UV-vis Absorption Studies Research Articles

Rhodamine-azobenzene based single molecular probe for multiple ions sensing: Cu2+, Al3+, Cr3+ and its imaging in human lymphocyte cells.

A photoinduced electron transfer (PET) and chelation-enhanced fluorescence (CHEF) regulated rhodamine-azobenzene chemosensor (L) was synthesized for chemoselective detection of Al3+, Cr3+, and Cu2+ by UV-Visible absorption study whereas Al3+ and Cr3+ by fluorimetric study in EtOH-H2O solvent. L showed a clear fluorescence emission enhancement of 21 and 16 fold upon addition of Al3+ and Cr3+ due to the 1:1 host-guest complexation, respectively. This is first report on rhodamine-azobenzene based Cr3+ chemosensor. The complex formation, restricted imine isomerization, inhibition of PET (photo-induced electron transfer) process with the concomitant opening of the spirolactam ring induced a turn-on fluorescence response. The higher binding constants 6.7 × 103 M-1 and 3.8 × 103 M-1 for Al3+ and Cr3+, respectively and lower detection limits 1 × 10-6 M and 2 × 10-6 M for Al3+ and Cr3+, respectively in a buffered solution with high reversible nature describes the potential of L as an effective tool for detecting Al3+ and Cr3+ in a biological system with higher intracellular resolution. Finally, L was used to map the intracellular concentration of Al3+ and Cr3+ in human lymphocyte cells (HLCs) at physiological pH very effectively. Altogether, our findings will pave the way for designing new chemosensors for multiple analytes and those chemosensors will be effective for cell imaging study.

Facile Photochemical Syntheses of Conjoined Nanotwin Gold-Silver Particles within a Biologically-Benign Chitosan Polymer.

A simple photochemical method for making conjoined bi-metallic gold-silver (Au/Ag) nanotwins, a new breed of nanoparticles (NPs), is developed. To the best of our knowledge, the photochemical method resulted in distinct, conjoined, bimetallic nanotwins that are different from any well-established alloyed or core-shell nanostructures in the literature. The conjoined Au-Ag NPs possessed surface plasmon resonance (SPR) properties of both metals. The bimetallic nanostructures possessing distinctive optical properties of both metals were obtained using Au NPs as seeds in the first step, followed by the addition of a silver precursor as feed in the second step during a photochemical irradiation process. In the first step, small, isotropic or large, anisotropic Au NPs are generated by photoinduced reduction within a biocompatible chitosan (CS) polymer. In the second step, a silver precursor (AgNO3) is added as the feed to the AuNPs seed, followed by irradiation of the solution in the ice-bath. The entire photochemical irradiation process resulting in the formation of bimetallic Au-AgNPs did not involve any other reducing agents or stabilizing agents other than the CS polymer stabilizer. The small, conjoined Au-Ag bi-metallic NPs exhibited SPR with peak maxima centering at ~400 nm and ~550 nm, whereas the large conjoined nanoparticles exhibited SPR with peak maxima centering at ~400 nm, 550 nm, and 680 nm, characteristic of both gold and silver surface plasmons in solution. The tunability in the SPR and size of the bimetallic NPs were obtained by varying the reaction time and other reaction parameters, resulting in average sizes between 30 and 100 nm. The SPR, size, distribution, and elemental composition of the bi-metallic NPs were characterized using UV-Vis absorption, electron microscopy, and energy dispersive X-ray spectroscopy (EDS) studies.

Enhanced Catalytic and Photocatalytic Degradation of Organic Pollutant Rhodamine‐B by LaMnO3 Nanoparticles Synthesized by Non‐Aqueous Sol‐Gel Route

The water crisis is one of the major problem of the 21st century. This has led to the development of various techniques for water purification such as wastewater treatment. In this technique, coloring dyes are one of the most challenging materials to treat. Rhodamine‐B (RhB) is one of the significant coloring agent and is very difficult to treat using conventional techniques. Here, the enhanced catalytic and photocatalytic degradation of RhB by LaMnO3 nanoparticles is reported. The sol‐gel route is used for the synthesis of LaMnO3 nanoparticles, and structural, magnetic, optical and zeta potential studies are performed. X‐ray diffraction analysis confirms the rhombohedral perovskite structure with R3c space group. The magnetic measurement at 5 K shows that saturation magnetization value increases with an increase in particle size. UV–vis absorption study of LaMnO3 nanoparticles confirms the optical band gap decreases with increasing size. Zeta potential study of LaMnO3 nanoparticles shows a negative charge on the surface. Degradation of organic pollutant RhB by nanoparticles of LaMnO3 is performed under dark, followed by visible light irradiation. Under the dark, 90–92% of the RhB is degraded. Subsequently, upon visible light irradiation, it increased above 99%, confirming enhanced catalytic and photocatalytic activity of LaMnO3 nanoparticles over RhB.

Enhanced photocatalytic degradation of industrial dye by g-C3N4/TiO2 nanocomposite: Role of shape of TiO2

The photocatalytic degradation of toxic dyes has brought a new revolution to reduce water pollution. To degrade industrial dyes, TiO2 is an important photocatalyst but the role of morphology is also important in degradation. We have synthesized g-C3N4/TiO2 nanocomposite (1:1) having different shapes of TiO2 (nanorods (NR), nanospheres (NS), and nanotubes (NT)), to show the effect of morphology on its photocatalytic activity. To improve the photocatalytic efficiency of TiO2 in visible light, we have incorporated g-C3N4, a visible light active photocatalyst. The HRTEM, FESEM and Electron Diffraction studies with color mapping indicate successful synthesis of g-C3N4/TiO2 nanocomposites. The increased photocatalytic efficiency of the nanocomposites regarding the degradation of Rhodamine B (RhB) dye under visible light irradiation is due to the incorporation of g-C3N4 with different shapes of TiO2. The studies show that, the shape of TiO2 has a remarkable effect in photodegradation. The best degradation performance (∼97%) was obtained from g-C3N4/TiO2 -nanotubes composite with a rate constant of 0.0403 min−1 within 80 min, whereas degradation efficiency of other shapes of TiO2 like NS (92%) and NR (94.5%) were also found to be greater than that of commercial TiO2 (P25) composite (74%). Results from UV–Vis absorption study, X-ray Diffraction studies, X-ray photoelectron spectroscopy and BET analysis suggest that the improvement in photocatalytic activity of composite is due to increased light absorption in visible region and increase in surface area (137.1 m2/g). Results from different scavengers study (DMSO, ascorbic acid and methanol) indicate that electron and superoxide ions act as main reactive species in photodegradation of RhB dye. The reusability efficiency of the catalyst shows 86% degradation after 5 consecutive cycles. The effect of pH and catalyst concentration was also determined which shows that maximum degradation occurs at pH ∼ 7 (98%) and degradation efficiency is increased with increase of catalyst dose from 0.1 mg/ml to 0.6 mg/ml and after that saturation occur due to increase in opacity and scattering of light. A comparative study was done with literature which suggests that this nanocomposites act as one of the best photocatalysts for degradation of toxic dyes.

Structural, Optical and Electrical Studies on Hybrid Material of In Situ Formed Silver sulfide in Polymer Blend Matrix

Organic–inorganic polymer hybrid films were prepared, using polyvinyl alcohol–polyethylene glycol blend as the organic host matrix. Silver sulfide (Ag2S) semiconductor particles have been synthesized in polymer blend matrix, by in-situ method. Polymer hybrid films, with various amounts of Ag2S were prepared and characterized structurally, optically and electronically by using various characterization techniques, such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV–Vis absorption spectroscopy, temperature and time dependent DC electrical studies. Hydrogen bonding interactions take place between hydroxyl groups (OH) and carbonyl groups (C=O) of polymer blend molecules with Ag+ ion of Ag2S filler, indicating complex formation between polymer matrix and filler, which is confirmed by FTIR technique. XRD results showed presence of additional multiple peaks (compared to pure blend film) corresponding to αʹ-Ag2S monoclinic crystal system. Changes in degree of crystallinity (%C) are observed for hybrid films with various amounts of Ag2S, showing a highest value of 18.2% for the film containing 0.372 g of Ag2S, when compared to 13.45% (%C) for pure blend film. Uniform distribution of Ag2S nanoparticles in polymer blend matrix is revealed by SEM analysis for hybrid film containing 0.372 g of Ag2S. UV–Vis absorption studies showed multiple absorption peaks due to added filler. Highest value of room temperature conductivity of 9.40 × 10−7 S/cm was obtained for the hybrid film containing 0.372 g of Ag2S. Values of transference numbers (tion and tele) in time dependent electrical studies indicated that the electrical conductivity in pure blend film as well as hybrid films is mainly due to ions.

Microstructural characterization and modified spectral response of cobalt doped NiO nanoparticles

Abstract The modifications in the microstructure and optical properties of cobalt doped nickel oxide nanoparticles (Ni1-xCoxO, x = 0, 0.01, 0.03, 0.05 and 0.10) synthesized by co-precipitation method is reported here. X-ray diffraction, field emission electron microscope, energy dispersive X-ray spectroscopy, and high resolution transmission electron microscopy techniques reveal successful incorporation of Co into the NiO lattice without compromising its intrinsic structure. X-ray photoelectron spectroscopy analysis confirms the compositional purity of the sample. The bandgap tuning of NiO is achieved by Co doping as confirmed by UV–visible absorption studies. Significant variation is observed in the luminescence intensity with Co doping. Surface oxygen vacancies and defects play a pivotal role in controlling the emission properties of NiO. This is the first report on the enhancement of PL intensity with Co doping of NiO nanoparticles. The modified spectral response of Co doped NiO is expected to have various optoelectronic applications.

Carbon Quantum Dot-Anchored Bismuth Oxide Composites as Potential Electrode for Lithium-Ion Battery and Supercapacitor Applications.

The present investigation elucidates a simple hydrothermal method for preparing nanostructured bismuth oxide (Bi2O3) and carbon quantum dot (CQD) composite using spoiled (denatured) milk-derived CQDs. The formation of the CQD–Bi2O3 composite was confirmed by UV–vis absorption, steady-state emission, and time-resolved fluorescence spectroscopy studies. The crystal structure and chemical composition of the composite were examined by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetric analysis. The surface morphology and the particle size distribution of the CQD–Bi2O3 were examined using field emission scanning electron microscope and high-resolution transmission electron microscope observations. As an anode material in lithium-ion battery, the CQD–Bi2O3 composite exhibited good electrochemical activity and delivered a discharge capacity as high as 1500 mA h g–1 at 0.2C rate. The supercapacitor properties of the CQD–Bi2O3 composite electrode revealed good reversibility and a high specific capacity of 343 C g–1 at 0.5 A g–1 in 3 M KOH. The asymmetric device constructed using the CQD–Bi2O3 and reduced graphene oxide delivered a maximum energy density of 88 Wh kg–1 at a power density of 2799 W kg–1, while the power density reached a highest value of 8400 W kg–1 at the energy density of 32 Wh kg–1. The practical viability of the fabricated device is demonstrated by glowing light-emitting diodes. It is inferred that the presence of conductive carbon network has significantly increased the conductivity of the oxide matrix, thereby reducing the interfacial resistance that resulted in excellent electrochemical performances.

Effect of iodine doping on the characteristics of polythiophene thin films prepared by aerosol assisted plasma jet polymerization at atmospheric pressure

Iodine-doped polythiophene thin films are prepared by aerosol assisted plasma jet polymerization at atmospheric pressure and room temperature. The doping of iodine was carried out in situ by employing iodine crystals in thiophene monomer by weight mixing ratios of 1%, 3%, 5% and 7%. The chemical composition analyses of pure and iodine-doped and heat-treated polythiophene thin films are carried out by FTIR spectroscopy studies. The optical band gaps of the films are evaluated from absorption spectrum studies. Direct transition energy gaps are determined from Tauc plots. The structural changes of polythiophene upon doping and the reduction of optical band gap are explained on the basis of the results obtained from FTIR spectroscopy, UV–VIS absorption studies, X-ray diffraction and atomic force microscope (AFM) analysis. The energy band gap will be different according to the concentration of polythiophene iodine. It can be concluded that iodine-doped polythiophene thin films can be prepare by aerosol assisted plasma jet polymerization and control the optical energy band gap regulars by controlling the thiophene -iodine weight mixing ratios.

Solvent and Substituents Effect on the UV/Vis Absorption Spectra of Novel Acidochromic 2-Aminothiazole Based Disperse Mono Azo Dyes

The effect of solvent atmosphere on the electronic absorption properties of 2-aminothiazole based monoazo disperse dyes are studied. The synthesized monoazo dyes with different substituents on the para position of phenyl ring led to changes in the absorption properties of these dyes. Further, the positive solvatochromism data was evaluated to get the excited and ground state dipole moment ratio of the dyes. The Kamlet-Taft and Catalan polarity scales were employed wherein the solvent basicity and dipolarity is responsible for the bathochromic shift with increase in solvent polarity. The free amino group in the dyes made it responsive towards protonation by trifluoroacetic acid. The acidochromic behavior of the dyes was studied and D1, D3, and D4 exhibited major color change to longer wavelength with emergence of a new red shifted absorption band at 556 nm, 580 nm, and 540 nm, respectively, in their absorption spectra. Thus with help of simple UV-Vis absorption studies, we have studied the intermolecular interactions of the 2-aminothiazole based mono azo acidochromic probe.

Design of Prototype Formulations for In Vitro Dermal Delivery of the Natural Antioxidant Ferulic Acid Based on Ethosomal Colloidal Systems

Ferulic acid (FA), a naturally occurring antioxidant, is currently used to prevent skin damage. However, FA is very unstable upon exposure to UV radiation and other factors, which decrease its shelf-life and effectiveness. Therefore, in this work, different prototypes of ethosomal FA vesicular systems were designed and developed to provide protection against different environmental factors. A two-level fractional factorial design was employed using particle size, zeta potential (ZP), incorporation efficiency (EE), polydispersity index (PDI), and the existing relationship between length and width of vesicles or aspect ratio (AR) as response variables. The optimal formulation was characterized using differential scanning calorimetry (DSC), infrared analysis, UV-Vis absorption, in-vitro permeability, and thermal degradation studies. Depending on the processing conditions, the EE and particle size varied between 3 and 87% and 470 and 1208 nm, respectively. Membrane studies indicated that the free product released ~4.8% of the compound, whereas the encapsulated material released ~7.1%. Because of their enhanced permeability, ethosomes could be a promising alternative for the topical administration of antioxidants to reduce the oxidative damage caused by solar radiation.

Effect of pH on the interaction of hypoxanthine and guanine with colloidal ZnS nanoparticles: A spectroscopic approach

The purpose of the current research was to study the interaction between the DNA nucleobases (hypoxanthine and guanine) and the ZnS nanoparticles (NPs). A good understanding of such interactions could be beneficial to researchers working in the field of bionanotechnology. The ZnS NPs were synthesized by a reported method and characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The interaction between the DNA nucleobases and the ZnS NPs was investigated by using UV–visible, fluorescence and infrared spectroscopy. The experiments were performed at pH 6.0 and 10.0 to investigate the role of the molecular charge on the interaction process. The UV–visible absorption studies revealed that the absorption bands of the DNA nucleobases were red shifted in the presence of the semiconductor NPs. The red shift was observed to be greater at pH 6.0. The steady-state fluorescence studies showed that the nucleobases quenched the fluorescence emission of ZnS. The quenching was found to depend on the pH of the solution. It was observed that hypoxanthine was more efficient in quenching the fluorescence of the ZnS NPs compared to guanine. The infrared spectroscopic measurements indicated that both hypoxanthine and guanine bonded to the semiconductor surface through their nitrogen atoms.

Insights into the interaction of potent antimicrobial chalcone triazole analogs with human serum albumin: spectroscopy and molecular docking approaches.

Mechanistic insights into the interaction of five previously chemically synthesized triazole-linked chalcone analogs (CTs) with human serum albumin (HSA) were sought using various spectroscopic techniques (UV-visible absorption, fluorescence, and circular dichroism) and molecular docking. The fluorescence quenching experiments performed at three different temperatures (288, 298 and 308 K) revealed the static mode of quenching and the binding constants (Kb ∼ 106–9) obtained indicated the strong affinity of these analogs for HSA. Furthermore, significant changes in the secondary structure of HSA in the presence of these analogs were also confirmed by far UV-CD spectroscopy. The thermodynamic properties such as the enthalpy change (ΔH°), Gibbs free energy change (ΔG°) and entropy change (ΔS°) revealed that the binding process was spontaneous and exothermic. Theoretical studies, viz., DFT and molecular docking corroborated the experimental results as these five analogs could bind with HSA through hydrogen bonding and hydrophobic interactions. The present study provides useful information regarding the interaction mechanism of these analogs with HSA, which can provide a new avenue to design more potent chalcone triazole analogs for use in the biomedical field.

Improved femtosecond third-order nonlinear optical properties of thin layered Cu3Nb2O8

Thin motif-layered triclinic Cu3Nb2O8 was prepared through solid-state reaction at 700 °C, 12 h and their nonlinear optical (NLO) properties with ultrafast [800 nm, 150 fs (fs) pulses, 80 MHz repetition rate] pulse laser excitation were studied. A peculiar shift from reverse saturable absorption (RSA) to saturable absorption (SA) at a peak intensity of 40 MW/cm2 was observed. The involvement of excited state absorption (ESA) is confirmed from the decrease in the nonlinear absorption coefficient with increase in peak intensity and the observed nonlinearity is ascribed to a sequential 2 PA process (1 PA+ESA). Formation of layered structure in Cu3Nb2O8 acted as a transport layers which yielded high nonlinear absorption coefficient (7.8 × 10−10 m/W), nonlinear refractive index (5.17 × 10−16 m2/W) and nonlinear optical susceptibility (25.6 × 10−11 esu) when compared to other known copper niobates. The observation of low onset-limiting threshold (78.79–26.26 μJ/cm2) renders Cu3Nb2O8 a prospective material for ultrashort pulse laser protecting device and biomedical microsurgery tools. A transition of mixed phase CuNb2O6Cu3Nb2O8 into pure triclinic Cu3Nb2O8 along with change in morphology from pore to layered structure with increase in sintering time was confirmed from powder XRD, Raman, FESEM measurements and UV–Visible absorption studies.

Supramolecular Photocatalyst with a Rh(III)-Complex Catalyst Unit for CO2 Reduction

The development of supramolecular photocatalysts has been an important target in the field of artificial photosynthesis because of their efficient reduction of CO2 and water oxidation and reduction, especially for solid materials, such as semiconductor particles, photoelectrodes, and mesoporous light-harvesting materials. We successfully developed the first supramolecular photocatalyst with a Rh complex as a catalyst unit for CO2 reduction. This new photocatalyst consisting of [Rh(BL)(Cp*)Cl]+ as the catalyst and [Ru(dmb)2(BL)]2+ as the photosensitizer (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl, BL = 1,2-bis(4′-methyl[2,2′-bipyridin]-4-yl)ethane, dmb = 4,4′-dimethyl-2,2′-bipyridine) mainly produced formic acid, even though a mixed system of the corresponding mononuclear complexes photocatalytically produced H2 as the main product. The photocatalytic reaction mechanism was investigated based on in situ UV–vis absorption studies and electrochemical measurements.

Solvent- and Temperature-Responsive Platinum(II)-Functionalized Flexible Lewis Pairs.

Metal-functionalized flexible Lewis pair (flexLP) complexes are described. Platinum(II) terpyridine (Pt-tpy) units added to a flexLP backbone through copper(I)-catalyzed coupling reactions yield monometallic (1) and bimetallic (2) Pt-tpy flexLP complexes. NMR and UV-vis absorption studies demonstrate that the complexes switch between the open unbound Lewis pair and closed Lewis adduct with solvents of varying hydrogen-bond-donating (HBD) strength as well as varying temperature. The charge-transfer (CT) energies of the complexes can be tuned by controlling the equilibrium between open and closed forms, demonstrating the ability to alter the photophysical behavior of the metal complexes by stimuli-responsive flexLP ligands.

An insight into the binding of 6-hydroxyflavone with hen egg white lysozyme: a combined approach of multi-spectroscopic and computational studies

The interaction of 6-hydroxyflavone (6HF) with hen egg white lysozyme (HEWL) has been executed using multi-spectroscopic and computational methods. Steady state fluorescence studies indicated that static quenching mechanism is involved in the binding of 6HF with HEWL, which was further supported by excited state lifetime and UV–vis absorption studies. The binding constant (Kb) of the HEWL–6HF complex was observed to be 6.44 ± 0.09 × 104 M−1 at 293 K, which decreases with the increase in temperature. The calculation of the thermodynamic quantities showed that the binding is exothermic in nature with a negative enthalpy change (ΔH = −11.91 ± 1.02 kJ mol−1) along with a positive entropy change (ΔS = +51.36 ± 2.43 J K−1 mol−1), and the major forces responsible for the binding are hydrogen bonding and hydrophobic interactions. The possibility of energy transfer from tryptophan (Trp) residue to the 6HF ligand was observed from Fo¨rster’s theory. The inclusion of 6HF within the binding site of HEWL induces some micro-environmental changes around the Trp residues as indicated by synchronous and three-dimensional (3D) fluorescence studies. The changes in secondary structural components of HEWL are observed on binding with 6HF along with a reduction in % α-helical content. Computational studies correlate well with the experimental finding, and the ligand 6HF is found to bind near to Trp 62 and Trp 63 residues of HEWL. Altogether, the present study provides an insight into the interaction dynamics and energetics of the binding of 6HF to HEWL.Communicated by Ramaswamy H. Sarma

DNA nanostructures doped with lanthanide ions for highly sensitive UV photodetectors.

Deoxyribonucleic acid (DNA) and lanthanide ions (Ln3+) exhibit exceptional optical properties that are applicable to the development of nanoscale devices and sensors. Although DNA nanostructures and Ln3+ ions have been investigated for use in the current state of technology for more than a few decades, researchers have yet to develop DNA and Ln3+ based ultra-violet (UV) photodetectors. Here, we fabricate Ln3+ (such as holmium (Ho3+), praseodymium (Pr3+), and ytterbium (Yb3+))‒doped double crossover (DX)‒DNA lattices through substrate-assisted growth and salmon DNA (SDNA) thin films via a simple drop-casting method on oxygen (O2) plasma-treated substrates for high performance UV photodetectors. Topological (AFM), optical (UV-vis absorption and FTIR), spectroscopic (XPS), and electrical (I‒V and photovoltage) measurements of the DX‒DNA and SDNA thin films doped with various concentrations of Ln3+ ([Ln3+]) are explored. From the AFM analysis, the optimum concentrations of various Ln3+ ([Ln3+]O) are estimated (where the phase transition of Ln3+‒doped DX‒DNA lattices takes place from crystalline to amorphous) as 1.2 mM for Ho3+, 1.5 mM for Pr3+, and 1.5 mM for Yb3+. The binding modes and chemical states are evaluated through optical and spectroscopic analysis. From UV-vis absorption studies, we found that as the [Ln3+] was increased, the absorption intensity decreased up to [Ln3+]O, and increased above [Ln3+]O. The variation in FTIR peak intensities in the nucleobase and phosphate regions, and the changes in XPS peak intensities and peak positions detected in the N 1 s and P 2p core spectra of Ln3+‒doped SDNA thin films clearly indicate that the Ln3+ ions are properly bound between the bases (through chemical intercalation) and to the phosphate backbone (through electrostatic interactions) of the DNA molecules. Finally, the I‒V characteristics and time-dependent photovoltage of Ln3+‒doped SDNA thin films are measured both in the dark and under UV LED illuminations (λLED = 382 nm) at various illumination powers. The photocurrent and photovoltage of Ln3+‒doped SDNA thin films are enhanced up to the [Ln3+]O compared to pristine SDNA due to the charge carriers generated from both SDNA and Ln3+ ions upon the absorption of light. From our observations, the photovoltages as function of illumination power suggest higher responsivities, and the photovoltages as function of time are almost constant which indicates the stability and retention characteristics of the Ln3+‒doped SDNA thin films. Hence, our method which provides an efficient doping of Ln3+ into the SDNA with a simple fabrication process might be useful in the development of high-performance optoelectronic devices and sensors.

Bio-inspired ZnS quantum dots as efficient photo catalysts for the degradation of methylene blue in aqueous phase

ZnS quantum dots are semiconductor nanoparticles characterized by superior optoelectronic properties. The amenability of these nanoparticles in initiating efficient photo-redox reactions enable their use as photocatalysts for environmental remediation. In the present study, ZnS quantum dots were biosynthesized from Zn tolerant Penicillium sp. under ambient reaction conditions. The biogenic ZnS quantum dots were characterized using TEM, SEM, XRD, FTIR and UV–Vis absorption studies that revealed the formation of spherical particles of average diameter 11.08 nm with a zinc blend crystal structure and the optical properties were in par with chemically synthesized ZnS. The biogenic ZnS were then used for the photodegradation of methylene blue (MB) dye. It was found that the green synthesized ZnS quantum dots exhibited good photocatalytic activity with a half-life of 4 h. Further, the dye degradation efficiency was enhanced as the ZnS nanocatalyst/dye ratio increased and reached equilibrium within 6 h. The present study reports an inexpensive and scalable method to fabricate ZnS nano hybrids with practical applicability in the remediation of pollutants in textile, paper and dyeing industry.

Enhanced blue-light emission on Cd0.9-xZn0.1CrxS(0 ≤ x ≤ 0.05) quantum dots

Zn, Cr dual doped CdS quantum dots (QDs) have been synthesized using co-precipitation method at room temperature without any capping agent. The prepared samples were analyzed by x-ray diffraction (XRD), Transmission electron microscopic (TEM) study, Scanning electron microscopic (SEM) study, Energy Dispersive X-ray (EDX) spectra, UV–Visible absorption & transmission spectra, Fourier Transform Infra-Red (FTIR) spectra and Photoluminescence studies (PL). All the samples were exhibited cubic structure and they confirmed that the presence of Cr did not alter the original structure. TEM study and SEM study revealed the structure and morphology of the particles. Crystallite size was reduced for the addition of Cr and it was ranged as ~2 nm. As large number of small particles aggregated on the surface, agglomeration was received on surface morphological study. EDX spectra confirmed the occurrence of doped elements in CdS as per the targeted ratio. In UV–visible absorption study, Cr doping caused blue shift on absorption peaks. UV–visible transmittance peaks intensity was reduced as a function of Cr doping. Optical energy band gap value was slightly increased for the addition of Cr. High intense blue light emission and red shifted red emission were received on PL study for the Cr, Zn dual doped CdS QDs. Since these materials offered better optical and luminescent properties, shall be suitable for the opto-electronic device applications.

Tuning the optical band Gap of pure TiO2 via photon induced method

Titanium dioxide, a well known photocatalyst will become more useful if it utilizes visible light. Many efforts have been made to achieve the utilization of visible light by TiO2 for photocatalytic activity by changing the preparation methods or by doping various transition metals. Herein, a novel Photon Induced Method (PIM) is being proposed to produce oxygen-rich TiO2 with modified optical band gap and high stability. The prepared TiO2 nanoparticles have been subjected to various characterizations such as XRD, HRSEM, HRTEM, FTIR, UV–vis and PL. XRD results reveal that as the calcination temperature is increased, the crystallite size of the TiO2 nanoparticles is seen to increase. Also, the XRD results reveal an increase in pure anatase phase stability upto 750 °C when compared to earlier reports of pure anatase phase stability upto 650 °C. HRTEM analysis shows the formation of nanosized bullet like structure. A narrowing of optical band gap to 3.09 eV is evident through UV–vis absorption studies. This tuning of band gap is expected to facilitate the absorption of visible light. The photocatalytic activity of the prepared TiO2 nanoparticles has also been studied. The results reveal that TiO2 nanoparticles prepared by this novel method exhibit an increased photocatalytic activity when compared to the standard Degussa P25 sample reported earlier.