Surface-Engineered Li4Ti5O12 Nanostructures for High-Power Li-Ion Batteries

Materials with high-power charge–discharge capabilities are of interest to overcome the power limitations of conventional Li-ion batteries.In this study,a unique solvothermal synthesis of Li4Ti5O12 nanoparticles is proposed by using an off-stoichiometric precursor ratio.A Li-deficient off-stoichiometry leads to the coexistence of phaseseparated crystalline nanoparticles of Li4Ti5O12 and TiO2 exhibiting reasonable high-rate performances.However,after the solvothermal process,an extended aging of the hydrolyzed solution leads to the formation of a Li4Ti5O12 nanoplate-like structure with a self-assembled disordered surface layer without crystalline TiO2.The Li4Ti5O12 nanoplates with the disordered surface layer deliver ultrahighrate performances for both charging and discharging in the range of 50–300C and reversible capacities of 156 and 113 mAh g−1 at these two rates,respectively.Furthermore,the electrode exhibits an ultrahigh-charging-rate capability up to 1200C(60 mAh g−1;discharge limited to 100C).Unlike previously reported high-rate half cells,we demonstrate a high-power Li-ion battery by coupling Li4Ti5O12 with a high-rate LiMn2O4 cathode.The full cell exhibits ultrafast charging/discharging for 140 and 12 s while retaining 97 and 66% of the anode theoretical capacity,respectively.Room-(25℃),low-(−10℃),and high-(55℃)temperature cycling data show the wide temperature operation range of the cell at a high rate of 100C.

WO_(3) passivation layer-coated nanostructured TiO_(2): An efficient defect engineered photoelectrode for dye sensitized solar cell

Major loss factors for photo-generated electrons due to the presence of surface defects in titanium dioxide(Ti O_2)were controlled by RF-sputtered tungsten trioxide(WO_3) passivation. X-ray photoelectron spectroscopy assured the coating of WO3 on the Ti O_2 nanoparticle layer by showing Ti 2 p, W 4 f and O 1 s characteristic peaks and were further confirmed by X-ray diffraction studies. The coating of WO_3 on the Ti O_2 nanoparticle layer did not affect dye adsorption significantly. Dye sensitized solar cells(DSSCs) fabricated using WO_3-coated Ti O_2 showed an enhancement of ~10% compared to DSSCs fabricated using pristine Ti O_2-based photo-electrodes. It is attributed to the WO_3 passivation on Ti O_2 that creates an energy barrier which favored photo-electron injection by tunneling but blocked reverse electron recombination pathways towards holes available in highest occupied molecular orbital of the dye molecules. It was further evidenced that there is an optimum thickness(duration of coating) of WO_3 to improve the DSSC performance and longer duration of WO_3 suppressed photo-electron injection from dye to Ti O_2 as inferred from the detrimental effect in short circuit current density values. RF-sputtering yields pinhole-free,highly uniform and conformal coating of WO_3 onto any area of interest, which can be considered for an effective surface passivation for nanostructured photovoltaic devices.

Synthesis of Co3O4 Nanoparticles Wrapped Within Full Carbon Matrix as an Anode Material for Lithium Ion Batteries

A facile polyol-assisted pyro-synthesis method was used to synthesize Co3O4 nanoparticles embedded into carbon matrix without using any conventional carbon source. The surface analysis by scanning electron microscopy showed that the Co3O4 nanoparticles（-20 ± 5 nm） are tightly enwrapped within the carbon matrix. CHN analysis determined the carbon content was only 0.11% in the final annealed sample. The Co3O4@carbon exhibited high capacities and excellent cycling performance as an anode at various current rates（such as 914.4 and 515.5 mAh g^-1 at 0.25 and1.0 C, respectively, after 50 cycles; 318.2 mAh g^-1 at a high current rate of 5.0 C after 25 cycles）. This superior electrochemical performance of the electrode can be attributed to the various aspects, such as,（1） the existence of carbon matrix, which acts as a flexible buffer to accommodate the volume changes during Li^＋ion insertion/deinsertion and facilitates the fast Li^＋and electron transfer and（2） the anchoring of Co3O4 nanoparticles within the carbon matrix prevents particles agglomeration.

Alginate nanobeads interspersed fibrin network as in situ forming hydrogel for soft tissue engineering

Hydrogels are a class of materials that has the property of injectability and in situ gel formation.This property of hydrogels is manipulated in this study to develop a biomimetic bioresorbable injectable system of alginate nanobeads interspersed in fibrin network.Alginate nanobeads developed by calcium cross-linking yielded a size of 200e500 nm.The alginate nanobeads fibrin hydrogel was formed using dual syringe apparatus.Characterization of the in situ injectable hydrogel was done by SEM,FTIR and Rheometer.The developed hydrogel showed mechanical strength of 19 kPa which provides the suitable compliance for soft tissue engineering.Cytocompatibility studies using human umbilical cord blood derived mesenchymal stem cells showed good attachment,proliferation and infiltration within the hydrogel similar to fibrin gel.The developed in situ forming hydrogel could be a suitable delivery carrier of stem cells for soft tissue regeneration.

Chitosan based metallic nanocomposite scaffolds as antimicrobial wound dressings

Chitosan based nanocomposite scaffolds have attracted wider applications in medicine,in the area of drug delivery,tissue engineering and wound healing.Chitosan matrix incorporated with nanometallic components has immense potential in the area of wound dressings due to its antimicrobial properties.This review focuses on the different combinations of Chitosan metal nanocomposites such as Chitosan/nAg,Chitosan/nAu,Chitosan/nCu,Chitosan/nZnO and Chitosan/nTiO2 towards enhancement of healing or infection control with special reference to the antimicrobial mechanism of action and toxicity.