Decrease In Absorbance Research Articles

Simultaneous detection of Pb2+ and Cu2+ based on catalytic etching of AgNTs@AuNHs colorimetric nanoprobe

A colorimetric gold nanohexagonals coated silver nanotriangles (AgNTs@AuNHs) nanoprobe has been constructed for the ultrasensitive detection of trace Pb2+ and Cu2+, based on the fact that Pb2+ and Cu2+ as the catalyzer can selectively enhance the etching rate of AgNTs@AuNHs by S2O32−. In the presence of Pb2+, the inner AgNTs within the AgNTs@AuNHs undergo complete etching to form the hollow AuNHs, leading to the marked decrease in both absorbance and chrominance at 585 nm. In contrast, Cu2+ initiates an etching reaction on the AgNTs, subsequently extending to the AuNHs. These transformations give rise to the formation of hollow gold nanotriangles, accompanied by pronounced red-shifts in the absorption peaks of the detection system. The distinct optical responses induced by Pb2+ and Cu2+ in the AgNTs@AuNHs nanoprobe enable the sensitive and selective detection and quantification of these heavy metal ions. Furthermore, we successfully extracted RGB data from the color changes of AgNTs@AuNHs nanoprobe, enabling a straightforward visual readout for detection of Pb2+ and Cu2+. This method yields satisfactory recoveries when applied to the analysis of Pb2+ and Cu2+ in river water, rice, and onion samples, with detection results closely matching those obtained using ICP-MS. These results collectively underscore the practical applicability of the AgNTs@AuNHs nanoprobe.

Utilization of Ferrate Ion (FeO42-) as Oxidizing Agent for Reducing Color Intensity of Peat Water

Peat water from Central Kalimantan is generally yellow to brownish-red in color. It causes peat water to not be used as a source of water for daily needs. Humic acid, fulvic acid, and humin are organic compounds that cause peat water to become colored. One alternative step that can be taken for reducing the color intensity of peat water is to degrade color-causing organic compounds by using an oxidizing agent. A hexavalent form of iron ion (Fe6+), commonly called ferrate (FeO42-) in potassium ferrate compound, is a powerful oxidizing agent used in the present study. Potassium ferrate (K2FeO4) was synthesized by a wet oxidation method and characterized using a UV-Vis spectrophotometer and an X-Ray Diffractometer (XRD). The ferrate solution is purplish-red in color with a maximum wavelength of 510 nm. The XRD pattern shows strong diffraction peaks at 2θ which are characteristic of K2FeO4. The ferrate solution was then used to degrade color-causing organic compounds in the peat water from Central Kalimantan. Determination of the optimum degradation conditions was monitored by the absorbance decrease of organic compounds in peat water at a wavelength of 370 nm. The results showed that ferrate solution with a concentration of 80 ppm was able to degrade organic compounds in peat water at pH 8, with a removal efficiency of 100%. Keywords: oxidizing agent, ferrate ion (FeO42-), peat water

Fabrication and optical characterization of zinc telluride thin films using electrodeposition technique

A well adherent thin film of Zinc Telluride (ZnTe) has been deposited on Flourine doped Tin oxide glass substrates from acidic baths containing Zinc heptahydrate and Tellurium dioxide. Films of different thicknesses with their molar concentrations were obtained. A mini Schimadzu UV-VIS Spectrophotometer was used to determine the optical absorbance of the films over the wavelength range of 300-900nm at room temperature. There is a decrease in absorbance as the molar concentrations of the precursors increases; while transmittance and energy band gap shown an increase. The band gap values obtained varied between 2.10eV and 2.7eV, for as deposited films. Also, photoelectrochemical cell (PEC) measurement reveals that ZnTe thin films exhibit p-type conductivity.

Investigation of cyanine-based infrared dyes as calibrants in radiochromic films.

Radiochromic material such as lithium pentacosa-10,12-diynoate (LiPCDA) has been suggested as the radiation-sensitive material for real-time in vivo fiber-optic dosimetry. In this configuration, micron-thick radiochromic coating would measure the absorbed dose, where a major challenge is the uncertainty in the active material thickness, necessitating calibration. A homogeneously incorporated inert infrared (IR) dye, which must also be stable in ambient conditions and against radiolysis, can be added to the radiochromic film to enable optical calibration. This study investigates four commercial cyanine-based dyes (IR-783, IR-806, IR-868, and IR-880) for use as an optical calibrant in fiber-optic radiochromic dosimeters. All dyes were dissolved in water to confirm solubility. IR-783 and IR-806 were dissolved in 10% w/w gelatin solution and coated onto a polyester substrate, which were then sandwiched between two layers of adhesives forming IR-783 and IR-806 films. A second batch of IR dyes in gelatin incorporated the LiPCDA, and was coated onto substrate and sandwiched between adhesive to form IR dye+LiPCDA films. The absorbance spectra of the films were measured periodically (176 and 102 days for IR-dye films, and IR dye+LiPCDA, respectively). The average percentage absorbance, normalized to day 1, was fit to either a single or a double exponential decay model to calculate the spectral stability lifetime (τ1 , τ2 ). Films were irradiated using a 6 MV LINAC beam with a standard setup of 100 source to axis distance (SAD), 10cm×10cm field size and 1.5cm depth. The change in absorbance of the IR-dye+LiPCDA films were measured after they were irradiated to 1, 2, 5, 10, and 20Gy at 3Gy/min. Only IR-783 and IR-806 were sufficiently water soluble. In gelatin matrix, these dyes demonstrated a decrease in absorbance with time for IR-783 and IR-806 dyes, with IR-783 films having an average τ1 =73±7 days and IR-806 films τ1 =7±3 days. When combined with LiPCDA, IR-806 degraded, losing its original peak at ∼820nm. Similarly, IR-783, combined with LiPCDA, showed signs of degradation; however, its original absorbance peak was still observed at ∼800nm. In the IR-783+LiPCDA films, the IR-783 dye had a τ=4±1 days, an order of magnitude faster than the IR-783 with no LiPCDA films. When exposed to x-ray irradiation, the IR-783 dye in the IR-783+LiPCDA films showed no change in absorbance with increasing absorbed dose. In contrast, the LiPCDA in the films responded as expected, increasing in optical density with increased absorbed dose. IR-783 and IR-806 dyes were observed to degrade over time following exponential decay curves. IR-806 could not be combined with the LiPCDA without degrading. The combination of IR-783 with LiPCDA demonstrated single exponential decay behavior at a comparatively faster rate than films that did not have LiPCDA. IR-783 was insensitive to ionizing radiation and thus may be suitable for thickness correction, but an alternative manufacturing procedure may need to be developed.

Formation and estimated toxicity of trihalomethanes and haloacetic acids from chlorination of nonylphenol-containing water: Effect of chlorine and bromide concentration, contact time, and pH

The presence of nonylphenol (NP), an endocrine-disrupting chemical (EDC), in water sources can form toxic chlorination disinfection by-products (DBPs) during the water disinfection process using chlorine. This study investigated the formation of trihalomethanes-4 (THM4) and haloacetic acids-5 (HAA5) as regulated DBPs during the chlorination process of NP-containing water. The effects of chlorine dose, bromide concentration, pH, chlorine contact time, and the presence of NP in real natural water on THM4 and HAA5 formation were investigated. The increase of chlorine dose increased all of the THM4 and HAA5 formation especially chlorinated DBPs (Cl-DBPs), including trichloromethane (TCM) (0.140 %) and dichloroacetic acid (DCAA) (0.722 %) when the chlorine concentration was 5 times higher than NP. However, the increase of bromide concentration increased the formation of brominated DBPs (Br-DBPs), reaching concentration yields of 1.615 % for tribromomethane (TBM) and 0.421 % for dibromoacetic acid (DBAA), but decreased the chlorinated (Cl-DBPs formation). Similarly, the increase of chlorine contact time and pH increased the DBPs formation significantly especially Br-DBPs. The TBM and DBAA concentration yields reached 1.615 % and 0.676 %, respectively, when chlorinated at pH 9 and reached 0.653 % and 0.751 %, respectively, when chlorinated for 168 h. The addition of NP in natural water also raised the hydrophilicity of dissolved organic matter (DOM), indicated by the decrease of specific ultraviolet absorbance (SUVA) value, which enhanced the formation of certain species including THM4 and HAA5. Based on toxicity calculation, the regulated DBPs formed were cytotoxic rather than genotoxic.

Carnauba Straw as Feedstock for Solid Biofuel Production

Carnauba straw (<em>Copernicia prunifera</em>), residual biomass derived from wax extraction, was evaluated as a potential feedstock for bioenergy production. The characterization was carried out using elemental analysis, proximate analysis, Higher Heating Value (HHV), FTIR spectroscopy, SEM, and FRX. The carbonization, using a Muffle Furnace, was applied as a thermal conversion technique to improve the fixed carbon content, and preliminary densification was done to assess the potential for future production of briquettes. The C, H, N, O, and S percentages were 44.43%, 5.34%, 2.25%, 46.17%, and 1.81%, respectively. The percentage of fixed carbon (14.17%) increased to 31.10% (250°C) and 35.68% (300°C) after carbonization. At 400°C, the HHV presented a decrease of 9.62%, and ash content increased by 177.66%. FTIR spectra showed bands characteristic of hemicellulose, cellulose, and lignin at 3414 - 3393 cm<sup>-1</sup> (O-H) and decrease of absorbance of 74.01% to 81.37% after carbonization; 1738 – 1603 cm<sup>-1</sup> (C=O), with reduction in the order of 73.94% to 78.31%, and 48.97% to 73.76%, when compared to the absorbances of the biomass in nature. The SEM of the carnauba straw in nature presented the main structural components (cellulose, lignin, and hemicellulose). After carbonization, evidence of degradation and coal formation was observed, which corroborates with the decrease in the HHV and increase of ash. The FRX was inserted in the SEM images, and the elements detected were Ca, K, and S. The quantities and order of abundance in biomass natural and carbonized were compatible with other biomasses used as biofuel. The carnauba straw in natural and carbonized was densified to understand the characteristics of the compacted material. The sample carbonized at 300°C presented a solid with the potential for future production of briquettes. All results follow other reported biomasses and could lead to further investigation of the carnauba straw as feedstock for solid fuel production without or in a mixture with other agricultural residues.

Small Molecule Interactions with Biomacromolecules: DNA Binding Interactions of a Manganese(III) Schiff Base Complex with Potential Anticancer Activities.

A manganese(III) complex, [MnIII(L)(SCN)(enH)](NO3)·H2O (1•H2O) (H2L = 2-((E)-(2-((E)-2-hydroxy-3-methoxybenzylidene-amino)-ethyl-imino)methyl)-6-methoxyphenol), has been synthesized and characterized by single-crystal X-ray diffraction analysis. The interaction of 1•H2O with DNA was studied by monitoring the decrease in absorbance of the complex at λ = 324 nm with the increase in DNA concentration, providing an opportunity to determine the binding constant of the 1•H2O-ct-DNA complex as 5.63 × 103 M-1. Similarly, fluorescence titration was carried out by adding ct-DNA gradually and monitoring the increase in emission intensity at 453 nm on excitation at λex = 324 nm. A linear form of the Benesi-Hildebrand equation yields a binding constant of 4.40 × 103 M-1 at 25 °C, establishing the self-consistency of our results obtained from absorption and fluorescence titrations. The competitive displacement reactions of dyes like ethidium bromide, Hoechst, and DAPI (4',6-diamidine-2'-phenylindole dihydrochloride) from dye-ct-DNA conjugates by 1•H2O were analyzed, and the corresponding KSV values are 1.05 × 104, 1.25 × 104, and 1.35 × 104 M-1 and the Kapp values are 2.16 × 103, 8.34 × 103, and 9.0 × 103 M-1, from which it is difficult to infer the preference of groove binding over intercalation by these DNA trackers. However, the molecular docking experiments and viscosity measurement clearly indicate the preference for minor groove binding over intercalation, involving a change in Gibbs free energy of -8.56 kcal/mol. The 1•H2O complex was then evaluated for its anticancer potential in breast cancer MCF-7 cells, which severely abrogates the growth of the cells in both 2D and 3D mammospheres, indicating its promising application as an anticancer drug through a minor groove binding interaction with ct-DNA.

Magnetic Molecular Imprinted Polymers-Based Nanozyme for Specific Colorimetric Detection of Protocatechuic Acid

Magnetic molecular imprinted polymers nanozyme MIPs@Fe3O4-NH2 with high specificity and excellent peroxidase-like activity was prepared for colorimetric detection of protocatechuic acid (PCA). Firstly, MIPs@Fe3O4-NH2 was obtained by self-polymerization of dopamine as a functional monomer on the surface of Fe3O4-NH2, enabling the formation of specific recognition cavities. Later, the elution of PCA using polar solvents resulted in the creation of well-defined recognition sites on the surface of MIPs@Fe3O4-NH2. The synthesized MIPs@Fe3O4-NH2 exhibits rapid and selective magnetic separation of PCA. Meanwhile, MIPs@Fe3O4-NH2 possesses peroxidase-like activity, enabling it to undergo a colorimetric reaction 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 and leading to a distinct color change. When the 3D recognition cavities on the surface of MIPs@Fe3O4-NH2 specifically bind to PCA, they restrict the exposures of the nanozyme’s activity sites and hinder their contact with the chromogenic substrate, which decreases the absorbance of the system. Based on this phenomenon, it demonstrates a good linear relationship between the decrease in absorbance and the concentration of PCA within the range of 1 to 250 μM, with a detection limit of 0.84 μM. Notably, this method offers excellent selectivity, and presents a straightforward preparation process, allowing for easy visualization of detection results. Consequently, it provides a promising and versatile strategy for the subsequent development of colorimetric sensors based on molecular imprinted polymers.

Study of the interaction between polyphenol, quercetin and three micelles with different electric charges in acidic and aqueous media

The interactions between the polyphenol quercetin, Q, with three surfactant aggregates with different electric charges named micelles, were studied in aqueous solutions with pH values 4.7 and 7.0, to determine the following parameters: critical micellar concentration (CMC), micelle size and binding constant of the complex (Q-Micelle) proposing interaction sites for the formation of the complex. The surfactants used were: hexadecyltrimethyl ammonium bromide (cationic surfactant), CTAB, sodium dodecyl sulfate (anionic surfactant), SDS, and triton X-100 (non-ionic surfactant), TX100, used as Q fluorescence promoters to determine the CMC. The CMC values of the above surfactants at pH 4.7 were: 0.80 ± 0.10, 1.39 ± 0.07 and 0.59 ± 0.05 mM respectively, being lower than those reported in the water. With dynamic light scattering measurements, the hydrodynamic diameters of each micelle were calculated resulting in values of: 2.4 ± 0.5, 5.0 ± 1.1 and 8.4 ± 4.3 nm at pH 4.7 and: 2.1 ± 0.4, 4.9 ± 1.1 and 11.5 ± 4.1 nm at pH 7.0 respectively. In addition, the binding constants of the complex (Q-Micelle) with 1:1 stoichiometry were calculated from emission fluorescence data giving Log K values: 2.94 ± 0.02, 2.54 ± 0.02, and 3.63 ± 0.05 M-1 respectively. Finally, from the experimental data by UV–Vis spectrophotometry, the change in the behavior of the Q spectrum upon the addition of each of the surfactants to the system was analyzed, showing a decrease in absorbance when SDS and TX100 were added in an acidic medium, as a consequence of the photo-instability of the drug, suggesting that Q interacts with the outside of these micelles and is not fully incorporated inside them.

A green compliant hand-held selective electrode device for monitoring active pharmaceuticals and the kinetics of their degradation

An in-line smartphone connected to a screen-printed selective electrode hand-held device was used to determine the concentration of distigmine bromide (DB) in its pure and dosage forms as well as its degradation kinetics by continuously measuring the change in the produced emf over time. The main objective, supported by the data presented, is to produce a highly reliable smartphone integrated selective sensor as a portable analyzer with potential high cloud connectivity combining a wide linear dynamic range, the fastest response time with the lowest limits of detection and quantitation while best integrating green analytical chemistry principles. The choice of ionophore used in this approach was guided by computation and the data obtained was compared with traditional analytical techniques. DB, for which there are no previously reported stability-indicating methods and for which four novel such methods are proposed here, was selected as a model drug for this work. At-line UV-spectrophotometry DB assay was obtained by measuring the difference between the spectra of the degradation product and the same concentration of intact drug. The degradation kinetics were studied by this method through tracking the decrease of DB absorbance and/or the increase of a generated degradation product signal over time. Off-line separation based HPLC and TLC stability-indicating methods for DB were also presented. All methods employed in this work were validated for accuracy, precision, specificity, repeatability, linearity, range, detection and quantification limits according to the ICH guidelines and were applied to the analysis of laboratory prepared mixtures as well as commercial products. While all methods proposed were shown to be highly reliable, the smartphone integrated selective sensor is highlighted as a portable analyzer with potential high cloud connectivity and was shown to combine a wide linear dynamic range, the fastest response time with the lowest limits of detection and quantitation while best integrating green analytical chemistry principles.

LSPR-Based Aptasensor for Rapid Urinary Detection of NT-proBNP.

N-terminal pro-brain natriuretic peptide (NT-proBNP) is a myocardial stress biomarker that can be found in serum or plasma, saliva, and urine in the context of cardiovascular disease. In this study, we developed a rapid (~25 min) and straightforward localized surface plasmon resonance (LSPR)-based assay for detecting NT-proBNP in urine. The assay employs citrate-capped gold nanoparticles (AuNPs) and an aptamer specific for NT-proBNP, which initially interacts with NT-proBNP. The remaining unbound aptamer then interacts with the AuNPs, and the addition of NaCl induces the aggregation of the unprotected AuNPs, resulting in a decrease in absorbance at the LSPR band (A521) and an increase in absorbance at 750 nm (A750). The concentration of NT-proBNP showed a linear correlation with the aggregation ratio (A521/A750), and the assay demonstrated a limit of detection (LOD) of 0.303 µg·L-1 and a detection range of 0.566-8 µg·L-1. However, the presence of sulfur-containing proteins in saliva and fetal bovine serum hindered the detection of NT-proBNP in these biofluids. Nevertheless, the assay successfully detected NT-proBNP in diluted urine with an LOD of 0.417 µg·L-1 and a detection range of 0.589-6 µg·L-1. The observed values in urine samples from preterm infants with cardiovascular disease fell within this range, indicating the potential clinical relevance of the assay. The recovery percentages ranged from 92.3 to 116.3%. Overall, our findings suggest that the LSPR-based assay for NT-proBNP detection in urine can be a valuable tool for the diagnosis and treatment of cardiovascular disease.

Comparative Bioactivity Study of some Organotin (IV) 2-Chlorobenzoate compounds as Disinfectant agent

This research was carried out to study the bioactivitytest as disinfectant of two derivatives of organotin(IV) carboxylate compounds; diphenyltin(IV) di-2-chlorobenzoate (DPT2-CBz) (2) and triphenyltin(IV) 2-chlorobenzoate (TPT2-CBz) (4), against two pathogenic bacteria. Compounds 2 and 3 were successfully prepared by reactingdiphenyltin(IV) oxide (DPTO) (1) and triphenyltin(IV) hydroxide (TPTOH) (3) with 2-chlorobenzoic acid(2-HCBz)with yieldsof 87.71% and 88.73%, respectively. The characterization of the synthesized compounds was performed with several spectroscopy techniques such as UV, IR, 1HNMR, 13CNMR, and microelemental analyzer. The optical density (OD) test for both compounds measured using UV-Vis at 600 nm showeda goodbioactivity against two bacteria, Gram-negative Salmonella sp. and Gram-positive Staphylococcus aureus. The data revealed that compound 4 has bigger bioactivity than compound 2 and the positive control ofcommercial disinfectant (2.5% pine oil). The bioactivity of compound 4was optimum at concentration of 5x10-4 M and contact timeof 15 minutes.These data corresponding to the decrease of absorbance from 0.6640 to 0.0955 for Salmonella sp., and 0.6565 to 0.1295 for S. aureus, whereas although compound 2reached the optimum activityat the same concentration and contact time with compound 4, but the decrease of absorbance was less namely 0.6640 to 0.1305 for Salmonella sp., and 0.6565 to 0.196 for S. aureus. The decrease of absorbance in the measurement of OD implies that both compounds are potential to be used as disinfectant agent.

UV-Vis spectrophotometric determination of isoprene in atmosphere based on Diels–Alder reaction

ABSTRACT Isoprene is the most abundant biogenic volatile organic compound in the atmosphere. Till now, chromatography is the main detection method for isoprene, dependent on sophisticated instruments and complex operations. An UV-Vis spectrophotometric method based on the Diels–Alder (D-A) reaction was developed to detect isoprene in the atmosphere. The fast D-A reaction between the probe 4-phenyl−1,2,4-triazolin−3,5-dione (PTAD) and isoprene may cause absorbance decrease, which enable it to detect isoprene in solution at 118 nmol·L−1 level. Further, isoprene in air at the level of ppbv was detected using this method. Compared with chromatography this method has the advantages of low cost, fast and less dependence on instrument.

Kinetic study of Ru(III) – catalyzed oxidation of L-phenylalanine by hexacyanoferrate(III) in an anionic surfactant medium

Abstract The kinetic investigation of Ru(III) promoted oxidation of L-phenylalanine (L-PheAla) by [Fe(CN)6]3− has been performed in anionic sodium dodecyl sulfate (SDS) micellar medium by recording the decrease in absorbance at 420 nm corresponding to [Fe(CN)6]3− using an UV–visible spectrophotometer. Using the pseudo-first-order condition, the course of the reaction was studied as a function of [Fe(CN)6 3−], ionic strength, [OH−], [SDS], [Ru3+], [L-PheAla] and temperature by changing one variable at a time. The results exhibit that [OH−], [SDS], and [L-PheAla] are the crucial parameters that have an appreciable influence on the reaction rate. The reaction exhibits first-order kinetics in concentration ranges of Ru(III), [Fe(CN)6]3− and at low [L-PheAla] and [OH−] concentrations. The incremental trend observed in the reaction rate with electrolyte concentration shows a positive salt effect. The reaction rate is almost 10 times faster in SDS micellar medium than in aqueous medium. [Fe(CN)6]3− has no appreciable effect on the CMC of SDS, since the polar head of SDS and [Fe(CN)6]3− are both negatively charged. The K+ obtained from K3[Fe(CN)6] and KNO3 decreases the repulsion between the negatively charged heads of the surfactant molecules, which decreases the CMC of SDS. The activation parameters also support the outer-sphere electron transfer mechanism.

Laser irradiation time influence on the optical and structural properties of copper phthalocyanine blue thin films

Copper phthalocyanine blue thin films were deposited on a glass substrate 219.12 nm thick at room temperature and deposited by a spin coating technique. After deposition, the thin films were irradiated at different laser wavelengths 650 532 and 405 nm for different irradiation times 0, 10, 20, and 30 min. The optical properties were measured before and after irradiating the thin films. The absorbance and reflectance decrease with increasing irradiation time. The same behavior is noticed for all laser wavelengths. The energy gap augment’s with augmenting irradiation time. XRD results show a decrease in the peak height with increasing time. Atomic mass microscopy data show that there is an obvious impact on thin films by laser radiation.

Enzyme-free colorimetric detection of uric acid on the basis of MnO2 nanosheets - mediated oxidation of 3, 3′, 5, 5′- tetramethylbenzidine

MnO2 nanosheets (MnO2 NSs) were prepared and used as both oxidant of 3, 3′, 5, 5′- tetramethylbenzidine (TMB) and recognizer of UA, a simple colorimetric approach for sensitive detection of uric acid (UA) was established. In the medium of weak acid, MnO2 NSs exhibited strong oxidation capacity and could oxidize colorless TMB to generate a blue oxidation product (oxTMB) with an absorbance signal. However, the introduction of UA could inhibit MnO2 NSs - mediated TMB oxidation and reduce the formation of oxTMB, resulting in the blue fading and the absorbance weakening. Under the conditions of incubation time 20 min, pH 3.0, TMB 0.5 mM, and MnO2 NSs 50 μM, the decrease in absorbance was linearly dependent on UA concentration in the range of 0.5–30.0 μM with a detection limit of 0.21 μM. Furthermore, the approach has been applied for determining UA in human urine samples with recoveries between 93.1 and 102.4 % and relative standard deviation less than 3.0 %.

Synthesis and characterization of a novel oxovanadium complex and stability of azo groups in the presence of laccase

A novel oxovanadium complex, prepared from the reaction of hydrated VOSO4 with an azo-ligand derived from the synthesis of 2‑hydroxy-5-(phenyldiazenyl)benzaldehyde and L‑serine, was structurally investigated using powder XRD, Rietveld analysis, infrared, ultraviolet-visible (UV-vis), circular dichroism (CD), fluorescence measurements, cyclic voltammograms (CV), electron spin resonance (ESR), and a superconducting quantum interference device (SQUID). In addition, the stability of the complex in the presence of laccase was also explored. The UV–vis absorption spectra of the studied complex exhibited a maximum degradation of ∼ 60% and minimum degradation of approximately ∼ 10% after two days of exposure to laccase based on the decrease in absorbance induced by azobenzene π-π* absorption. However, the rate of degradation is considerably slower than predicted.

Synthesis of SnS/SnO Nanostructure Material for Photovoltaic Application

Research Highlights
 
 Successfully synthesized SnS/SnO nanostructured material using successors ionic layer absorption and reaction (SILAR) technique.
 Granular nanocrystals were visible in the materials, and they were strewn unevenly and randomly throughout the glass surface.
 It was found that the sample processed at room temperature had the largest energy band gap.
 The transmittance in the visible area of the spectrum was stable and SnS/SnO was at its maximum in the UV region
 
 In this research, the SILAR method was used to synthesize environmentally-friendly SnS/SnO material for photovoltaic application, where 0.1 M of tin (II) chloride dihydrate (SnCl2.2H2O) was used to create the cationic precursor solution, and 0.01 M of thioacetamide (C2H5NS) was used to create the anionic precursor solution. The X-ray diffraction patterns of SnS/SnO material deposited on glass substrate at various deposition temperatures recorded a major peak at 45oC at 2 theta of 31.8997o, which corresponds to the face-centered cubic crystal structure (FCC). Diffraction peaks are visible in the pattern at planes 111, 200, 210, 211, and 300, which correspond to angles of 26.58°, 31.89°, 39.61°, 44.18°, and 54.85°, respectively. It was discovered that the crystallite/grain size and the lattice parameters decrease as the temperature of the deposition material rises. Granular nanocrystals were visible in the materials, and they were strewn unevenly and randomly throughout the glass surface. The spectra of the absorbance demonstrate that as light radiation passed through SnS/SnO films, it absorbed radiation as the wavelength increased from the UV region to the ultraviolet region of the spectra. It was discovered that the precursor temperature influences the material's absorbance; as the temperature rises, the absorbance decreases, making SnS/SnO an excellent material for photovoltaic systems. The transmittance in the visible area of the spectrum was stable and SnS/SnO was at its maximum in the UV region, it increased as the wavelength increased in the NIR region. It was found that the sample processed at room temperature had the largest energy band gap. SnS/SnO reveals an increase in thickness from 114.42 – 116.54 nm which resulted in a downturn in the resistivity of the deposited film from 9.040×109 – 6.455×109 (Ω·cm) while the conductivity of the deposited material increased from 1.106×10-10 – 1.549×10-10 (Ω·cm)-1.

Experimental and theoretical photocatalytic potential of binary NiTiO2 and ternary CdNiTiO2 nanocomposites of TiO2

The large band gap and the high electron–hole pair recombination rate of neat TiO2 limit its practical applications. Among different approaches, the nanocomposite formation by coupling TiO2 with other semiconducting materials of lower gap energy is a magnificent option. The same approach was followed for synthesizing NiTiO2 and CdNiTiO2 nanocomposites by co-precipitation method. The morphological analysis of the synthesized materials performed via scanning electron microscopy shows aggregated spherical shaped TiO2 NPs, while the synthesized nanocomposites have irregular shapes found in both dispersed and aggregated forms. The components of the nanocomposites are well mixed and intercalated to each other as confirmed by transmission electron microscopy. The X-Ray diffraction and energy dispersive X-ray analyses confirmed the anatase TiO2 of high purity. Brunauer Emmett Teller analysis has shown a 50.2 m2/g surface area for the ternary CdNiTiO2 nanocomposite. A red shift in the absorbance wavelength and decrease in band gap energy of the NiTiO2 (2.5 eV) and CdNiTiO2 (2.4 eV) compared to TiO2 (2.6 eV) shows efficient photocatalytic activity for the nanocomposites. The photo-degradation experiments in aqueous media by UV light interaction revealed about 72, 77, and 91.2% methylene blue and 69, 80, and 94.5 methyl orange dyes degradation for TiO2, NiTiO2 and CdNiTiO2, respectively within 100 min. Maximum photo-degradation is achieved in the basic medium (pH 10) and with a 0.030 g of photo-catalyst dosage. The density functional theory (DFT) simulations show that both the nanocomposites are energetically favorable, stable and show significantly tuned electronic properties compared to neat TiO2.

Tracking the Seconds of a Clock Reaction: A Multiparametric Experimental Study on the Catalytic Reduction of Methylene Blue

The catalytic reduction and subsequent reoxidation of methylene blue (MB) is a well-known reaction, commonly referred to as a “clock reaction”. Specifically, the reduction process is accompanied by a color change from intense blue to clear and can be readily monitored by UV–vis spectroscopy via the decrease in absorbance at λmax = 664 nm, providing facile access to valuable reaction kinetics. Unsurprisingly, the reduction of methylene blue has become a widely used probe for heterogeneous catalyst reactivity. Yet, despite its broad utility, the mechanism of reduction is not well-understood. Herein, we report an experimental study on the mechanism of MB reduction using Pt/C nanoparticles. Through a multiparametric study incorporating in situ probing of reaction kinetics, pH, dissolved oxygen, and variable catalyst and reductant loading, the multiple factors impacting the reaction are disentangled. We demonstrate that the reaction steps that limit the reduction of MB are the H2 evolution and reoxidation sequences. We limit these competitive reactions by optimizing reductant concentration and catalyst loading, N2 purging, and restriction of O2 redissolution. This achieves a highly competitive activity parameter of 25,740 min–1 gPt–1 L.