UV Vis Spectroscopy Research Articles

Enhancement-mode ZnGa2O4-based Phototransistor with high UV–visible rejection ratio grown by metalorganic chemical vapor deposition

In this study, a high-crystallinity zinc gallium oxide (ZnGa2O4) epilayer of about 80 nm thickness was successfully grown using metalorganic chemical vapor deposition. X-ray diffraction, atomic force microscopy, UV–visible spectroscopy measurements, and X-ray photoelectron spectroscopy were used to investigate the quality of the epilayer. Transmission line measurement analysis revealed the electrical properties of the ZnGa2O4 epilayer: a sheet resistance of 276 MΩ/□, a transfer length of 0.28 μm, and a specific contact resistivity of 21.63 Ω/mm2. A phototransistor made of ZnGa2O4 was designed with a channel width of 250 μm and a channel length of 20 μm. The source-drain electrodes were fabricated using a Ti/Al/Ni stacking technique. The gate dielectric comprised 30 nm thick Al2O3, and the gate contact was made of Ni. The device possessed a higher threshold voltage value of about 4.8 V and an impressive On/Off current ratio of 106. Under 240 nm UV light exposure, the phototransistor exhibited a transition from enhancement mode to depletion mode, leading to a remarkable shift in the threshold voltage from 5 V to approximately −16 V. Moreover, the responsivity and rejection ratio at 240 nm was 128.5 A/W and 105 at a gate voltage of −10 V. The study shows that an increasing thickness of the ZnGa2O4 epilayer from 80 nm to 135 nm results in a depletion mode transistor. The higher concentration of about twenty percent oxygen vacancies resulted in a longer fall time for the phototransistor. These results underscore the significant potential of ZnGa2O4 in facilitating deep UV-based detection applications.

Green synthesis and characterisation of silver nanoparticles utilising a bioflocculant obtained from Pichia kudriavzevii isolated from kombucha tea SCOBY

ABSTRACT A Pichia kudriavzevii produced bioflocculant was used in the biosynthesis of silver nanoparticles (AgNPs). The generated Ag nanoparticles were given several analytical treatments to determine their properties. These techniques included transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FT-IR), transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), thermogravimetric analysis (TGA), and UV–vis spectroscopy. The SEM scans showed particles that were smooth and nearly spherical in shape. EDX analysis showed the element silver with a percentage weight of 61.93% in addition to the elements present in the bioflocculant. Through FT-IR spectra functional groups for instance carboxyl, polyphenols, aromatics, alcohol, amine, and halo compounds were observed. The TEM picture displayed spherical particles that had a size range between 7 and 12 nm. TGA analysis revealed that AgNPs are thermally stable with over 85% mass retained at high temperatures, while the bioflocculant retained 60% weight after exposure to higher temperatures. UV–visible spectroscopy revealed an SPR band at 450 nm, while X-ray diffraction showed a crystallite size of 19 nm. Utilising bioflocculant as stabilising and coating agents in the biosynthesis of AgNPs is an ecologically safe technique that offers synthesis rates that are quicker and on par with chemical methods.

Effects of K, Rb, and Br doping on Cs3Bi2I9 perovskites: A design of experiments approach

This work presents the effect of doping with different species on the structural sites of lead-free halide perovskites, aiming to evaluate the potential of the produced materials as photoabsorbing layers in 3rd generation solar cells. Lead-free perovskite films of Cs3Sb2I9, CsCu2I3, Cs3Bi2I9, and CsPbI3 were synthesized via the spin-coating method and characterized using X-ray diffraction, scanning electron microscopy with chemical microanalysis (SEM-EDS), and Uv-Vis spectroscopy. Computational models based on Density Functional Theory (DFT) were used to simulate the structures and properties of some of the perovskites synthesized in this study, in order to validate the experimentally obtained data. The Cs3Bi2I6Br3 perovskite was subjected to modification through A-site doping with K and Rb and X-site doping with Br, with a comprehensive study on the effects of processing variables, anti-solvent quantity, and crystallization temperature using a 23 experimental design. The outcomes highlighted the critical role of the anti-solvent quantity in structure formation and electronic properties. Toluene, as an anti-solvent, produced unique morphologies not commonly reported. Computational studies were performed using Density Functional Theory (DFT) to complement the experimental findings. The optimization process revealed that Cs3Bi2I9 structures mainly constituted [CsI12] and [BrI6] clusters, with Cs–I and Bi–I average bond lengths consistent with experimental results. X-site Br doping induced slight distortion, while A-site Rb/K doping showed minimal lattice parameter changes. Notably, K-induced morphological alterations suggested potential electronic transformations. From an electronic structure perspective, Cs3Bi2I9 had a band gap of 2.07 eV, slightly increased to 2.10 eV with Br doping. Rb maintained Br-doped structure, while K significantly reduced the band gap to 1.96 eV. These computational results align well with our experimental data, showcasing the accuracy of our calculations in predicting material properties. The results confirmed that the perovskites selected through experimental design and validated by computational simulation are promising semiconductor materials for photovoltaic applications, as well as being a lead-free photoabsorbing material option.

Long-Term Stability and Efficacy of NCT Solutions.

To realize the potential for the use of N-chlorotaurine (NCT) in healthcare, a better understanding of the long-term stability of the compound in water is needed. An array of analytical procedures is required that can measure changes in NCT concentration over time and allow for the detection and identification of contaminants and likely degradation end products. We used UV-Vis and NMR spectroscopy, HPLC, and LCMS to establish the stability of NCT in solutions subjected to prolonged ambient and elevated temperatures. Stability proved to be dependent on concentration with half-lives of ~120 days and ~236 days for 1% and 0.5% solutions of NCT at ~20 °C. Regardless of initial pH, all solutions shifted toward and maintained a pH of ~8.3 at 20 °C and 40 °C. NCT at 500 µg/mL and 250 µg /mL inhibited biofilm formation by Pseudomonas aeruginosa and Staphylococcus aureus but did not disperse established biofilms. NCT exposure to the biofilms had profound effects on the viability of both bacteria, reducing live organisms by >90%. Exposure of Interleukin-6 (IL-6) to 11 µM NCT reduced the binding of IL-6 to an immobilized specific antibody by ~48%, which is 5× the amount required for HOCl to bring about the same effect in this test system. Our data demonstrate the potency of the compound as an antimicrobial agent with potential benefits in the management of infected chronic wounds and suggest that NCT may contribute to anti-inflammatory processes in vivo by direct modification of cytokine mediators.

Synthesis of Calcium Carbonate from Orange Peel Waste Extract: A Mechanistic Investigation

The present work reports the mechanism and synthesis of calcium carbonate (CaCO3) formation from orange peel, which is one of the most common agriculture waste generated throughout the globe. The zest of oranges was co-distilled with distilled water to separate the essential oil content. Further, the residue was washed twice with distilled water to get the desired extract. For the green synthesis of CaCO3, a saturated solution of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) was mixed thoroughly with orange peel extract in the 1:3 proportion. This solution was kept on magnetic stirrer while maintaining temperature at 85˚C, heated at 100˚C for 13 h which was further annealed at 300˚C, 500˚C and 700˚C. X-ray diffraction (XRD) shows the presence of calcite phase corresponding to CaCO3. Fourier transform infrared spectra (FTIR) exhibits the bands corresponding to Ca-O, C-O and vibrations of CO3-2 bonds whereas UV–Visible spectroscopy shows the optical behavior of CaCO3. The qualitative analysis of orange peel extract as well as the black-brown gel formed as a result of sol–gel synthesis method was examined using Gas Chromatography & Mass Spectrometry (GCMS). It revealed the presence of acidic groups (2,3-butanediol & 1,4-benzenediol) which led to the development of a mechanism, governing the formation of CaCO3.

Improved electrocatalytic efficiency of nitrogen-doped Nb2CTx MXene in basic electrolyte for overall water splitting

Two-dimensional MXene is demonstrating promising efficiency for the generation of oxygen (O2) and hydrogen (H2). For cost-effective water-splitting electrolysis that performs well in both Oxygen evolution reaction (OER) and Hydrogen evolution reaction (HER), the electrolyzer can effectively serve as both electrodes. In this paper, we enhanced the MXene structural properties to use it as bifunctional by following a hydrothermal route in which nitrogen is doped by using Urea. The prepared samples were characterized by utilizing XRD, Raman, SEM, EDX and UV–vis spectroscopy. An increase in d-spacing from 8.9 Å to 10.0 Å was observed after doping in pristine and EDX has confirmed the presence of nitrogen in MXene. Charge carrier mobility is enhanced by doping of nitrogen in MXene as the bandgap is reduced from 1.45 eV to 1.17 eV. The Linear Sweep Voltammetry for overall water splitting was conducted in 1 M KOH and the Nitrogen-doped Nb2CTx MXene displayed an overpotential of 370 mV (vs. RHE) at the current density of 10 mAcm−2 with a Tafel slope of 126 mV/dec where pristine MXene Nb2CTx has shown an overpotential of 439 mV with a Tafel slope of 184 mV/dec for the OER. The composite also exhibited an overpotential (vs. RHE) of 263 mV with a Tafel slope of 103 mV/dec at the current density of 10 mAcm−2 for the HER. The durability of the electrocatalyst was tested via chronoamperometry for 14 h, the undoped MXene retained 81% of current stability, whereas nitrogen-doped retained 95%. The EIS revealed the reduced charge transfer resistance for the composite material that collectively points towards advancements in the efficiency and kinetics of water-splitting reactions.

Glassy Oxides as Positive Electrode Materials for Sustainable and High Energy Density Li-Ion and Na-Ion Batteries: First Attempts to Establish Relationships between Glass Compositions, Physicochemical Characterizations and Electrochemical Properties with Machine Learning and Design of Experiments Approaches

Today, rechargeable lithium-ion batteries (LIBs) represent one of the best alternatives to reduce our dependency on fossil fuels. LIBs are using cathode materials based on polycrystalline oxides or polyanionic compounds [1]. However, their performances can be limited by their crystalline structure when other compounds suffer from metallic dissolution and irreversible phase changes during cycling [2]. To overcome these key shortcomings, implementing glasses or glass-ceramics as cathode materials is an interesting approach [3]. Glasses have a structure composed of more free volume, and, in the literature that is mainly concerning glasses containing Vanadium transition metal, the glasses can so accept a large amount of lithium [4] and easily accommodate structural changes upon lithium ions extraction/insertion [5]. Furthermore, glass production is a scalable process and can be commercially easier to implement than most of synthesis processes of conventional cathode materials.The main objective targeted is to develop high capacity positive electrodes (up to 300mAh/g) for Li-ion batteries based on glassy oxides without critical transition metals such as Cobalt and Vanadium. The ambitious target is to exceed 1000Wh/kg at the active material level and so enable energy densities of 300-350 Wh/kg at the Li-Ion cell level. Additionally, the electrochemical behavior of some alkali-free glass compositions will be evaluated in sodium-ion configuration. The major scientific objective is to correlate the most relevant physicochemical properties of glass with the corresponding electrochemical performances using machine learning approaches or design of experiment methodology. For a better understanding of involved processes, three oxides glass families are studied as promising cathode materials for sustainable and high energy density lithium batteries. These oxides are composed of: i) a glass network-forming element (Si, B, P) leading to the 3 different families, ii) a transition metal (Mn, Fe, ...) and optionally iii) an alkali (Li, Na).The influence of the nature of the transition metal and the polyanionic group corresponding to the network-forming element (PO4, BO3, SiO4) on the electrical properties of the as-prepared glasses measured at different temperatures will be presented mainly for the lithiated compounds. For microstructural characterization, several techniques were coupled such as X-Ray Diffraction (XRD), SEM-EDX, DTA/TGA, Raman, IR and UV-Vis spectroscopies, Electrochemical Impedance Spectroscopy (EIS) and chronoamperometry.Finally, the electrochemical properties in terms of specific capacity, redox potentials, first cycle capacity loss, coulombic and energetic efficiencies of these materials were investigated in coin-cells vs lithium (or sodium) metal electrode. To understand the electrochemical processes involved in these materials at room temperature, SEM-EDX, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Mossbauër Spectroscopy for iron based compounds were coupled and performed on the as-prepared glasses and on ex-situ (after cycling) materials at different electrochemical states of charge.All the generated data and measurements were analyzed by machine learning approach and tools and in some cases compared with a more classical Design of Experiments (DOE) approach. For instance, figure 1 illustrates the contour diagram of first discharge capacities in the mixture diagram of phosphate glasses based on 3 different transition metal oxides. The final goal is to establish more precisely the relationships between the different glassy oxides structures and their electrochemical performances. First results of this important work of elaboration, characterization and data analysis will be presented here. This new study will bring significant elements to optimize both the glass composition and its elaboration conditions to obtain high performance cathode materials without critical materials.[1] Nitta, N. et al., Li-ion battery materials: present and future. Materials Today 18, 252–264 (2015).[2] Tesfamhret, Y. et al., On the Manganese Dissolution Process from LiMn2O4 Cathode Materials. ChemElectroChem 8, 1516–1523 (2021).[3] K. Kercher et al., « Mixed polyanion glass cathodes: Glass-state conversion reactions », J. Electrochem. Soc., vol. 163, no 2, p. A131-A137, 2016, doi: 10.1149/2.0381602jes [4] Afyon, S. et al., New High Capacity Cathode Materials for Rechargeable Li-ion Batteries. Scientific Reports 4, 7113 (2015).[5] Kindle, M. et al., Alternatives to Cobalt. ACS Sustainable Chemistry Engineering 9, 629–638 (2021). Figure 1

Effect of Heterojunction Dynamics on Charge Transfer Mechanism in Type-II ZnS/MoS2 Nanocomposite

The development of novel nanocomposites holds immense potential for various applications in optoelectronics, catalysis, energy storage systems and photovoltaic applications. In this manuscript, the synthesis and comprehensive characterization of type-II ZnS/MoS2 nanocomposite synthesized by hydrothermal roue are reported. The synthesized nanocomposite was characterized by numerous analytical techniques to analyse its structural, morphological, optical, and electrochemical properties. XRD analysis revealed the presence of both ZnS and MoS2 phases in the nanocomposite, validating its successful formation. UV-visible spectroscopy (UV) was utilized to study its optical properties which revealed a band gap of 3.2 eV. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging demonstrated the presence of large ZnS sheets with smaller nanoparticles of MoS2 dispersed over the surface, indicating the hierarchical structure of the composites. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to evaluate the electrochemical performance and charge transfer dynamics of the nanocomposite. These techniques facilitated the investigation of their suitability for solar cells. CV analysis displayed prominent reduction peaks, indicating the presence of active electrochemical sites in the nanocomposites. Furthermore, it revealed diffusion-controlled behaviour which indicates the potential of the nanocomposite for efficient solar cells. EIS analysis revealed the presence of Warburg diffusion in the Nyquist plot which indicates the possibility of efficient charge transport and ion diffusion within the nanocomposites. This shows the suitability of nanocomposite material for solar cell applications.

Probing the Photocatalytic Pathways of Iron (III) Protoporphyrin IX-Functionalized TiO2: A Study on Oxo-Iron(IV) Porphyrin π-Cation Radical Formation

The presence of phenolic compounds in aquatic environments, resulting from industrial activities such as coal processing and petroleum refining, poses significant concerns due to their adverse effects on water safety, even at minimal concentrations. These compounds present challenges during remediation using traditional techniques such as solvent extraction, biological treatments or chemical oxidations. In response to these challenges, Advanced Oxidation Processes have emerged as a promising solution, with methods like heterogeneous photocatalysis, ozonation, sonification and so on, showing potential for degrading persistent organic molecules[1] [2].Titanium dioxide (TiO2) has gained importance in environmental remediation due to its ease of synthesis, cost-effectiveness, and versatility. Its unique properties, including exceptional chemical stability and non-toxic nature, make it suitable for water purification among other applications. Several studies aim to extend responsiveness of TiO2 beyond UV-A radiation, seeking to harness the wider and more prevalent visible light spectrum. This endeavor is driven by the desire to optimize the utilization of solar energy in various applications. To enhance TiO2 absorption of visible light, alternative chromophores, particularly porphyrins, are employed. Porphyrins, known for their extended lifespan in the excited state and efficient photoabsorption in the visible region, serve as excellent sensitizers when combined with TiO2, enabling effective charge separation[3].This study explores the activity enhancement of TiO2 catalyst by incorporating iron (III) protoporphyrin IX (FePPIX). The objective is to understand how hydrogen peroxide (H2O2), generated through photocatalysis on the TiO2 surface, influences the formation of oxo-iron(IV) porphyrin π-cation radicals. These radicals specifically form through the interaction with iron porphyrin attached to TiO2, offering a unique pathway for efficiently degrading phenolic compounds, as is proposed in Figure 1. The investigation underscores the significance of TiO2 surface sensitization and the simultaneous emergence of porphyrin radicals in shaping the dynamics of the photocatalytic process.We fabricated TiO2 nanotube sheets (TiO2-NTs) by anodizing metallic titanium sheets and then functionalized them with FePPIX. The process involved degreasing, chemical cleaning, anodization, exfoliation, and thermal treatment for anatase phase formation. Additionally, we utilized anatase-TiO2 nanoparticles. We carried out functionalization, which included ozone exposure, UV-C light treatment, and immersion in an acidic FePPIX solution in methanol, reacting with the hydroxylated surface induced by ozone treatment. After functionalization, we carefully washed away the excess iron protoporphyrin with methanol, and we air-dried the materials at room temperature. We comprehensively characterized the nanomaterials using diverse analytical techniques, including Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR), Raman and UV-Vis spectroscopies, and ESR analyses. We further investigated the photogeneration of hydroxyl radicals (•OH) on FePPIX-functionalized and non-functionalized TiO2 nanotube arrays through the photobleaching of N-N-dimethyl-4-nitrosoaniline. Additionally, we studied phenol degradation under UV irradiation. Our findings provide detailed insights into the physical and chemical properties, morphology, and composition of the fabricated nanomaterials.The SEM images reveal well-defined nanotube arrays, underscoring the efficacy of the fabrication technique. Energy-Dispersive X-ray Spectroscopy mapping further solidifies this observation, confirming a uniform distribution of iron in functionalized nanoparticles and supporting the success of functionalization. FTIR and Raman spectroscopy provide detailed insights into the presence of functional groups and vibrational modes, establishing the success of the functionalization process as well. Tauc plots show a narrowed energy gap in functionalized nanotubes, hinting at their potential for visible light activity.Photocatalytic assessments uncover diminished behavior, with lower •OH generation rates observed under UV-A light for functionalized nanotubes but notable activity under visible light, aligning with the reduced band gap energy. Furthermore, enhanced phenol degradation on functionalized nanotubes under UV-A light, potentially associated with compound I, introduces complexity to the photocatalytic pathways. The application of ESR study confirms the presence of paramagnetic species, such as [PPFeIV=O]+•, thereby highlighting the influence of protoporphyrin on the TiO2 surface and its integral role in photocatalysis.In summary, the study confirms successful TiO2 nanomaterial functionalization with FePPIX, promising applications in environmental remediation. Analyses validate binding with hydroxyl groups, Tauc plots indicate enhanced photocatalytic activity under visible light, and ESR analysis suggests the presence of paramagnetic species that could improved phenol degradation. Further investigation is needed for a comprehensive understanding. Overall, these findings hold potential for efficient and sustainable wastewater treatment.[1] S. Rasalingam, R. Peng, R. T. Koodali, J. Nanomater. 2014, 617405.[2] Y. Deng, R. Zhao, Curr Pollut. Rep 2015, 1, 167.[3] C. C. Huang, P.S. Parasuraman, H. C. Tsai, J. J. Jhu, T. Imae, RSC Adv. 2014, 4, 6540. Figure 1

(Invited) 1. Chalcogen-Substituted PC61/71BX Derivatives in Perovskite Solar Cells

Taking into account the outstanding electronic and physical properties of fullerenes, novel functionalized fullerenes are synthesized, with adapted structures aimed at improving the efficiency and stability of inverted PSC architectures.By means of [2+1] cycloadditions, chalcogen-substituted fullerene C60 and C70 derivatives were successfully synthesized using tosylhydrazone derivatives containing thiophene, selenophene, and furan. These derivatives were based on the chemical structures of PC71BM and PC61BM, resulting in the preparation of PC71BX: T70, S70, and F70, and PC61BX: T60, S60 and F60. The chemical structure of the synthesized mono-adducts PC61/71BM was confirmed through 1H and 13C NMR spectroscopy, MALDI-TOF mass spectroscopy, UV-Vis spectroscopy, and cyclic voltammetry.Inverted PSCs were fabricated employing the synthesized chalcogen-substituted PC61/71BM as dopant-free ETLs. In the current presentation we will comment on the data obtained in this photovoltaic study and the explanation for the different behaviour of these PC61BX and PC71BX materials. Figure 1

Title: Investigation of Kinetically Favorable Chromium Speciation Distribution for Iron Chromium Redox Flow Batteries

Chromium is a promising active material for redox flow battery (RFB) electrolytes due to its low cost and reduction potential very near the negative limit of the electrochemical window of water. However, many challenges exist with the performance of the Cr3+/2+, most notably sluggish electron-transfer kinetics and parasitic hydrogen evolution during the charge cycle. This presentation will focus on our recent efforts to overcome these challenges by understanding the interplay between electrolyte composition, speciation, and electron-transfer kinetics for the aqueous Cr3+/2+ redox couple.Among the earliest published work on flow batteries was a program based at NASA introducing the iron chromium redox flow battery (ICRFB) [1,2]. These studies were valuable in demonstrating both the promise and the complications of chromium for flow battery electrolytes. The NASA team went to great lengths to enhance chromium redox kinetics and suppress the hydrogen evolution via extensive modification of the carbon negative electrode with Au, Pb, and Bi additives. The present study is based on a key observation from this early work that the electron-transfer rates for Cr-chloride complexes depend strongly on the inner-sphere coordination environment, and specifically the number of chloride ions directly bound to the Cr center.Extensive prior studies from the inorganic coordination chemistry literature further demonstrate that Cr(III) chloride complexes undergo slow equilibration in aqueous solutions to form distributions of four species where the coordination environment around the metal center can be described generally as [CrClx(H2O)6-x](3-x)+ with 0 < x < 3 [3,4]. Each of these species yields a distinct optical absorption signature, enabling quantification of the composition with UV-VIS spectroscopy. Our overarching hypothesis, based on the early NASA work, was that increased chloride coordination (i.e., higher values of x in CrClx(H2O)6-x) would yield enhanced electron-transfer kinetics by reducing inner-sphere reorganization barriers associated with aquo ligands, or by enhancing catalytic mechanisms mediated by chloride surface adsorbates. Thus, we measured optical absorbance and electrochemical reversibility for Cr(III) chloride solutions with HCl, NaCl, and LiCl supporting electrolytes over a range of total chloride concentration from 0.1 to ~10 mol/L.Representative results are summarized in Figure 1 for 0.1 M CrCl3 in aqueous LiCl. Notably, at Au electrodes the reversibility of the Cr3+/2+ redox feature increases dramatically as chloride concentration increases above 5 mol/L (Figure 1a). This shift in reversibility is broadly correlated with UV-VIS results (Figure 1b) demonstrating that the primary Cr(III) species present initially remains the predominant species in the aqueous environment for high concentrations of chloride over time, but the predominant species shifts significantly at lower concentrations of LiCl. Ongoing work, which will be discussed in this presentation, is focused on full quantification of the relationship between speciation and electron-transfer kinetics as well as performance properties for ICRFBs with a range of supporting electrolyte concentrations. We anticipate that understanding the most kinetically favorable speciation distribution will allow us to develop improved electrolytes for functional ICRFBs.

Electrochemical and Spectroscopic Investigations of Bismuth(III) Pharmaceuticals with L-Glutathione

Due to the importance of L-cysteine in the human system, the interaction of metals with this amino acid are worthy of investigation by various methods. In this laboratory1, we have investigated the interaction of bismuth(III) compounds with L-cysteine by both cyclic voltammetry and UV-VIS spectroscopy in an attempt to understand the role of bismuth in treating gastrointestinal maladies.2 The addition of bismuth(III) compounds to solutions of L-cysteine causes a negative potential shift for bismuth(III) reduction as an indication of complex formation between bismuth(III) and L-cysteine. This interaction is also evident by the appearance of a UV-VIS spectroscopic band at 340 nm (Bi-sulfur bond). Even at low pH values (pH 1.0), electrochemical studies show evidence of some kind of interaction even when there is no 340 nm band. These investigations have been conducted at pH 1.00 and 3.00 to simulate conditions in the human stomach and at pH 7.40 MOPS [(3-N-morpholino)propanesulfonic acid] to simulate general physiological conditions, in particular the intestinal tract. Recent work has involved extension of this work to L-glutathione, a tripeptide incorporating L-cysteine, under similar conditions. As might be expected, these interactions are considerably more complicated than those involving L-cysteine. As an example, there is a considerable positive potential shift for the reduction of bismuth(III) citrate in the presence of L-glutathione on the first and second voltammetric sweeps at gold and glassy carbon electrodes. This behavior evidently reflects the rather long (several seconds) time required for the re-formation of the bismuth complex with L-glutathione after its reductive ligand (L-glutathione) loss during bismuth(III) reduction on the first sweep. In addition, there is evidence of a film buildup on the electrode surface as observed by peak current increases during multiple potential sweeps. These observations are planned for inclusion in this symposium presentation.References T. Cheek and D. Peña, J. Electrochem. Soc., 167, 155522 (2020)Li, R. Wang, and H. Sun, Acc. Chem. Res., 52, 216 (2019).

Electrochemical Detection of Neutrophil Gelatinase-Associated Lipocalin (NGAL) in Simulated Urine Using Au@Si/Ni-Porphyrin Nanocomposite for the Prediction of Kidney Injury

Kidney Injury is multifactorial out of which ureteropelvic junction obstruction is one of the major causes of concern. There are a multitude of methods for monitoring the deterioration of renal function like serum creatinine levels, ultrasound scans, renograms, and nuclear scans like radiolabelled MAG3 and DMSA which require repeat evaluation or sedation during the process. Many of the biomarkers utilized for the assessment of kidney injury are expressed at the later stages. Urine NGAL is a promising biomarker for risk stratification which is reported to be expressed at the onset of ureteropelvic junction obstruction (UPJO) and is a gold standard for the estimation of tubular injury. Urinary NGAL is also reported to be a specific marker for the prediction of hydronephrosis in children who require surgical intervention. The kidney injury cut-off for NGAL in urine is 185ng/mL and 48 ng/mL in the adult and pediatric population groups respectively. Electrochemical detection of NGAL in patient urine is a fast, reliable, non-invasive, accurate, and cost-effective method for monitoring kidney health to segregate patient groups that require surgical intervention.In this study, an electrochemical sensor was designed with Au(150nm) electrodes fabricated using thermal evaporation on a flexible substrate (PET; 250μm) by using Cr(20nm) as the seed layer. The electrode was immobilized with Au@Si core-shell decorated on Ni-porphyrin nanosheets functionalized with anti-NGAL using covalent chemistry. The nanocomposite was synthesized through a bottom-up approach where the Ni-tetrakis(4-carboxyphenyl) porphyrin nanosheets were synthesized using the solvothermal method in an organic phase (DMF) followed by purification and suspension in ethanol medium. The Si nanocrystals were synthesized in a citrate medium with APTMS as the precursor followed by purification via dialysis. The purified Si nanocrystals (60ppm) and Ni-porphyrin nanosheets (880ppm) were treated in chloroauric acid (0.25mM) and the reducing agent trisodium citrate (34mM) to form Au shell. The physicochemical and electronic properties of the synthesized nanocomposite were evaluated through XRD, XPS, microscopic analysis(TEM, SEM), AFM, UV-Vis, FTIR, and Raman spectroscopy. The resultant nanocomposite was purified and linked to anti-NGAL (100μg/mL) through EDC (0.4M)/NHS (0.1M) chemistry. The antibody-nanocomposite was immobilized on the fabricated Au electrodes (working electrode surface area: 0.35mm2) through BSA(1.2mM)/glutaraldehyde (2.5% v/v) crosslinking. The quantitative electrochemical estimation of NGAL antigen spiked in 0.1M PBS (pH=7.2±0.2) and simulated urine was performed using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The shelf life of the fabricated sensors was evaluated for 30 days (stored at 4˚ C until use) over the concentration range of 0-5000 ng/mL. The amount of test solution required per measurement for the miniaturized electrodes was 6μL.The sensing mechanism of the electrochemical platform was established through CV by varying the scan rate (0.05 V/s - 2.5 V/s) for 500ng/mL in 0.1M PBS and urine. With increasing scan rate a linear relationship between log ip and log ν was observed. For 0.1M PBS, the process was largely capacitive at various detected potentials (b=0.94 @ 0.5V; b=0.86 @ 0.3V; b=0.85 @ 0.07V). However, in the case of simulated urine, the electrochemical process was diffusion-limited at 0.6V (b=0.49). Therefore, to obtain higher current sensitivity in the diffusion-limited regime, DPV was adopted. With increasing concentration of antigen NGAL, a monotonic decrease in the redox current at 0.6V and 0.45V potential was observed. This signifies that the presence of NGAL antigen leads to the formation of antigen-antibody complex immobilized on the surface of the nanocomposite translating into an increase in the resistance at the electrode surface leading to a decrease in the redox current. The decrease in the current was proportional to the increase in the amount of the test antigen. The sensitivity of the sensor at 0.45V and 0.6V was 2.22 nA/ng mL-1/mm2 and 0.51 nA/ng mL-1/mm2 respectively with the lowest limit of NGAL detection as 12.5ng/mL in simulated urine by using DPV. Similarly, for CV the sensitivity of the sensor at 0.56V was 3.48 nA/ng mL-1/mm2 with 22ng/mL as the limit of detection. The sensor performance was evaluated without the use of nanocomposite (only antibody) as a control for comparison.Therefore, this study is a proof of concept for an effective electrochemical sensor platform design for urinary NGAL detection using a novel nanocomposite. It was established that the use of nanocomposite provides a better surface area to volume ratio through the core-shell nanostructures decorated on the nanosheets translating into higher electrochemical activity. The sensing platform was found to be specific, sensitive, and stable making it a perfect candidate for a point-of-care-testing(POCT) platform. Figure 1

Shedding Light on Lithium-Sulfur Battery Dynamics: Real-Time Insights through in-Situ UV-Vis Spectroscopy on Modified Lab Equipment

In current post-lithium-ion research, the focus is directed toward Lithium-Sulfur (Li-S) batteries, motivated by their outstandingly high energy density (2640 Wh/kg) and the widespread availability of sulfur in the Earth's crust. Moreover, in-situ UV-Vis spectroscopy has proven to be instrumental, allowing for the real-time observation of alterations in the chemical composition of various battery components during operational cycles [1,2].Our current study delves into the influence of solvent selection, particularly donor and acceptor numbers, in formulating gel polymer electrolytes for Lithium-Sulfur batteries. Leveraging in-situ UV-Vis spectroscopy, our research provides real-time insights into dynamic interactions within the gel during battery operation, shedding light on evolving electrochemical processes. Systematically analyzing the impact of solvent properties on gel characteristics reveals a meaningful relationship, underscoring the importance of tailored solvent selection for optimizing gel performance. Moreover, this technique tracks polysulfide behavior, offering a comprehensive understanding of the gel's role in mitigating polysulfide shuttling. Notably, our study introduces a novel dimension by employing a custom-built in-situ UV-Vis cell featuring 3D-printed components, enhancing the versatility and applicability of these spectroscopic techniques in probing intricate interactions within gel polymer electrolytes. Moreover, by combining the UV-Vis results with Nuclear Magnetic Resonance and FTIR, we aim to advance fundamental knowledge and provide a pathway for optimizing battery performance and mitigating degradation mechanisms.References1- Patel, Manu UM, Rezan Demir‐Cakan, Mathieu Morcrette, Jean‐Marie Tarascon, Miran Gaberscek, and Robert Dominko. "Li‐S Battery Analyzed by UV/Vis in Operando Mode." ChemSusChem 6, no. 7 (2013): 1177-1181.2- He, Qi, Anna TS Freiberg, Manu UM Patel, Simon Qian, and Hubert A. Gasteiger. "Operando identification of liquid intermediates in lithium–sulfur batteries via transmission UV–vis spectroscopy." Journal of The Electrochemical Society 167, no. 8 (2020): 080508.

Multifunctional Nanocomposites Synthesized By Solid-Phase Method with High Photocatalytic, Antibacterial, and Fungicidal Activity

An easily scalable technology was developed for the solid-state synthesis of multifunctional hybrid Ag3PO4/AgCl nanocomposites. This innovative approach relies on solution-free (dry) mechanical activation, implemented through successive ion-exchange reactions in a planetary ball mill. The nanosized hybrid structure of the synthesized Ag3PO4/AgCl nanocomposites was substantiated through the utilization of XRD, SEM, TEM, DSC, and UV-visible spectroscopy methods. The investigation also unveiled a synergistic effect between Ag3PO4 and AgCl.The Ag3PO4/AgCl nanocomposites with a ratio of 75:25 mas. % exhibited the highest and most stable photocatalytic activity under visible light irradiation (λ≥400 nm). The rate constant for the photocatalytic degradation of Methylene Blue (10 mg/L) was found to be two times greater than that observed with Ag3PO4 nanoparticles and four times faster than for AgCl nanoparticles, as illustrated in Figure 1. "In addition, the synthesized nanocomposites remained stable after five cycles of the photocatalytic process, with their activity remaining almost unchanged.Furthermore, the antimicrobial and fungicidal efficacy of these nanocomposites was assessed using Staphylococcus aureus, Candida albicans, Escherichia coli, Pseudomonas aeruginosa, and Erwinia amylovora test strains. The results of the microbiological tests revealed, that almost all prepared materials were able to suppress pathogenic microorganisms. The conducted study identified these nanocomposites as promising candidates for further detailed and targeted studies concerning their interaction with specific microorganisms. Figure - 1. (a) Visible spectrum changes of MB during its photodegradation by the Ag3PO4/AgCl -75/25 composite. (b) Photocatalytic degradation profiles of MB over AgCl, Ag3PO4 and Ag3PO4/AgCl catalysts under visible light irradiation. (c) Graphs for determining the kinetics of decomposition of MS under the influence of different catalysts. (d) Photodegradation stability of MB using the Ag3PO4/AgCl – 75/25 catalyst.AcknowledgmentsThis research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan, grant number АР13068426. Figure 1

Green synthesis of silver nanoparticles from southern Eucalyptus globulus: Potent antioxidants and photocatalysts for rhodamine B dye degradation

Nanotechnology and nanoscience provide innovative foundations for delivering a wide range of new and enhanced technologies to the modern world. To break down Rhodamine B (RhB) dye solutions, this work describes the creation of silver nanoparticles (Ag-NPs) using the aqueous leaf extract of Eucalyptus globulus (E. globulus). The biosynthesized Ag-NPs were studied using UV–vis spectroscopy and SEM in conjunction with EDX, TEM, FTIR, HPLC and XRD. Stable Ag-NPs were synthesized using E. globulus, as evidenced by the absorption peaks at 431 nm seen in the UV–vis spectrum analysis. Spherical-shaped particles were visible in the SEM images, and the metallic form of the synthesised Ag-NPs was verified by EDX. The initial concentration of RhB, reaction duration, temperatures, and pH were all adjusted to optimise the photocatalytic degradation of RhB using Ag-NPs. The results indicated that photocatalytic effectiveness increased with rising pH. After 80 min at room temperature, the degradation reached 91.20 % at pH 12. The antioxidant EC50 results demonstrate that Ag-NPs exhibited a higher level of protective antioxidants (20.15 ± 0.3 µg/mL for DPPH and 10.24 ± 0.2 µg/mL for ABTS) compared to the E. globulus leaf extracts.

Improving Cs2AgBiBr6 double perovskite solar cells through graphdiyne doping: A Stride towards enhanced performance

Lead-free halide double perovskites (LFHDPs) based on Cs2AgBiBr6 provide a promising replacement for conventional lead-based LBPs, offering significant benefits in terms of non-toxicity and chemical stability. Nevertheless, the efficiency of Cs2AgBiBr6 solar cells is restricted due to their significant bandgap (Eg). The proposed solution involves optimizing the optical and photovoltaic properties of Cs2AgBiBr6 through graphdiyne (GD) doping. The synthesized Cs2Ag0.95GD0.05BiBr6 is extensively characterized by means of X-ray diffraction (XRD), solar simulator studies, and UV–vis spectroscopy. XRD analysis reveals peak position shifts, indicating changes in the crystal structure caused by GD doping. Optical examination indicates a drop in Eg, this results in enhanced light absorption in the visible region. The increased performance of the Cs2Ag0.95GD0.05BiBr6 solar cell is demonstrated by its higher fill factor (FF), open-circuit voltage (Voc), and short-circuit current (Jsc), which are measured at 0.91 V, 5.58 mA-cm−2, and 0.75, respectively. As a result, the power conversion efficiency (PCE) increases to 3.74 % from 3.37 %. Our research not only tackles film formation issues but also develops stable Cs2Ag0.95GD0.05BiBr6 as a high-performance material for solar applications. All in all, our effort promotes solar technology that is environmentally benign. This work develops stable Cs2Ag0.95GD0.05BiBr6 as a high-performance substance that aids in overcoming film forming challenges in solar applications. Overall, our work advances ecologically friendly solar technology.

Understanding the Mechanisms of Methylammonium-Induced Thermal Instability in Mixed-FAMA Perovskites.

Despite a recent shift toward methylammonium (MA)-free lead-halide perovskites for perovskite solar cells, high-efficiency formamidinium lead iodide (FAPbI3) devices still often require methylammonium chloride (MACl) as an additive, which evaporates away during the annealing process. In this article, it is shown that the residual MA+, however, triggers thermal instability. To investigate the possibility of an optimal concentration of MA+ that may improve thermal stability, the intrinsic thermal stability of pure FA, FA-rich, MA-rich, and pure MA perovskite films (FA1-xMAxPbI3, FAMA) is studied. The results show that the thermal stability of FAMA perovskites decreases with more MA+, under degradation conditions that isolate the intrinsic thermal stability of the material (i.e., without moisture and oxygen effects). X-ray diffraction (XRD), proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS), photoluminescence (PL) and UV-visible spectroscopy, and depth-profiling X-ray Photoelectron Spectroscopy (XPS) are employed to show that the observed trend is mainly due to the decomposition of the MA+ cation, as opposed to other effects such as the precursor solvent and film morphologies. It is also found that the surfaces of these FAMA films are MA+ rich, although this phenomenon does not appear to affect thermal stability. Finally, it is demonstrated that this trend is unaffected by the presence of Spiro-OMeTAD atop the film, and thus solar cell devices should preserve this trend.

Intelligent Biopolymer-Based Films: Promising New Solutions for Food Packaging Applications.

The development of biopolymer-based films represents a promising direction in the packaging industry that responds to stringent needs for sustainability, reducing the ecological impact. Traditional fossil-derived polymers present major concerns because of their long decomposition time and their significant contribution to the pollution of the environment. On the contrary, biopolymers such as chitosan, PVA, and PLA offer viable alternatives. This study aimed to obtain an innovative pH indicator for smart packaging using a synthetic non-toxic anthocyanin analogue dye incorporated in bio-based films to indicate meat freshness and quality. The pH-responsive color-changing properties of the dye make it suitable for developing intelligent films to monitor food freshness. The obtained polymeric films were characterized by FT-IR and UV-VIS spectroscopy, and their thermal properties were assessed using thermogravimetric methods. Moisture content, swelling capacity, and water solubility of the polymeric films were also evaluated. The sensitivity of the biopolymer-flavylium composite films to pH variations was studied in the pH range of 2 to 12 and noticeable color variations were observed, allowing the monitoring of the meat's quality damage through pH changes. The pH-responsive films were applied directly on the surface or in the proximity of pork and chicken meat samples, to evaluate their colorimetric response to fresh and spoilt meat. This study can be the starting point for creating more durable packaging solutions leading to a circular economy.

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.