Prem Felix Siril

Goldcore–polyanilineshell composite nanowires as a substrate for surface enhanced Raman scattering and catalyst for dye reduction

Composite nanowires with a gold core (Aucore) and polyaniline shell (PANIshell) were prepared using swollen liquid crystals (SLCs) as a soft, structure directing template. The composite nanowires were prepared by simply pouring the SLC containing AuCl3 over the SLC containing aniline. SLCs were formed by a quaternary mixture containing brine, sodium dodecyl sulphate (SDS) as the surfactant, 1-pentanol as the co-surfactant and cyclohexane as oil. A portion of cyclohexane was replaced by aniline to make SLCs containing aniline in the oil phase. Similarly, brine was replaced with a solution of gold chloride to make the mesophase containing Au3+ ions. Simultaneous chemical oxidation of aniline and reduction of Au3+ ions takes place upon mixing the above mentioned mesophases, leading to the formation of the nanocomposite. Small spherical nanoparticles or short nanorods that are initially formed join together to form nanowires within the PANI shell due to the confinement, typical diffusion path and also due to the strong interaction between Au and PANI. The prepared composite nanowires exhibited good surface enhanced Raman scattering (SERS) for an organic dye. The composite also showed excellent catalytic behavior for the chemical reduction of organic dyes.

Green synthesis of a palladium–polyaniline nanocomposite for green Suzuki–Miyaura coupling reactions

A palladium–polyaniline (Pd–PANI) nanocomposite was successfully synthesized using a one-pot green synthetic procedure in water by the reaction between aniline hydrochloride and potassium hexachloropalladate. Strong interaction between PANI and Pd was clearly evident in the UV-visible and Fourier transform infrared (FTIR) spectrum of the nanocomposite. Powder X-ray diffraction (XRD) patterns revealed the presence of Pd(0) in the nanocomposite with a fcc crystal structure. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) imaging showed that the Pd–PANI nanocomposite has spherical morphology with an average particle size of 175 ± 42 nm. High resolution TEM imaging and energy dispersive X-ray (EDX) spectroscopy studies revealed that very small nanoparticles of Pd (3.1 ± 0.9 nm) were found dispersed throughout the PANI matrix. X-ray photoelectron spectroscopy (XPS) revealed the presence of Pd(0) in the nanocomposite. The catalytic behavior of the Pd–PANI nanocomposite was studied for Suzuki–Miyaura coupling reactions in the presence of different bases in both organic and aqueous media. The results revealed that the Suzuki–Miyaura reaction proceeds much faster in water than in toluene. The excellent catalytic activity of the nanocomposite resulted in 86 and 91% yield in water and toluene respectively, when potassium carbonate was used as the base.

Ultrafine carbamazepine nanoparticles with enhanced water solubility and rate of dissolution

Carbamazepine (CBZ) is an antiepileptic drug having poor water solubility and hence poor bioavailability. Spherical nanoparticles of CBZ with particle size below 50 nm were successfully prepared by the evaporation assisted solvent–antisolvent interaction (EASAI) method. CBZ nanoparticles that are stabilized by polyvinylpyrrolidone (PVP) were also prepared by the same method. Solubility of CBZ nanoparticles and CBZ–PVP nanoparticles was 11.9 and 21.5 times higher than the raw-CBZ. In vitro dissolution studies showed that almost 100% of the drug was released from CBZ nanoparticles and CBZ–PVP nanoparticles in less than 60 min whereas only 34% of the drug was released from raw-CBZ even after 180 min. The effect of different experimental parameters such as the concentration of drug and the presence of PVP on particle size, morphology, solubility and in vitro drug release rate of CBZ was thoroughly investigated. The spherical morphology of the nanoparticles was confirmed by field emission scanning electron microscopy (FESEM) and transmission electron microcopy (TEM). FTIR spectroscopy studies revealed that there is hydrogen bonding between PVP and CBZ molecules in the CBZ–PVP nanoparticles. The X-ray diffraction (XRD) pattern of CBZ–PVP nanoparticles revealed the subtle change in crystal structure of raw-CBZ. Differential scanning calorimetry (DSC) studies showed that the nanoparticles were relatively less crystalline than the raw-CBZ.

Tuning the surface enhanced Raman scattering and catalytic activities of gold nanorods by controlled coating of platinum

Galvanic replacement of silver (Ag) by platinum (Pt) on bi-metallic nanorods (NRs) having gold (Au) core and silver shell (Au@Ag) resulted in discontinuous coating of Pt over Au (Au@Pt-DC) NRs. However, a novel method has been developed in this work for the preparation of Au NRs having smooth and continuous coating of Pt (Au@Pt-C NRs) using galvanic replacement reaction of Au@Ag NRs in presence of sulphuric acid. Selective blocking by the bisulfate ions that are adsorbed on Pt surface, preventing Pt on Pt deposition seems to be the mechanism of formation of Au@Pt-C NRs. Effect of the nature of Pt shell (i.e. whether continuous or discontinuous) on SERS activity of the NRs was investigated with methylene blue (MB) as a reporter molecule. The specific enhancement of the Raman signals were in the order Au@ Pt-C NRs<Au NR<Au@Pt-DC NRs. Catalytic reduction of MB by NaBH4 using the NRs also followed a similar trend with Au@Pt-DC NRs showing almost three times better activity than Au and Au@Pt-C NRs.

Optimized Synthesis of HMX Nanoparticles Using Antisolvent Precipitation Method

Nanoparticles of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) were prepared by an antisolvent precipitation method. The effect of different experimental parameters such as temperature of antisolvent and concentration of solution on particle size of nano-HMX was studied systematically. A higher temperature (70°C) of the antisolvent and lower concentration of HMX in acetone (5 mM) favored the formation of smaller particles. Average particle size ranged from 30 to 128 nm under different experimental conditions. Nano-HMX was characterized using dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM), ultraviolet-visible spectrophotometry, powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis coupled with differential scanning calorimetry (TGA-DSC). FTIR, XRD, and TGA-DSC studies revealed that the nano-HMX was in the β-polymorphic form.

Solid lipid nanoparticles for the controlled delivery of poorly water soluble non-steroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (IBP) are among the most prescribed drugs across the globe. However, most NSAIDs are insoluble in water leading them to have poor bioavailability and erratic absorption. Moreover, NSAIDs such as IBP and ketoprofen (KP) have to be administered very frequently due to their short plasma half-life leading to side effects. Controlled release formulations of IBP, KP and nabumetone (NBT) based on solid lipid nanoparticles (SLNs) were successfully synthesised in the present study to solve the above-mentioned challenges that are associated with NSAIDs. SLNs were prepared in two steps; hot-melt homogenization followed by sonication to formulate SLNs with spherical morphology. While capmul® GMS-50K (capmul) was used as the lipid due to the high solubility of the studied drugs in it, gelucire® 50/13 (gelucire) was used as the surfactant. It was found that particle size was directly proportional to drug concentration and inversely proportional to surfactant concentration, volume of water added and temperature of water. Ultrasonication in a pulse mode with optimum duration of 15min was essential to obtain smaller nanoparticles through the formation of a nanoemulsion. Drug loaded SLNs with small particle size and narrow size distribution with good solid loading, encapsulation efficiency and drug loading percentage could be prepared using the optimised conditions. SLNs prepared at the optimised condition were characterized thoroughly by using different techniques such as dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The cytotoxicity results showed that the prepared SLNs are non-toxic to Raw cell line. The drugs IBP, KP and NBT showed 53, 74 and 69% of percentage entrapment efficiency with drug loading of 6, 2 and 7% respectively. Slow, steady and sustained drug release was observed from the SLNs for over 6days.

Swollen liquid crystals (SLCs): a versatile template for the synthesis of nano structured materials

Liquid crystal (LCs) is the state of matter that exhibits properties between a conventional liquid and solid crystals. Liquid crystals mainly can be classified into two types: thermotropic and lyotropic liquid crystals. A thermotropic liquid crystal shows properties that are dependent on temperature conditions. On the other hand in lyotropic liquid crystals (LLCs), the amphiphiles are dissolved in a solvent and exhibit liquid crystalline properties in certain concentration ranges. In the literature, lot of reviews have been presented on thermotropic and lyotropic liquid crystals (LLCs). But nowadays, swollen liquid crystals (SLCs) have become a much more important area of research because of their easily tunable properties, their stability and versatility of the system. Swollen liquid crystals (SLCs) consist of infinite liquid crystalline non polar cylinders organized on a hexagonal lattice in a polar medium and are prepared with the proper ratios of salted water and non polar solvents with cationic or anionic or non ionic surfactants and co surfactants i.e. water : oil : surfactant : cosurfactant. In this review article, we will briefly discuss the synthesis of swollen liquid crystals (SLCs), factors affecting their stability, different kinds of nanomaterials such as metallic, bimetallic, polymeric nanostructures synthesized inside swollen liquid crystals (SLCs) using different methods and the effect of swollen liquid crystal (SLC) confinement on the final morphology of nanomaterials with their potential applications.

Calcination temperature as a probe to tune the non-enzymatic glucose sensing activity of Cu–Ni bimetallic nanocomposites

The present paper discusses the role of calcination in tuning the non-enzymatic glucose sensitivities of Cu–Ni bimetallic nanocomposites. Nanoparticles of Cu, a layered hydroxide of Ni and Cu–Ni nanocomposites were synthesized via the polyol reduction method. The prepared nanomaterials were thoroughly characterized by X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS). Thermogravimetric analysis (TGA) was done in order to understand the thermal behavior of the nanoparticles. The prepared nanomaterials were subjected to calcination at three different temperatures viz. 400, 500 and 600 °C. The non-enzymatic glucose sensing activity of the nanomaterials was studied electrochemically. The nanocomposites showed the best sensing performance among the prepared nanomaterials. Interestingly, calcination resulted in a seven-fold increase in the sensitivity of the nanocomposites. The nanocomposite that was calcined at 600 °C showed the maximum sensitivity of 63.87 μA mM−1 cm−2 with a low detection limit of 8 μM at a signal to noise ratio of 3. The nanocomposite showed a distinct linear response in the range of 0.01 to 18 mM with a regression coefficient of 0.99162. The nanocomposite also exhibited excellent selectivity for glucose in the presence of other interfering agents. The nanocomposite also demonstrated good agreement with the pathology laboratory data for whole blood and blood serum samples.

Unusual anti-leukemia activity of nanoformulated naproxen and other non-steroidal anti-inflammatory drugs.

The non-steroidal anti-inflammatory drugs (NSAIDs) are the most widely used pharmaceuticals worldwide. Interestingly, many of them have significant anticancer properties too. However, the poor water solubility of certain NSAIDs limits their application for cancer treatment. Nanosizing of such drugs can help to improve the solubility and this may result in enhanced anticancer activities too. Moreover, over dosages and the accompanying side effects of NSAIDs can be minimized by improving their solubility and bioavailability. Successful nanoformulation of three NSAIDs: ibuprofen (IBP), ketoprufen (KP) and naproxen (NAP) using a novel evaporation assisted solvent-antisolvent interaction (EASAI) method is reported here. Three water soluble and biocompatible polymers: polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA) and hydroxypropyl methylcellulose (HPMC) were used to stabilize the drug nanoparticles. Particles having spherical morphology with average size below 30nm were thoroughly characterized using dynamic light scattering and field emission scanning electron microscopy (FESEM) imaging. The nanoformulation resulted in ten to fifteen fold improvements in the solubility and significant enhancement in the in-vitro drug release profiles of the NSAIDs. Anticancer screening of the nanoformulated NSAIDs against five different cancer cell lines such as MCF-7 (Human breast cancer cell line), (Human pancreatic cancer cell line) MIA-PA-CA-2, (Human colon cancer cell line) HT-29, (Human leukemia cell line) Jurkat and (human ovarian carcinoma cell line) A2780 was performed. All the nanoformulated samples showed improved anticancer activity against the Leukemia cancer cell line, out of which NAP-PVP showed the highest anti-cancer activity. The anti-Leukemia activity of NAP-PVP was more than twice that of doxorubicin which is a standard anticancer drug.

Synthesis of polyaniline–magnetite nanocomposites using swollen liquid crystal templates for magnetically separable dye adsorbent applications

Solid phase extraction of pollutants requires the adsorbents to have high adsorption capacities, ease of separation and fast adsorption–desorption kinetics. Here we describe the development of magnetically separable adsorbents for dyes based on nanocomposites of polyaniline–iron oxide having a unique rod like morphology of polyaniline in which nanowires of iron oxide are embedded. Polyaniline–iron oxide nanocomposites having unique morphology were synthesized using swollen liquid crystals (SLCs) as soft structure directing agents. The SLCs are formed from a quaternary mixture of aqueous phase, oil phase, surfactant and co-surfactant. Mesophases of aniline or ferric chloride were synthesized by trapping a small amount of aniline in the oil phase or by replacing the brine phase with aqueous ferric chloride in the SLCs, respectively. The unique morphology of the nanocomposites enables them to adsorb dyes rapidly from an aqueous medium. Moreover, the adsorption kinetics could be modelled using a pseudo second order reaction indicating that the adsorption was not limited by mass transport, probably due to the short diffusion lengths in the nanocomposites. The nanocomposites showed adsorption based on electrostatic interaction and had very high adsorption capacities of upto ∼100 mg g−1.