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.

No abstract

Hollow silver nanoshells with tunable plasmon bands have been synthesized using Ag2O nanoparticles at an optimized temperature of 20 °C. The plasmon peak has been tuned in a wide range from 460 nm to 605 nm employing a combination of mild reductant and a mild stabilizer, hydrazine hydrate and sodium citrate, respectively. In contrast, the combination of strong reductant and strong stabilizer, NaBH4 and hydrophilic thiols, resulted in limited plasmon tunability (455-510 nm). The differential behaviour is attributed to the change in dynamics of the diffusion-reaction process. For thiols, the effect of free end-groups was quite evident as plasmon peak shifted from 449 nm to 470 nm on replacing thioglycolic acid (HS-CH2-COOH) with mercaptoethanol (HS-CH2-CH2-OH). Transmission electron microscopy (TEM) revealed that the aspect ratio [outer diameter (d)/shell thickness (t)] was 2.8 (d: 40.0 ± 1.6 nm, t: 14.0 ± 1.3 nm) and 5 (d: 84 ± 2.3 nm, t: 16.8 ± 1.9 nm) for the nanoshells exhibiting a plasmon peak at 460 nm and 605 nm, respectively. The crystal phase of nanoshells was found to be face centered cubic (fcc) as deduced from HR-TEM and electron diffraction data. Using the same Ag2O template, morphological transformation from non-porous to mesoporous has also been achieved by simply reversing the order of addition.

No abstract

No abstract

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 ($10 6 ) with low loss was observed at 1 kHz and at 30 C, which is even very high compared to conventional dielectric materials such as CaCu 3 Ti 4 O 12 . The conductivity of our GO was calculated and found to be 3.980 Â 10 À5 to 1.943 Â 10 À5 (DC) and 2.0 Â 10 À3 to 1.7 Â 10 À2 (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 p-p 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.

Polymeric hollow nanocapsules have attracted significant research attention as novel drug carriers and their preparation is of particular concern owing to the feasibility to encapsulate a broad range of drug molecules. This work presents for the first time the synthesis and development of novel poly-N-acryloyl l-phenylalanine methyl ester hollow core nanocapsules (NAPA-HPNs) of avg. size ca. 100-150 nm by the mini-emulsion technique. NAPA-HPNs are biocompatible and capable of encapsulating sodium nitroprusside (SNP) at a rate of ∼1.3 μM per mg of capsules. These NAPA-HPNs + SNP nano-formulations maintained homeostasis of macrophages which carry and facilitate the action of various drug molecules used against various diseases. These NAPA-HPNs also facilitate the prolonged release of a low level of nitric oxide (NO) and enhance the metabolic activities of pro-inflammatory macrophages, which are important for the action of various drugs in body fluids. NAPA-HPN mediated skewing of naïve macrophages toward the M1 phenotype potentially demonstrates its adjuvant action on the innate immune system. These results potentially suggested that NAPA-HPNs can serve both as a carrier of drugs as well as an adjuvant for the immune system. Thus, these nanocapsules could be used for the effective management of various infectious or tumor diseases where immune-stimulation is paramount for treatment.

Hollow mesoporous-SiO2 nanocapsules have been synthesized at room temperature using unmodified cowpea Mosaic Virus (CPMV) as a template, and without using any catalyst or surfactant during the synthesis. The average size of the capsules synthesized was ∼200-250 nm with a 60-100 nm hollow core. The resulting nanocapsules were characterized using high resolution transmission electron microscopy (HRTEM). The biocompatibility of the hollow mesoporous SiO2 nanocapsules was investigated with an MTT assay using the RAW 264.7 cells, HepG2 cells (human liver carcinoma cells), and Hek293 cells (human embryonic kidney cells). The nanocapsules were loaded with fluorescent molecules (rhodamine 6G), doxorubicin (DOX) – an anticancer drug, and chloroquine diphosphate (CQDP) – an antimalarial drug, and their release was studied using a UV-Vis spectrometer. The development of surfactant free, bio-safe, hollow and mesoporous SiO2 nanocapsules with CPMV provides a route for the synthesis of porous nanocapsules for drug loading and the sustained delivery of drugs. The synthesis method for hollow mesoporous SiO2 nanocapsules using CPMV is novel, straightforward, and further demonstrates that, in general, nanoformulated capsules can be used for various drug-delivery-based therapeutic applications. To check the in vitro efficacy in medical biotechnology, Hek293 and HepG2 cell lines were used to study the cell viability of DOX-loaded hollow silica nanocapsules. The results show that the bio SiO2 nanocapsules synthesized with CPMV present an effective cargo and are suitable for nanoformulating with DOX, with the resultant nanoformulation showing good promise for killing cancer specific cells.