Ultraviolet-visible Absorption Spectroscopy Research Articles

Effects of Heat Treatment in Air Atmosphere on Dip Coating Deposited CdS Thin Films for Photo Sensor Applications

Objective: In this report, photo sensitive materials with enhanced charge carriers have been prepared using dip coating technique. Methods: Cadmium sulphide (CdS) is N-type semiconductor compound belonging to II-VI group. CdS nanoparticles were synthesized using non-aqueous chemical method and characterized by ultraviolet-visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy. CdS films were deposited on fluorine doped tin oxide (FTO) glass slides using dip coating method at different dip times and heat treated in air and analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis by X-rays (EDAX), mapping and atomic force microscopy (AFM). Results: Quantum confinement effect was observed in UV-Vis absorption spectra of CdS nanoparticles. Quenching of luminescence intensity and blue shift at smaller wavelengths were observed in PL spectra. Presence of highly dense rectangular shaped grains in CdS films and increment in particle sizes with increase in dip time were shown by AFM images. Selected area electron diffraction images showed ring patterns indicating polycrystalline nature of CdS nanoparticles. Increase in crystallite size and decrease in crystal defects by heat treatment in air and increment in grain size with increase in dip time were shown by SEM images. XRD analysis of CdS films showed polycrystalline nature. Conclusion: In previous work, preparation of dip coating deposited CdS films on FTO glass substrates for optoelectronic device applications such as photo sensors has not been reported. In this study, I-V characteristics of heterojunctions under dark and illumination conditions were discussed. Experimental results obtained in our study and their comparison with previous reports were also discussed.

An Electrochemical Screen-Printed Sensor Based on Gold-Nanoparticle-Decorated Reduced Graphene Oxide-Carbon Nanotubes Composites for the Determination of 17-β Estradiol.

In this study, a screen-printed electrode (SPE) modified with gold-nanoparticle-decorated reduced graphene oxide-carbon nanotubes (rGO-AuNPs/CNT/SPE) was used for the determination of estradiol (E2). The AuNPs were produced through an eco-friendly method utilising plant extract, eliminating the need for severe chemicals, and remove the requirements of sophisticated fabrication methods and tedious procedures. In addition, rGO-AuNP serves as a dispersant for the CNT to improve the dispersion stability of CNTs. The composite material, rGO-AuNPs/CNT, underwent characterisation through scanning electron microscopy (SEM), ultraviolet-visible absorption spectroscopy (UV-vis), Fourier-transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). The electrochemical performance of the modified SPE for estradiol oxidation was characterised using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The rGO-AuNPs/CNT/SPE exhibited a notable improvement compared to bare/SPE and GO-CNT/SPE, as evidenced by the relative peak currents. Additionally, we employed a baseline correction algorithm to accurately adjust the sensor response while eliminating extraneous background components that are typically present in voltammetric experiments. The optimised estradiol sensor offers linear sensitivity from 0.05-1.00 µM, with a detection limit of 3 nM based on three times the standard deviation (3δ). Notably, this sensing approach yields stable, repeatable, and reproducible outcomes. Assessment of drinking water samples indicated an average recovery rate of 97.5% for samples enriched with E2 at concentrations as low as 0.5 µM%, accompanied by only a modest coefficient of variation (%CV) value of 2.7%.

High Photosensitivity Nanocrystalline p-Cu2S/n-FTO Heterojunction Photodetectors Prepared by Dip Coating Method

Objective: The aim of present work is to fabricate nanocrystalline p-Cu2S/n-FTO heterojunction photo detectors with high photosensitivity. Methods: Copper sulphide (Cu2S) is semiconductor compound belonging to I-VI group. Cost effective chemical method was used to synthesize thioglycerol capped Cu2S nanoparticles with improved optoelectronic and physical properties. These nanoparticles were investigated by ultraviolet-visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy (TEM). Cu2S films were deposited on fluorine doped tin oxide (FTO) glass slides using cost effective dip coating method at different dip times and heat treated in air atmosphere. Wide band gap fluorine doped tin oxide, n-type semiconductor was used as transparent window material together with narrow band gap Cu2S, p-type semiconductor used as absorber layer in case of Cu2S/FTO heterojunction photo detectors under reverse biased mode and illumination. Results: Cu2S films were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Analysis by X-rays (EDAX), Mapping and Atomic Force Microscopy (AFM). Selected Area Electron Diffraction (SAED) images showed ring patterns indicating that Cu2S nanoparticles are polycrystalline in nature and spot patterns indicating that Cu2S nanoparticles are monocrystalline in nature. Conclusion: Previously, preparation of optoelectronic devices such as photo detectors using Cu2S films has not been reported. In this study, photo detectors having enhanced photosensitivity were prepared using Cu2S films. I-V characteristics of p-Cu2S/n-FTO heterojunctions under dark and illumination conditions were examined. It was observed that film conductivity decreases under dark condition and increases under illumination condition with increase in dip time in case of Cu2S/FTO heterojunction photo detectors.

Study on the Interaction Mechanism of Theaflavin with Whey Protein: Multi-Spectroscopy Analysis and Molecular Docking.

The interaction mechanism of whey proteins with theaflavin (TF1) in black tea was analyzed using multi-spectroscopy analysis and molecular docking simulations. The influence of TF1 on the structure of bovine serum albumin (BSA), β-lactoglobulin (β-Lg), and α-lactoalbumin (α-La) was examined in this work using the interaction of TF1 with these proteins. Fluorescence and ultraviolet-visible (UV-vis) absorption spectroscopy revealed that TF1 could interact with BSA, β-Lg and α-La through a static quenching mechanism. Furthermore, circular dichroism (CD) experiments revealed that TF1 altered the secondary structure of BSA, β-Lg and α-La. Molecular docking demonstrated that the interaction of TF1 with BSA/β-Lg/α-La was dominated by hydrogen bonding and hydrophobic interaction. The binding energies were -10.1 kcal mol-1, -8.4 kcal mol-1 and -10.4 kcal mol-1, respectively. The results provide a theoretical basis for investigating the mechanism of interaction between tea pigments and protein. Moreover, the findings offered technical support for the future development of functional foods that combine tea active ingredients with milk protein. Future research will focus on the effects of food processing methods and different food systems on the interaction between TF1 and whey protein, as well as the physicochemical stability, functional characteristics, and bioavailability of the complexes in vitro or in vivo.

Histidine-Mediated Synthesis of Chiral Cobalt Oxide Nanoparticles for Enantiomeric Discrimination and Quantification.

Chiral transition metal oxide nanoparticles (CTMOs) are attracting a lot of attention due to their fascinating properties. Nevertheless, elucidatingthe chirality induction mechanism often remains a major challenge. Herein, the synthesis of chiral cobalt oxide nanoparticles mediated by histidine (Co3 O4 @L-His and Co3 O4 @D-His for nanoparticles synthesized in the presence of L- and D-histidine, respectively) is investigated. Interestingly, these CTMOs exhibit remarkable and tunable chiroptical properties. Their analysis by x-ray photoelectron, Fourier transform infrared, and ultraviolet-visibleabsorption spectroscopy indicates that the ratio of Co2+ /Co3+ and their interactions with the imidazole groups of histidine are behind their chiral properties. In addition, the use of chiral Co3 O4 nanoparticles for the development of sensitive, rapid, and enantioselective circular dichroism-based sensors is demonstrated, allowing direct molecular detection and discrimination between cysteine or penicillamine enantiomers. The circular dichroism response of the chiral Co3 O4 exhibits a limit of detection and discrimination of cysteine and penicillamine enantiomers as low as 10µm. Theoretical calculations suggest that the ligand exchange and the coexistence of both species adsorbed on the oxide surface are responsible for the enantiomeric discrimination. This research will enrich the synthetic approaches to obtain CTMOs and enable the extension of the applications and the discovery of new chiroptical properties.

Construction of dual-channel ratio sensing platform and molecular logic gate for visual detection of oxytetracycline based on biomass carbon dots prepared from cherry tomatoes stalk

In this work, blue carbon dots (Stalk-Trp CDs) with high fluorescence quantum yield were successfully prepared from biological waste cherry tomato stalk and tryptophan. The morphology, composition, and properties of Stalk-Trp CDs were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, infrared spectroscopy, ultraviolet–visible absorption spectroscopy, and fluorescence spectroscopy. On this basis, a dual-channel ratio sensing platform (Stalk-Trp CDs@Eu) was constructed using the interaction of Stalk-Trp CDs with Eu3+, which reduced the detection limit of the antibiotic oxytetracycline from 0.15 µmol/L to 0.018 µmol/L. Channel 1 of the dual-channel ratio sensing platform is a neutral environment (pH = 6.5), and the specific response of the probe to OTC causes its fluorescence to change from blue to purple. Channel 2 is an alkaline environment (pH = 11.5), and the fluorescence of the probe turns green only in the presence of OTC. The interaction mechanism of the dual-channel ratio sensing platform with the antibiotics oxytetracycline (OTC), chlortetracycline (CTC), and tetracycline (TC) was also revealed. The detection results of OTC in honey and milk by using Stalk-Trp CDs@Eu were highly consistent with the HPLC method recommended by the national standard. This shows that the dual-channel ratio sensing platform has great practical application value in the field of antibiotic detection.

Heptacoordinated lanthanide(III) complexes based on 2,6-bis(1H-benzo[d]imidazol-2-yl)pyridine ligands (bbp, bmbp and bdmbp): Computational calculations, luminescent properties and cytotoxic evaluation.

Two new series of heptacoordinated obtained of hydrated lanthanide(III) nitrates (Ln3+ = La, Nd, Sm, Eu, Gd, Tb and Dy) with 2,6-bis(1H-benzo[d]imidazol-2-yl)pyridine (bbp) and 2,6-bis(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)pyridine (bdmbp) were synthesized and characterized by high-resolution mass spectrometry (HR-MS), elemental analysis (EA), melting point (MP), molar electrical conductivity (MEC), effective magnetic moment (EMM) and Fourier-transform infrared spectroscopy (FT-IR). The optical properties of complexes were evaluated by ultraviolet-visible (UV–Vis) absorption and emission spectroscopy in solution. Samarium(III), europium(III), and terbium(III) complexes exhibited luminescent properties and characteristic emission bands. IR and MEC studies indicated that only two of the three nitrate groups were coordinating with the lanthanide(III) ion in a bidentate manner and confirmed the presence of the third nitrate group outside the coordination sphere. EMM analyses indicated that the metal complexes present paramagnetism, except for those of lanthanum(III). The third series of these complexes with these same trivalent lanthanide ions derived from the ligand 2,6-bis(5-methyl-1H-benzo[d]imidazol-2-yl)pyridine (bmbp) were previously reported by our research group in this same research journal (10.1016/j.molstruc.2018.03.065). Therefore, the cytotoxic activity of the three series of complexes and their ligands against NIH-3T3, J774A.1 and HeLa cell lines was studied. Only the bdmbp-based complexes exhibited moderate cytotoxic activity versus the HeLa cell line compared to the other two cell lines, while the bbp- and bmbp-derived complexes exhibited weak cytotoxic activity against all three cell lines.

Eco-Friendly Synthesis of Functionalized Carbon Nanodots from Cashew Nut Skin Waste for Bioimaging

In this study, Anacardium occidentale (A. occidentale) nut skin waste (cashew nut skin waste) was used as a raw material to synthesize functionalized carbon nanodots (F-CNDs). A. occidentale biomass-derived F-CNDs were synthesized at a low temperature (200 °C) using a facile, economical hydrothermal method and subjected to XRD, FESEM, TEM, HRTEM, XPS, Raman Spectroscopy, ATR-FTIR, and Ultraviolet-visible (UV–vis) absorption and fluorescence spectroscopy to determine their structures, chemical compositions, and optical properties. The analysis revealed that dispersed, hydrophilic F-CNDs had a mean diameter of 2.5 nm. XPS and ATR-FTIR showed F-CNDs had a crystalline core and an amorphous surface decorated with –NH2, –COOH, and C=O. In addition, F-CNDs had a quantum yield of 15.5% and exhibited fluorescence with maximum emission at 406 nm when excited at 340 nm. Human colon cancer (HCT-116) cell assays showed that F-CNDs readily penetrated into the cells, had outstanding biocompatibility, high photostability, and minimal toxicity. An MTT assay showed that the viability of HCT-116 cells incubated for 24 h in the presence of F-CNDs (200 μg mL–1) exceeded 95%. Furthermore, when stimulated by filters of three different wavelengths (405, 488, and 555 nm) under a laser scanning confocal microscope, HCT-116 cells containing F-CNDs emitted blue, red, and green, respectively, which suggests F-CNDs might be useful in the biomedical field. Thus, we describe the production of a fluorescent nanoprobe from cashew nut waste potentially suitable for bioimaging applications.

Linear and thermo-optically generated nonlinear optical response of bovine serum albumin and its constituent amino acids in continuous wave z-scan

Proteins are large biomolecules in the form of polypeptide chains consisting of amino acid (AA) residues. Ultraviolet–visible absorption spectroscopy and continuous wave (CW) z-scan of bovine serum albumin (BSA) and some of its constituent AAs were examined to deduce the relationship between the optical properties of this protein molecule and its constituents. From the analysis of their optical spectra, the absorption at 278 nm by BSA is found to be the outcome of the cumulative effects of the absorptions by constituent aromatic AA residues, cysteine disulfide bonds, and methionine. Similarly, the closed aperture CW z-scan of BSA and those of the constituent AAs at 74–106 mW incident optical power at 655 nm indicate that thermally generated third-order optical effects arise in BSA and its aromatic AA residues due to multiphoton absorptions. The nonlinear optical (NLO) responses of BSA and those of the AA residues are compared in terms of their molar phase shift per unit power, which indicate a possible relationship between the NLO property of BSA and its AA residues.

High quantum yield nitrogen doped carbon dots for Ag+ sensing and bioimaging

N-doped carbon dots (NCDs) with green fluorescence is developed by the hydrothermal reaction with o-aminophenol and ethylenediamine as carbon and nitrogen sources, and the quantum yield (QY) is 38.4%. The NCDs are characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Ultraviolet-visible absorption spectroscopy (UV–vis) and fluorescence spectroscopy. The results show that NCDs have good fluorescence properties and stability, and the NCDs are further utilized as a sensor for Ag+ via the static quenching effect (SQE) (λex=430 nm, λem=510 nm). The linear range of Ag+ is 30–210 µmol/L with a limit of detection (LOD) of 4.7 µmol/L (S/N = 3). On this basis, we quantitatively detect Ag+ in real samples. Furthermore, due to the excellent fluorescence performance, the NCDs are found to be an effective tool for Ag+ sensing in bioimaging.

Nitrogen and copper-doped saffron-based carbon dots: Synthesis, characterization, and cytotoxic effects on human colorectal cancer cells

AimDoped carbon dots (CDs) have attracted tremendous attention in cancer therapy. We aimed to synthesize copper, nitrogen-doped carbon dots (Cu, N-CDs) from saffron and investigated their effects on HCT-116 and HT-29 colorectal cancer (CRC) cells. Main methodsCDs were synthesized by hydrothermal method and characterized by transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV–Vis) absorption spectroscopy, and fluorescence spectroscopy. HCT-116 and HT-29 cells were incubated with saffron, N-CDs, and Cu, N-CDs for 24 and 48 h for cell viability. Cellular uptake and intracellular reactive oxygen species (ROS) were evaluated by immunofluorescence microscopy. Oil Red O staining was used to monitor lipid accumulation. Apoptosis was evaluated using acridine orange/propidium iodide (AO/PI) staining and quantitative real-time polymerase chain reaction (Q-PCR) assay. The expression of miRNA-182 and miRNA-21 was measured by Q-PCR, while the generation of nitric oxide (NO) and lysyl oxidase (LOX) activity was calculated by colorimetric methods. Key findingsCDs were successfully prepared and characterized. Cell viability decreased in the treated cells dose- and time-dependently. HCT-116 and HT-29 cells uptook Cu, N-CDs with a high level of ROS generation. The Oil Red O staining showed lipid accumulation. Concomitant with an up-regulation of apoptotic genes (p < 0.05), AO/PI staining showed increased apoptosis in the treated cells. In comparison to control cells, NO generation, and miRNA-182 and miRNA-21 expression significantly changed in the Cu, N-CDs treated cells (p < 0.05). SignificanceThe results indicated that Cu, N-CDs could inhibit CRC cells through the induction of ROS generation and apoptosis.

Up-conversion and downconversion studies of Nd3+ doped borophosphate glasses

Neodymium doped borophosphate glasses have been synthesizsed by melt quenching technique to investigate their luminescence properties. The increase in density and decrease in molar volume with increasing concentration of Nd2O3 (0.1 mol% to 0.5 mol%) established the participation of Nd3+ in the glass structure. Non-crystalline nature of prepared glasses is confirmed by the absence of sharp peaks in X-ray diffraction spectra. The various structural units due to B2O3, P2O5, and PbO were identified by Fourier transform infrared spectroscopy. Ultraviolet visible absorption spectroscopy showed various absorption peaks/bands at 742 nm (4F7/2+4S3/2), 684 nm (4F9/2), 626 nm (2H11/2), 581 nm (4G5/2+2G7/2), 523 nm (4G7/2+4G9/2+ 2K13/2), 431 nm (2D5/2+2P1/2), 358 nm (4D3/2+4D5/2), 338 nm (2I11/2), and 315 (4D7/2+2I13/2+2L15/2). The optical parameters, namely indirect band gap, molar refractivity, molar polarizability, electronic polarizability and dielectric constant showed linear trend with increasing concentration of Nd2O3. Judd-Ofelt parameters followed Ω6> Ω4> Ω2 trend. The experimental and calculated oscillator strength for 584 nm is highest among all transitions because it is hypersensitive in nature. Upon 806 nm excitation, four visible peaks at 489 nm, 540 nm, 605 nm and 671 nm were observed. Excited state absorption up-conversion and energy transfer up-conversion mechanisms were responsible for visible up-conversion. At 338 nm, ultraviolet energy is downconverted to 448 nm, 529 nm, 591 nm. Commission International de I'Eclairage (CIE) chromaticity coordinates were evaluated from the up-conversion emission spectra and the coordinates lie in green region.

A nostoxanthin-producing bacterium, Sphingomonas nostoxanthinifaciens sp. nov., alleviates the salt stress of Arabidopsis seedlings by scavenging of reactive oxygen species.

A novel, nostoxanthin-producing, endophytic bacterium, designated as AK-PDB1-5T, was isolated from the needle-like leaves of the Korean fir (Abies koreana Wilson) collected from Mt. Halla in Jeju, South Korea. A 16S rRNA sequence comparison indicated that the closest phylogenetic neighbors were Sphingomonas crusticola MIMD3T (95.6%) and Sphingomonas jatrophae S5-249T (95.3%) of the family Sphingomonadaceae. Strain AK-PDB1-5T had a genome size of 4,298,284 bp with a 67.8% G + C content, and digital DNA-DNA hybridization and OrthoANI values with the most closely related species of only 19.5-21% and 75.1-76.8%, respectively. Cells of the strain AK-PDB1-5T were Gram-negative, short rods, oxidase- and catalase-positive. Growth occurred at pH 5.0-9.0 (optimum pH 8.0) in the absence of NaCl at 4-37°C (optimum 25-30°C). Strain AK-PDB1-5T contained C14:0 2OH, C16:0 and summed feature 8 as the major cellular fatty acids (> 10%), while sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, phospholipids and lipids were found to be the major polar lipids. The strain produces a yellow carotenoid pigment; natural products prediction via AntiSMASH tool found zeaxanthin biosynthesis clusters in the entire genome. Biophysical characterization by ultraviolet-visible absorption spectroscopy and ESI-MS studies confirmed the yellow pigment was nostoxanthin. In addition, strain AK-PDB1-5T was found significantly promote Arabidopsis seedling growth under salt conditions by reducing reactive oxygen species (ROS). Based on the polyphasic taxonomic analysis results, strain AK-PDB1-5T was determined to be a novel species in the genus Sphingomonas with the proposed name Sphingomonas nostoxanthinifaciens sp. nov. The type strain is AK-PDB1-5T (= KCTC 82822T = CCTCC AB 2021150T).

Biobased, Degradable, and Conjugated Poly(Azomethine)s.

Carotenoids are a class of biobased conjugated molecules that bear a resemblance to the substructure of polyacetylene, a well-known conductive but insoluble polymer. Solubility is an important physical attribute for processing materials using different techniques. To impart solubility in polymers, alkyl side chains are often included in the molecular design. While these design strategies are well explored in conjugated systems, they have not been implemented with carotenoids as a building block in polymers. Here, we show a series of carotenoid-based polymers with varying side chain lengths to tune solubility. Using carotenoid and p-phenylenediamine-based monomers, degradable and biobased poly(azomethine)s were synthesized via imine polycondensation. Maximum solubilities corresponding to the varying alkyl chain lengths were quantitatively determined by ultraviolet-visible (UV-vis) absorption spectroscopy. Since carotenoids are biobased with known degradation products, the effect of acidic and artificial sunlight-promoted degradation was systematically investigated using UV-vis spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, gel permeation chromatography (GPC), and high-resolution mass spectroscopy (HRMS). Our polymer system was found to have two modes of on-demand degradation, with acid hydrolysis accelerating the rate of polymer degradation and artificial sunlight generating additional degradation products. This work highlights carotenoid monomers as viable candidates in the design of biobased, degradable, and conjugated polymers.

Influence of a transient spark plasma discharge on producing high molecular masses of chemical products from l-cysteine

Cold atmospheric pressure plasmas are considered a forthcoming method in many research areas. Plasma modification of biomolecules has received much attention in addition to plasma-treated biomaterials. Hence, in this work, we operated a transient spark plasma (TSP) discharge to study its effect on the l-cysteine chemical structure. the TSP was configured in a pin-to-ring electrode arrangement and flowed by Ar gas. We also investigated the effect of two chemicals; dimethyl sulfoxide (DMSO) and hydrogen peroxide (H2O2) by the bubbling method to show how they can change the creation of new chemical bioproducts. Ultraviolet–Visible absorption spectroscopy, Fourier transform infrared spectroscopy and Liquid chromatography–mass spectroscopy were used to investigate any changes in chemical bonds of cysteine structure and to depict the generation of new biomolecules. Based on the displayed results plasma-generated reactive species had a great role in the chemical structure of the cysteine. Entering DMSO and H2O2 into the plasma caused the creation of new products and the heaviest biomolecule was produced by the simultaneous addition of DMSO and H2O2. The results also predicted that some chemical products and amino acids with a higher value molecular masse produced from the polymerization process of cysteine solution. The strong oxidation process is responsible for the heavy chemical compounds.

Insights into surface circulation and mixing in James Bay and Hudson Bay from dissolved organic matter optical properties

Hudson Bay and James Bay are fed by numerous rivers, which also deliver large amounts of dissolved organic matter (DOM). The objective of this study is to assess Hudson Bay wide DOM spatial distribution using ultraviolet-visible light absorption and excitation-emission matrix fluorescence spectroscopies. Overall, a five-component PARAFAC model was validated using 1060 discrete samples collected over nine field campaigns between 2009 and 2018 and including the first samples from James Bay ( n = 112). Regional and seasonal variations were observed. Particularly striking was a 9-fold difference in concentration between coastal and marine zones of these bays, which implies limited mixing between those regions. Seasonal variations in absorption coefficient at 355 nm and terrestrial humic-like components were found only in east Hudson Bay, revealing a regional disparity in seasonal DOM behaviour. The summer intensities and relative abundances of DOM revealed that cyclonic circulation transports terrestrial DOM around James Bay following its eastern shores before being transported northward along the western coast of Belcher Islands. The vertical distribution of DOM indicated that fluorescent DOM is delivered to the deeper layer by winter convective mixing in northern Hudson Bay. • Limited mixing between the coastal and marine regions of the bay is observed. • The strong terrestrial signal of east James Bay is found in northern Belcher Island. • DOM is delivered to the deeper layer by winter convection in northern Hudson Bay.

Interactions between polycyclic musks and human lactoferrin: Multi-spectroscopic methods and docking simulation.

Galaxolide (1,3,4,6,7,8-hexahydro-4,6,6,7,8-hexamethylcyclopenta-γ-2-benzopyrane; HHCB) and Tonalide (7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene; AHTN) are "pseudo-persistent" pollutants that can cause DNA damage, endocrine disruption, organ toxicity, and reproductive toxicity in humans. HHCB and AHTN are readily enriched in breast milk, so exposure of infants to HHCB and AHTN is of concern. Here, the molecular mechanisms through which HHCB and AHTN interact with human lactoferrin (HLF) are investigated using computational simulations and spectroscopic methods to identify indirectly how HHCB and AHTN may harm infants. Molecular docking and kinetic simulation studies indicated that HHCB and AHTN can interact with and alter the secondary HLF structure. The fluorescence quenching of HLF by HHCB, AHTN was static with the forming of HLF-HHCB, HLF-AHTN complex, and accompanied by non-radiative energy transfer and that 1:1 complexes form through interaction forces. Time-resolved fluorescence spectroscopy indicated that binding to small molecules does not markedly change the HLF fluorescence lifetime. Three-dimensional fluorescence spectroscopy indicated that HHCB and AHTN alter the peptide chain backbone structure of HLF. Ultraviolet-visible absorption spectroscopy, simultaneous fluorescence spectroscopy, Fourier-transform infrared spectroscopy, and circular dichroism spectroscopy indicated that HHCB and AHTN change the secondary HLF conformation. Antimicrobial activity experiments indicated that polycyclic musks decrease lactoferrin activity and interact with HLF. These results improve our understanding of the mechanisms involved in the toxicities of polycyclic musks bound to HLF at the molecular level and provide theoretical support for mother-and-child health risk assessments.

Inhibition of albendazole and 2-(2-aminophenyl)-1H-benzimidazole against tyrosinase: mechanism, structure-activity relationship, and anti-browning effect.

Tyrosinase is the key enzyme involved in enzymatic browning of plant-derived foods. Inhibition of tyrosinase activity contributes to the control of food browning. Due to safety regulations or other issues, most identified tyrosinase inhibitors are not suitable for practical use. Therefore, it is necessary to search for novel tyrosinase inhibitors. In this study, the anti-tyrosinase activity and mechanism of albendazole and 2-(2-aminophenyl)-1H-benzimidazole (2-2-A-1HB) were investigated through ultraviolet-visible absorption spectroscopy, fluorescence spectra, molecular docking, and molecular dynamic (MD) simulation. The anti-browning effect of albendazole on fresh-cut apples was then elucidated. Albendazole and 2-2-A-1HB were both efficient tyrosinase inhibitors with IC50 of 51 ± 1.5 and 128 ± 1.3 μmol L-1 , respectively. Albendazole suppressed tyrosinase non-competitively and formed tyrosinase-albendazole complex statically. Hydrogen bond and hydrophobic interaction were major driving forces in stabilizing the tyrosinase-albendazole complex. While 2-2-A-1HB inhibited the enzyme competitively and quenched its intrinsic fluorescence through a static mechanism, it generated strong binding affinity with tyrosinase through hydrophobic interaction. MD simulations further validated that albendazole/2-2-A-1HB could form stable complexes with tyrosinase and loosened its basic framework structure, leading to a change in secondary structure and conformation. In addition, albendazole could delay the browning of fresh-cut apples by inhibiting the activity of polyphenol oxidase, peroxidase and phenylalanine ammonia-lyase, and reducing the oxidation of phenolic compounds. This research might provide a deep view of tyrosinase inhibition by benzimidazole derivatives and a theoretical basis for developing albendazole as a potential fresh-keeping agent. © 2023 Society of Chemical Industry.

Green synthesis of silver nanoparticles using Eupatorium adenophorum leaf extract: characterizations, antioxidant, antibacterial and photocatalytic activities.

The green synthesis of metallic nanoparticles has tremendous impacts in various fields as found in recent years due to their low cost, easy and environmentally friendly synthesis. In this article, we report a simple and eco-friendly method for the synthesis of silver nanoparticles (AgNPs) using an aqueous Eupatorium adenophorum (E. adenophorum) leaf extract as a bioreductant. Interestingly, Fourier transform infrared (FTIR) spectroscopy analysis established that the E. adenophorum extract not only served as a bioreductant but also acted as a capping agent to stabilize the nanoparticles by functionalizing the surfaces. Various characterization techniques were adopted, such as X-ray powder diffraction (XRD), FTIR, ultraviolet-visible absorption (UV-Vis) spectroscopy, dynamic light scattering, scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDX) to analyze the biosynthesized AgNPs. Biosynthesized nanoparticles were also explored for antioxidant, antibacterial and photocatalytic activities. The AgNPs showed improved free radical scavenging activity (IC50 48.96 ± 0.84µg/mL) and bacterial inhibitory effects against both gram-positive (Staphylococcus aureus; 64.5µg/mL) and gram-negative (Escherichia coli; 82.5µg/mL) bacteria. Photocatalytic investigation showed AgNPs were effective at degrading rhodamine dye (78.69% in 90min) when exposed to sunlight. These findings collectively suggest that E. adenophorum AgNPs were successfully prepared without the involvement of any hazardous chemical and it may be an effective antibacterial, antioxidant and promising agent for the removal of hazardous dye from waste water produced by industrial dyeing processes.

Fabrication of Two Luminescent Imidazolyl Cadmium-Organic Frameworks and Their Sensing Mechanism for 2,6-Dichloro-4-nitroaniline.

2,6-Dichloro-4-nitroaniline, alias dicloran (DCN), is a broad-spectrum pesticide that can cause irreversible damage to the human body. Therefore, it is of great significance to develop a technology for the rapid and convenient detection of DCN. Luminescent metal organic frameworks have attracted extensive attention in the field of sensing and detection due to their excellent optical properties. In this study, two kinds of 2D Cd-MOFs (CdMOF-1 and CdMOF-2) were developed for the detection of residual DCN in the environment. Both CdMOFs exhibit excellent solvent and acid-base stability and can respond to DCN quickly and sensitively in a short time (30 s). CdMOFs not only have good selectivity and anti-interference toward DCN but also have good reusability. Under the conditions of DCN concentrations of 1-15 and 0.3-30 μM, the change in fluorescence intensity of CdMOF-1 and CdMOF-2 showed a good linear relationship with DCN concentration (R2 = 0.999/0.991), and the detection limits were 0.36 and 0.12 μM, respectively. Through ultraviolet-visible absorption spectroscopy (UV-Vis), X-ray photoelectron spectroscopy, fluorescence lifetime, and density functional theory calculations, it is revealed that the fluorescence quenching mechanisms of DCN for two kinds of Cd-MOFs are competitive absorption and photoinduced electron transfer, and there may be a weak π-π interaction. Finally, it is demonstrated that by using two types of fluorescent CdMOFs to make the fluorescent test paper and detect actual soil, these can be applied to the actual scene and achieve onsite real-time detection.