Graphene Oxide Quantum Dots Covalently Functionalized PVDF Membrane with Significantly-Enhanced Bactericidal and Antibiofouling Performances

Covalent bonding of graphene oxide quantum dots (GOQDs) onto amino modified polyvinylidene fluoride (PVDF) membrane has generated a new type of nano-carbon functionalized membrane with significantly enhanced antibacterial and antibiofouling properties. A continuous filtration test using E. coli containing feedwater shows that the relative flux drop over GOQDs modified PVDF is 23%, which is significantly lower than those over pristine PVDF (86%) and GO-sheet modified PVDF (62%) after 10 h of filtration. The presence of GOQD coating layer effectively inactivates E. coli and S. aureus cells, and prevents the biofilm formation on the membrane surface, producing excellent antimicrobial activity and potentially antibiofouling capability, more superior than those of previously reported two-dimensional GO sheets and one-dimensional CNTs modified membranes. The distinctive antimicrobial and antibiofouling performances could be attributed to the unique structure and uniform dispersion of GOQDs, enabling the exposure of a larger fraction of active edges and facilitating the formation of oxidation stress. Furthermore, GOQDs modified membrane possesses satisfying long-term stability and durability due to the strong covalent interaction between PVDF and GOQDs. This study opens up a new synthetic avenue in the fabrication of efficient surface-functionalized polymer membranes for potential waste water treatment and biomolecules separation

The multi-facets of sustainable nanotechnology : lessons from a nanosafety symposium

An international symposium for nanosafety was held recently at the Nanyang Technological University in Singapore. Topics relating to understanding nanomaterial properties, tools, and infrastructure required for predicting hazardous outcomes, measuring nanomaterial exposure levels, systems approach for risk assessment and public's perception of nanotechnology were covered. The need for a multidisciplinary approach, across both natural and social sciences, for developing sustainable nanotechnology solutions was heavily emphasized. This commentary highlights the major issues discussed and the commitment of the nanosafety research community in Singapore to contribute collectively to realise the vision of sustainable nanotechnology

Understanding the photoelectrochemical properties of a reduced graphene oxide-WO3 heterojunction photoanode for efficient solar-light-driven overall water splitting

WO3-reduced graphene oxide (WO3-RGO) heterojunction electrodes were prepared for photoelectrochemical (PEC) overall water splitting. The WO3 photoanode incorporated with RGO showed significantly enhanced PEC properties and, hence, photocatalytic water splitting, compared to the bare WO3 at a bias larger than 0.7 V vs. Ag/AgCl, while a decrease in the PEC properties of WO3-RGO compared to the WO3 electrode was observed at a bias smaller than 0.7 V vs. Ag/AgCl. RGO could play a favorable role in enhancing the electron-hole separation due to the presence of interface states according to the Bardeen model, but it could also provide active sites for the electron-hole recombination. A more positive applied bias is in favor of effective electron-hole separation, by means of quick collection and transport of electrons by RGO. As a result, a higher PEC performance of WO3-RGO can only be realised at a relatively more positive bias. This study gives insights into the complex nature of a RGO-semiconductor heterojunction, and its implications on the overall photoconversion efficiency

Superhydrophilicity-assisted preparation of transparent and visible light activated N-doped titania film

A novel and environmental friendly method was developed to prepare transparent, uniform, crack-free and visible light activated nitrogen doped (N-doped) titania thin films without the use of organic Ti precursors and organic solvents. The N-doped titania films were prepared from heating aqueous peroxotitanate thin films deposited uniformly on superhydrophilic uncoated glass substrates. The pure glass substrates were superhydrophilic after being heated at 500 degrees C for 1 h. Nitrogen concentrations in the titania films were adjusted by changing the amount of ammonia solution. The optimal photocatalytic activity of the N-doped titania films was about 14 times higher than that of a commercial self-cleaning glass under the same visible light illumination. The current reported preparative technique is generally applicable for the preparation of other thin films.Nanyang Technological University [1 RG29/07

Nanosized silica particles for achiral drug separation

It is widely recognized that the full potential of rapid chromatography can be realized with very small support particulates and tailor-made chiral stationary phase. However, there has been limited open publication in this area. This work reports the use of a novel monodispersed porous nanosized silica column in UPLC application. In this work, we have demonstrated about 3 times enhanced separation using a C18 functionalized nanosilica column compared to a commercial column. The main objectives of the project are: (1) to synthesize and functionalize silica nanoparticles and (2) apply the nanosilica for achiral drug separation. A modified Stober method is used to synthesize the silica nanoparticle. The nanoparticles were then functionalized with octadecylsilane (C18). Achiral compounds were then separated using a Ultra Performance Liquid Chromatography (UPLC).RG 37/0

Nanosized silica particles for chiral drug separation

The current work addresses the urgent need of novel stationary phases for rapid enantionseparation, and it complements and supports the projects by the PI in the synthesis and application of nanoparticles for achiral and chiral drug separation. The emphasis of this work lies on nanoparticle synthesis and functionalization. This objective has been met. Nanoparticles of various sizes and porosity have been successfully synthesized, C18-functionalized and chiral-functionalized via two different methods using the small equipment support obtained from the current work. Preliminary chromatographic evaluation has also been carried out using ultra performance liquid chromatography (UPLC) and supercritical fluid chromatography (SFC), but will be discussed in other reports. The chiral compounds can be separated but future work needs to be done to fine-tune the nanoparticles properties to optimize separation efficiencies. We intend to vary particles porosity or surface functional group loading in order to optimize the separation resolution. Small equipment procured from this work has helped the specific tailoring of nanoparticles of desired morphology and porosity for the generation of chiral stationary phase. Two publications, 1 accepted and 1 submitted, have been produced from this work. 2 more publications will ensue. The creation of silica nanoparticles for rapid chiral and achiral separation will open up new areas in separation technologies.RG114/0

Tailoring lanthanide nanocrystals for nanomedicine

Lanthanide nanocrystals have demonstrated strong potentials in nanomedicine due to its up-conversion and strong magnetic properties, and low toxicity. This talk will focus on strategies in lanthanide nanostructure tailoring to achieve up-conversion color emission tuning, MRI T1 and T2 contrast tuning, and the use of up-conversion fluorescence in drug delivery and cancer cells ablation.Published versio

Sub-2 μm porous silica materials for enhanced separation performance in liquid chromatography

Fully or partially sub-2 μm porous silica materials have garnered strong interests as column packing materials in separation and analytical technologies due to the promise of rapid separation, enhanced efficiency and separation resolution. Silica support materials of different morphology and sub-2 μm size have been developed to improve separation performances in liquid chromatography (LC) and capillary electrochromatography (CEC). The current review highlights the recent development of sub-2 μm fully/partially porous silica materials and the demonstrations of their enhanced performance in achiral and chiral chromatography

Graphene quantum dots (GQDs) and its derivatives for multifarious photocatalysis and photoelectrocatalysis

Graphene quantum dots (GQDs), as a unique category of zero-dimensional (0D) carbon nanomaterial, has ignited tremendous interest in the past few years owing to its gorgeous electronic and physicochemical properties in conjunction with quantum-confinement and edge effects. In this review article, we predominantly focus on the recent developments of GQDs-semiconductor composited systems for heterogeneous photocatalysis and photoelectrocatalysis under ambient conditions including non-selective pollutant degradation, selective organic transformation, hydrogen or oxygen production, CO2 reduction, and photoelectrochemical (PEC) water splitting. It is anticipated that our current review article will provide enriched information on the promising applications of GQDs and its derivatives and simultaneously, offer new insights for exploring a large variety of GQDs-semiconductor composited systems for advanced solar energy conversion

A metal-catalyst free flexible and free-standing chitosan/vacuum-stripped graphene/polypyrrole three dimensional electrode interface for high performance dopamine sensing

A three dimensional chitosan/vacuum-stripped graphene/polypyrrole interface with a hierarchical porous structure was fabricated as a free-standing and flexible electrochemical sensing electrode for dopamine detection, which exhibits unprecedented good selectivity, high sensitivity (632.1 μA mM−1 cm−2), wide linear response range (0.1–200 μM), low detection limit (19.4 nM, S/N = 3) and good sensing performance in human serum samples, outperforming the previously reported 2D and 3D graphene and/or the PPy modified electrode, and exhibiting comparable performance with the Au modified electrode