Vyom Parashar

Mechanism of uptake of ZnO nanoparticles and inflammatory responses in macrophages require PI3K mediated MAPKs signaling.

The inflammatory responses after exposure to zinc oxide nanoparticles (ZNPs) are known, however, the molecular mechanisms and direct consequences of particle uptake are still unclear. Dose and time-dependent increase in the uptake of ZNPs by macrophages has been observed by flow cytometry. Macrophages treated with ZNPs showed a significantly enhanced phagocytic activity. Inhibition of different internalization receptors caused a reduction in uptake of ZNPs in macrophages. The strongest inhibition in internalization was observed by blocking clathrin, caveolae and scavenger receptor mediated endocytic pathways. However, FcR and complement receptor-mediated phagocytic pathways also contributed significantly to control. Further, exposure of primary macrophages to ZNPs (2.5 μg/ml) caused (i) significant enhancement of Ras, PI3K, (ii) enhanced phosphorylation and subsequent activation of its downstream signaling pathways via ERK1/2, p38 and JNK MAPKs (iii) overexpression of c-Jun, c-Fos and NF-κB. Our results demonstrate that ZNPs induce the generation of reactive nitrogen species and overexpression of Cox-2, iNOS, pro-inflammatory cytokines (IL-6, IFN-γ, TNF-α, IL-17 and regulatory cytokine IL-10) and MAPKs which were found to be inhibited after blocking internalization of ZNPs through caveolae receptor pathway. These results indicate that ZNPs are internalized through caveolae pathway and the inflammatory responses involve PI3K mediated MAPKs signaling cascade.

Ag/PVA nanocomposites: optical and thermal dimensions

A single-step synthesis of homogenous Ag/PVA nanocomposites is carried out and characterized by X-ray diffraction. A validation of the crystal information is established by transmission electron microscopy (TEM) and a homogenous mixing morphology is confirmed by SEM micrographs. Surface plasmon resonance (SPR) optical absorption shows a red shift compared to bare Ag NPs. The degradation mechanisms are explained for both pristine PVA and Ag/PVA nanocomposites, aided by the increase in thermal stability of the PVA support with an enthalpy change for each decomposition reaction.

Investigations on structural, optical and second harmonic generation in solvothermally synthesized pure and Cr-doped ZnO nanoparticles

At the forefront of the current scientific revolution of nanoscience nanocrystals (NCs), crystalline particles grown in liquid media, stand out over other classes of inorganic nanomaterials due to the high degree of control with which their crystal structure, size, shape, and surface functionalities can be engineered in the synthesis stage and to the versatility with which they can be processed and implemented into a large spectrum of devices and processes. Doped semiconductor nanostructures can yield both high luminescence efficiencies and lifetime shortening at the same time. In the present manuscript pure and Cr-doped ZnO nanoparticles were successfully synthesized from the solution phase chemistry and investigated with respect to their structural and optical properties. The resulting powder consisting of nanocrystalline particles were characterized by X-ray diffraction (XRD), UV-Visible spectroscopy, photoluminescence spectroscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray analysis (EDX) techniques. A UV emission peak was observed from the exciton transition at 380 nm in the room temperature photo luminescent (PL) spectra. The blue emission band was assigned to the Zn interstitial and vacancy level transition. Even though Cr ions are known to act as an efficient non-radiative loss centre for near band gap emission (NBE), a pronounced NBE is obtained at room temperature even for a nominal Cr concentration of 8 at. %. XRD data analysis shows that the chromium dopant atoms are incorporated into the wurtzite host lattice. The grain size decreases with increasing dopant concentration. The lattice constants extracted by the Rietveld method from XRD data vary slightly with doping concentration.

An ultra sensitive saccharides detection assay using carboxyl functionalized chitosan containing Gd2O3:Eu3+ nanoparticles probe

A novel saccharides detection assay based on covalent immobilization of amino phenyl boronic acid (APBA) in thin films of carboxyl functionalized chitosan (HOOC-chitosan) containing <5 nm Gd2O3 : Eu3+ nanoparticles at a platinum disc electrode was developed. The resulting HOOC-chitosan/Gd2O3 : Eu3+ nanocomposite film exhibited excellent electrochemical response to changes in the pKa values of boronate esters yielded from different vicinal diols of sugars. The covalent interaction of APBA onto the HOOC-chitosan/Gd2O3 : Eu3+ Pt-disc electrode was characterized with FT-IR, SEM, contact angle and cyclic voltammetry, whereas Gd2O3 : Eu3+ nanoparticles and HOOC-chitosan/Gd2O3 : Eu3+ nanocomposite was identified using XRD, EDX and TEM. A wide linear response was measured to boronate esters ranging from 25 nM to 13.5 μM (r2 = 0.963) with good reproducibility. The excellent electrochemical activity of the assay might be attributed to the synergistic effects of the balanced de-/protonated HOOC-chitosan, APBA and Gd2O3 : Eu3+ nanoparticles. With APBA as a model, the HOOC-chitosan/Gd2O3 : Eu3+ nanocomposite-modified Pt-electrode was constructed through a simple drop coating method. The resulting assay exhibited a good potentiometric response to different saccharides including glucose, and could be a promising application for the precise electrochemical detection of vicinal diols of specific sugars for clinical diagnostics, medicine validation, bioscience research and food analysis.

Low-temperature synthesis of quantum size gadolinium monosulfide (GdS) nanoparticles and their pathogen capture efficiency

Synthesis of paramagnetic gadolinium monosulfide nanoparticles at low temperature is achieved using dextrose ligands.

High-performance and high-sensitivity applications of graphene transistors with self-assembled monolayers.

Charge impurities and polar molecules on the surface of dielectric substrates has long been a critical obstacle to using graphene for its niche applications that involve graphenes high mobility and high sensitivity nature. Self-assembled monolayers (SAMs) have been found to effectively reduce the impact of long-range scatterings induced by the external charges. Yet, demonstrations of scalable device applications using the SAMs technique remains missing due to the difficulties in the device fabrication arising from the strong surface tension of the modified dielectric environment. Here, we use patterned SAM arrays to build graphene electronic devices with transport channels confined on the modified areas. For high-mobility applications, both rigid and flexible radio-frequency graphene field-effect transistors (G-FETs) were demonstrated, with extrinsic cutoff frequency and maximum oscillation frequency enhanced by a factor of ~2 on SiO2/Si substrates. For high sensitivity applications, G-FETs were functionalized by monoclonal antibodies specific to cancer biomarker chondroitin sulfate proteoglycan 4, enabling its detection at a concentration of 0.01 fM, five orders of magnitude lower than that detectable by a conventional colorimetric assay. These devices can be very useful in the early diagnosis and monitoring of a malignant disease.

Methanol derived large scale chemical synthesis of brightly fluorescent graphene

We report an interesting carbon material MD-bf-G (methanol derived brightly fluorescent graphene) synthesized using low-priced methanol and sodium hydroxide. MD-bf-G emits red and white light when subjected to infrared laser pulses at 976 nm and 1064 nm respectively. The MD-bf-G offers a low cost imaging probe for various biomedical applications.

Synchronized detection and removal of thiols using a Gd(OH)3 nanosheet-sodium pentacyanonitrosylferrate(II) complex

We described a novel procedure for visible detection and separation of thiols and disulfides. The method uses a Gd(OH)3 nanosheets–sodium pentacyanonitrosylferrate(II) paramagnetic complex which produce an intermediate chromophore when coupled with a sulfur containing analyte, which is detectable with the naked eye and simultaneously can be removed by applying an external magnetic field.

Optical Stability and Photoluminescence Enhancement of Biotin Assisted ZnS:Mn2+ Nanoparticles

We synthesized the ZnS: Mn2+ nanoparticles passivated by biocompatible layer namely ‘biotin‘ by chemical precipitation route and studied their temporal evolution for optical and photoluminescence stability. Structural analysis was carried out using high resolution transmission electron microscope. To monitor the optical and photoluminescence properties of the nanoparticles with time, we have characterized the grown product by UV‐Visible and photoluminescence spectroscopy at regular interval for the period three months. Results showed that the properties of nanophosphors capped with biotin are remaining same even after three months. We found that, biotin capping will enhance the luminescence from ZnS: Mn2+ nanoparticles as compared to without cap particles. Absence of biotin will gradually degrade the luminescence upon aging while drastic degradation in the luminescence intensity was observed after annealing.