of 2-MP worsens with an increasing content of corrosive ions. Molecular dynamics simulations reveal the inhibitor desorption mechanism. This work enhances understanding of ion effects on corrosion inhibition and film degradation in high salinity environments.

Affinity Constants of Bovine Serum Albumin for 5 nm Gold Nanoparticles (AuNPs) with ω-Functionalized Thiol Monolayers Determined by Fluorescence Spectroscopy.

A detailed understanding of the binding of serum proteins to small (dcore <10 nm) nanoparticles (NPs) is essential for the mediation of protein corona formation in next generation nanotherapeutics. While a number of studies have investigated the details of protein adsorption on large functionalized NPs, small NPs (with a particle surface area comparable in size to the protein) have not received extensive study. This study determined the affinity constant (Ka) of BSA when binding to three different functionalized 5 nm gold nanoparticles (AuNPs). AuNPs were synthesized using three ω-functionalized thiols (mercaptoethoxy-ethoxy-ethanol (MEEE), mercaptohexanoic acid (MHA), and mercaptopentyltrimethylammonium chloride (MPTMA)), giving rise to particles with three different surface charges. The binding affinity of bovine serum albumin (BSA) to the different AuNP surfaces was investigated using UV-visible absorbance spectroscopy, dynamic light scattering (DLS), and fluorescence quenching titrations. Fluorescence titrations indicated that the affinity of BSA was actually highest for small AuNPs with a negative surface charge (MHA-AuNPs). Interestingly, the positively charged MPTMA-AuNPs showed the lowest Ka for BSA, indicating that electrostatic interactions are likely not the primary driving force in binding of BSA to these small AuNPs. Ka values at 25 °C for MHA, MEEE, and MPTMA-AuNPs were 5.2 ± 0.2 × 107, 3.7 ± 0.2 × 107, and 3.3 ± 0.16 × 107 M-1 in water, respectively. Fluorescence quenching titrations performed in 100 mM NaCl resulted in lower Ka values for the charged AuNPs, while the Ka value for the MEEE-AuNPs remained unchanged. Measurement of the hydrodynamic diameter (Dh) by dynamic light scattering (DLS) suggests that adsorption of 1-2 BSA molecules is sufficient to saturate the AuNP surface. DLS and negative-stain TEM images indicate that, despite the lower observed Ka values, the binding of MPTMA-AuNPs to BSA likely induces significant protein misfolding and may lead to extensive BSA aggregation at specific BSA:AuNP molar ratios.

Supramolecular assemblies of amphiphilic donor-acceptor Stenhouse adducts as macroscopic soft scaffolds.

In the design of photoharvesting and photoresponsive supramolecular systems in aqueous medium, the fabrication of amphiphilic photoswitches enables a noninvasive functional response through photoirradiation. Although most aqueous supramolecular assemblies are driven by high-energy and biodamaging UV light, we have previously reported a design of amphiphilic donor-acceptor Stenhouse adducts (DASAs) controlled by white light. Herein, we present a series of DASA amphiphiles (DAs) with minor structural modifications on the alkyl linker chain length connecting the DASA motif with the hydrophilic moiety. The excellent photoswitchability in organic medium and the photoresponsiveness in aqueous medium, driven by visible light, were investigated by UV-vis absorption spectroscopy. The assembled supramolecular nanostructures were confirmed by electron microscopy, while the supramolecular packing was revealed by X-ray diffraction analysis. Upon visible-light irradiation, significant transformations of the DA geometry enabled transformations of the supramolecular assemblies on a microscopic scale, subsequently disassembling macroscopic soft scaffolds of DAs. The current work shows promising use for the fabrication of visible-light-controlled macroscopic scaffolds, offering the next generation of biomedical materials with visible-light-controlled microenvironments and future soft-robotic systems.

Investigation of amorphous-SiC thin film deposition by RF magnetron sputtering for optical applications

Silicon carbide (SiC) is a rapidly emerging material for photonic applications, thanks to its exceptional optical properties. To be used as a waveguide, SiC thin films must be deposited directly on silica at low temperature. Amorphous SiC films were deposited by RF magnetron sputtering using a single source of high-purity polycrystalline SiC. A systematic study of the chemical, structural and optical properties of the films was carried out, using a combination of XRD, XPS, SIMS, spectroscopic ellipsometry, Raman spectroscopy and UV–Vis absorption spectroscopy. The aim was to link deposition conditions to film properties. By exploring a three-parameter space (RF power, substrate temperature, pressure), we have demonstrated that RF power is the main parameter which controls the entire deposition process and film properties. By simply adjusting the RF plasma power between 150 and 450 W, it is possible to adjust the refractive index at a wavelength of 1.5 μm in the range 2.50–2.75 and vary the bandgap from 2.5 to 1.7 eV. This is attributed to a slight variation in film composition, particularly in terms of Si/C ratio and C–C bond concentration.

Catalytic Asymmetric Dearomative [2 + 2] Photocycloaddition/Ring-Expansion Sequence of Indoles with Diversified Alkenes.

Developing novel strategies for catalytic asymmetric dearomatization (CADA) reactions is highly valuable. Visible light-mediated photocatalysis is demonstrated to be a powerful tool to activate aromatic compounds for further synthetic transformations. Herein, a catalytic asymmetric dearomative [2 + 2] photocycloaddition/ring-expansion sequence of indoles with simple alkenes was reported, providing a facile access to enantioenriched cyclopenta[b]indoles with good to high yields and enantioselectivities by means of chiral lanthanide photocatalysis. This protocol exhibited a broad substrate scope and good functional group tolerance, as well as potential applications in the synthesis of bioactive molecules. Mechanistic studies, including control experiments, UV-vis absorption spectroscopy, emission spectroscopy, and DFT calculations, were carried out, shedding insights into the reaction mechanism and the origin of enantioselectivity.

Biogenic synthesis and characterization of gold nanoparticles using transformed mesophilic Escherichia coli BL21 and thermophilic Thermus thermophilus HB27

Gold nanoparticles have numerous applications, many of which are notable in industries. The biosynthesis of gold nanoparticles offers an easy, effective, green, and eco-friendly approach. In organisms capable of synthesizing nanoparticles, enzymes and proteins are responsible for the structural and functional modifications that lead to their formation. These include ABC transporter, peptide-binding proteins, which are dependent on abiotic parameters. This study uses the purified ABC transporter, peptide-binding protein transformed from Thermus scotoductus SA-01 and expressed in mesophilic Escherichia coli BL21 and thermophilic Thermus thermophilus HB27 hosts for the biosynthesis of gold nanoparticles at different concentrations, temperatures, and pH values. Gold nanoparticle formation was evaluated with a range of gold (III) concentrations (0–10 mM), incubated at temperatures ranging from 30–85 ºC and pH levels from 3.6–9.0. Transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDX), and UV–Vis absorption spectroscopy were used to characterise the formation of nanoparticles. In all of the protein reactions, UV–Vis absorbance peaks at approximately 520–560 nm confirmed the formation of gold nanoparticles. Optimum nanoparticle synthesis was observed at pH values ranging from 5.5 to 9.0, gold (III) solution (HAuCl4) concentrations from 0.5–2.0 mM, and a maximum temperature of 65ºC in the mesophilic host and 85ºC in the thermophilic host, indicating the significance of temperature in both hosts for the expression and bioactivity of the purified ABC transporter protein. However, the biogenic formation of gold nanoparticles using E. coli and T. thermophilus hosts was not monodispersed, suggesting a necessity for further development of the procedure.

Spray-Coated Transition Metal Dichalcogenides as Hole Transport Layers in Inverted NFA-Based Organic Photovoltaics with Enhanced Stability under Solar and Artificial Light

In this study, we explored the potential of exfoliated transition metal dichalcogenides (TMDs) as innovative spray-coated hole transport layers (HTLs) in organic photovoltaics (OPVs), addressing the need for efficient and stable materials in solar cell technology. This research was motivated by the need for alternative HTLs that can offer enhanced performance under varying lighting conditions, particularly in indoor environments. Employing UV-visible absorption and Raman spectroscopy, we characterized the optical properties of MoS2, MoSe2, WS2, and WSe2, confirming their distinct excitonic transitions and direct bandgap features. The nanocrystalline nature of these TMDs, revealed through XRD patterns and crystallite size estimation using the Scherrer method, significantly contributes to their enhanced physical properties and operational efficiency as HTLs in OPVs. These TMDs were then integrated into OPV devices and evaluated under standard solar and indoor lighting conditions, to assess their effectiveness as HTLs. The results demonstrated that MoS2, in particular, displayed remarkable performance, rivalling traditional HTL materials like MoO3. It maintained high power conversion efficiency across a spectrum of light intensities, illustrating its versatility for both outdoor and indoor applications. Additionally, MoS2 showed superior stability over extended periods, suggesting its potential for long-term usage in OPVs. This study contributes significantly to the field of photovoltaic materials, presenting TMDs, especially MoS2, as promising candidates for efficient and stable OPVs in diverse lighting conditions, thereby broadening the scope of solar cell applications.