Synthesis Route Impact on BiVO4 Nanoparticles and their Visible Light Photocatalytic Activity Under Green LED Irradiation.

The present study demonstrates the BiVO4 nanoparticles synthesized by co-precipitation (CPM), hydrothermal (HTM) and solution combustion method (SCM) and their visible light photocatalytic activity under irradiation of green light emitting diodes. The synthesized catalysts were characterized by Powder X-ray Diffraction, UV-vis Diffuse reflectance spectroscopy, BET Surface area analysis, Fourier Transform Infrared spectroscopy and Scanning electron microscopy. Result demonstrated that the photocatalytic activity of BiVO4 catalyst synthesized by solution combustion method has 4.7, 1.9 and 6.7 times higher photocatalytic activity under irradiation of green light emitting diodes as compared to ultraviolet, blue and red light emitting diodes respectively. It has also been found that the photocatalytic activity of the synthesized BiVO4 by SCM is 6.5 times more as compared to commercial TiO2 under green light emitting diodes irradiation. Furthermore, the room temperature fluorescence and quenching analysis was carried out for the determination of hydroxyl radical generation and understanding photocatalytic activity of the catalyst under green light emitting diodes irradiation. Additionally, the effect of operational parameters under irradiation of green light emitting diodes was studied to optimize catalyst amount, pH, initial dye concentration and amount of H2O2. Recyclability study concern about solution combustion synthesized BiVO4 catalyst has also been done up to 5 cycles in presence of green light emitting diodes irradiation.

Recent advances based on the synergetic effect of adsorption for removal of dyes from waste water using photocatalytic process.

The problem of textile dye pollution has been addressed by various methods, mainly physical, chemical, biological, and acoustical. These methods mainly separate and/or remove the dye present in water. Recently, advanced oxidation processes (AOP) have been focused for removal of dye from waste water due to their advantages such as ecofriendly, economic and capable to degrade many dyes or organic pollutant present in water. Photocatalysis is one of the advance oxidation processes, mainly carried out under irradiation of light and suitable photocatalytic materials. The photocatalytic activity of the photocatalytic materials mainly depends on the band gap, surface area, and generation of electron-hole pair for degradation dyes present in water. It has been observed that the surface area plays a major role in photocatalytic degradation of dyes, by providing higher surface area, which leads to the higher adsorption of dye molecule on the surface of photocatalyst and enhances the photocatalytic activity. This present review discusses the synergic effect of adsorption of dyes on the photocatalytic efficiency of various nanostructured high surface area photocatalysts. In addition, it also provides the properties of the water polluting dyes, their mechanism and various photocatalytic materials; and their morphology used for the dye degradation under irradiation of light along with the future prospects of highly adsorptive photocatalytic material and their application in photocatalytic removal of dye from waste water.

Oxazoline-based organocatalyst for enantioselective strecker reactions: a protocol for the synthesis of levamisole.

A chiral oxazoline-based organocatalyst has been found to efficiently catalyze asymmetric Strecker reactions of various aromatic and aliphatic N-benzhydrylimines with trimethylsilyl cyanide (TMSCN) as a cyanide source at -20 °C to give α-aminonitriles in high yield (96 %) with excellent chiral induction (up to 98 % ee). DFT calculations have been performed to rationalize the enantioselective formation of the product with the organocatalyst in these reactions. The organocatalyst has been characterized by single-crystal X-ray diffraction analysis, as well as by other analytical methods. This protocol has been extended to the synthesis of the pharmaceutically important drug molecule levamisole in high yield and with high enantioselectivity.

Asymmetric aminolytic kinetic resolution of racemic epoxides using recyclable chiral polymeric Co(III)-salen complexes: a protocol for total utilization of racemic epoxide in the synthesis of (R)-Naftopidil and (S)-Propranolol.

Chiral polymeric Co(III) salen complexes with chiral ((R)/(S)-BINOL, diethyl tartrate) and achiral (piperazine and trigol) linkers with varying stereogenic centers were synthesized for the first time and used as catalysts for aminolytic kinetic resolution (AKR) of a variety of terminal epoxides and glycidyl ethers to get enantio-pure epoxides (ee, 99%) and N-protected ß-amino alcohols (ee, 99%) with quantitative yield in 16 h at RT under optimized reaction conditions. This protocol was also used for the synthesis of two enantiomerically pure drug molecules (R)-Naftopidil (α1-blocker) and (S)-Propranolol (ß-blocker) as a key step via AKR of single racemic naphthylglycidyl ether with Boc-protected isoproylamine with 100% epoxide utilization at 1 g level. The catalyst 1 was successfully recycled for a number of times.

Synthetically amenable amide derivatives of tosylated-amino acids as organocatalysts for enantioselective allylation of aldehydes: computational rationale for enantioselectivity.

A phenylalanine derived chiral amide is developed that serves as an effective organocatalyst for the reaction of allyltrichlorosilane with aryl, hetero-aryl and α,ß-unsaturated aldehydes to afford the desired homoallylic alcohols in good yield (up to 90%) and high enantioselectivity (up to 99%). The experimental results and DFT calculations suggest that para substituted aromatic aldehydes as substrate show higher ee in the product than their ortho/meta counterparts. The (1)H and (13)C NMR spectra study corroborated the calculated results. The chiral organocatalyst can be easily synthesized from optically pure phenylalanine in two simple steps with 90% overall yield.

Asymmetric hydrolytic kinetic resolution with recyclable macrocyclic Co(III)-salen complexes: a practical strategy in the preparation of (R)-mexiletine and (S)-propranolol.

A chiral cobalt(III) complex (1e) was synthesized by the interaction of cobalt(II) acetate and ferrocenium hexafluorophosphate with a chiral dinuclear macrocyclic salen ligand that was derived from 1R,2R-(-)-1,2-diaminocyclohexane with trigol bis-aldehyde. A variety of epoxides and glycidyl ethers were suitable substrates for the reaction with water in the presence of chiral macrocyclic salen complex 1e at room temperature to afford chiral epoxides and diols by hydrolytic kinetic resolution (HKR). Excellent yields (47% with respect to the epoxides, 53% with respect to the diols) and high enantioselectivity (ee>99% for the epoxides, up to 96% for the diols) were achieved in 2.5-16 h. The Co(III) macrocyclic salen complex (1e) maintained its performance on a multigram scale and was expediently recycled a number of times. We further extended our study of chiral epoxides that were synthesized by using HKR to the synthesis of chiral drug molecules (R)-mexiletine and (S)-propranolol.

Modified asymmetric Strecker reaction of aldehyde with secondary amine: a protocol for the synthesis of S-clopidogrel (an antiplatelet agent).

A first approach for catalytic asymmetric Strecker reaction of aldehydes with a secondary amine in the presence of sodium fluoride using hydroquinine as chiral catalyst was developed. The catalytic system gave α-aminonitriles in excellent yields (up to 95%) and high enantioselectivities (er up to 94:6). The efficacy of the chiral product was successfully fulfilled in the improved synthesis of (S)-clopidogrel (an antiplatelet agent).

C2-symmetric recyclable organocatalyst for enantioselective Strecker reaction for the synthesis of α-amino acid and chiral diamine--an intermediate for APN inhibitor.

Recyclable chiral amide-based organocatalyst 5 efficiently catalyzed asymmetric Strecker reaction of various aromatic and aliphatic N-benzhydrylimines with ethyl cyanoformate as cyanide source at -10 °C to give a high yield (95%) of α-aminonitriles with excellent chiral induction (ee, up to 99%) with the added advantage of recyclability. Based on experimental observations a probable mechanism was proposed for this reaction. This protocol with catalyst 5 was extended for the synthesis of (R)-phenylalanine and pharmaceutically important drug intermediate (R)-3-phenylpropane-1,2-diamine in high yield with high enantioselectivity.

DNA binding, antioxidant activity, and DNA damage protection of chiral macrocyclic Mn(III) salen complexes.

We are reporting the synthesis, characterization, and calf thymus DNA binding studies of novel chiral macrocyclic Mn(III) salen complexes S-1, R-1, S-2, and R-2. These chiral complexes showed ability to bind with DNA, where complex S-1 exhibits the highest DNA binding constant 1.20 × 10(6) M(-1). All the compounds were screened for superoxide and hydroxyl radical scavenging activities; among them, complex S-1 exhibited significant activity with IC(50) 1.36 and 2.37 µM, respectively. Further, comet assay was used to evaluate the DNA damage protection in white blood cells against the reactive oxygen species wherein complex S-1 was found effective in protecting the hydroxyl radicals mediated plasmid and white blood cells DNA damage.

Enantioselective desymmetrization of meso-epoxides with anilines catalyzed by polymeric and monomeric Ti(IV) salen complexes.

The active catalysts for the enantioselective ring opening (ARO) of meso-stilbene oxide, cis-butene oxide, cyclohexene oxide, cyclopentene oxide, and cyclooctene oxide with various substituted anilines were generated in situ by the reaction of Ti(O(i)Pr)(4) with poly-[(R,R)-N,N'-bis-{3-(1,1-dimethylethyl)-5-methylene salicylidene} cyclohexane-1,2-diamine]-1 and (1R,2R)-N,N'-bis[3,5-di(tert-butyl)salicylidene] cyclohexane-1,2-diamine-2. These catalysts in the presence of nonracemic imine as an additive provided ß-amino alcohol in excellent yield (99%) and chiral purity (enantiomeric excess (ee) up to 99%) for the ARO of meso-stilbene oxide with aniline. The same protocol was less effective for the ARO of cyclic epoxides; however, when triphenylphosphine was used as an additive, there was a significant improvement in catalyst performance for the ARO of cyclohexene oxide (yield, 85-90%; ee, 63-67%). Both in situ generated polymeric and monomeric catalysts performed in a similar manner except that the polymeric catalyst Ti(IV)-1 was more active and recycled several times with retention of enantioselectivity when compared with the monomeric catalyst Ti(IV)-2, which was nonrecyclable.

Heterogeneous chiral copper complexes of amino alcohol for asymmetric nitroaldol reaction.

Chiral amino alcohols supported on mesoporous silicas were synthesized and evaluated as a new class of chiral ligands in copper-catalyzed nitroaldol reaction under heterogeneous and mild reaction conditions. The activity and enantioselectivity of the present catalytic system is immensely influenced by the presence of achiral and chiral bases as an additive. The heterogenized chiral copper(II) complex of amino alcohol was found to be an effective recyclable catalyst for the nitroaldol reaction of different aldehydes such as aromatic, aliphatic, alicyclic, and α-ß unsaturated aldehydes to produce nitroaldol products with remarkably high enantioselectivity (≥99%) and yields.

Influence of chirality using Mn(III) salen complexes on DNA binding and antioxidant activity.

Chiral Mn(iii) salen complexes S-1, R-1, S-2, R-2, S-3 and R-3 derived from the respective chiral salen ligands, viz., (1S,2S)-N,N'-bis-[3-tert-butyl-5-chloromethyl-salicylidine]-1,2-cyclohexanediamine S-1'/(1R,2R)-N,N'-bis-[3-tert-butyl-5-chloromethyl-salicylidine]-1,2-cyclohexanediamine R-1'/(1S,2S)-N,N'-bis-[3-tert-butyl-5-N,N'N'triethylaminomethyl-salicylidine]-1,2-cyclohexanediamine dichloride S-2'/(1R,2R)-N,N'-bis-[3-tert-butyl-5-N,N'N'triethylaminomethyl-salicylidine]-1,2-cyclohexanediamine dichloride R-2'/(1S,2S)-N,N'-bis-[3,5-di-tert-butylsalicylidene]-1,2-cyclohexanediamine S-3' and (1R,2R)-N,N'-bis-[3,5-di-tert-butyl-salicylidene]-1,2-cyclohexanediamine R-3', were synthesized. Characterization of the complexes was done by microanalysis, IR, LC-MS, UV-vis. and circular dichroism (CD) spectroscopy. Binding of these complexes with calf thymus DNA (CT-DNA) was studied by absorption spectroscopy, competitive binding study, viscosity measurements, circular dichroism measurements, thermal denaturation study and observation of their different antioxidant activities. Among all the complexes used, the best result in terms of binding constant (intercalative) (130.4 x 10(4)) was achieved with the complex S-1 by spectroscopic titration. The complex S-1 showed strong antioxidant activity as well.

Enantioselective cyanoformylation of aldehydes catalyzed with solid base mediated chiral V(V) salen complexes.

Polymeric and monomeric V(V) chiral salen complexes-catalyzed enantioselective ethyl cyanoformylation of aldehydes using ethyl cyanoformate as a source of cyanide was accomplished in the presence of several basic cocatalysts viz., NaOH, KOH, basic Al2O3 and hydrotalcite. Excellent yield (>95%) of chiral ethyl cyanohydrincarbonate with high enantioselectivity up to 94% was achieved in 24-36 h when hydrotalcite was used as an additive. The polymeric catalyst 1 is more reactive than the monomeric catalyst 2 to produce chiral ethyl cyanohydrincarbonate in high optical purity. The chiral polymeric catalyst 1 and cocatalysts hydrotalcite and basic alumina used in this study were recoverable and recyclable several times with retention of its performance.

Controlled release formulation of ranitidine-containing montmorillonite and Eudragit E-100.

AIM: The objective of this work was to illustrate the suitability of montmorillonite (MMT) as a drug delivery carrier, by developing a new clay-drug composite of ranitidine hydrochloride (RT) intercalated in MMT. METHODS: The MMT-RT composite was prepared by ion-exchange process. X-ray diffraction and Fourier transform infrared spectra were employed to confirm the intercalation of RT in the MMT interlayers. The prepared MMT-RT hybrid was coated with cationic polymer Eudragit E-100 by oil-in-water solvent evaporation method. The release processes of RT from MMT-RT and MMT-RT/Eudragit E-100 were monitored under in vitro condition in the gastric fluid. RESULTS: X-ray diffraction and Fourier transform infrared spectra analysis indicated the intercalation of RT molecules within the clay lattice. The in vitro release studies showed that MMT-RT released RT in a controlled manner. In the case of MMT-RT/Eudragit E-100, both the release rate and the release percentages noticeably increased in the presence of Eudragit E-100, because of its effective exchange with intercalated RT molecules. The release kinetics followed parabolic diffusion mechanism. CONCLUSION: MMT has great potential as a drug delivery carrier with various scenarios. The dosage of the MMT-RT/Eudragit E-100 can be in the tablet form. The hybrid material and polymer-coated hybrids are microparticles.

Bio-waste chitosan-derived N-doped CNT-supported Ni nanoparticles for selective hydrogenation of nitroarenes.

In this study, a facile method for the synthesis of leach proof and earth-abundant non-noble Ni nanoparticles on N-doped carbon nanotubes is reported. The catalyst was synthesized by an impregnation-carbonization method, wherein a Ni-chitosan complex upon carbonization in a 5% H2/N2 atmosphere at 800 °C yielded Ni-containing N-doped CNTs. Chitosan served as a single source of carbon and nitrogen, and the nanotube growth was facilitated by the in situ formed Ni nanoparticles. The nanocatalyst was thoroughly characterized by several techniques; elemental mapping by SEM and TEM analysis confirmed the uniform distribution of Ni nanoparticles on the surface of N-doped CNTs with an average size in the range of 10-15 nm. The catalyst efficiently reduced a variety of nitroarenes (>99%) into their corresponding amines at a moderate pressure (5 bar) and a comparatively lower temperature (80 °C). Furthermore, the easy recovery of the catalyst using an external magnetic field along with high activity and easy recyclability makes the protocol eco-friendly.

Synthesis of highly dispersed gold and silver nanoparticles anchored on surfactant intercalated montmorillonite.

Gold and silver nanoparticles anchored on surfactant intercalated montmorillonite were prepared by two methodologies. In the first case, gold and silver nanoparticles were synthesized by reduction of gold and silver salt in hexadecyltrimethylammonium bromide (HDTA) and dioctadecyldimethylammonium chloride (DODA), followed by exchange of HDTA and DODA solution containing gold and silver nanoparticles into montmorillonite (MMT). In second case, HDTA and DODA with gold and silver salt was exchanged with MMT, and then reduced to obtain gold and silver nanoparticles. The particle size of gold and silver varies with the path of reduction as well as type of surfactant used for the modification of MMT. Gold and silver nanoparticles synthesized using quaternary ammonium salt with two long alkyl chain resulted into finer particles than a single long alkyl chain. The present study demonstrates the effect of reduction path, type of surfactants, and concentration of gold and silver on the particle size of gold and silver nanoparticles anchored on organoclay. Gold and silver nanoparticles supported organoclay were characterized by High resolution transmission electron microscopy (HRTEM), powdered X-ray diffraction (PXRD) and Inductive coupled plasma-atomic emission spectroscopy (ICP-AES).

Recovery of value-added products from cathode and anode material of spent lithium-ion batteries.

Herein we report a low cost and eco-friendly approach for the recovery of metals from cathode and anode materials of mobile phone spent lithium-ion batteries (LIBs). Li-based metal oxide and graphite were efficiently separated from their respective foils and used for lixiviation. Acetic acid (CH3COOH) and water were used as lixiviants for the recovery of metals from cathode and anode materials respectively. It was found that with 3 M Acetic acid and 7.5 vol% H2O2 as reducing agent 99.9% Li, 98.7% Co, and 99.5% Mn were leached out from cathode material in 40 min at 70 °C and a pulp density of 20 g/L. Besides the cathode leaching, Li was also extracted from anodic material graphite using water as a solvent and further recovered as solid Li2CO3 (99.7% Li). The kinetic evaluation of the cathode lixiviate process was studied using three different shrinking-core kinetic Models and established that the reaction follows the product layer diffusion controlled mechanism. From the cathode leach liquor, 99% Co was recovered as metal sulfide by controlled sulfide precipitation with 99.2% purity, and subsequently, MnCO3 and Li2CO3 were obtained with the purity of 98.7% and 99.4%, respectively. The purity of the salts revealed that these products recovered from spent LIBs might be utilized in the electrochemical energy-storage applications. In addition, this recycling process would promote the sustainable development of the battery industry.

Recovered spinel MnCo2O4 from spent lithium-ion batteries for enhanced electrocatalytic oxygen evolution in alkaline medium.

A facile way of recovering 3d transition metals of industrial importance from spent lithium-ion batteries (LIBs) without using any surfactants has been developed. Mn- and Co-rich spent LIBs were chosen as sustainable sources for recovering the oxides of the respective elements. The physical dismantling of Li-ion batteries, chemical leaching with 2 M acetic acid, precipitation with ammonium carbonate, hydrothermal conditioning and calcination at 650 °C led to the facile formation of spherical spinel MnCo2O4 with very high morphological selectivity. The obtained spherical MnCo2O4 was identified by various advanced characterization techniques. Detailed electrochemical characterization revealed that the recovered spheres of spinel MnCo2O4 were effective in catalyzing the oxygen evolution reaction (OER) in 1 M KOH and required an overpotential of 358 and 400 mV to generate a current density of 5 and 10 mA cm-2, respectively, with a relatively low catalyst loading (0.001025 g cm-2). Comparative electrocatalytic studies carried out with recovered LiCoO2, recovered LiXMnOX+1 and commercially available catalysts such as RuO2 (c-RuO2), Co3O4 (c-Co3O4) and MnO2 (c-MnO2) revealed that the recovered spheres of spinel MnCo2O4 were more effective OER catalysts than the recovered LiCoO2, recovered LiXMnOX+1, c-Co3O4 and c-MnO2 and exhibited comparable activity to that of c-RuO2 with very little difference in overpotential (∼50 mV) at current densities of 5 and 10 mA cm-2. With such a low catalyst loading, the observed electrocatalytic performance in water oxidation of a material recovered from waste is highly significant and will surely attain greater industrial importance when the recycling of spent LIBs from electronic wastes is considered.

Al-intercalated acid activated bentonite beads for the removal of aqueous phosphate.

The separation of fine spent sorbents from treated water after remediation is a major difficulty associated with phosphate wastewater treatment technology. In this study, a novel aluminium-pillared acid activated bentonite powder (Al-ABn) and alginate immobilized aluminium-pillared acid activated bentonite beads (Al-ABn-AB) were synthesized and used for the removal of aqueous phosphate. The phosphate removal behaviour of adsorbents were evaluated by batch experiments as a function of various parameters such as pH, initial concentration, contact time, temperature, adsorbent dose and presence of coexisting ions. The sorption isotherm studies by Langmuir model showed 12.87 and 11.11 mgP/g maximum phosphate uptake capacity for Al-ABn and Al-ABn-AB, respectively. The kinetic studies confirm that the adsorption of phosphate by Al-ABn and Al-ABn-AB follows a pseudo-second-order model. The feasibility of Al-ABn-AB was also assessed in continuous mode in fixed bed column and the loading capacity obtained was 4.55mg/g. The adsorption capacity of Al-ABn-AB beads remained at relatively high even after four regeneration cycles. Furthermore, the applicability of the synthesized adsorbents towards real municipal wastewater confirmed that novel synthesized Al-ABn and Al-ABn-AB are the promising adsorbents for the removal of phosphate from contaminated water.

Self-Supported Chiral Polymeric MnIII Salen Complexes as Highly Active and Recyclable Catalysts for Epoxidation of Nonfunctionalized Olefins.

A series of self-supported chiral polymeric MnIII N,N'-ethylenebis(salicylimine) (salen) complexes were synthesized through metalation of the corresponding salen ligands obtained by condensation of several bis/tris-aldehydes with (1R,2R)-1,2-diaminocyclohexane. Upon employment in the asymmetric epoxidation reaction of nonfunctionalized olefins, all complexes showed enhanced activity and enantioselectivity relative to the classical Jacobsen's monomeric salen complex. However, 1,3,5-triazole-based polymeric MnIII salen complex 7 was noticeably preferred over others owing to its ability to render higher enantioselectivity at the expense of lower catalyst loading. Furthermore, complex 7 was recycled and reused in eight recycling experiments with marginal loss in catalytic activity.