UV-vis Absorption Spectroscopy Research Articles

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

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

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

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

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

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

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

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

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

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

The mechanism of interaction between tri-para-cresyl phosphate and human serum protein: a multispectroscopic and in-silico study

Organophosphate flame retardants (OPFRs) pose the significant risks to the environment and human health and have become a serious public health issue. Tricresyl phosphates (TCPs), a group of aryl OPFRs, exhibit neurotoxicity and endocrine disrupting toxicity. However, the binding mechanisms between TCPs and human serum albumin (HSA) remain unknown. In this study, through fluorescence and ultraviolet-visible (UV-vis) absorption spectroscopy, molecular docking and molecular dynamics (MD), tri-para-cresyl phosphate (TpCP) was selected to explore potential interactions between HSA and TCPs. The results of the fluorescence spectroscopy demonstrated that a decrease the fluorescence intensity of HSA and a blue shift were observed with the increasing concentrations of TpCP. The binding constant (Ka) was 2.575 × 104 L/mol, 4.701 × 104 L/mol, 5.684 × 104 L/mol and 9.482 × 104 L/mol at 293 K, 298 K, 303 K, and 310 K, respectively. The fluorescence process between HSA and TpCP involved a mix of static and dynamic quenching mechanism. The gibbs free energy (ΔG0) of HSA-TpCP system was -24.452, -25.907, 27.363, and 29.401 kJ/mol at 293 K, 298 K, 303 K, and 310 K, respectively, suggesting that the HSA-TpCP reaction was spontaneous. The enthalpy change (ΔH0) and thermodynamic entropy change (ΔS0) of the HSA-TpCP system were 291.08 J/K mol and 60.83 kJ/mol, respectively, indicating that hydrophobic force was the major driving forces in the HSA-TpCP complex. Furthermore, multispectral analysis also revealed that TpCP could alter the microenvironment of tryptophan residue and the secondary structure of HSA and bind with the active site I of HSA. Molecular docking and MD simulations confirmed that TpCP could spontaneously form a stable complex with HSA, which was consistent with the fluorescence experimental results. This study provides novel insights into the mechanisms of underlying the transportation and distribution of OFPRs in humans.

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

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

Simultaneous purification and oxidation of the as-synthesized MWCNTs with KMnO4 using phase transfer catalyst at three different pH medium by the hydrothermal method

Improving and streamlining current oxidation techniques for experimental is the main goal of the research described in the present article. By applying the pressure created while on the hydrothermal process to an autoclave walled with Teflon, simplifying the procedure was accomplished. By comparing the degrees of functionalization attained with the dispersibility in the substantially pure and functionalized multi-walled carbon nanotubes (MWCNTs) final product, the beneficial effect of the procedure was evaluated. In order to achieve this, the study looked at and investigated how as-synthesized MWCNTs from Fe-Mo/MgO catalyst were simultaneously purified and oxidized using the chemical vapor deposition (CVD) method. Aliquot-336 was used as phase transfer catalyst (PTC) by hydrothermal method under three different pH conditions. Following functionalization, nanotubes of carbon might easily combine with various chemical reagents to generate homogeneous dispersions or even well-aligned structures because of the functional groups linked to their surfaces. In this case, a chemical called reagent potassium permanganate (KMnO4) is necessary in order to target particular π-bonds while entirely destroying the nanotubes' graphene structures. The techniques have been explained in terms of mechanism, and the Fourier transform-infrared (FT-IR) spectroscopy has confirmed the functionalizations of the CNTs. These approaches were further explored through FT-Raman spectrum analysis, thermal assessments, energy dispersive X-ray spectroscopy (EDX), TEM (transmission electron microscopy) along with the help of EDX, and visible-near IR absorption and UV–visible absorption spectroscopy (ABS) procedures.

Hydrothermally synthesized Nb -doped TiO2 nanosheets for efficient removal of methylene blue dye on photocatalytic performance

In this work, Niobium-doped (1%, 3%, and 5%) titanium dioxide (Nb-TiO2) nanosheets were successfully formed via the hydrothermal route and further characterized using TEM, XRD, XPS and UV–vis absorption spectroscopy techniques. Phase purity and structural information of the prepared materials were analysed by XRD measurements. The band gap values ranged from 3.27 to 2.98 eV as Nb doping increased, leading to improved photocatalytic activity by creating new energy levels close to the conduction band. The XPS results confirm the amalgamation of Nb5+ ions into TiO2 without affecting the crystallinity, structure or orientation of the occurrence of oxygen vacancies. In 3% Nb-doped TiO2, the degradation efficiency for removing (Methylene blue) MB dye increased by ∼96% for the removal of MB dye within 70 min in comparison to pure and other doped TiO2 catalysts The better photocatalytic activity of 3% Nb-TiO2 is due to the longer time between electron–hole pairs before they recombine into one pair. Hydroxyl radicals (HO•) and superoxide radicals (O2 •−) are the primary reactive entities responsible for the deterioration of MB dye. Therefore, incorporating Nb into TiO2 nanostructures represents an auspicious material for the decomposition of hazardous and toxic pollutants in aquatic environments.

In situ nitrogen-doped graphene-TiO2 nano-hybrid as an efficient photocatalyst for pollutant degradation.

To solve environmental-related issues (wastewater remediation, energy conservation and air purification) caused by rapid urbanization and industrialization, synthesis of novel and modified nanostructured photocatalyst has received increasing attention in recent years. We herein report the facile synthesis of in situ nitrogen-doped chemically anchored TiO2 with graphene through sol-gel method. The structural analysis using X-ray diffraction showed that the crystalline nitrogen-doped graphene-titanium dioxide (N-GT) nanocomposite is mainly composed of anatase with minor brookite phase. Raman spectroscopy revealed the graphene characteristic band presence at low intensity level in addition to the main bands of anatase TiO2. X-ray photoelectron spectroscopy analysis disclosed the chemical bonding of TiO2 with graphene via Ti-O-C linkage, also the substitution of nitrogen dopant in both TiO2 lattice and into the skeleton of graphene nanoflakes. UV-Vis absorption spectroscopy analysis established that the modified material can efficiently absorb the longer wavelength range photons due to its narrowed band gap. The N0.06-GT material showed the highest degradation efficiency over methylene blue (MB, ∼98%) under UV and sulfamethoxazole (SMX, ∼ 90.0%) under visible light irradiation. The increased activity of the composite is credited to the synergistic effect of high surface area via greater adsorption capacity, narrowed band gap via increased photon absorption, and reduced e-/h+ recombination via good electron acceptability of graphene nanoflakes and defect sites (Ti3+ and oxygen vacancy(Vo)). The ROS experiments further depict that primarily hydroxyl radicals (OH•) and superoxide anions (O2•-) are responsible for the pollutant degradation in the process redox reactions. In summary, our findings specify new insight into the fabrication of this new material whose efficiency can be further tested in applications like H2 production, CO2 conversion to value-added products, and in energy conservation and storage.

Biosynthesis, Antibacterial and Antifungal Activities of Ag Nanoparticles Prepared Using Piper nigrum Fruit Extract

Nanomaterials are promising alternatives to antibiotics with the potential to handle the menace of emerging multidrug resistance in pathogenic microbes. We report a simple biosynthetic approach to prepare Ag nanoparticles (NPs) with strong antibacterial and antifungal actions by using Piper nigrum fruit extract as a bioreducing agent. The biosynthesized material was characterized by SEM, AFM, TEM, HRTEM, XRD and UV–Visible absorption spectroscopy. SEM, AFM and TEM analyses provided evidence that the average diameter of the Ag NPs was 18[Formula: see text]nm, while XRD and HRTEM confirmed the FCC structure of Ag NPs. The biosynthesized Ag NPs demonstrated extremely strong antibacterial activity against Bacillus oceanisediminis and Escherichia coli, and showed extremely strong antifungal action against Schizosaccharomyces pombe, inhibiting their growth at very low concentrations of 3[Formula: see text][Formula: see text]g/mL, 4[Formula: see text][Formula: see text]g/mL and 3[Formula: see text][Formula: see text]g/mL, respectively. The molecular origin of their antibacterial and antifungal activity was studied using various molecular and biochemical assays. The results of these assays revealed a major role for reactive oxygen species (ROS) in the antifungal and antibacterial actions of the biosynthesized Ag NPs. Furthermore, morphological changes in cells and cell wall damage upon Ag NP treatment were observed by scanning electron microscopy. In addition, significant enhancement in protein leakage and fragmentation of DNA was also observed upon treatment of S. pombe, B. oceanisediminis and E. coli with Ag NPs. In conclusion, the observed extremely strong antibacterial and antifungal activities of biosynthesized Ag NPs are due to the oxidative stress triggered by ROS, causing cell wall damage and subsequent protein leakage and DNA fragmentation.

Quick methylene blue dye elimination via SDS-Ag nanoparticles catalysts

Methylene blue dye, being toxic, carcinogenic and non-biodegradable, poses a serious threat for human health and environmental safety. The effective and time-saving removal of such industrial dye necessitates the use of innovative technologies such as silver nanoparticle-based catalysis. Utilizing a pulsed Nd:YAG laser operating at the second harmonic generation of 532 nm with 2.6 J energy per pulse and 10 ns pulse duration, Ag nanoparticles were synthesized via an eco-friendly method with sodium dodecyl sulphate (SDS) as a capping agent. Different exposure times (15, 30, and 45 min) resulted in varying nanoparticle sizes. Characterization was achieved through UV–Vis absorption spectroscopy, scanning electron microscopy (SEM) imaging, and energy dispersive X-ray (EDX). Lorentzian fitting was used to model nanoparticle size, aligning well with SEM results. Mie’s theory was applied to evaluate the absorption, scattering, and extinction cross-sectional area spectra. EDX revealed increasing Ag and carbon content with exposure time. The SDS-caped AgNPs nanoparticles were tested as catalyst for methylene blue degradation, achieving up to 92.5% removal in just 12 min with a rate constant of 0.2626 min−1, suggesting efficient and time-saving catalyst compared to previously reported Ag-based nanocatalysts.

Studying the ability of olive leaves nanoparticles to reduce free radicals resulting from the effect of gamma rays on water

This study aims to explore the potential of olive leaves nanoparticles (OLNPs) in scavenging free radicals, particularly 2,2-diphenyl-1- picryl-hydrazyl-hydrate (DPPH), and their capability to mitigate the effects of ionizing radiation. The in vitro assessment of antioxidant activity revealed promising results for OLNPs, exhibiting effective DPPH scavenging within a concentration range of 0.00002 to 0.0001 g/l. Additionally, the natural nanoparticles demonstrated significant antioxidant capacity, suggesting their potential as radical scavengers against free radical-induced damages. Characterization of OLNPs was conducted using UV-Visible absorption spectroscopy, revealing surface Plasmon resonance absorption peaks around 287 nm. Furthermore, atomic force microscopy was employed to determine the morphology and size of the OLNPs, indicating an average diameter of 65 nm.

Facile synthesis of iodine variants-incorporated lithium perrhenate crystal and film: Resistive switching device and synaptic behavior

This study investigates the integration of iodine as a dopant into lithium perrhenate (LiReO4) using rhenium oxide (Re2O7) as a precursor, aiming to enhance the electrical conductivity of the compound, with implications for various material science applications. The iodine variants-incorporated LiReO4 (Iv@LiReO4·H2O) exhibits a notable improvement in the average electrical conductivity (∼ 2 S/cm) and light absorption across a broad spectrum, extending to the near-infrared range. Additionally, the doping process induces resistive switching and synaptic behaviors due to iodine diffusion. The presence of iodine and the partial reduction of Re oxide is confirmed by X-ray photoelectron spectroscopy, while UV-Vis absorption spectroscopy indicates the existence of incorporated iodine variants species. Density functional theory calculations further elucidate the mechanism by which iodine doping triggers a significant enhancement in electrical conductance, primarily by introducing a mixed-valence oxidation state in rhenium, leading to the narrowing of the band gap from 3.68 eV to 0.33 eV. This research suggests potential uses for Iv@LiReO4·H2O in applications to memristive neuromorphic devices.

Solvothermal Synthesis of Cu2ZnSnSe4 Nanoparticles and Their Visible-Light-Driven Photocatalytic Activity.

Cu2ZnSnSe4 (CZTSe) nanoparticles (NPs) were successfully synthesized via a solvothermal method. Their structural, compositional, morphological, optoelectronic, and electrochemical properties have been characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Field-emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), UV-vis absorption spectroscopy, and electrochemical impedance spectroscopy (EIS) techniques. Porosimetry and specific surface area in terms of the Brunauer-Emmett-Teller (BET) technique have also been studied. XRD indicates the formation of a polycrystalline kesterite CZTSe phase. Raman peaks at 173 and 190 cm-1 confirm the formation of a pure phase. TEM micrographs revealed the presence of nanoparticles with average sizes of ~90 nm. A BET surface area of 7 m2/g was determined. The CZTSe NPs showed a bandgap of 1.0 eV and a p-type semiconducting behavior. As a proof of concept, for the first time, the CZTSe NPs have been used as a visible-light-driven photocatalyst to Congo red (CR) azo dye degradation. The nanophotocatalyst material under simulated sunlight results in almost complete degradation (96%) of CR dye after 70 min, following a pseudo-second-order kinetic model (rate constant of 0.334 min-1). The prepared CZTSe was reusable and can be repeatedly used to remove CR dye from aqueous solutions.

Aqueous Two-Phase Flotation Combined with Gold Nanoparticle Colorimetry for Determination of Thiocyanate in Raw Milk

Thiocyanates are effective in inhibiting the growth of microorganisms in raw milk to extend shelf life, but excessive addition can cause human health problems. Currently, ion chromatography and spectrophotometry are the main methods used in industry to determine SCN, but the pre-treatment process is cumbersome and time-consuming and has low sensitivity. Aqueous two-phase flotation (ATPF) technology has the advantages of simplicity, rapidity and economy. In this study, an acetonitrile/ammonium sulfate ATPF–gold nanoparticle (AuNP) colorimetric method was developed for the determination of SCN− in raw milk, and ATPF was used to separate and concentrate SCN− in raw milk to improve the detection sensitivity under convenient and economical conditions. The separation conditions were optimized by single-factor experiments and RSM, while the detection conditions, effects of CTAB concentration, pH and reaction time, were investigated. The “aggregation–anti-aggregation” mechanism of the gold-nano colorimetric method for the determination of SCN− was investigated by UV-vis absorption spectroscopy (UV-vis) and transmission electron microscopy (TEM). Under the optimal separation and detection conditions, the SCN− concentration showed a linear relationship with A630/A520 values in the concentration range of 0–2.5 mg/L with R2 of 0.9933, limit of detection (LOD) of 0.0919 mg/L, limit of quantitation (LOQ) of 0.306 mg/L, intra-day precision of 5.3% and spiked recoveries of 80.91–101.25%. In addition, the ATPF-AuNP colorimetric method demonstrated high selectivity and stability.

Radiation-Induced Synthesis and Superparamagnetic Properties of Ferrite Fe3O4 Nanoparticles.

Ultra-small magnetic Fe3O4 nanoparticles are successfully synthesized in basic solutions by using the radiolytic method of the partial reduction in FeIII in the presence of poly-acrylate (PA), or by using the coprecipitation method of FeIII and FeII salts in the presence of PA. The optical, structural, and magnetic properties of the nanoparticles were examined using UV-Vis absorption spectroscopy, high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and SQUID magnetization measurements. The HRTEM and XRD analysis confirmed the formation of ultra-small magnetite nanoparticles in a spinel structure, with a smaller size for radiation-induced particles coated by PA (5.2 nm) than for coprecipitated PA-coated nanoparticles (11 nm). From magnetization measurements, it is shown that the nanoparticles are superparamagnetic at room temperature. The magnetization saturation value Ms = 50.1 A m2 kg-1 of radiation-induced nanoparticles at 60 kGy is higher than Ms = 18.2 A m2 kg-1 for coprecipitated nanoparticles. Both values are compared with nanoparticles coated with other stabilizers in the literature.

Label-free colorimetric analysis strategies based on adsorption-responsive surface-enhanced photochromic phenomena of tungsten(VI) oxide nanoparticles for amino acids.

Herein, we present a colorimetric detection method based on the surface-enhanced photochromic phenomenon of tungsten (VI) oxide (WO3) nanocolloid particles for α-amino acid (AA) molecules, including L-aspartic acid (Asp), L-glutamic acid (Glu), L-histidine (His), L-isoleucine (Ile), L-leucine (Leu), L-lysine (Lys), L-phenylalanine (Phe), and L-valine (Val). The UV-induced photochromic phenomena in the AA/WO3 binary aqueous systems were investigated using UV-Vis absorption spectrometry. The adsorption properties of the AA molecules on the surface of the WO3 nanocolloid particles have been identified using a combination of adsorption isotherm analysis and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. A good linear correlation between the concentration of the AAs adsorbed on the surface of the WO3 nanocolloid particles and the initial photochromic coloration rate in the corresponding UV-irradiated WO3 colloidal aqueous solution was obtained with over three orders of magnitude, indicating that the surface-enhanced photochromic phenomenon of the WO3 nanocolloid particle can be used to detect the AA molecules. In addition, based on the results of the UV-Vis absorption, ATR-FTIR, and adsorption isotherm analyses, we have experimentally demonstrated that the AA/WO3 binary aqueous system with inner-sphere adsorbed Ile, Leu, Lys, or Val molecules on the surface of the WO3 nanocolloid particles exhibits a more significant surface-enhanced photochromic phenomenon than the system with outer-sphere adsorbed Asp, Glu, His, or Phe molecules. The strong inner-sphere adsorption of the AA molecules successfully improved the limit of detection. This study provides valuable insights into a "label-free" colorimetric assay system based on the surface-enhanced photochromic phenomenon of the WO3 nanocolloid probe.

One-pot microwave-assisted approach of polydiacetylene/zinc oxide nanocomposite for reversible thermochromic

This study introduces a new technique to fabricate the reversible poly(PCDA/ZnO) nanocomposites thermochromism. Our preparation process is the solution-mixing method, which is supported by microwave synthesis time instead of ultrasonic bath or stirrer. The presence of ethanol molecules in aqueous media in the solution-mixing method induces dipolar polarization. In addition, the presence of Zn2+ leaking out of the ZnO can produce ionic polarization. These factors affect the shape of poly(PCDA/ZnO) nanocomposites based on their thermochromic properties. The optical properties of poly(PCDA/ZnO) nanocomposite were determined through UV-Vis absorption spectroscopy. The morphology of this nanocomposite was examined by scanning electron microscopy, and its crystallinity was investigated by X-ray diffraction. The inter-intrachain interaction was confirmed by infrared spectroscopy. In addition, the poly(PCDA/ZnO) nanocomposite embedding PVA was prepared. The reversible theromochromic properties of poly(PCDA/ZnO) nanocomposites demonstrated a higher color transition temperature with increasing microwave synthesis time. It is an important observation to understand the effect of microwave synthesis time on the morphology and reversible thermochromism of the poly(PCDA/ZnO) nanocomposite

Solid-state green synthesis of two (1:1) organic intermolecular compounds; their physico-chemical, thermal, single crystal growth, and atomic packing studies

The solid-state solvent free reaction method has been adopted for the one-pot synthesis of novel organic materials with utmost 100 % yield. To identify the composition forming the intermolecular compound (IMC), the solid-liquid equilibria of entire compositions have been studied by establishing the phase diagram of n, n-dimethylaminobenzaldehyde (DMAB) with anthranilamide (AN) and 2-chloro-4-nitro benzoic acid (CNBA). The structural changes and novelty of the IMCs to that of parents are studied using FTIR, NMR and X-ray diffraction. The studies of optical properties of intermolecular compounds using UV–vis absorption and fluorescence spectroscopy infer the significant fluorescence emission. The single crystals of both intermolecular compounds, ANDMAB and DMABCNBA, are grown from solution using slow evaporation technique. The single crystal X-ray diffraction studies reveal that IMC of AN and DMAB is a racemic mixture whereas IMC of DMAB and CNBA is a co-crystal, and both the crystals have crystallized in triclinic P1‾ space group. The thermal stability and thermal behaviors are also studied using the experimental heat of fusion values obtained from differential scanning calorimetry (DSC).