Sanjeev R. Shukla

Simple, Efficient, and Green Method for Synthesis of Trisubstituted Electrophilic Alkenes Using Lipase as a Biocatalyst

Abstract A simple and efficient Knoevenagel condensation method for the synthesis of trisubstituted electrophilic alkenes was developed using lipase as a biocatalyst. Knoevenagel condensation was performed using the conventional method and using lipases (Aspergillus oryzae or Rhizopus oryzae) as biocatalysts, and reaction time, reaction temperature, yield, and recyclability were compared. Using a lipase as a biocatalyst eliminated the need for bases such as piperidine and pyridine. A wide range of aromatic aldehydes and ketones readily undergo condensation with active methylene compounds. The workup procedure is also very simple, and yields of the reactions are in the range of 75% to 95%. Both the biocatalysts were effectively recycled four times with no major decrease in the yield of product. The remarkable catalytic activity and reusability of lipase widens its applicability in Knoevenagel condensation with good to excellent yields for synthesis of trisubstituted electrophilic alkenes. GRAPHICAL ABSTRACT

Development of multifunctional cotton fabric using atmospheric pressure plasma and nano-finishing

The possibility of using atmospheric pressure dielectric barrier discharge plasma treatment for textile surface activation to facilitate deposition of nano TiO2/SiO2 onto cotton fabric is investigated. It is aimed to develop a multifunctional cotton textile using plasma and nanotechnology. The treated fabric is evaluated through measuring the ultraviolet protection factor, antimicrobial activity, and flame retardancy as functional finishes. Surface morphology (Scanning electron microscopy, SEM), thermogravimetric analysis, and mechanical properties were also studied. SEM shows deposition of nanoparticles onto the fabric. He–O2 plasma pretreatment improves the flame retardancy, antibacterial activity, and thermal stability of the samples were compared with the untreated samples.

Antibacterial properties of silk fabric treated with silver nanoparticles

Silk is hygroscopic and is affected by microorganisms easily. Hence, treatment with antimicrobial agents can facilitate to make silk resistant to microbes. Silver nanoparticles have been attempted by researchers and applied as antimicrobial chemical finish on textiles. Silk has also been applied with silver nanoparticles through exhaust method to obtain antimicrobial properties. However, use of cross-linking agents such as 1,2,3,4 butane tetra carboxylic acid (BTCA) for entrapping silver nanoparticles in the interstitials of the silk molecular chain has not been attempted. The present study is focused on the application of BTCA on silk in the presence of sodium hypophosphite (SHP) simultaneously using silver nanoparticles has been done by pad-dry-cure (2dip/2nip) method. Application of 6% BTCA with 3% SHP and 250 ppm of silver nanoparticles gave satisfactory antimicrobial properties. Infrared spectroscopic (FTIR) studies showed good cross-linking of BTCA. X-ray diffraction studies depict that the crystal structure and crystallinity % of treated silk did not change due to the treatment. SEM studies showed the impregnation of silver nanoparticles on to the fibre matrix. Different physical properties of silk fabric did not change due to the treatment. Based on the studies, it is inferred that BTCA cross-links with silk fibroin at the carboxyl and amine groups, create a lattice void and trap silver nanoparticles giving durable antimicrobial finish.

Antimicrobial activity of silk treated with Aloe-Vera

Natural Silk in its native form is made up of the filament fibroin, coated with sericin - gummy matter which is antimicrobial in nature. However, sericin is removed during the pretreatment process. Silk being a natural and hygroscopic, fiber gets attacked by microbes easily. Hence antimicrobial treatment can add value to the wear and care of silk textiles. Synthetic antimicrobial agents may be toxic and even carcinogenic and hence the natural and eco-friendly antimicrobial agents are good substitutes for imparting the desired properties. In the present paper, ready for dyeing (RDF) silk fabric was treated with Aloe-Vera using 1,2,3,4-butanetetracarboxylic acid (BTCA) as crosslinking agent and sodium hypophosphite (SHP) as catalyst. The treated fabric with a concentration of 15 % of Aloe-Vera showed excellent antimicrobial properties. Since BTCA was used as a crosslinking agent, crease recovery angle, improved with minimal loss in breaking and tearing strength. The mechanism of treatment of Aloe-Vera is found to be chemical binding with silk and not simply of coating or impregnation. FTIR studies showed that the carboxyl side groups and short chain amino acids side groups act as sites for BTCA crosslinking interalia chemical binding of Aloe-Vera. SEM studies revealed that no coating or tangible impregnation on the surface of the fiber is visible substantiating the chemical binding phenomenon. This is further substantiated by the durability of the finish to dry cleaning of treated silk. Since Aloe-Vera is a natural product and BTCA is an eco-friendly resin, the treatment of silk with Aloe-Vera is eco-friendly in nature.

Novel synthesis, characterization and application of dibutyrate bis(2-hydroxyethyl) terephthalamide as a plasticizer in PVC compounding

This study focuses on the synthesis and application of dibutyrate of bis(2-hydroxyethyl) terephthalamide (DB-BHETA) as a plasticizer in poly(vinyl chloride) (PVC) compounding. DB-BHETA was synthesized from poly(ethylene terephthalate) bottle waste through aminolysis followed by condensation reaction with butyric acid. Synthesized DB-BHETA was characterized by FTIR, DSC and NMR. Plasticized PVC was prepared by melt blending of PVC in different ratios with DB-BHETA and the mechanical, thermal and rheological properties were investigated. The glass transition temperature (Tg) decreased with increasing concentration of DB-BHETA, confirming its plasticizing effect. The impact properties of PVC/DB-BHETA were maximum at weight ratio of 80/20. Shore hardness continuously reduced with increase in the concentration of DB-BHETA in PVC. Also, incorporation of DB-BHETA results in a gradual decrease in the loss modulus (viscous) and an increase in the storage modulus (elastic).

Synthesis of Some Novel Pyrimidinedione and Pyrimidinetrione Derivatives by a Greener Method: Study of Their Antimicrobial Activity and Photophysical Properties

Abstract A series of novel pyrimidinedione- and pyrimidinetriones-based compounds were synthesized by different techniques such as with conventional Knoevenagel condensation alone, with a Rhizopus oryzae lipase biocatalyst, and with a deep eutectic solvent (DES). The yield was found to be maximum by using lipase and DES. Reuse of the lipase and DES was possible up to four consecutive cycles. These methods are mild, highly efficient, and amenable to scaleup. The products were found to exhibit appreciable in vitro antibacterial activity against Echerichia coli, Pseudomonas neumoniae, and Micrococcus and in vitro antifungal activity against Aspergillus niger and Candida albicans. All the compounds exhibited appreciable in vitro activity against the tested strains. The photophysical properties and thermal stability of the products were also investigated. GRAPHICAL ABSTRACT

A simple and efficient protocol to develop durable multifunctional property to cellulosic materials using in situ generated nano-ZnO

This article focuses on the development of a durable multi-functional finish for cotton fabric by direct synthesis of nano zinc oxide (nano-ZnO) particles in the pores of the fibres. Anions and cations of zinc nitrate interacted with cellulose molecules and opened up the internal pore structure of cellulosic fibrils that in turn acted as nucleating sites for the formation of nano-ZnO on reaction with sodium hydroxide. The finished fabric was characterized using XRD, FTIR, SEM, TEM, AAS, DSC and AFM. The finished fabric displayed excellent antibacterial activities (>99%) against two pathogens, Staphylococcus aureus (Gram-positive) and Klebsiella pneumoniae (Gram-negative) with 40 UPF even after 30 washes confirming the utility of this method. Inherent physical and mechanical properties of the fabric were found to be unaffected. Low stress mechanical properties evaluated by Kawabata Evaluation System for Fabrics indicated that the total hand value of the finished fabric changed from 3.54 to 3.40. A plausible mechanism for in situ formation of nano-ZnO and its durability on cotton fabric has been proposed.

Degumming of eri silk using ionic liquids and optimization through response surface methodology

The application of imidazolium ionic liquids (ILs) as green material for degumming of silk has been investigated. In this study, degumming of eri silk was attempted using ILs 1-butyl-3-methylimidazolium chloride [BMIM]Cl and 1-butyl-3-methylimidazolium hydrogen sulphate [BMIM]HSO4, synthesized in the laboratory. The molecular structures of the ILs were confirmed by FTIR, 1H-NMR, and 13C-NMR. The thermal properties and solubility were also analysed. Experiments were designed to find out the optimum processing parameters for degumming of eri silk by response surface methodology. The statistical software, Design-Expert 6.0, was used for regression analysis and graphical analysis of the responses obtained by running the set of designed experiments. Analysis of variance was used to estimate the statistical parameters. The polynomial equation of quadratic order was employed to fit the experimental data. The quality and model terms were evaluated by F-test. Three-dimensional surface plots were prepared to study the effect of variables on different responses. The comparison of responses obtained from the experiments of highest desirability with those obtained by alkaline H2O2 (control) indicates that ILs give better results in terms of weight loss and absorbency.

Ionic liquid mediated application of nano zinc oxide on cotton fabric for multi-functional properties

Abstract In this work, nano zinc oxide (nano-ZnO) was applied onto cotton fabric by exhaustion method using an ionic liquid (IL), 1-butyl 3-methyl imidazolium chloride [BMIM][Cl], to improve its uptake and fixation. Effect of temperature on the exhaustion of nano-ZnO in the presence of ionic liquid was investigated. A spectrophotometric method was established to determine the concentration of nano-ZnO in the exhausted bath. Treated cotton fabrics were characterized using Fourier transform infrared, scanning electron microscope, atomic absorption spectroscopy, X-ray diffraction, Thermo gravimetric analysis and UV spectrophotometry. Washing durability test using the AATCC 61-2003 method demonstrated that the amount of nano-ZnO retained in the cotton substrate was sufficient enough to exhibit 50+ UV protection and 99% inhibition against the tested pathogenic micro-organisms. A plausible mechanism for better exhaustion of nano-ZnO on cotton fabric has been proposed on the basis of ionic liquid driven swelling property of the cotton polymer.

Intrinsic catalytic activity of Brønsted acid ionic liquids for the synthesis of triphenylmethane and phthalein under microwave irradiation

A microwave-irradiated, ionic liquid-catalyzed, solvent-free method for the synthesis of triphenylmethane and a phthalein derivative has been developed from different aldehydes or anhydrides and substituted phenols or N,N-diaryl amines, respectively. Short reaction time, ambient reaction conditions, recyclability of catalyst, simple work up and high yields are some of the striking features of the present protocol. The immobilized catalyst could be easily recovered by simple filtration and recycled for up to four cycles without significant decrease in the catalytic activity.