UV Vis Spectroscopy Research Articles

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.

Wavelength-Selective Xanthene-Based Monochromophoric Photoremovable Protecting Groups for Tuning Soft Matter Material Properties.

Photocontrolled deprotection of specific functional groups has garnered significant interest over the past two decades. Notably, the selective deprotection of distinct groups based on wavelength has emerged as a prominent focus in recent research. The achievement of this objective has primarily involved the utilization of linker-based bichromophoric systems and diverse cocktail mixtures of photoresponsive protecting groups (PRPGs), each responsive to varying wavelengths of light. Herein, we present the first wavelength-selective monochromophoric system based on a hydroxanthene moiety, enabling the wavelength-selective release of two distinct functionalities under 450 and 600 nm light, respectively. The mechanism of the wavelength-selective photodegradation was thoroughly investigated by 1H NMR, UV-vis, and fluorescence spectroscopy, suggesting a proton-coupled electron transfer mechanism in the first photorelease step and electron transfer based arylmethyl type of photorelease in the second step. The utility of the xanthene-based wavelength-selective PRPGs was demonstrated in the multistep degradation of microparticles and dual-color tuning of polymer chain architecture, thus opening an avenue to design advanced photoreactive wavelength-controlled systems for applications in soft matter materials.

Unveiling the role of heterophase nanostructure in MnO2-based colorimetric sensors for ascorbic acid detection.

Nanozymes based on manganese oxide (MnO2) are demonstrated to be promising probes in colorimetric sensing applications. In this study, the r-MnO2/β-MnO2 heterophase nanostructure was simply prepared by a calcination process with controllable temperature. The characterization of the nanostructured material was confirmed by SEM, UV-vis spectroscopy, Raman, TGA-DSC, and XRD analysis. The r-MnO2/β-MnO2 exhibits a remarkably good catalytic activity in the oxidation process of 3,3',5,5'-tetramethylbenzidine (TMB) compared withthe r-MnO2 or Mn2O3 nanostructure owing to its heterophase junctions. The enhanced performance of the colorimetric sensor for ascorbic acid (AA) detection was investigated using the r-MnO2/β-MnO2 heterophase nanostructure as probe. The r-MnO2/β-MnO2 material enhanced the monitoring of AA in the wide linear range from 1µM to 50μM with alimit of detection of0.84µM. This work presents a promising and straightforward approach for the construction of MnO2-based colorimetric sensor and their practical application in plant growth monitoring.

Determination of Antioxidant, Cytotoxicity, and Anti-human Lung Cancer Properties of Silver Nanoparticles Green-Formulated by Foeniculum vulgare Extract Combined with Radiotherapy.

The current investigation involved the silver nanoparticles green synthesis utilizing the aqueous extract derived from the Foeniculum vulgare leaves (AgNPs@FV). The effectiveness of these newly developed nanoparticles in conjunction with radiotherapy was evaluated on lung cancer cells. The synthesized AgNPs@FV underwent characterization through various analytical techniques such as energy dispersive X-ray (EDX), field emission-scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and ultraviolet-visible (UV-Vis) spectrophotometry. The efficacy of AgNPs@FV in conjunction with radiotherapy against human lung cancer was assessed through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. The AgNPs@FV exhibited a spherical morphology ranging in size from 10.16 to 42.74 nm. The EDX diagram of nanoparticles shows energy signals at 3.02 and 2.64 keV, which are attributed to Ag Lβ and Ag Lα, respectively. During the antioxidant evaluation, AgNPs@FV and butylated hydroxytoluene (BHT) displayed IC50 values of 166 and 59 µg/mL, respectively. The cells treated with AgNPs@FV in conjunction with radiotherapy were evaluated using the MTT assay over 48h to determine cytotoxicity and anti-human lung cancer characteristics on normal (human umbilical vein endothelial cell (HUVEC)) and lung cancer cells and exhibited IC50 values of 211, 166, and 296µg/mL against NCI-H2126, NCI-H1299, and NCI-H1437, respectively. Furthermore, the malignant lung cell viability decreased when treated with a combination of AgNPs@FV and radiotherapy. Based on the aforementioned findings, it is possible that the newly developed AgNPs@FV could serve as a novel chemotherapeutic medication or adjunct for addressing lung cancer following the completion of clinical trials involving human subjects.

Ag20 Nanoclusters with Surface Azides as an Easily Functionalized Platform for Diverse Chemical Applications.

Modifying atomically precise nanocluster surfaces while maintaining the cluster core remains a key challenge. Herein, the synthesis, structure, and properties of two targeted Ag20 nanoclusters (NCs) with eight surface azide moieties, [CO3@Ag20(StBu)10(m-N3-C6H4COO)8(DMF)4] (1-m) and [CO3@Ag20(StBu)10(p-N3-C6H4COO)8(DMF)4] (1-p) are reported, where DMF is N,N-dimethylformamide. These AgNCs are designed to undergo cluster surface strain-promoted azide-alkyne cycloaddition (CS-SPAAC) reactions, introducing new functionality to the cluster surface. Reactivity is screened using model strained cyclooctynes. Reaction products and parent clusters are characterized by UV-vis, FT-IR, and NMR spectroscopies. The structure of the parent clusters and presence of surface azides is confirmed by single crystal X-ray diffraction (SCXRD) analysis. Clusters 1-m and 1-p are found to be amenable to CS-SPAAC reactions with retention of the NC frameworks, opening new routes for efficient modification of AgNC for applications.

Bioinspired copper oxide nanocomposites: harnessing plant extracts for enhanced photocatalytic performance.

This study focuses on developing copper oxide-based nanocomposites using plant extracts for photocatalytic applications. Curcuma amada leaf and Alysicarpus vaginalis leaf extracts were utilized alongside recycled copper precursors to synthesize photocatalysts via a green synthesis approach. Structural characterization through X-ray diffraction confirmed the formation of monoclinic CuO with reduced crystallite sizes due to plant extract incorporation. Fourier-transform infrared spectroscopy identified additional functional groups from the plant extracts, enhancing the material's properties. UV-Vis spectroscopy demonstrated increased light absorption and narrowed bandgaps in the nanocomposites, crucial for efficient photocatalysis under visible light. Morphological studies using FESEM revealed unique leaf-like structures in nanocomposites, indicative of the plant extract's influence on morphology. Photocatalytic degradation of methylene blue, rhodamine B, Congo red, and reactive blue 171 dyes showed enhanced performance of plant extract-modified CuO compared to without plant extract mediated CuO, attributed to improved charge carrier separation and extended lifetime. The effects of pH, catalyst dosage, and dye concentration on degradation efficiency were systematically investigated, highlighting optimal conditions for each dye type. Radical scavenger studies confirmed the roles of holes and hydroxyl radicals in the degradation process. Kinetic analysis revealed pseudo-second-order kinetics for dye degradation, underscoring the effectiveness of the nanocomposites. Overall, this research provides insights into sustainable photocatalytic materials using plant extracts and recycled copper, showcasing their potential for environmental remediation applications.

A comparative analysis of crustacean exoskeletons: structural, microstructural, morphological, and UV absorption studies

Abstract This study aims to investigate the structural, thermal, and spectral characteristics along with ultra-violet (UV) absorption of various marine benthos exoskeletons, such as various species of crabs (Portunus sanguinolentus, Portunus pelagicus, Charybdis feriata) and mantis shrimp (Oratosquilla oratoria). Their unique properties and ability to survive in harsh oceanic environments make them interesting research subjects. This research utilized powder X-ray diffraction (XRD) analysis to determine the crystal structure of the benthic varieties. The sample surface was analysed using high-resolution micrographs obtained from field-emission scanning electron microscopy (FESEM) identified the presence of chitin and calcite in the marine benthos, which was further confirmed by differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The optical characteristics were investigated using UV-visible spectroscopy. The proximate analysis revealed high protein content in the mantis shrimp exoskeleton compared to other crab species, revealing its excellent UV-absorption characteristics. Overall, this research has the potential to broaden our understanding of marine organisms, which can have potential applications in biotechnology and materials science to develop nature-inspired innovative materials sustainably.

ZnO/TiO2 photocatalytic nanocomposite for dye and bacteria removal in wastewater

Abstract The remediation of pollution from textile dyes poses a significant challenge. Recently, photocatalytic nanomaterials derived from semiconductor oxides have garnered attention to address this issue. This study focuses on the synthesis of ZnO/TiO2 nanocomposites with various Zn(II):Ti(IV) molar ratios via the sol-gel method for textile wastewater treatment. The properties of these materials are thoroughly characterized using a suite of analytical techniques, including transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, X-ray fluorescence (XRF) spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis, and UV-Vis spectroscopy. Analysis via XRD and XRF confirms the formation of a ZnO/TiO2 heterostructure, while TEM imaging reveals a quasi-spherical morphology with slight agglomeration. Notably, the ZnO/TiO2 nanocomposite with a Zn(II):Ti(IV) molar ratio of 1:5 demonstrates the largest BET surface area (91.345 m2g-1) and the narrowest band gap (Eg = 3.06 eV) as compared to other synthesized compositions. The impact of precursor ratios on photocatalytic activity is assessed through the measurement of methylene blue dye discoloration under sunlight irradiation. Additionally, the antibacterial efficacy against Salmonella typhi and Staphylococcus aureuswas quantitatively evaluated for the ZnO/TiO2 nanocomposites, suggesting potential applications in the treatment of pollutants present in textile wastewater.

Eco-Friendly Synthesis, Characterization, and Biomedical Applications of Biosynthesized Bimetallic Silver-Gold Nanoparticles by Culture Supernatant of Aspergillus niger.

Green synthesis of bimetallic nanoparticles of noble metals is highly desirable in nanomedicine because of their potential use as anticoagulant, thrombolytic and anticancer agents. In this study, it was discovered that the filamentous fungus Aspergillus niger proved effective in producing bimetallic Ag-Au nanoparticles. A. niger culture supernatant was able to produce Ag-AuNPs by reducing the solution of chloroauric acid/silver nitrate (1.0:1.0 mM) within 2 min at 100 °C and pH 8. Experimental Ag-AuNP detection was performed by visually observing the color change to reddish brown. The produced nanoparticles displayed maximal absorbance at 530 nm in UV-vis spectroscopy. According to transmission electron microscopy, most of the nanoparticles were spherical, with a mean diameter of 8-10 nm. The biosynthesis of Ag-AuNPs by A. niger was confirmed by Fourier transform infrared spectroscopy, X-ray diffraction and energy dispersive X-ray analytical techniques. Its zeta potential was discovered to be -34.01 mV. The biosynthesized Ag-AuNPs exhibited effective thrombolytic and antiplatelet aggregation actions by totally preventing and dissolving the blood clot which was verified by microscopic examination, amelioration of blood coagulation assays, and carrageenan-induced tail thrombosis model. The findings verified the effectiveness of biosynthesized Ag-AuNPs as a powerful antitumor agent against HepG2 and A549 cell lines with IC50 values of 15.57 and 27.07 μg/mL, respectively. Crystal violet assay validated the cytopathic effects of Ag-AuNPs on A549 and HepG2 cell lines. Therefore, the produced Ag-AuNPs from A. niger are a promising candidate in the management of thrombosis.

Synthesis of Ag Doped ZnO Nanowire by Hydrothermal Method and its Characterization

This research is mainly focused over synthesizing zinc oxide (ZnO) nanowire (NW) and silver doped zinc oxide nanowires (Ag/ZnO) using two step hydrothermal method which comprises of seed layer deposition and hydrothermal nanowire growth step. Hydrothermally grown nanowires are of great significance. The synthesized nanowires were characterized by UV-Vis Spectroscopy (UV-Vis), X- ray Diffraction Spectroscopy (XRD), Energy Dispersive Spectroscopy (EDS), Field Emission Scanning Electron Microscopy (FE-SEM) and High-Resolution Transmission Electron Spectroscopy (HR-TEM). XRD pattern revealed as-synthesized materials are of crystalline nature having crystallite size of 166.27 nm and 42.32 nm for ZnO nanowire and Ag doped nanowire, respectively. Further confirmation was done by EDS, SEM and TEM. The microscopic images of SEM and TEM evidenced for successful fabrication of nanowires.

Structural and biophysical insights into the interactions of anisotropic gold nanoparticles with human telomeric G-quadruplex DNA: Spectroscopic and calorimetric approach

We are reporting curcumin-induced synthesis of anisotropic citrate capped Gold nanoparticles (ctGNPs). The techniques such as UV–visible spectroscopy, Raman spectroscopy, FT-IR, X-ray diffraction (XRD), and Transmission Electron Microscopy (TEM) were used to characterize the nanoparticles. The synthetic route shows the formation of an anisotropic gold nanostructure consisting of spherical, triangles, hexagonals, and a low-yield rod with an aspect ratio ranging from 4.2 to 8.5. Curcumin-derived ctGNPs shows stability at different physiological conditions and better biocompatibility. Synthesized nanoparticles are found non-toxic towards eukaryotic cells but more effective against the cancer cell lines HeLa and MCF-7. The interaction of these synthesized nanoparticles with human telomeric G-quadruplex (GQ) DNA was studied using different physiochemical methods. The spectroscopic studies show that synthesized nanoparticles have stronger binding affinity towards telomeric GQ as compared to ds DNA through Van der Waals and H-bonding interactions. Thermodynamic interpretation reveals that the formation of the complex between the telomeric GQ and ctGNPs are enthalpy driven and entropy unfavourable process, resulting in motion freezing and, eventually, AuNP aggregation. Thus, our study shows a new approach to understand the interaction of telomeric G-quadruplexes with gold nanoparticles generated via the green route.

Advancements in bandgap engineering: bromide-doped cesium lead perovskite thin films

Perovskite materials have emerged as promising candidates for next-generation photovoltaic devices due to their unique optoelectronic properties. In this study, we investigate the incorporation of bromine into cesium lead mixed iodide and bromide perovskites (CsPbI3(1-x)Br3x) to enhance their performance. By depositing films with varying bromine concentrations (x = 0, 0.25, 0.5, 0.75), we employ a combination of structural and optical characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectroscopy, and photoluminescence. Our analysis reveals that introducing bromine leads to structural modifications, influencing the perovskite films’ optical properties and energy gap. Specifically, we observe semiconductor behavior with a tunable energy gap controlled by the intercalation of bromine atoms into the CsPbI3 lattice. Furthermore, heat treatment induces phase transitions in the perovskite films, affecting their optical responses and crystalline quality. SCAPS-1D simulations confirm the improved stability and efficiency of bromine-doped CsPbI3 films compared to undoped counterparts. Our findings demonstrate that bromine incorporation facilitates the formation of highly crystalline perovskite films with reduced trap defects and enhanced carrier transport properties. These results underscore the potential of bromine-doped CsPbI3 perovskites as promising materials for high-performance photovoltaic applications, paving the way for further optimization and device integration.

Elucidation of mode of anticancerous activity of metal guanidinobenzimidazoles: A computational and experimental screening

DNA‐binding agents often exhibits dual behavior of simultaneous binding with protein associated with cancerous cell development pathways. This simultaneous protein binding if contributed to malfunctioning of pro‐apoptotic proteins will reduce anticancerous potential of drugs. The elucidation of binding target for anticancerous agent can give an insight into the cancer cell apoptotic pathway. Therefore, anticancerous Zn(II) and Ni(II) complexes of 2‐guanidinobenzimidazole (2GBz) were subjected to DNA‐binding mode assay along with protein‐binding interference assay. The stoichiometry Zn‐2GBz and Ni‐2GBz were determined through density functional theory (DFT) and UV–Vis spectroscopy, followed by structural verification by X‐ray crystallography. The 2GBz and Ni‐2GBz were found to bind with grooves of DNA while groove binding of Zn‐2GBz induced unwinding of DNA through interactive pi‐stacking. Binding constant revealed the M‐2GBz to be a strong binder of DNA molecule with the effect of enhanced cell killing potential of M‐2GBz against MCF‐7 cell lines. Protein‐binding assay revealed that despite of significant interaction of M‐2GBz with chick serum albumin, DNA binding was not altered by simultaneous protein binding. The most potent Zn‐2GBz was found to be sphingosine 1 kinase 2 (SPhK2) which can be a cause of enhanced cancer cell apoptosis with lesser normal cell apoptosis than standard fluorouracil in MCF‐7 cell lines. Co‐administered Zn‐2GBz increased cancer cell sensitivity towards fluorouracil as potent anticancerous agent.

Ternary nanostructure of CdS-rGO-Ag for enhanced photoelectrochemical application.

In the present study, we have synthesized the ternary nanostructure of CdS-rGO-Ag by using the solvothermal method for the enhanced photocatalytic as well as electrocatalytic activity of the material. The optical properties of the prepared samples were characterized by using UV-visible spectroscopy and photoluminescence (PL) spectroscopy. A decline in the energy gap of CdS-rGO-Ag nanostructure to 1.90 ± 0.05 from 2.40 ± 0.08eV (CdS) is observed and may be attributed due to the rGO-Ag-induced creation of trap states in between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of CdS. The observed significant PL quenching also confirms the inclusion of trap states in the prepared nanostructure CdS-rGO-Ag, suggesting efficient photoactivity. The enhanced photocatalytic activity of CdS-rGO-Ag for methylene blue (MB) dye degradation supports the photocatalytic activity of prepared nanostructures. Furthermore, the photoelectrochemical catalytic activity of the CdS-rGO-Ag catalyst investigated by using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) depicts the improved current density, lowering of overpotential. The decrement in charge transfer resistance and enhancement in photocurrent density under light illumination indicates the better photoelectrochemical performance of CdS-rGO-Ag.

Disposable electrochemical sensors based on reduced graphene oxide/polyaniline/poly(alizarin red S)-modified integrated carbon electrodes for the detection of ciprofloxacin in milk.

Anelectrochemical sensor based on an electroactive nanocomposite was designedfor the first timeconsisting of electrochemically reduced graphene oxide (ERGO), polyaniline (PANI), and poly(alizarin red S) (PARS) for ciprofloxacin (CIPF) detection. The ERGO/PANI/PARS-modified screen-printed carbon electrode (SPCE) was constructed through a three-step electrochemical protocol and characterized using FTIR, UV-visible spectroscopy, FESEM, CV, LSV, and EIS. The new electrochemical CIPF sensor demonstrated a low detection limit of 0.0021μM, a broad linear range of 0.01 to 69.8μM, a high sensitivity of 5.09 μA/μM/cm2, and reasonable selectivity and reproducibility. Moreover, the ERGO/PANI/PARS/SPCE was successfully utilized to determine CIPF in milk with good recoveries and relative standard deviation (< 5%), which were close to those with HPLC analysis.

Novel approach for green synthesis of stable gold nanoparticles with dried turmeric root extract: investigations on sensor and catalytic applications.

In this study, we present the synthesis of gold nanoparticles (AuNPs) using a completely green synthesis method without the use of any additional functionalizing agent, except dried turmeric root extract. The significant synthesis parameters were optimized, and the applicability of AuNPs was investigated in areas such as plasmonic and fluorescent sensing of aluminum (Al3⁺) and chromium (Cr3⁺) ions, reduction of 4-nitrophenol (4-NP), and degradation of methylene blue (MB) and methyl orange (MO) dyes. Characterization studies were performed using UV-Vis spectroscopy, TEM, FTIR, and XRD, revealing that the AuNPs predominantly had a spherical morphology and a very small particle size of 8.5 nm, with stability maintained up to 120 days. The developed AuNP-based plasmonic sensors relied on aggregation-induced decreases in absorption, along with a red shift in the spectra. Fluorescence sensing demonstrated a linear increase in intensity with increasing concentrations of Al3⁺ and Cr3⁺, with detection limits of 0.83 and 1.19 nM, respectively. The catalytic activities of AuNPs were tested in reducing 4-NP and degradations of MB and MO dyes (binary system) in tap water and wastewater, with the reactions following pseudo-first-order kinetics. This study highlights the potential of AuNPs synthesized from turmeric roots for various environmental and sensing applications.

Insights into Spectral Distortion and Nonlinearity in UV-Vis and Fluorescence Spectroscopy of Molecular Fluorophore Solutions: Effects of Cascading Optical Processes (Part IV).

Reproducibility and linearity are crucial benchmarks for any measurement technology. However, UV-vis and fluorescence spectral distortion and nonlinearity are prevalent, even in seemingly simple fluorescent solutions that comprise only one dissolved molecular fluorophore, without exogenous absorbing or scattering species. In this report, we introduce an analytical model for the quantification of fluorescence interference on UV-vis measurements and a conceptual model for mechanistically understanding the impacts of higher-order cascading optical processes on fluorescence measurements. The experimental UV-vis transmittance can be dominated by interfering fluorescence, even for fluorophore solutions with theoretical absorbance values far below the instrument's linear dynamic range (LDR). Absorption-inner-filter-effect (aIFE) correction drastically improves the fluorescence LDR. However, the efficacy of aIFE correction hinges on two competing factors that strongly depend on the fluorophore's optical properties: the degree of fluorescence interference in UV-vis and the significance of secondary or higher-order emission triggered by fluorophore absorption of emitted photons. Our research sheds light on the remarkable complexity of cascading optical processes that can occur even in the simplest fluorescent solutions. It emphasizes the necessity of critically evaluating optical spectroscopic measurements of fluorescent solutions to improve the reliability of analyzing and interpreting optical spectra. Moreover, it lays the groundwork for future development of methods capable of handling challenging samples that exceed the capabilities of the current tools.

Novel ternary nanocomposite (TiO2@Fe3O4-chitosan) system for nitrate removal from water: an adsorption cum photocatalytic approach.

Nitrate pollution of water emerging from various anthropogenic activities has become a major environmental concern because of its deleterious effects on natural water resources. The present work deals with the synthesis of the ternary nanocomposite based on chitosan, iron oxide (Fe3O4), and titanium dioxide (TiO2) and its application for the removal of nitrates from model-contaminated water. Fe3O4 derived through a coprecipitation method was incorporated into the chitosan matrix which was fabricated in the form of beads. The wet gel beads were then successfully coated with sol-gel-derived silver-doped titanium dioxide sol followed by drying under suitable conditions to get the functional nanocomposite beads. The synthesized functional materials were further characterized for their structural, morphological, and textural features using X-ray diffraction analysis, physical property measurement (PPMS), Fourier transform infrared (FTIR) analysis, UV visible spectroscopy analysis (UV-vis), BET surface area analysis (BET), field emission scanning electron microscopic (FESEM), and transmission electron microscopy (TEM) analysis. The ternary nanocomposites were further used for the removal of nitrates via adsorption cum photocatalytic reduction technique from the model contaminated water when subjected to an adsorption study under dark conditions and photocatalytic study under UV/visible/sunlight for a definite time. Fe3O4 in the nanocomposite provides enhanced adsorption features whereas the functional coating of titanium dioxide aids in the removal of nitrates through the photocatalytic reduction technique. The functional beads containing 3% Fe3O4 in the wet gel form (CTA-F3) have excellent nitrate removal efficiency of ~ 97% via adsorption cum solar photocatalysis towards the removal of nitrate ions from 50ppm nitrate solution, whereas the dried nanocomposite beads have got a nitrate removal efficiency of ~ 68% in 1h from 100ppm nitrate solution. Continuous flow adsorption cum photocatalytic study was performed further using the oven-dried functional beads in which flow rate and bed height were varied while maintaining the concentration of feed solution as constant. A nitrate removal efficiency of 65% and an adsorption capacity of 4.1 mgg-1 were obtained for the CTA-F3 beads in the continuous flow adsorption cum photocatalysis experiment for up to 5h when using an inlet concentration of 100ppm, bed height 12cm, and flow rate 5.0mlmin-1. A representative fixed-bed column adsorption experiment conducted using CTA-F3 beads for the treatment of a real groundwater sample shows reasonable results for nitrate removal (71.7% efficiency) along with a significant removal rate for the other anions as well. Thus, the novel adsorbent/photocatalyst developed is suitable for the removal of nitrates from water due to the synergistic effect between Fe3O4, chitosan, and titanium dioxide.

Synthesis of antibacterial fluorescent carbon dots and green coal-like hydrochar from tea Industry byproducts via hydrothermal carbonization

This study introduces an experimental framework employing hydrothermal carbonization (HTC) for the valorisation of factory tea waste as a solid fuel. Employing a centre composite design and response surface methodology, the investigation systematically assesses the influence of two critical process parameters, temperature (180–220 °C) and time (0–240 min), on higher heating value (HHV), hydrochar yield, and energy yield. The study identifies an optimized HTC condition (220°C, 55 min) resulting in the recorded HHV of 22.26±1.10 Mj/Kg. Combustion characteristics and kinetics of the factory tea waste-derived hydrochar (TW-hydrochar) is analysed through TGA and DTG, complemented by structural elucidation via FTIR and FE-SEM. Concurrently, the study reports the observation of carbon dots (TW-CDs) generation during TW-hydrochar production, characterized comprehensively through UV–visible spectroscopy, TEM, XRD, XPS, Zeta potential, and fluorescence methods. Further, antimicrobial properties of TW-CDs are rigorously investigated against Bacillus subtilis and Escherichia coli, manifesting pronounced antibacterial activity against B. subtilis and E. coli as evidenced by a 12 mm and 11 mm inhibition zone, respectively. This research contributes to the scientific understanding of tea waste valorization through HTC, providing insights into cleaner fuel options and the emergence of carbon dots with potential antibacterial applications.

Optimizing photocatalytic performance with Ag-doped ZnO nanoparticles: Synthesis and characterization

The development of nanotechnology has significantly impacted the improvement of photocatalytic performance of ZnO NPs. In this study synthesis of pure ZnO and Ag–ZnO nanoparticles via a co-precipitation method at varying Ag concentrations (1 %, 2 %, 3 %, 4 % and 6 %) to enhance their photo catalytic efficacy. X-ray diffraction (XRD) analysis estimates crystallite size which decreased by increasing Ag concentration, ranging from 30.6 nm (Pure ZnO) to 22.5 nm 6 % Ag-doped ZnO. Scanning electron microscopy (SEM) revealed decrease in particle size with increasing Ag content. UV–Vis spectroscopy indicating a narrowed band gap of optimal sample. Photocatalytic activity of the synthesized nanoparticles was evaluated using methylene orange (MO) dye degradation under light irradiation. The MO concentration exhibited a decrease with increasing irradiation time in the presence of photocatalysts. Recombination rate of NPs decreases by increasing the concentration of Ag i.e. 4%Ag dope ZnO NPs have lowest recombination rate and maximum degradation efficiency. FTIR analysis confirms the preparation of Ag-doped ZnO NPs. This improvement can be credited to the synergistic effect of Ag doping, leading to a narrowed band gap and potentially maximum degradation of MO by using Ag-doped ZnO NPs.