Pradip Paik

Recent Advancement in Functional Core-Shell Nanoparticles of Polymers: Synthesis, Physical Properties, and Applications in Medical Biotechnology

This paper covers the core-shell nanomaterials, mainly, polymer-core polymer shell, polymer-core metal shell, and polymer-core nonmetal shells. Herein, various synthesis techniques, properties, and applications of these materials have been discussed. The detailed discussion of the properties with experimental parameters has been carried out. The various characterization techniques for the core-shell nanostructure have also been discussed. Their physical and chemical properties have been addressed. The future aspects of such core-shell nanostructures for biomedical and various other applications have been discussed with a special emphasis on their properties.

Chiral-mesoporous-polypyrrole nanoparticles: Its chiral recognition abilities and use in enantioselective separation

Chiral-mesoporous-polypyrrole (CMPPy) nanoparticles are synthesized by templating chiral block copolymers (CBCs) of poly(ethylene oxide), (PEO) and chiral L-/D- glutamic acid [PEO-b-(L-/D-GluA)10] and blocks of chiral L-/D-phenylalanine [PEO-b-(L-/D-Phe)10]. The well ordered chiral mesopores of nanoparticles are characterized by HRTEM and BET. The CMPPy nanoparticles have well organized pores with sizes ca. 3.5–3.7 nm in diameter and with a high surface area. These CMPPy nanoparticles are able to recognize chiral molecules. Using the selective chiral recognition abilities, the chiral resolution of the copolymer-extracted CMPPy nanoparticles and the chiral separation kinetics using a racemic mixture of valine are probed by circular dichroism (CD) and optical polarimetry. Further, the chiral resolution of the CMPPy is confirmed with a racemic mixture of alanine. The chiral selectivity factor is 5.05 for a specific enantiomer which is adsorbed preferably by the CMPPy. These results allow a new approach towards the enantiomeric separation and other enantiomeric applications of novel CMPPy.

Enantioselective Separation Using Chiral Mesoporous Spherical Silica Prepared by Templating of Chiral Block Copolymers

In this work, we synthesized chiral mesoporous silica (CMS) spheres, which can be used as a potential candidate for chiral separation. The CMS spheres with controllable pore sizes (of 2-3 nm) and high surface areas of ca. 614 m(2) g(-1) were synthesized by chiral templating with chiral block copolymers based on poly(ethylene oxide) and dl-glutamic acid [PEO(113)-b-(GluA)(10)]. The ordered structure of the chiral mesopores was characterized by high-resolution transmission electron microscopy, and the average pore diameters of chiral mesopores were estimated from the nitrogen adsorption-desorption measurements. The enantioselectivity properties and chiral resolution kinetics of the mesopores of silica spheres, after extraction of chiral polymers of PEO(113)-b-(l/d-GluA)(10), were scrutinized using a racemic solution of valine and measuring the circular dichroism and optical polarimetery. A chiral selectivity factor of 5.22 was found with a specific enantiomer of valine adsorbed preferably. These results raise the new possibilities of CMS spheres for enantiomeric separation and other enantioselective applications.

Nanoniobia Modification of CdS Photoanode for an Efficient and Stable Photoelectrochemical Cell

Herein we report the surface modification of a CdS film by niobia nanoparticles via thioglycerol as an organic linker and thus fabricate an efficient and a stable photoanode for a photoelectrochemical (PEC) cell. We have synthesized three differenly sized (∼3, ∼6 ,and ∼9 nm) niobia nanoparticles by a hydrothermal synthesis approach and have further investigated the particle-size-dependent PEC performance of the nanoparticle-modified CdS photoanode. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirm the formation of Nb2O5 nanoparticles that are prepared via decomposition of the niobium peroxo complex during the hydrothermal reaction and reveal the presence of surface OH(-) groups over niobia nanoparticles that impart a high catalytic property to a material. The nano-Nb2O5-modified photoanode displayed a 23-fold higher power conversion efficiency compared to that of CdS. This modified structure increases the open circuit voltage (OCV) from 0.65 to 0.77 V, which is attributed to the nano-Nb2O5-induced surface passivation effect over bare CdS. Linking of nanoparticles on the CdS surface improves the photocorrosion stability of the CdS photoanode for even longer than 4 h in contrast to the tens of minutes for the base CdS surface. The uniform coverage of the CdS photoanode surface by niobia nanoparticles is thus found to be the controlling parameter for achieving a higher PEC performance and stability of the photoanode. This finding directed us to design an improved CdS photoanode for efficient and prolonged PEC hydrogen generation from a PEC cell.

A new single/few-layered graphene oxide with a high dielectric constant of 106: contribution of defects and functional groups

In this study, we introduce a single/few-layered graphene oxide (GO) synthesized with ultrasonication, and demonstrate its high dielectric permittivity in the frequency range of 20 Hz to 2 MHz and temperature range of 30 °C to 180 °C. A high dielectric constant of GO (∼106) with low loss was observed at 1 kHz and at 30 °C, which is even very high compared to conventional dielectric materials such as CaCu3Ti4O12. The conductivity of our GO was calculated and found to be 3.980 × 10−5 to 1.943 × 10−5 (DC) and 2.0 × 10−3 to 1.7 × 10−2 (AC). The various conducting mechanisms governing the conductivity (AC and DC) of GO with varying frequency and temperature are assessed using impedance spectroscopy. The mechanistic approach and the role of functional groups, defects, temperature and frequency are elucidated and discussed with regard to the high dielectric constant. The variation of activation energy from 1.15 (1 kHz) to 0.58 (2.0 MHz) is related to the frequency dependent conductivity of the π–π conjugated electrons and their hopping has also been discussed. The present dielectric results are superior to those of GOL (with fewer defects/less sonication time). Moreover, the present findings suggest that the new GO can be used for scaling advances high performance electronic devices and high dielectric-based electronic and energy storage devices.

Synthesis of hollow and mesoporous polycaprolactone nanocapsules.

New polycaprolactone (PCL) nanocapsules with a hollow core and mesoporous shell have been synthesized. The PCL nanocapsules have an average size of about 100 nm and a mesopores shell of about 20 nm. The size of the mesopores on the shell is about 4 nm. Fluorescent dye Rhodamin 6G was loaded into the nanocapsules to demonstrate the mesoporous structure of the capsules and their ability to load small molecules. The nanocapsules with such a structure can be used in many areas for various applications such as drug and gene delivery.

Silver nanoparticles embedded mesoporous SiO2 nanosphere: an effective anticandidal agent against Candida albicans 077

Candida albicans is a diploid fungus that causes common infections such as denture stomatitis, thrush, urinary tract infections, etc. Immunocompromised patients can become severely infected by this fungus. Development of an effective anticandidal agent against this pathogenic fungus, therefore, will be very useful for practical application. In this work, Ag-embedded mesoporous silica nanoparticles (mSiO2@AgNPs) have successfully been synthesized and their anticandidal activities against C. albicans have been studied. The mSiO2@AgNPs nanoparticles (d ∼ 400 nm) were designed using pre-synthesized Ag nanoparticles and tetraethyl orthosilicate (TEOS) as a precursor for SiO2 in the presence of cetyltrimethyl ammonium bromide (CTAB) as an easily removable soft template. A simple, cost-effective, and environmentally friendly approach has been adopted to synthesize silver (Ag) nanoparticles using silver nitrate and leaf extract of Azadirachta indica. The mesopores, with size-equivalent diameter of the micelles (d = 4-6 nm), were generated on the SiO2 surface by calcination after removal of the CTAB template. The morphology and surface structure of mSiO2@AgNPs were characterized through x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), particle size analysis (PSA), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) and high-resolution transmission electron microscopy (HRTEM). The HRTEM micrograph reveals the well-ordered mesoporous structure of the SiO2 sphere. The antifungal activities of mSiO2@AgNPs on the C. albicans cell have been studied through microscopy and are seen to increase with increasing dose of mSiO2@AgNPs, suggesting mSiO2@AgNPs to be a potential antifungal agent for C. albicans 077.

Designing idiosyncratic hmPCL-siRNA nanoformulated capsules for silencing and cancer therapy.

UNLABELLED In this work, we have designed a siRNA-nanoformulation with mesoporous polycaprolactone (hmPCL) for silencing and cancer therapy. Average hollow core size of hmPCL nanocapsules used for nanoformulation is ~180 nm with shell thickness of 10-20 nm and mesopore size of ~5-10nm in diameter. Idiosyncratic capsules are biocompatible which has been confirmed with normal lymphocyte, K562 leukaemia cancer cells and on HepG2/EGFP cancer cells. In 1mg of hmPCL capsules up to 400 ng of siRNA can be loaded. This nanoformulation enables to tune the dose dependent delivery up to ~93.25% (373 ng) siRNA during therapy. hmPCL-siRNA nanoformulation mediated siRNA transfection on HepG2 cancer cells has been investigated and exhibited 32% silencing activity within 24h of post transfection. Obtained results directed us that the hmPCL-siRNA nanoformulation could be an efficient tool in siRNA mediated therapy for knocking down the infected cells. FROM THE CLINICAL EDITOR siRNA could be used in cancer therapy if naked nucleic acid could be transported using a suitable carrier. In this article, the authors developed a nano-carrier system using mesoporous polycaprolactone (hmPCL) and showed its efficacy in knocking down cancer cells. This approach may open another way of gene therapy.

Polyaniline nanotubes with rectangular-hollow-core and its self-assembled surface decoration: high conductivity and dielectric properties

Polyaniline (PANI) nanotubes with a rectangular hollow core and decorated outer surface-wall with self-assembled nanobeads and triangular flakes of PANI have been synthesized in the presence of ZnO NPs by a sonochemical approach. This is the first example of the formation of well-defined hollow PANI nanotubes with a rectangular hollow interior. The hollow PANI nanotubes have an average length of ca. 10 μm and a hollow core with rectangular geometry. Nanobeads of PANI with diameter ca. 50 nm have been decorated/self-assembled on the surface of the outer wall of rectangular hollow PANI nanotubes to obtain a “Date-tree-like” 3D structure. The crystal structure has been characterized through XRD. The conduction bands and electronic environment have been confirmed through Raman, FT-IR, UV-Vis-NIR, XPS and EPR. Impedance measurements of rectangular hollow PANI nanotubes demonstrate their higher electrical conductivity (σ = 1.1 ± 0.1 × 10−4 S m−1 to 3.0 ± 0.23 × 10−3 S m−1) and dielectric properties, depending on the frequency range compared to the PANI particles synthesized in the presence of H+ and solid PANI fibres. PANI nanotubes with this novel rectangular hollow core structure and surface decorated texture are a unique type of nanostructure, which can be used in various conductive polymer based device applications.

Surface roughness and morphology of polypropylene nanospheres: effects of particles size

Abstract Nanosphere of polypropylene was synthesised under controlled growth condition. Its molecular weight is equivalent to the commercial grade polypropylene. The SEM is conducted in order to inspect the surface morphology. The surface roughness, i.e. surface roughness amplitude parameters R a (arithmetic average roughness) and root mean square roughness (RMS or R q) at nanoscale was calculated for nanoparticles by AFM. It is found that the surface profiles depend on particle size and it increases with increasing particle size. The asperity teeth height R p, valley R v and RMS R q of particles were also calculated and it was found that these parameters are particle size depended. The RMS values are found to be 6˙38 to 77˙72 Å as the particle size varies from 40 to 500 nm. The lower RMS values of polymer nanoparticles acknowledge the atomic scale chain folding. The surface roughness variability (R q/R a) of nanoparticles are also calculated and found to be above unity, which denotes an irregular spread of surface height.