Yuvaraj Haldorai

Magnetic polymer nanocomposites for environmental and biomedical applications

Hybrid nanomaterials have received voluminous interest due to the combination of unique properties of organic and inorganic component in one material. In this class, magnetic polymer nanocomposites are of particular interest because of the combination of excellent magnetic properties, stability, and good biocompatibility. Organic–inorganic magnetic nanocomposites can be prepared by in situ, ex situ, microwave reflux, co-precipitation, melt blending, and ceramic–glass processing and plasma polymerization techniques. These nanocomposites have been exploited for in vivo imaging, as superparamagnetic or negative contrast agents, drug carriers, heavy metal adsorbents, and magnetically recoverable photocatalysts for degradation of organic pollutants. This review article is mainly focused on fabrication of magnetic polymer nanocomposites and their applications. Different types of magnetic nanoparticles, methods of their synthesis, properties, and applications have also been reviewed briefly. The review also provides detailed insight into various types of magnetic nanocomposites and their synthesis. Diverse applications of magnetic nanocomposites including environmental and biomedical uses have been discussed.

Porous three-dimensional graphene foam/Prussian blue composite for efficient removal of radioactive 137Cs

In this study, a simple one-step hydrothermal reaction is developed to prepare composite based on Prussian blue (PB)/reduced graphene oxide foam (RGOF) for efficient removal of radioactive cesium (137Cs) from contaminated water. Scanning electron microscopy and transmission electron microscopy show that cubic PB nanoparticles are decorated on the RGO surface. Owing to the combined benefits of RGOF and PB, the composite shows excellent removal efficiency (99.5%) of 137Cs from the contaminated water. The maximum adsorption capacity is calculated to be 18.67 mg/g. An adsorption isotherm fit-well the Langmuir model with a linear regression correlation value of 0.97. This type of composite is believed to hold great promise for the clean-up of 137Cs from contaminated water around nuclear plants and/or after nuclear accidents.

Direct electrochemistry of cytochrome c immobilized on titanium nitride/multi-walled carbon nanotube composite for amperometric nitrite biosensor.

In this report, titanium nitride (TiN) nanoparticles decorated multi-walled carbon nanotube (MWCNTs) nanocomposite is fabricated via a two-step process. These two steps involve the decoration of titanium dioxide nanoparticles onto the MWCNTs surface and a subsequent thermal nitridation. Transmission electron microscopy shows that TiN nanoparticles with a mean diameter of ≤ 20 nm are homogeneously dispersed onto the MWCNTs surface. Direct electrochemistry and electrocatalysis of cytochrome c immobilized on the MWCNTs-TiN composite modified on a glassy carbon electrode for nitrite sensing are investigated. Under optimum conditions, the current response is linear to its concentration from 1 µM to 2000 µM with a sensitivity of 121.5 µA µM(-1)cm(-2) and a low detection limit of 0.0014 µM. The proposed electrode shows good reproducibility and long-term stability. The applicability of the as-prepared biosensor is validated by the successful detection of nitrite in tap and sea water samples.

Chitosan-Zinc Oxide hybrid composite for enhanced dye degradation and antibacterial activity

In this report, chitosan (CS) encapsulated zinc oxide (ZnO) hybrid composite was prepared by chemical precipitation method. The CS-ZnO composite was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis (TGA), transmission electron microscopy, and zeta potential. The composite exhibited high photocatalytic activity as evident from the degradation of methylene blue dye under UV irradiation. Approximately, 64% of the dye was degraded under UV irradiation within 3 h. In addition, the CS-ZnO composite showed excellent antibacterial activity against Escherichia coli as measured by colony forming units. Based on the data of present investigation, the composite being a biocompatible, eco-friendly, and low-cost material could find potential applications in various fields.

Porous Covalent Triazine Polymer as a Potential Nanocargo for Cancer Therapy and Imaging.

A microporous covalent triazine polymer (CTP) network with a high surface area was synthesized via the Friedel-Crafts reaction and employed as a potential transport system for drug delivery and controlled release. The CTP was transformed to the nanoscale region by intense ultrasonication followed by filtration to yield nanoscale CTP (NCTP). This product showed excellent dispersibility in physiological solution while maintaining its chemical structure and porosity. An anticancer drug, doxorubicin (DOX), was loaded onto the NCTP through hydrophobic and π-π interactions, and its release was controlled at pH 4.8 and 7.4. The NCTP showed no toxicity toward cancer or normal cells, but the NCTP-DOX complex showed high efficacy against both types of cells in vitro. In-vitro cell imaging revealed that NCTP is a potential material for bioimaging. The potency of NCTP on cellular senescence was confirmed by the expression of senescence associated marker proteins p53 and p21. These results suggest that NCTP can be used as a new platform for drug delivery and imaging with potential applications in diagnosis and therapy.

Electrodeposition of flower-like nickel oxide on CVD-grown graphene to develop an electrochemical non-enzymatic biosensor

We demonstrated a non-enzymatic cholesterol sensor based on a nickel oxide (NiO) and high quality graphene composite for the first time. Graphene was grown by a chemical vapor deposition technique (CVD). The nanocomposite was fabricated through the electrodeposition of nickel hydroxide onto the surface of the CVD-grown graphene, which was followed by thermal annealing. The successful formation of the NiO/graphene composite was confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The deposition of flower-like NiO onto the graphene surface was confirmed by scanning electron microscopy. Electrochemical analyses were conducted to investigate the characteristics of the sensor during the detection of cholesterol. The sensor showed a high sensitivity of 40.6 mA μM-1 cm-2, a rapid response time of 5 s, and a low detection of limit of 0.13 μM. We also investigated the effects of common interfering substances on the ability of the sensor to detect cholesterol. Furthermore, we successfully determined the cholesterol in a milk sample using the developed sensor. The composite electrode exhibited excellent detection of cholesterol with good reproducibility and long-term stability owing to the combined effects of NiO and graphene.

Multifunctional Chitosan-Copper Oxide Hybrid Material: Photocatalytic and Antibacterial Activities

Chitosan (CS) anchored copper oxide (CuO) hybrid material was prepared by chemical precipitation method. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) confirmed the formation of CS-CuO hybrid. Transmission electron microscopy (TEM) analysis showed the immobilization of CuO nanoparticles on the surface of CS. The hybrid was also characterized by thermogravimetric analysis (TGA) and zeta potential. The hybrid exhibited high photocatalytic activity as evident from the degradation of methylene blue (MB) dye. The result revealed substantial degradation of the MB dye (84%) under UV-light illumination. The antibacterial activity of hybrid against Escherichia coli was examined by colony forming units. It was proved that the CS encapsulated CuO hybrid exhibited excellent antibacterial activity.

Zinc oxide nanoparticles reinforced conducting poly(aniline-co- p-phenylenediamine) nanocomposite

Zinc oxide (ZnO) nanoparticles were synthesized by thermal decomposition method and formation of composite with conducting copolymer via in situ chemical oxidative polymerization. Transmission electron microscopy showed that the nanoparticles with an average diameter of 15–25 nm were dispersed in the copolymer matrix. The comonomer molecules were adsorbed on the surface of ZnO particles and then polymerized to form core–shell nanocomposite. The obtained nanocomposite showed a significant improvement in the thermal behavior as indicated by thermogravimetric analysis. The nanocomposite was also confirmed by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, and X-ray diffraction. Room temperature conductivity of nanocomposite was higher than the value obtained for the pure copolymer. Photocatalytic activity of the nanocomposite was evaluated by measuring the degradation of methylene blue dye under UV irradiation.

Nanostructured Materials with Conducting and Magnetic Properties: Preparation of Magnetite/Conducting Copolymer Hybrid Nanocomposites by Ultrasonic Irradiation

Conducting copolymer poly(aniline-co-p-phenylenediamine) [poly(Ani-co-pPD)] and surface-modified magnetite (Fe3O4) composites were synthesized by ultrasonically-assisted chemical oxidative polymerization. Fe3O4 nanoparticles were surface-modified with silane coupling agent methacryloxypropyltrimethoxysilane (MPTMS) in order that they would be well dispersed for the reaction process. It was also found that the aggregation of Fe3O4 nanoparticles could be reduced under ultrasonic irradiation. TEM analysis confirmed that the resulting poly(Ani-co-pPD)/Fe3O4 nanocomposite showed core–shell morphology, in which Fe3O4 nanoparticles were well dispersed. The incorporation of Fe3O4 in the nanocomposites was endorsed by FT-IR. The nanocomposites were also confirmed by UV-visible, TGA and XRD. Conductivity of the nanocomposites was found to be in the range of 7.02 × 10−4–6.54 × 10−6 S/cm. Higher saturated magnetization of 12 emu/g was observed for composite with 20% Fe3O4.

Chemo-responsive bilayer actuator film: fabrication, characterization and actuator response

A chemo-responsive bilayer actuator was fabricated by cross-linking a polysaccharide based highly hydrophilic material with the polyamide-6 (PA-6) substrate. The hydrogel material was prepared by grafting the polyacrylamide (PAAm) and poly(acrylic acid) (PAA) copolymer onto carboxymethyl cellulose (CMC) [poly(AA-co-AAm)-g-CMC]. The successful grafting of the copolymer onto CMC was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis. The swelling behavior of the poly(AA-co-AAm)-g-CMC hydrogel was examined at a range of pH values and ionic strengths. Fabrication of the bilayer actuator was performed by drop casting a poly(AAm-co-AA)-g-CMC solution onto a PA-6 substrate followed by subsequent cross-linking under ultraviolet radiation. Cross-linking was performed to make the material readily swellable in water but prevent complete dissolution. The actuator response was measured in both water and ethanol.