Timothy Thatt Yang Tan

Functional and Multifunctional Nanoparticles for Bioimaging and Biosensing

Herein, we describe the synthesis of functional and multifunctional nanoparticles (NPs), derived from our recent work, for bioimaging and biosensing applications. The functionalized NPs involve quantum dots (QDs), magnetic particles (MPs) and noble metal NPs for the aforementioned applications. A diverse silica coating approaches (reverse microemulsion and thin silanization) are delineated for the design of water-soluble NPs. We also review the synthesis of silica-coated bifunctional NPs consisting of MPs and QDs for live cell imaging of human liver cancer cells (HepG2) and mouse fibroblast cells (NIH-3T3). Using silica coated NPs, various NPs that are functionalized with antibody, oligonucleotide, biotin and dextran are efficiently used for protein detection.

Al doped graphene: A promising material for hydrogen storage at room temperature

A promising material for hydrogen storage at room temperature–Al doped graphene is proposed theoretically by using density functional theory calculation. Hydrogen storage capacity of 5.13 wt % is predicted at T=300 K and P=0.1 GPa with an adsorption energy Eb=−0.260 eV/H2. This is close to the target specified by U.S. Department of Energy with a storage capacity of 6 wt % and a binding energy of −0.2 to −0.4 eV/H2 at ambient temperature and modest pressure for commercial applications. It is believed that the doped Al alters the electronic structures of both C and H2. The bands of H2 overlapping with those of Al and C simultaneously are the underlying mechanism of hydrogen storage capacity enhancement.

Recent development of cyclodextrin chiral stationary phases and their applications in chromatography.

The current article reviews the development and applications of novel cyclodextrin chiral stationary phases (CD-CSPs) in liquid chromatography (LC), capillary electrochromatography (CEC), gas chromatography (GC) and supercritical fluid chromatography (SFC) over the period of January 2007 to March 2012. The synthetic routes of CD-CSPs, as well as the presence of selective functional groups in effecting inclusion complexation and molecular interactions have been found to exert profound influence in the enantioseparation process. In this article, various synthetic and functional groups immobilization strategies of novel CD-CSPs, and their applications in chiral resolution using different chromatography techniques are discussed. After introducing the topic in Section 1, Section 2 describes novel CD-CSPs in LC applications, where the CSPs are classified according to its coating approaches (physical and chemical manners) for ease of readership. Section 3 discusses recent development of CD-CSPs in open tubular CEC (OT-CEC), packed-bed CEC (P-CEC), pseudostationary phase CEC (PSP-CEC) and monolithic CEC. The last part illustrates novel CD-CSPs in gas chromatography (GC) and supercritical fluid chromatography (SFC).

Gadolinium oxide ultranarrow nanorods as multimodal contrast agents for optical and magnetic resonance imaging.

We demonstrate a simple synthetic strategy for the fabrication of single-phase rare earth (RE) doped gadolinium oxide (Gd(2)O(3):RE where RE = terbium (Tb), ytterbium (Yb), and erbium (Er)) nanorods (NRs) as multimodal imaging probes. The NRs are ultranarrow and exhibit both emission and magnetic characteristics. The Tb-doped and Yb/Er-codoped Gd(2)O(3) NRs exhibit down- and up-conversion fluorescence respectively, and also exhibit paramagnetism. Importantly, these codoped NRs possess excellent magnetic characteristics, as shown in their longitudinal relaxation time (T1) -weighted image contrast, which is closer to that of commercial Gadovist for magnetic resonance imaging (MRI) applications. This property opens up new avenues in the development of contrast agents.

Architecture Engineering of Hierarchically Porous Chitosan/Vacuum-Stripped Graphene Scaffold as Bioanode for High Performance Microbial Fuel Cell

The bioanode is the defining feature of microbial fuel cell (MFC) technology and often limits its performance. In the current work, we report the engineering of a novel hierarchically porous architecture as an efficient bioanode, consisting of biocompatible chitosan and vacuum-stripped graphene (CHI/VSG). With the hierarchical pores and unique VSG, an optimized bioanode delivered a remarkable maximum power density of 1530 mW m(-2) in a mediator-less MFC, 78 times higher than a carbon cloth anode.

Nanostructure control of graphene-composited TiO2 by a one-step solvothermal approach for high performance dye-sensitized solar cells

We present a one-step solvothermal approach to prepare uniform graphene-TiO(2) nanocomposites with delicately controlled TiO(2) nanostructures, including ultra-small 2 nm nanoparticles, 12 nm nanoparticles and nanorods. Using three composites as photoanode materials, the effect of nanostructure of graphene-composited TiO(2) on the performance of dye-sensitized solar cells was investigated, and results showed that the ultra-small 2 nm TiO(2)-graphene composite based photoanode exhibited the highest power conversion efficiency of 7.25%.

Bimodal magnetic-fluorescent probes for bioimaging.

Fluorescent optical probes have been intensively used in the area of bio‐imaging. In this review article, we describe the recent advancements in the synthesis and application of bimodal magnetic–fluorescent probes for bioimaging. The bimodal probes consist of fluorescent [semiconducting quantum dots (e.g., CdSe/ZnS) or rare‐earth doped (e.g., NaYF4:Yb,Er)] nanoparticles (NPs) and magnetic (iron oxide or gadolinium based) NPs for optical and magnetic resonance (MR) imaging. Microsc. Res. Tech., 2011.

Cytotoxic and genotoxic characterization of titanium dioxide, gadolinium oxide, and poly(lactic-co-glycolic acid) nanoparticles in human fibroblasts†

Engineered nanomaterials have become prevalent in our everyday life. While the popularity of using nanomaterials in consumer products continues to rise, increasing awareness of nanotoxicology has also fuelled efforts to accelerate our understanding of the ill effects that different nanomaterials can bring to biological systems. In this study, we investigated the potential cytotoxicity and genotoxicity of three nanoparticles: titanium dioxide (TiO(2)), terbium-doped gadolinium oxide (Tb-Gd(2)O(3)), and poly(lactic-co-glycolic acid) (PLGA). To evaluate nanoparticle-induced genotoxicity more realistically, a human skin fibroblast cell line (BJ) with less mutated genotype compared with cancer cell line was used. The nanoparticles were first characterized by size, morphology, and surface charge. Cytotoxicity effects of the nanoparticles were then evaluated by monitoring the proliferation of treated BJ cells. Genotoxic influence was ascertained by profiling DNA damage via detection of γH2AX expression. Our results suggested that both TiO(2) and Tb-Gd(2)O(3) nanoparticles induced cytotoxicity in a dose dependent way on BJ cells. These two nanomaterials also promoted genotoxicity via DNA damage. On the contrary, PLGA nanoparticles did not induce significant cytotoxic or genotoxic effects on BJ cells.

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.

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.