Timothy Thatt Yang Tan

Nd3+-sensitized upconversion nanoparticles are among the most promising emerging fluorescent nanotransducers. They are activated by 808 nm irradiation, which features merits such as limited tissue overheating and deeper penetration depth, and hence are attractive for diagnostic and therapeutic applications. Recent studies indicate that ultrasmall nanoparticles (<10 nm) are potentially more suitable for clinical application due to their favorable biodistribution and safety profiles. However, upconversion nanoparticles in the sub-10 nm range suffer from poor luminescence due to their ultrasmall size and greater proportion of lattice defects. To reconcile these opposing traits, we adopt a combinatorial strategy of energy migration manipulation and crystal lattice modification, creating ultrasmall-superbright Nd3+-sensitized nanoparticles with 2 orders of magnitude enhancement in upconversion luminescence. Specifically, we configure a sandwich-type nanostructure with a Yb3+-enriched intermediate layer [Nd3+]–[Yb3+–Yb3+]–[Yb3+–Tm3+] to form a positively reinforced energy migration system, while introducing Ca2+ into the crystal lattice to reduce lattice defects. Furthermore, we apply the nanoparticles to 808 nm light-mediated drug release. The results indicate time-dependent cancer cells killing and better antitumor activities. These ultrasmall-superbright dots have unraveled more opportunities in upconversion photomedicine with the promise of potentially safer and more effective therapy.Keywords: controlled drug release; energy migration manipulation; lattice modification; Nd3+-sensitized upconversion nanoparticles; near-infrared; ultrasmall;

A Periosteum-Inspired 3D Hydrogel-Bioceramic Composite for Enhanced Bone Regeneration

Co-reporter:Yong Yao Chun;Jun Kit Wang;Nguan Soon Tan;Peggy Puk Yik Chan;Cleo Choong

Macromolecular Bioscience 2016 Volume 16( Issue 2) pp:276-287

Publication Date(Web):

DOI:10.1002/mabi.201500258

A 3D injectable hydrogel-bioceramic composite consisting of gelatin-3-(4-hydroxyphenyl) propionic acid (Gtn-HPA) and carboxymethyl cellulose-tyramine (CMC-Tyr), incorporated with fish scale-derived calcium phosphate (CaP), is developed for bone applications. The hydrogel-bioceramic composite has significantly improved the elastic modulus compared to the non-filled hydrogel, of which the addition of 10 w/v% CaP showed zero order fluorescein isothiocyanate (FITC)-dextran release profile and a significantly higher proliferation rate of encapsulated cells. All the samples promote the nucleation and growth of CaP minerals when exposed to 1× SBF. Overall, the hydrogel-bioceramic composite with 10 w/v% CaP can potentially be used as a periosteum-mimicking membrane to facilitate bone regeneration.

Electropolymerization of Uniform Polyaniline Nanorod Arrays on Conducting Oxides as Counter Electrodes in Dye-Sensitized Solar Cells

Co-reporter:Dr. Ziming He;Dr. Jing Liu;Si Yun Khoo ; Timothy Thatt Yang Tan

ChemSusChem 2016 Volume 9( Issue 2) pp:172-176

Publication Date(Web):

DOI:10.1002/cssc.201501584

Abstract

Conventional techniques for the synthesis of oriented polyaniline (PANI) nanostructures are often complex or time consuming. Through an innovative reduced graphene oxide (rGO) modified FTO and a low-potential electropolymerization strategy, the rapid and template-free growth of a highly ordered PANI nanorod array on the FTO substrate is realized. The highly ordered nanostructure of the PANI array leads to a high electrocatalytic activity and chemical stability. The importance of the polymerization potential and rGO surface modification to achieve this nanostructure is revealed. Compared to platinum, the PANI nanorod array exhibits an enhanced performance and stability as counter electrodes in dye-sensitized solar cells, with a 17.6 % enhancement in power conversion efficiency.

Bandgap engineering of ternary sulfide nanocrystals by solution proton alloying for efficient photocatalytic H2 evolution

Co-reporter:Peng Hu, Chee Keong Ngaw, Yupeng Yuan, Prince Saurabh Bassi, Say Chye Joachim Loo, Timothy Thatt Yang Tan

Nano Energy 2016 Volume 26() pp:577-585

Publication Date(Web):August 2016

DOI:10.1016/j.nanoen.2016.06.006

•First report on proton alloying process for bandgap energy of ternary sulfide.•Different effects on bandgap energy were exhibited by current strategy.•Enhanced optoelectronic properties were achieved for proton alloyed nanocrystals.Bandgap engineering is an important strategy for tailoring the optical and electronic properties of semiconductor nanocrystals. This work describes the first solution proton alloying process for tuning the bandgap energy of ternary sulfide nanocrystals at room temperature. The proposed strategy circumvents the use of toxic heavy metal ions, while maintaining the size and morphology of the nanocrystals, through a seamless tuning of the bandgap over a wide range. It was shown that proton alloying exhibited different effects on the bandgap energies of ternary sulfide nanocrystals and this could be explained by Density-Of-States (DOS) calculations. Using this approach, enhanced optoelectronic properties of ternary sulfide semiconductor nanocrystals were achieved and proton alloyed ZnIn2S4 showed eight times higher photocatalytic H2 evolution rate than that of the untreated ones due to increased carrier density and decreased charge transfer resistance.

A “uniform” heterogeneous photocatalyst: integrated p–n type CuInS2/NaInS2 nanosheets by partial ion exchange reaction for efficient H2 evolution

Co-reporter:Peng Hu, Chee Keong Ngaw, Yee Yan Tay, Shaowen Cao, James Barber, Timothy Thatt Yang Tan and Say Chye Joachim Loo

Chemical Communications 2015 vol. 51(Issue 45) pp:9381-9384

Publication Date(Web):27 Apr 2015

DOI:10.1039/C5CC02237A

Single-crystalline-like P–N type CuInS2/NaInS2 heterogeneous nanosheets were synthesized by partial cation exchange reaction and show highly improved photocatalytic H2 evolution activity attributed to the increased efficiency of interfacial charge transfer.

One-Step Hydrothermal Tailoring of NiCo2S4 Nanostructures on Conducting Oxide Substrates as an Efficient Counter Electrode in Dye-Sensitized Solar Cells

Co-reporter:Si Yun Khoo;Jianwei Miao;Hong Bin Yang;Ziming He;Kam Chew Leong;Bin Liu

Advanced Materials Interfaces 2015 Volume 2( Issue 18) pp:

Publication Date(Web):

DOI:10.1002/admi.201500384

A one-step in situ tailoring of NiCo₂S₄ nanostructures is demonstrated on fluorine-doped tin oxide (FTO) as Pt-free counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) with performance surpassing that of a conventional Pt-sputtered CE. An interconnected NiCo₂S₄ nanosheet network is successfully constructed on the FTO glass via a hydrothermal method, attributed to the synergistic effect of structure-directing hexamethylenetetramine and L-cysteine. A growth mechanism is proposed, and the effects of nanostructures and sulfur atomic percentages on the electrocatalytic performance are discussed in depth. A DSSC with the optimized interconnected NiCo₂S₄ nanosheet CE exhibits higher power conversion efficiency (7.22%) compared to that with a conventional Pt-sputtered CE (6.87%) due to excellent charge transport properties and enhanced electrocatalytic activity of the NiCo₂S₄ nanostructures. This work showcases the strong potential of nanostructured ternary chalcogenides, which are composed of earth-abundant elements and prepared through a single-step hydrothermal process without tedious posttreatments, to reduce the dependence of platinum in DSSCs and other electrochemical devices.

An environmentally friendly approach to treat oil spill: Investigating the biodegradation of petrodiesel in the presence of different biodiesels

Co-reporter:Yan Fei Ng, Liya Ge, Wen Kiat Chan, Swee Ngin Tan, Jean Wan Hong Yong, Timothy Thatt Yang Tan

Fuel 2015 Volume 139() pp:523-528

Publication Date(Web):1 January 2015

DOI:10.1016/j.fuel.2014.08.073

•Biodiesels were used as an environmental-friendly method for treating oil spills.•Biodegradation rate of biodiesel and petrodiesel mixtures was effectively enhanced.•Increased biodegradation rate could be due to cometabolism and solvation effects.Petroleum oil spills constitute a major source of contamination for the ecosystem and can cause serious human health problems. In this work, therefore, biodiesels were used as cost effective and sustainable means in treating oil spills. A comparative study was conducted on the biodegradation of petrodiesel mixed with Jatropha, palm and soybean biodiesels at different ratios (20%, 50% and 80% by carbon mass). The experimental results showed positive synergistic effects for all cases. The biodegradation of the mixtures was enhanced by as much as 12.8%, 19.4% and 17.5% for the Jatropha, palm and soybean biodiesel blends, respectively (when the blend ratio was Jatropha 50%, palm 80% and soybean 20%). The enhancements could be caused by the effects of cometabolism and solvation. Maximum mixing ratios where the biodegradation enhancement was the highest under the experimental conditions (Jatropha 50%, palm 80% and soybean 20%) were attributed to the solvation properties of the surfactant-like fatty acid esters of the biodiesels.

Cross Relaxation Induced Pure Red Upconversion in Activator- and Sensitizer-Rich Lanthanide Nanoparticles

Co-reporter:Wei Wei, Yan Zhang, Rui Chen, Julian Goggi, Na Ren, Ling Huang, Kishore K. Bhakoo, Handong Sun, and Timothy Thatt Yang Tan

Chemistry of Materials 2014 Volume 26(Issue 18) pp:5183

Publication Date(Web):August 21, 2014

DOI:10.1021/cm5022382

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

Co-reporter:Jing Liu, Ziming He, Jingwen Xue and Timothy Thatt Yang Tan

Journal of Materials Chemistry A 2014 vol. 2(Issue 17) pp:2478-2482

Publication Date(Web):19 Dec 2013

DOI:10.1039/C3TB21355B

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.

A one-pot solvothermal synthesis of hierarchical microspheres with radially assembled single-crystalline TiO2-nanorods for high performance dye-sensitized solar cells

Co-reporter:Ziming He, Jing Liu, Jianwei Miao, Bin Liu and Timothy Thatt Yang Tan

Journal of Materials Chemistry A 2014 vol. 2(Issue 8) pp:1381-1385

Publication Date(Web):10 Dec 2013

DOI:10.1039/C3TC32061H

A simple one-pot method to prepare complex morphology-tunable hierarchical TiO2 microspheres consisting of radially assembled single-crystalline rutile TiO2 nanorods is developed by combining an acid thermal crystallization process and a self-assembly process of the nanorods via a solvothermal amphiphile–water microreactor strategy. Using P25 nanoparticles as void fillers to generate a mesoporous electrode film, the microsphere based photoanode exhibits a maximum power conversion efficiency of 7.95% at an anode film thickness of 27.2 μm, highlighting the importance of material architecture tailoring in improving the electron transport properties of dye-sensitized solar cells.

“Smart” theranostic lanthanide nanoprobes with simultaneous up-conversion fluorescence and tunable T1–T2 magnetic resonance imaging contrast and near-infrared activated photodynamic therapy

Co-reporter:Yan Zhang, Gautom Kumar Das, Vimalan Vijayaragavan, Qing Chi Xu, Parasuraman Padmanabhan, Kishore K. Bhakoo, Subramanian Tamil Selvan and Timothy Thatt Yang Tan

Nanoscale 2014 vol. 6(Issue 21) pp:12609-12617

Publication Date(Web):08 Aug 2014

DOI:10.1039/C4NR01717J

The current work reports a type of “smart” lanthanide-based theranostic nanoprobe, NaDyF4:Yb3+/NaGdF4:Yb3+,Er3+, which is able to circumvent the up-converting poisoning effect of Dy3+ ions to give efficient near infrared (980 nm) triggered up-conversion fluorescence, and offers not only excellent dark T2-weighted MR contrast but also tunable bright and T1-weighted MR contrast properties. Due to the efficient up-converted energy transfer from the nanocrystals to chlorin e6 (Ce6) photosensitizers loaded onto the nanocrystals, cytotoxic singlet oxygen was generated and photodynamic therapy was demonstrated. Therefore, the current multifunctional nanocrystals could be potentially useful in various image-guided diagnoses where bright or dark MRI contrast could be selectively tuned to optimize image quality, but also as an efficient and more penetrative near-infrared activated photodynamic therapy agent.

Injectable 3D Hydrogel Scaffold with Tailorable Porosity Post-Implantation

Co-reporter:Aswan Al-Abboodi;Jing Fu;Pauline M. Doran;Timothy T. Y. Tan;Peggy P. Y. Chan

Advanced Healthcare Materials 2014 Volume 3( Issue 5) pp:725-736

Publication Date(Web):

DOI:10.1002/adhm.201300303

Since rates of tissue growth vary significantly between tissue types, and also between individuals due to differences in age, dietary intake, and lifestyle-related factors, engineering a scaffold system that is appropriate for personalized tissue engineering remains a significant challenge. In this study, a gelatin-hydroxyphenylpropionic acid/carboxylmethylcellulose-tyramine (Gtn-HPA/CMC-Tyr) porous hydrogel system that allows the pore structure of scaffolds to be altered in vivo after implantation is developed. Cross-linking of Gtn-HPA/CMC-Tyr hydrogels via horseradish peroxidase oxidative coupling is examined both in vitro and in vivo. Post-implantation, further alteration of the hydrogel structure is achieved by injecting cellulase enzyme to digest the CMC component of the scaffold; this treatment yields a structure with larger pores and higher porosity than hydrogels without cellulase injection. Using this approach, the pore sizes of scaffolds are altered in vivo from 32–87 μm to 74–181 μm in a user-controled manner. The hydrogel is biocompatible to COS-7 cells and has mechanical properties similar to those of soft tissues. The new hydrogel system developed in this work provides clinicians with the ability to tailor the structure of scaffolds post-implantation depending on the growth rate of a tissue or an individual's recovery rate, and could thus be ideal for personalized tissue engineering.

Surface-up constructed tandem-inverted bilayer cyclodextrins for enhanced enantioseparation and adsorption

Co-reporter:Jie Zhao, Xiaohong Lu, Yong Wang, Timothy Thatt Yang Tan

Journal of Chromatography A 2014 Volume 1343() pp:101-108

Publication Date(Web):23 May 2014

DOI:10.1016/j.chroma.2014.03.061

•The first demonstration of a surface-up bilayer CD structure on silica surfaces.•Synergistic effect of the duplex CDs affords superior enantioselectivity and adsorption ability.•A practical approach to design novel functional materials with cooperative CD dimers.A new generation of triazole-bridged bilayer cyclodextrins (CDs) chiral stationary phase (CSP) material was constructed via a surface-up ‘click’ approach. The synergistic effect of the tandem-inverted duplex CDs was evidenced by the superior enantioresolution ability toward selected chiral compounds and the enhanced adsorption ability toward hesperetin. The enantioselectivities of dansyl amino acids and aryl carboxylic acids were promoted by 10–20%, while the resolutions of some aryl carboxylic acids were significantly increased from 0 to 3.5 and beyond. Adsorption experiments of hesperetin reveal that the binding ability of the target bilayer CDCSP is nearly 2.8 times than that of the single layer CDCSP. The current work provides a simple and practical approach to design and synthesize novel functional materials with cooperative CD dimers on surfaces.

TiO2 promoted by two different non-noble metal cocatalysts for enhanced photocatalytic H2 evolution

Co-reporter:Jing-Dong Lin, Shi Yan, Qin-Dong Huang, Mei-Ting Fan, You-Zhu Yuan, Timothy Thatt-Yang Tan, Dai-Wei Liao

Applied Surface Science 2014 Volume 309() pp:188-193

Publication Date(Web):1 August 2014

DOI:10.1016/j.apsusc.2014.05.008

Highlights

•: Ni and Co were used as HER and OR cocatalysts for photocatalytic H₂ evolution.
•: Ni and Co are the promising substitutes for noble metals as HER and OR cocatalysts.
•: A synergistic effect of cobalt and nickel was found on 0.1%Co + 0.2%Ni/TiO₂.
•: TiO₂ promoted by Co and Ni shows more photocatalytic activity for H₂ evolution.

Engineering lanthanide-based materials for nanomedicine

Co-reporter:Yan Zhang, Wei Wei, Gautom Kumar Das, Timothy Thatt Yang Tan

Journal of Photochemistry and Photobiology C: Photochemistry Reviews 2014 20() pp: 71-96

Publication Date(Web):1 September 2014

DOI:10.1016/j.jphotochemrev.2014.06.001

•Design of high performance optical and magnetic lanthanide nanomaterials.•Strategies to enhance their multifunctional properties.•Implementation in diagnostics, therapeutics, or theranostics.•Demonstration of in vitro and in vivo medical applications.•Toxicity concerns of biomedical lanthanide nanomaterials.Multifunctional lanthanide-based nanomaterials are envisioned to create a huge impact in nanomedicine through improved diagnosis and treatment of diseases. This review focuses on the opportunities and advantages afforded by “designer” lanthanide-based nanomaterials in medical application in the recent 5 years. We begin with a brief overview of the unique properties of lanthanide nanomaterials and then move onto their synthesis, surface modification and bioconjugation strategies, which help one in the design of promising agents for imaging and therapeutic applications. We discuss approaches to fabricate down-conversion, up-conversion and persistent luminescent probes for optical imaging. We present the recent development of lanthanide-based nanoprobes in T1 and T2 magnetic resonance imaging, which show superior performances over currently used commercials agents. The potential benefits of multifunctional lanthanide-based nanomaterials in multimodal diagnostics are also highlighted. An important feature of lanthanide-based nanomaterials is the external controllability of light emission from UV to NIR wavelengths. This unique capability makes this class of nanomaterials useful for not only controlled/triggered release of drugs and gene delivery but also photodynamic or photothermal therapy at targeted sites. Finally, we discuss recent efforts to address concerns of short-term and long-term toxicity of lanthanide materials. The wide range of unique features of lanthanide-based nanomaterials accentuates their promise as efficient platforms for nanomedicine.Download full-size image

Understanding TiO2 Size-Dependent Electron Transport Properties of a Graphene-TiO2 Photoanode in Dye-Sensitized Solar Cells Using Conducting Atomic Force Microscopy

Co-reporter:Ziming He;Hung Phan;Jing Liu;Thuc-Quyen Nguyen

Advanced Materials 2013 Volume 25( Issue 47) pp:6900-6904

Publication Date(Web):

DOI:10.1002/adma.201303327

Enhanced charge extraction of polymer solar cell by solution-processable gold nanoparticles

Co-reporter:Si Yun Khoo, Hongbin Yang, Ziming He, Jianwei Miao, Kam Chew Leong, Chang Ming Li and Timothy Thatt Yang Tan

Journal of Materials Chemistry A 2013 vol. 1(Issue 34) pp:5402-5409

Publication Date(Web):01 Jul 2013

DOI:10.1039/C3TC30956H

The utilization of metallic nanoparticles is one of the key strategies to improve the performance of photovoltaic devices. In this work, we elucidate the power conversion efficiency (PCE) enhancement mechanism by gold nanoparticles (Au-NPs) through a bilayer anodic buffer structure in polymer solar cells. The results show that the PCE of the device based on a Au-NP:poly(sodium-4-styrenesulfonate)/V2O5 bilayer buffer exhibits a ∼16% enhancement compared with the device without Au-NP. By controlling the density of Au-NPs to minimize plasmonic effects, the Au-NP induced enhancement of charge extraction and crystallinity of the photoactive layer were demonstrated for the first time. Our work indicates that the plasmonic effect may not be the only factor that enhances the PCE of polymer solar cells, while providing new insights into the roles of Au-NPs in performance improvement of a bulk-heterojunction polymer solar cell.

Multifunctional P(PEGMA)–REDV conjugated titanium surfaces for improved endothelial cell selectivity and hemocompatibility

Co-reporter:Yang Liu, Timothy Thatt Yang Tan, Shaojun Yuan and Cleo Choong

Journal of Materials Chemistry A 2013 vol. 1(Issue 2) pp:157-167

Publication Date(Web):02 Oct 2012

DOI:10.1039/C2TB00014H

Pre-vascularization of scaffolds using endothelial cells (ECs) and preservation of hemocompatibility are effective strategies to improve the long-term viability of tissue engineered constructs. The current work reports a multifunctional titanium (Ti) surface for simultaneous enhancement of EC selectivity while preserving hemocompatibility. This is achieved by REDV conjugation on surface-grafted PEGMA polymer brushes via surface-initiated atom transfer radical polymerization (ATRP) on a dopamine (DOPA)-modified Ti surface. Our results showed that the proliferation and attachment of human umbilical vein endothelial cells (HUVECs) were substantially improved by P(PEGMA)–REDV conjugation compared to pristine Ti surfaces, whilst no significant effects were observed for the mesenchymal stem cells (MSCs), thus confirming the selectivity of REDV for ECs. Platelets adhesion assay further revealed that the immobilization of PEGMA polymer brushes led to the amelioration of surface hemocompatibility, and this enhancement was not negated by the conjugation of REDV. The current multifunctional Ti-surface can potentially be useful in tissue engineered constructs for bone and dental applications as it allows for early and selective EC attachment and improved hemocompatibility whilst at the same time supporting MSC proliferation and growth.

Enantioselective separation of dansyl-DL-amino acids and some racemates on “click” functionalized native α-cyclodextrin based sub-2 μm columns

Co-reporter:Feng Ai, Yong Wang, Hui Chen, Yanhui Yang, Timothy Thatt Yang Tan and Siu-Choon Ng

Analyst 2013 vol. 138(Issue 8) pp:2289-2294

Publication Date(Web):05 Feb 2013

DOI:10.1039/C3AN36125J

The current work demonstrates that native α-cyclodextrin, anchored onto sub-2 μm silica particles via “click” reactions and packed into a 5 cm column, was found to be effective for the resolution of 11 pairs of dansyl-DL-amino acids (DAAs) using ultra-high performance liquid chromatography (UHPLC). All DAAs were completely or partially separated on the column and the resolution achieved for 7 pairs of DAAs was significantly greater than 1.5. It was found that the buffer type exerted a profound impact on the separation. The effects of analyte substituents adjacent to the chiral center of analytes as well as operation conditions with respect to the separation efficiency were discussed. Five racemic compounds with single or double rings also got resolved on this short α-CD column to some extent.

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

Co-reporter:Jingdong Lin, Peng Hu, Yan Zhang, Meiting Fan, Ziming He, Chee Keong Ngaw, Joachim Say Chye Loo, Daiwei Liao and Timothy Thatt Yang Tan

RSC Advances 2013 vol. 3(Issue 24) pp:9330-9336

Publication Date(Web):03 Apr 2013

DOI:10.1039/C3RA40550H

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.

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

Co-reporter:Ziming He, Jing Liu, Yan Qiao, Chang Ming Li, and Timothy Thatt Yang Tan

Nano Letters 2012 Volume 12(Issue 9) pp:4738-4741

Publication Date(Web):August 13, 2012

DOI:10.1021/nl302175j

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.

Tuning sub-10 nm single-phase NaMnF3 nanocrystals as ultrasensitive hosts for pure intense fluorescence and excellent T1 magnetic resonance imaging

Co-reporter:Yan Zhang, Jing Dong Lin, Vimalan Vijayaragavan, Kishore K. Bhakoo and Timothy Thatt Yang Tan

Chemical Communications 2012 vol. 48(Issue 83) pp:10322-10324

Publication Date(Web):21 Aug 2012

DOI:10.1039/C2CC34858F

We report ultrasensitive sub-10 nm NaMnF3 nanocrystals codoped with Yb3+, Er3+/Tm3+ ions, and their intense pure red and near-infrared upconversion emissions in the presence of Mn2+. The nanocrystals showed excellent T1 contrast in 7 T MRI, implying their potential as single-phase contrast agents for fluorescent deep tissue and MR imaging.

Anti-cAngptl4 Ab-Conjugated N-TiO2/NaYF4:Yb,Tm Nanocomposite for Near Infrared-Triggered Drug Release and Enhanced Targeted Cancer Cell Ablation

Co-reporter:Qing Chi Xu;Yan Zhang;Ming Jie Tan;Yang Liu;Shaojun Yuan;Cleo Choong;Nguan Soon Tan

Advanced Healthcare Materials 2012 Volume 1( Issue 4) pp:470-474

Publication Date(Web):

DOI:10.1002/adhm.201200055

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

Co-reporter:Yong Wang, Feng Ai, Siu-Choon Ng, Timothy Thatt Yang Tan

Journal of Chromatography A 2012 Volume 1228() pp:99-109

Publication Date(Web):9 March 2012

DOI:10.1016/j.chroma.2011.08.085

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.

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

Co-reporter:Yin Xiao, Siu-Choon Ng, Timothy Thatt Yang Tan, Yong Wang

Journal of Chromatography A 2012 Volume 1269() pp:52-68

Publication Date(Web):21 December 2012

DOI:10.1016/j.chroma.2012.08.049

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).Highlights► Review of novel cyclodextrin chiral stationary phases (CD-CSPs) in chromatography. ► Review period from January 2007 to March 2012. ► The synthetic strategy of CD-CSPs was found to affect enantioseparation. ► CD functional groups affect inclusion complexation and molecular interactions.

Single-Phase NaDyF4:Tb3+ Nanocrystals as Multifunctional Contrast Agents in High-Field Magnetic Resonance and Optical Imaging

Co-reporter:Yan Zhang;Vimalan Vijayaragavan;Gautom K. Das;Kishore K. Bhakoo

European Journal of Inorganic Chemistry 2012 Volume 2012( Issue 12) pp:2044-2048

Publication Date(Web):

DOI:10.1002/ejic.201101203

Abstract

The current work reports single-phase, terbium-doped sodium dysprosium fluoride (NaDyF₄:Tb³⁺) nanocrystals with green luminescence and good T₂ contrast in 7.0-T MRI phantom and animal imaging. The current nanocrystals demonstrate good potential as a dual modal contrast agent for high-field magnetic resonance (MR) and fluorescence imaging.

Single-Phase Dy2O3:Tb3+ Nanocrystals as Dual-Modal Contrast Agent for High Field Magnetic Resonance and Optical Imaging

Co-reporter:Gautom Kumar Das, Yan Zhang, Loyola D’Silva, Parasuraman Padmanabhan, Boon Chin Heng, Joachim Say Chye Loo, Subramanian Tamil Selvan, Kishore K. Bhakoo, and Timothy Thatt Yang Tan

Chemistry of Materials 2011 Volume 23(Issue 9) pp:2439-2446

Publication Date(Web):April 12, 2011

DOI:10.1021/cm2003066

Ultrasmall terbium ions (Tb3+) doped dysprosium oxide (Dy2O3) nanocrystals (NCs) of ∼3 nm diameter have been synthesized and applied as a single-phase dual modality contrast agent for high field magnetic resonance imaging (MRI) and optical imaging. The NCs show excellent positive contrast at 7.0 T MRI in phantom and in vivo imaging in a mouse breast tumor model (MCF-7 cells) injected with NCs. In vitro confocal fluorescence microscopy images show the staining of cultured human bronchial epithelial cells (BEAS-2B) with green fluorescent NCs. In vitro cytotoxicity studies in BEAS-2B and L929 cells indicate that the bifunctional NCs have no appreciable toxicity at a concentration of up to 1000 μg/mL. These results suggest the potential application of these NCs as dual modality contrast agents in a combined high field MRI and fluorescence imaging.

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

Co-reporter:Ziming He, Guanhong Guai, Jing Liu, Chunxian Guo, Joachim Say Chye Loo, Chang Ming Li and Timothy Thatt Yang Tan

Nanoscale 2011 vol. 3(Issue 11) pp:4613-4616

Publication Date(Web):17 Oct 2011

DOI:10.1039/C1NR11300C

We present a one-step solvothermal approach to prepare uniform graphene–TiO2 nanocomposites with delicately controlled TiO2 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 TiO2 on the performance of dye-sensitized solar cells was investigated, and results showed that the ultra-small 2 nm TiO2–graphene composite based photoanode exhibited the highest power conversion efficiency of 7.25%.

Understanding bactericidal performance on ambient light activated TiO2–InVO4 nanostructured films

Co-reporter:Ziming He, Qingchi Xu and Timothy Thatt Yang Tan

Nanoscale 2011 vol. 3(Issue 12) pp:4977-4983

Publication Date(Web):20 Oct 2011

DOI:10.1039/C1NR11126D

TiO2–InVO4 nanostructured films were coated onto glass substrates and systematically investigated for their bactericidal activities using Escherichia coli (E. coli) as the model bacterium under ambient light illumination. The uniform TiO2–InVO4 nanostructured films were prepared using titanium isopropoxide (TTIP) as the precursor via a simple sol–gel approach. Polyethylenimine (PEI) was used as a surfactant to ensure uniform dispersion of InVO4 and a sacrificial pore-inducing agent, generating nanostructured films. Compared to unmodified TiO2 film, the current TiO2–InVO4 films exhibited enhanced bactericidal activities under ambient light illumination. Bacterial cell “photo-fixation” was demonstrated to be crucial in enhancing the bactericidal activity. A bacterial–nanostructured surface interaction mechanism was proposed for the current ambient-light activated nanostructured film.

A three-way synergy of triple-modified Bi2WO6/Ag/N–TiO2 nanojunction film for enhanced photogenerated charges utilization

Co-reporter:Qing Chi Xu, Yun Hau Ng, Yan Zhang, Joachim Say Chye Loo, Rose Amal and Timothy Thatt Yang Tan

Chemical Communications 2011 vol. 47(Issue 30) pp:8641-8643

Publication Date(Web):01 Jul 2011

DOI:10.1039/C1CC13159A

We demonstrate a general strategy to prepare Bi2WO6/Ag/N–TiO2 film with double visible-light-active components bridged by Ag nanoparticles as an electron shuttle, which exhibits enhanced photocatalytic activity and photoelectrochemical performance under visible light.

Enantioseparation of dansyl amino acids by ultra-high pressure liquid chromatography using cationic β-cyclodextrins as chiral additives

Co-reporter:Yin Xiao, Timothy Thatt Yang Tan and Siu-Choon Ng

Analyst 2011 vol. 136(Issue 7) pp:1433-1439

Publication Date(Web):14 Feb 2011

DOI:10.1039/C0AN00631A

This work reports the application of ultra-high pressure liquid chromatography (UHPLC) for reasonably fast enantiorecognition of some dansyl amino acids by employing three cationic β-cyclodextrins (β-CDs) as chiral additives. Good resolutions were obtained on an Agilent C18 column (2.1 mm i.d.; 1.8 μm; 50 mm length) with 1% (v/v) triethylammonium acetate buffered at pH 4.7 and acetonitrile as the mobile phase. Most of the analytes could be baseline resolved within 10 min. Increased cationic CD concentration or acetonitrile proportion in the mobile phase results in a decreased retention factor but accentuated selectivity. Furthermore, molecular mechanics calculation was performed and found to be consistent with the experimental results.

Synthesis of Porous and Visible-Light Absorbing Bi2WO6/TiO2 Heterojunction Films with Improved Photoelectrochemical and Photocatalytic Performances

Co-reporter:Qing Chi Xu ; Diana V. Wellia ; Yun Hau Ng ; Rose Amal

The Journal of Physical Chemistry C 2011 Volume 115(Issue 15) pp:7419-7428

Publication Date(Web):March 24, 2011

DOI:10.1021/jp1090137

This work reports the preparation of porous and visible-light absorbing Bi2WO6/TiO2 heterojunction films as a photoelectrode and their photoelectrochemical and photocatalytic performances. The Bi2WO6 underlayers with high surface roughness were prepared by a superhydrophilicity-assisted method. The Bi2WO6/TiO2 bilayer films showed high interface area between the Bi2WO6 and TiO2 layers. Significant enhancement in visible light photocurrent generation on the optimal Bi2WO6/TiO2 film was observed as compared with unmodified Bi2WO6 (a factor of 2) and unmodified TiO2 (a factor of 13) films. The optimal visible-light photocatalytic activity of the Bi2WO6/TiO2 film was 15.1 nm of stearic acid degraded, which was 6 and 4.6 times higher than that of unmodified Bi2WO6 and TiO2 films, respectively. The enhanced photoelectrochemical and photocatalytic performances of Bi2WO6/TiO2 films were attributed to the improved charge separation efficiency derived from the suitable valence band interaction between the two semiconductors, as well as high interface area and porous structure of the heterojunction bilayer films. Charge separation between Bi2WO6 (underlayer) and TiO2 (overlayer) was verified by photoluminescence (PL) and current−voltage (I−V) characteristics studies.

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

Co-reporter:Qing Chi Xu, Diana V. Wellia, Rose Amal, Dai Wei Liao, Say Chye Joachim Loo and Timothy Thatt Yang Tan

Nanoscale 2010 vol. 2(Issue 7) pp:1122-1127

Publication Date(Web):15 May 2010

DOI:10.1039/C0NR00105H

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 °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.

“Click” preparation of hindered cyclodextrin chiral stationary phases and their efficient resolution in high performance liquid chromatography

Co-reporter:Yong Wang, David James Young, Timothy Thatt Yang Tan, Siu-Choon Ng

Journal of Chromatography A 2010 Volume 1217(Issue 50) pp:7878-7883

Publication Date(Web):10 December 2010

DOI:10.1016/j.chroma.2010.10.059

This communication reports the preparation of two new cyclodextrin (CD) chiral stationary phases (CSPs): heptakis(6-deoxy-6-azido)-β-CD and heptakis(6-deoxy-6-azido-phenylcarbamoylated)-β-CD CSPs that perform quite differently to our previously reported “click” immobilized CD-CSPs. These CSPs are sterically congested at the narrow mouth of the CD and exhibit chiral discrimination between over 40 pairs of enantiomers in high performance liquid chromatography. The free hydroxyl CSP afforded better separation of indoprofen, ketoprofen, Tröger's base, hydroxyl, carboxylic and dansyl amino acids than did the phenylcarbamoylated CSP, while the latter was better at resolving aryl alcohols, flavonoids, β-blockers and β-agonists. The current work shows that enantiodiscrimination achieved with different CSPs for different classes of analyte may be correlated with CD accessibility and peripheral functionality.

Sub-1-micron mesoporous silica particles functionalized with cyclodextrin derivative for rapid enantioseparations on ultra-high pressure liquid chromatography

Co-reporter:Feng Ai, Laisheng Li, Siu-Choon Ng, Timothy Thatt Yang Tan

Journal of Chromatography A 2010 Volume 1217(Issue 48) pp:7502-7506

Publication Date(Web):26 November 2010

DOI:10.1016/j.chroma.2010.09.061

Mesoporous silica particles of relatively uniform sub-1-micron size (0.6–0.9 μm) were successfully prepared by a modified synthesis strategy and applied in chiral separation in an ultra-high pressure liquid chromatography system. These particles were prepared via a ternary surfactant system (Pluronic P123, F127 and hexadecyltrimethyl-ammonium bromide) and subsequently derivatized with perphenylcarbamoylated-β-cyclodextrin moieties. The mesoporous silica particles, despite their submicron size, enabled low back-pressure operation on an ultra-high pressure liquid chromatography system at a maximum flow rate of 2 ml/min. In addition, the particles possessed high surface area (480 m2/g) and thus afforded high cyclodextrin derivative loading (32 μmol/g), demonstrating rapid enantioseparation and good resolution of 6 basic and neutral racemates.

“Click” immobilized perphenylcarbamated and permethylated cyclodextrin stationary phases for chiral high-performance liquid chromatography application

Co-reporter:Yong Wang, David J. Young, Timothy Thatt Yang Tan, Siu-Choon Ng

Journal of Chromatography A 2010 Volume 1217(Issue 31) pp:5103-5108

Publication Date(Web):30 July 2010

DOI:10.1016/j.chroma.2010.06.003

Two cyclodextrin-based chiral stationary phases have been prepared by immobilization of functionalized mono-6-azido-β-CD derivatives to alkynyl modified silica via “click” chemistry and applied to the HPLC enantioseparation of various chiral compounds. The perphenylcarbamated CD CSP (CCP-CSP) exhibited excellent chiral recognition of a wide range of analytes including racemic aryl alcohols, flavonoids, bendroflumethiazide, atropine and some β-blockers. Methanol proved to be a better organic modifier than acetonitrile for most of the analytes with the exception of bendroflumethiazide. The “click” chemistry immobilized permethylated CD CSP (CCM-CSP) afforded poor chiral recognition for most analytes, but could resolve non-aromatic ionone derivatives which were not separated on CCP-CSP. These results suggest that resolution with cyclodextrin derived CSPs depend on a complex interplay of ‘host’–‘guest’ inclusion, hydrogen bonding, π–π and hydrophobic interactions.

In vitro cytotoxicity evaluation of biomedical nanoparticles and their extracts

Co-reporter:Gautom Kumar Das;Peggy P. Y. Chan;Ailing Teo;Joachim Say Chye Loo;James M. Anderson

Journal of Biomedical Materials Research Part A 2010 Volume 93A( Issue 1) pp:337-346

Publication Date(Web):

DOI:10.1002/jbm.a.32533

Abstract

The present study presents a new approach for evaluating in vitro cytotoxicity of nanoparticles. The approach is based on American National Standard ISO 10993-5. Hepatoma HepG2 and fibroblast NIH3T3 cell lines were incubated with nanoparticles, and their associated extracts were derived at 70 and 121°C. Nanoparticles proposed as potential biomedical imaging probes were evaluated on the basis of the detection of metabolic activities and cell-morphology changes. In general, nanoparticles incubated directly with cells showed higher cytotoxicity than their associated extracts. CdSe and core-shell CdSe@ZnS quantum dots resulted in low cell viability for both cell lines. The cytotoxicity of the quantum dots was attributed to the Cd ion and the presence of the nanoparticle itself. A statistically significant (p < 0.05) decrease in cell viability was found in higher dosage concentrations. Rare earth nanoparticles and their extracts appear to affect NIH3T3 cells only, with cell viability as low as 71.4% ± 4.8%. Magnetic nanoparticles have no observable effects on the cell viabilities for both cell lines. In summary, we found the following: (1) both direct incubation and extracts of nanoparticles are required for complete assessment of nanoparticle cytotoxicity, (2) the rare earth oxide nanoparticles are less cytotoxic than the Cd-based quantum dots, and (3) the extent of cytotoxicity is dependent upon the cell line. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2010

Gadolinium Oxide Ultranarrow Nanorods as Multimodal Contrast Agents for Optical and Magnetic Resonance Imaging

Co-reporter:Gautom Kumar Das, Boon Chin Heng, Sui-Choon Ng, Tim White, Joachim Say Chye Loo, Loyola D’Silva, Parasuraman Padmanabhan, Kishore K. Bhakoo, Subramanian Tamil Selvan and Timothy Thatt Yang Tan

Langmuir 2010 Volume 26(Issue 11) pp:8959-8965

Publication Date(Web):February 11, 2010

DOI:10.1021/la904751q

We demonstrate a simple synthetic strategy for the fabrication of single-phase rare earth (RE) doped gadolinium oxide (Gd2O3: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 Gd2O3 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.

Transparent visible light activated C–N–F-codoped TiO2 films for self-cleaning applications

Co-reporter:Qing-chi Xu, Diana V. Wellia, Mahasin Alam Sk, Kok Hwa Lim, Joachim Say Chye Loo, Dai Wei Liao, Rose Amal, Timothy Thatt Yang Tan

Journal of Photochemistry and Photobiology A: Chemistry 2010 210(2–3) pp: 181-187

Publication Date(Web):

DOI:10.1016/j.jphotochem.2009.12.017

Tb-doped iron oxide: bifunctional fluorescent and magnetic nanocrystals

Co-reporter:Yunxia Zhang, Gautom Kumar Das, Rong Xu and Timothy Thatt Yang Tan

Journal of Materials Chemistry A 2009 vol. 19(Issue 22) pp:3696-3703

Publication Date(Web):20 Apr 2009

DOI:10.1039/B817159A

A new class of fluorescent and superparamagnetic bifunctional nanocrystal has been successfully prepared by a facile, non-hydrolytic method. The synthesized Tb-doped γ-Fe2O3nanocrystals are highly monodispersed with a diameter of 13 nm, show superparamagnetic behaviour with saturation magnetism strength of 30 emu g−1, and exhibit photoluminescence at room temperature. The nanocrystals are amine-functionalized to render them water-dispersible and ease of further functionalization by other biomolecules. In vitro cytotoxicity tests indicate that these nanocrystals are non-toxic. Nanocrystals of such bifunctionality are envisioned to have potential as probes in integrated imaging technique, of which at least two imaging modalities (for example magnetic resonance imaging (MRI) and fluorescence microscopy) are combined to provide enhanced visualization at tissues and cellular levels.

Enantioseparation of a novel “click” chemistry derived native β-cyclodextrin chiral stationary phase for high-performance liquid chromatography

Co-reporter:Yong Wang, Teng-Teng Ong, Lai-Sheng Li, Timothy Thatt Yang Tan, Siu-Choon Ng

Journal of Chromatography A 2009 Volume 1216(Issue 12) pp:2388-2393

Publication Date(Web):20 March 2009

DOI:10.1016/j.chroma.2009.01.039

A novel native β-cyclodextrin chiral stationary phase was prepared via “click” chemistry with cuprous iodide–triphenylphosphine complex as the catalyst and applied for enantioseparation of Dns-amino acids, substituted phenyl and phenoxy group modified propionic acids, flavonoids, and some pharmaceutical compounds such as nimodipine, propranolol, brompheniramine and bendroflumethiazide in reversed-phase high-performance liquid chromatography. The studied analytes could be resolved under different separation conditions. The resolution of Dns-DL-Leu could reach 5.08 using a mobile phase consisting of 1% (w/w) triethylammonium acetate buffer (pH 4.11) and methanol (50:50 v/v). The effects of buffer pH and the content of organic modifier on enantioseparation of Dns-amino acids by this novel chiral phase were being investigated. The separation results demonstrate that click chemistry, a versatile reaction, affords a facile approach towards the preparation of stable chiral stationary phases.

Synthesis and application of a novel single-isomer mono-6-deoxy-6-(3R,4R-dihydroxypyrrolidine)-β-cyclodextrin chloride as a chiral selector in capillary electrophoresis

Co-reporter:Yin Xiao, Teng-Teng Ong, Timothy Thatt Yang Tan, Siu-Choon Ng

Journal of Chromatography A 2009 Volume 1216(Issue 6) pp:994-999

Publication Date(Web):6 February 2009

DOI:10.1016/j.chroma.2008.12.015

A novel positively charged single-isomer of β-cyclodextrin, mono-6-deoxy-6-(3R,4R-dihydroxypyrrolidine)-β-CD chloride (dhypy-CDCl), was synthesized and employed as a chiral selector for the first time in capillary electrophoresis (CE) for the enantioseparation of anionic and ampholytic acids. The effects of the running buffer pH, chiral selector concentration, analyte structure and organic modifier on the enantioseparation were studied in detail. The chiral selectivity and resolution for most of the studied analytes decreased as the buffer pH increased in the range of 6.0–9.0. Increasing selector concentration led to decreased effective mobility, increased chiral selectivity and resolution for most of the studied analytes. Moreover, the hydroxyl groups located on the dihydroxypyrrolidine substituent of the dhypy-CDCl could have influence on the chiral separation.

Rare-Earth-Doped and Codoped Y 2O 3 Nanomaterials as Potential Bioimaging Probes

Co-reporter:Gautom Kumar Das and Timothy Thatt Yang Tan

The Journal of Physical Chemistry C 2008 Volume 112(Issue 30) pp:11211-11217

Publication Date(Web):July 2, 2008

DOI:10.1021/jp802076n

The synthesis and characterization of various rare-earth (RE)-doped and codoped yttrium oxide (Y 2O 3) nanomaterials were undertaken in the current work. RE dopants such as terbium (Tb), europium (Eu), and erbium (Er) were successfully doped, and ytterbium (Yb)−Er was codoped into Y 2O 3 nanomaterials. The as-synthesized nanomaterials are highly dispersed in the organic phase. X-ray diffraction peaks can be assigned to cubic Y 2O 3, which confirms the crystallinity of the as-prepared Y 2O 3 samples. Room temperature photoluminescence (PL) spectra showed characteristic emission peaks of Tb-, Eu-, and Er-doped Y 2O 3 samples. Up-conversion spectra of green and red emissions were also shown for Er−Yb-codoped Y 2O 3 samples. It was found that the intensities of the green and red emissions could be altered by varying the dopant concentration. The nanocrystals were surface-functionalized with an amine (NH 2) group via a reverse microemulsion method. The amine groups render the nanocrystals water-soluble and also afford them with the possibility of further functionalization by other biomolecules. in vitro cytotoxicity studies showed that the synthesized nanocrystals have no appreciable toxicity on human hepatocellular carcinoma (Hep-G2) cells at concentrations of 0.007−0.063 mg/mL. Because of the Y 2O 3:RE nanomaterials’ well-dispersity in water, low toxicity, and good PL, they can potentially be used as fluorophores in bioimaging.

Effect of silver on the photocatalytic degradation of humic acid

Co-reporter:Ankesh Bansal, S. Madhavi, Timothy Thatt Yang Tan, T.M. Lim

Catalysis Today (29 February 2008) Volume 131(Issues 1–4) pp:250-254

Publication Date(Web):29 February 2008

DOI:10.1016/j.cattod.2007.10.078

In this study, humic acid was mineralized and degraded photocatalytically in presence of bare TiO2 and silver loaded TiO2 (0.5–5.0 at.% Ag). X-ray diffraction (XRD) and inductive coupled plasma (ICP) analysis confirm the complete photodeposition of silver over TiO2 by photodeposition method. X-ray photoemission spectroscopy (XPS) studies confirmed the presence of Ag0 in all Ag–TiO2 samples and the absence of Ag+ ions. Silver loading over TiO2 improved the rate of mineralization and degradation of humic acid with a maximum loading of 1.0 at.% Ag. Ninety percent carbon from humic acid was mineralized to CO2 only after 60 min by using bare TiO2 as a photocatalyst. However, this conversion was possible within 40 min by using 1.0 at.% Ag-loaded TiO2. This observation verifies that coating of metals like silver over TiO2 acts as an electron sink and can improve the redox reaction by preventing electron–hole recombination reaction. The optimum 1.0 at.% Ag loading in the current work is indicative that the blocking of the TiO2 surface active sites by silver also plays an important role in the photocatalytic mineralization and degradation of humic acid. As the silver loading is increased, less number of active site are available over the surface of photocatalyst TiO2 for redox reaction. This finding was supported by the TEM analysis of the photocatalyst samples.

Experimental and theoretical studies of Fe-doped TiO2 films prepared by peroxo sol–gel method

Co-reporter:Diana V. Wellia, Qing Chi Xu, Mahasin Alam Sk, Kok Hwa Lim, Tuti Mariana Lim, Timothy Thatt Yang Tan

Applied Catalysis A: General (15 July 2011) Volume 401(Issues 1–2) pp:98-105

Publication Date(Web):15 July 2011

DOI:10.1016/j.apcata.2011.05.003

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

Co-reporter:Jing Liu, Ziming He, Jingwen Xue and Timothy Thatt Yang Tan

Journal of Materials Chemistry A 2014 - vol. 2(Issue 17) pp:NaN2482-2482

Publication Date(Web):2013/12/19

DOI:10.1039/C3TB21355B

A one-pot solvothermal synthesis of hierarchical microspheres with radially assembled single-crystalline TiO2-nanorods for high performance dye-sensitized solar cells

Co-reporter:Ziming He, Jing Liu, Jianwei Miao, Bin Liu and Timothy Thatt Yang Tan

Journal of Materials Chemistry A 2014 - vol. 2(Issue 8) pp:NaN1385-1385

Publication Date(Web):2013/12/10

DOI:10.1039/C3TC32061H

Tuning sub-10 nm single-phase NaMnF3 nanocrystals as ultrasensitive hosts for pure intense fluorescence and excellent T1 magnetic resonance imaging

Co-reporter:Yan Zhang, Jing Dong Lin, Vimalan Vijayaragavan, Kishore K. Bhakoo and Timothy Thatt Yang Tan

Chemical Communications 2012 - vol. 48(Issue 83) pp:NaN10324-10324

Publication Date(Web):2012/08/21

DOI:10.1039/C2CC34858F

A three-way synergy of triple-modified Bi2WO6/Ag/N–TiO2 nanojunction film for enhanced photogenerated charges utilization

Co-reporter:Qing Chi Xu, Yun Hau Ng, Yan Zhang, Joachim Say Chye Loo, Rose Amal and Timothy Thatt Yang Tan

Chemical Communications 2011 - vol. 47(Issue 30) pp:NaN8643-8643

Publication Date(Web):2011/07/01

DOI:10.1039/C1CC13159A

Enhanced charge extraction of polymer solar cell by solution-processable gold nanoparticles

Co-reporter:Si Yun Khoo, Hongbin Yang, Ziming He, Jianwei Miao, Kam Chew Leong, Chang Ming Li and Timothy Thatt Yang Tan

Journal of Materials Chemistry A 2013 - vol. 1(Issue 34) pp:NaN5409-5409

Publication Date(Web):2013/07/01

DOI:10.1039/C3TC30956H

Multifunctional P(PEGMA)–REDV conjugated titanium surfaces for improved endothelial cell selectivity and hemocompatibility

Co-reporter:Yang Liu, Timothy Thatt Yang Tan, Shaojun Yuan and Cleo Choong

Journal of Materials Chemistry A 2013 - vol. 1(Issue 2) pp:NaN167-167

Publication Date(Web):2012/10/02

DOI:10.1039/C2TB00014H

A “uniform” heterogeneous photocatalyst: integrated p–n type CuInS2/NaInS2 nanosheets by partial ion exchange reaction for efficient H2 evolution

Co-reporter:Peng Hu, Chee Keong Ngaw, Yee Yan Tay, Shaowen Cao, James Barber, Timothy Thatt Yang Tan and Say Chye Joachim Loo

Chemical Communications 2015 - vol. 51(Issue 45) pp:NaN9384-9384

Publication Date(Web):2015/04/27

DOI:10.1039/C5CC02237A

Tb-doped iron oxide: bifunctional fluorescent and magnetic nanocrystals

Co-reporter:Yunxia Zhang, Gautom Kumar Das, Rong Xu and Timothy Thatt Yang Tan

Journal of Materials Chemistry A 2009 - vol. 19(Issue 22) pp:NaN3703-3703

Publication Date(Web):2009/04/20

DOI:10.1039/B817159A

Cyanamide, cyano-, compd. with 3-butyl-1-methylpyrrolidine (1:1)

CAS:637316-81-5

Cyanamide, cyano-, compd. with 3-butyl-1-methylpyrrolidine (1:1)

4H-1-Benzopyran-4-one, 2,3-dihydro-6-methoxy-2-phenyl-, (2S)-

CAS:84963-03-1

4H-1-Benzopyran-4-one, 2,3-dihydro-6-methoxy-2-phenyl-, (2S)-

Methionine, N-[[5-(dimethylamino)-1-naphthalenyl]sulfonyl]-

CAS:48208-47-5

Methionine, N-[[5-(dimethylamino)-1-naphthalenyl]sulfonyl]-

D-Aspartic acid, N-[[5-(dimethylamino)-1-naphthalenyl]sulfonyl]-

CAS:95465-25-1

D-Aspartic acid, N-[[5-(dimethylamino)-1-naphthalenyl]sulfonyl]-

CAS:42808-07-1

Aspartic acid, N-[[5-(dimethylamino)-1-naphthalenyl]sulfonyl]-

Serine, N-[[5-(dimethylamino)-1-naphthalenyl]sulfonyl]-

CAS:48196-47-0

Serine, N-[[5-(dimethylamino)-1-naphthalenyl]sulfonyl]-

1,3-Benzenediol, 5-[(1S)-2-[(1,1-dimethylethyl)amino]-1-hydroxyethyl]-

CAS:90877-48-8

1,3-Benzenediol, 5-[(1S)-2-[(1,1-dimethylethyl)amino]-1-hydroxyethyl]-

4H-1-Benzopyran-4-one, 2,3-dihydro-5-methoxy-2-phenyl-, (2R)-

CAS:221362-69-2

4H-1-Benzopyran-4-one, 2,3-dihydro-5-methoxy-2-phenyl-, (2R)-

4H-1-Benzopyran-4-one, 2,3-dihydro-6-hydroxy-2-phenyl-, (2S)-

CAS:190831-08-4

4H-1-Benzopyran-4-one, 2,3-dihydro-6-hydroxy-2-phenyl-, (2S)-

4H-1-Benzopyran-4-one, 2,3-dihydro-6-methoxy-2-phenyl-, (2R)-

CAS:190831-06-2

4H-1-Benzopyran-4-one, 2,3-dihydro-6-methoxy-2-phenyl-, (2R)-