National University of Singapore homepage

Research Proposals arising from NUSNNI YOUNG INVESTIGATORS CLUB meeting under NUSNNI YOUNG INVESTIGATORS’ RESEARCH SCHOLARSHIPS (2002)

Application for graduate research is now open. Prospective graduate students can download application forms from the Faculty of Engineering or the Faculty of Science websites.

Students will need to register with either the Faculty of Engineering or the Faculty of Science. To apply for NUSNNI scholarships, send the completed application forms to:

**********************************************************************************
Engineering                                                     Science
Ms Jasmin Lee                                                    Ms Amanda Lee
NUS Nanoscience and Nanotechnology Initiative,      NUS Nanoscience and Nanotechnology Initiative
c/o Faculty of Engineering,                                   c/o Faculty of Science,
E3-05-29, 2 Engineering Drive 3, Singapore 117576.  S13-02-12A, 2 Science Drive 3, Singapore 117542.
Email: nnilsf@nus.edu.sg                                      Email: nnilml@nus.edu.sg

Main Supervisor: Prof Seeram Ramakrishna (Department of Mechanical Engineering)

Co-Supervisor: Dr Teik-Cheng Lim (nnilimtc@nus.edu.sg) (NUS NNI)

The electrospinning process is the most effective method for the production of polymeric nanofibers – fibers with diameter less than 100nm. The effectiveness lies in the charged droplet which is electrically forced by an electrical field, coupled with the bending instability of the jet flow. The objective of this project is to develop some user-friendly theoretical models which can predict key flow characteristics based on input parameters such as processing conditions and raw material properties. The second objective is to correlate these input parameters with the final dimension, surface morphology, and physical properties of the electrospun nanofibers as a function of the input parameters. Results of this project will be beneficial for optimization purposes whereby a set of guideline will be generated for practitioners of the electrospinning process.

Please use the application forms of the Faculty of Engineering.

Development of Electrochemical Carbon Nanotubes Micro Sensors and Device
(Nanoscience and Nanotechnology is intrinsically an interdisciplinary research. Students with background in Biochemistry and
other Natural sciences such as Physics and Materials Science Engineering are in advantage for admission)

We propose to develop real-time chemical and biological sensors based on carbon nanotubes optimized to selectively detect a given molecular species from a gaseous or liquid mixture containing many other components. The sensor will be based on an array of carbon nanotubes functionalized non-covalently with conjugated ligands. The rationale of choice of the ligand will optimize both the speed and the reliability of the sensor. Our long-term goal is to select, design and fabricate sensing elements to be deployed in a detection chip that is able to identify nanomole quantities of targeted contaminants.

Main supervisor: A/P Sibudjing Kawi (Dept of Chemical & Biomolecular Engrg, FOE)

Controlled drug delivery technology represents one of the most rapidly advancing areas of biomedical science contributed by chemists and chemical engineers for humans and mammal’s health care. The controlled delivery systems have the significant advantages compared to conventional dosage forms, as the efficiency of medicine is enhanced, and patient compliance and convenience are improved. The method by which a drug is delivered can have a significant effect on its therapeutic efficacy because some drugs have an optimum range of concentration within which the maximum therapeutic benefit is derived.

The objective of this project is to develop uniform nanoporous materials with proper internal surface chemical properties and tunable pore opening for application in dual-controlled drug delivery system. The chemically-modified surface will provide moderate interaction with molecules of target drugs to control the desorbing release rate. The tunable nanopore-opening results in dual-efficiency to control diffusion of drugs from pore channels of nanoporous materials. These nano-scaled controlled drug delivery materials will be tested to control the release of certain drugs with constant desired concentration. Equipments (such as HPLC, XRD, TGA-DTA, FTIR, TPD/TPR/TPO, GC-MS, UV-Vis, BET) are available in our lab for this research program. PhD and Master students are welcome to join this interesting research project.

In the fabrication of nanodevices, a key step is in the fabrication of nanostructures and electrodes with features down to 10 nm in size. The key idea behind nanoimprint lithography is that one can produce desired patterns by stamping rather than the conventional multi-step photolithography or e-beam lithography techniques. The fabrication of such nanostructures and nanoelectrodes can then facilitate the subsequent fabrication of nanodevices using nanotubes, macromolecules, nanoparticles or other novel nanomaterials and structures.

Rapid and sensitive molecular techniques of the detection of interested microorganisms (e.g. pathogens and biological warfare agents) in environmental sources serve as an important means of warning and prevention. Fluorescence reporting systems are the most commonly used means for the current methods, but are limited to the availability of specific and expensive equipment with fluorescence detection capability, and the number (4 maximum) of targets simultaneously examined. The use of nanoprobes (<30nm in diameter) as the reporting system has emerged as a promising approach since it provides better specificity than fluorescence dyes, can be seen under visible light (low equipment cost), and provide multiple targets (>10) to be examined at the same time. In the proposed research, oligonucleotide, peptide and antibody-based probes will be initially synthesized with quantum-dot labeling at different level of specificity to different phylogenetic microorganisms and specific functional genes, proteins and cellular antigens of model microorganisms. The synthesized probes will be used to detect the model microorganisms separately and in combination. The results will be compared to those using fluorescence reporters. Techniques will involve cell hybridization, DNA/DNA or DNA/RNA hybridization and antibody/antigen reaction using for example real-time PCR and fluorescence microscope. The outcome should serve as a solid base for further applications into DNA microchip and lab-on-a-chip devices in life science research.

Design & Self-Assembly of DNA-Peptide Nanoparticles for Nonviral Gene Delivery
(Students with background in Biology, Biochemistry or Materials Science Engineering)

Nonviral gene delivery systems based upon plasmid DNA/chemical complexes have gained increasing attention for their potentials in avoiding problems inherent in viral gene vectors. In view of biocompatible and biodegradable natures and flexibility in design and fabrication with chemical or molecular biology methods, peptides provide an excellent and relevant material to form DNA nanoparticles through self-assembly of oppositely charged polymers. We propose to design and produce peptides with multiple functional domains that may act for DNA binding, DNA condensation and cell targeting. Endosomal lysis and nuclear uptake domains may be included for further improvement in the efficiency of DNA nanoparticle-based gene therapy. We will focus on peptides that may target the neurons with TrkB receptors, which are involved in Parkinson’s disorders, at the first stage of the work.

Please use the application forms of the Faculty of Science.

Nano scale devices such as nano-electromechanical systems (NEMS) are limited in their performance by the tribological properties (such as adhesion, friction and wear) between two dynamically interacting surfaces. For atomically smooth surfaces, surface modification is one way of changing and controlling the tribology. In this project, the concept of molecular bearing will be utilized to design a surface with embedded molecular size bearings. Atomically smooth substrate will be modified to include patterned nano-particles. Polymeric nano-particles and carbon nano-tube will be deposited on the surface such as that they provide free rotational motion when another moving surface comes in contact, providing very low interfacial friction. The presence of nano-particles on the surface will be tested for the tribological characteristics such as friction, adhesion and wear. A successful design of molecular bearing surface will have great technological applications in the nanotechnology area.

Coatings and thin layered materials have shown great promise not only in enhancing the appearance but also the durability and functional properties of products. With current technology, thin films used in many technologies can be extremely thin, such as in hard disc drives. Meaningful characterization must involve nanometer scale measurements. With advances in microscopy, qualitative information of surface properties at such length scale has now been made available. However, there are technical problems in the measurement of important mechanical properties such as hardness, elasticity, and friction of such thin films. Quantitative evaluation of Scanning Probe Microscopy data usually gives large errors (~50%) and controlled surface environments are required. An effort will be made to use molecular scale simulations to analyze data derived from such tests. The objective is to direct efforts at improving the tribological properties of surfaces and thin films. The project will require interdisciplinary expertise in fabrication, testing and characterization and simulation."

This is a new technique and has a great of promise for printing small features at a fast rate as well as without the assistance of complicated optics. Here a small "pen" such as AFM tip can be used to write or deposited multilayers of molecules on a substrate. This would allow us to develop interesting nanostructures and nanodevices. So far a few molecules have been tried as ink and the technology appeared to be successful. However, the complete potential of this technology has not yet established due to the lack of interesting compounds or inks. We will try to explore this missing link and work towards designing a "nanoptrinter" or other devices.

Computer Modeling of spin-dependent charge transport and spin electronic devices
(Students should preferably have some background in physics)

Main supervisor: Dr Mansoor B. A. Jalil (Dept of Electrical and Computer Engineering, FOE)

Spin electronics or "spintronics" devices is a new class of nanoscale devices which exploit both the charge and spin properties of carriers. This class of devices promises a manifold increase in processing speed and power efficiency over conventional semiconductor devices. For instance, device speed can theoretically reach the THz range of spin precessional frequency. The first generation spintronics devices such as the magnetic RAM chip, utilize "passive" spin control, in which spin filtering and spin-dependent conductivity arise from material and interfacial properties of the device. The next generation of devices makes use of active spin control in which the individual spins of carriers are controlled by electrical, magnetic and optical means.

Computer simulation of spin transport is a new and rapidly developing area of research. A vast majority of present carrier transport theories and models have completely ignored the spin property, and needs to be revised substantially. At a fundamental level, we aim to develop spin transport models which can describe novel phenomenon such as spin-orbit (Rashba and Dresselhaus) effects, spin transfer torque, carrier-moment RKKY exchange in diluted magnetic semiconductor and interplay between spin and charge quantization. The models will range from simple effective mass approximation to more refined techniques of second quantized form, and non-equilibrium Green's function approach. At a more practical level, new computational models need to be developed for novel devices such as the spin-FET, spin injector, magnetic tunneling transistors, and spin qubit devices. A successful development of this model will have a significant impact in this emerging field of computational research.

Computer Modeling of Magnetic Nanoparticles
(Students should preferably have some background in engineering, physics or material sciences)

Main supervisor: Dr Mansoor B. A. Jalil (Dept of Electrical and Computer Engineering, FOE)

Magnetic nanoparticles have important applications for storing information and as advanced nanosensors. It is thus important to model the magnetization dynamics of these particles when they are subjected to an external field and/or in the presence of thermal fluctuations. Theoretically, the study of stochastic magnetization dynamics is divided into two broad areas, i.e. via the Langevin dynamics/Landau-Lifshiftz-Gilbert (LD/LLG) or the Monte-Carlo/Master Equation (MC/ME) method, each having their own advantages. However, the linkage between the two distinct methods has proved problematic. From a theoretical standpoint, this situation is unsatisfactory because results obtained from one method cannot be analytically confirmed with the other method. More crucially, a link will help overcome a major weakness of the MC/ME method, where time evolution is calibrated in arbitrary MC steps rather than real time step as in the LD approach. A successful computer model combining both methods, will be extremely useful in modeling the switching behavior and thermal stability of perpendicular magnetic recording (PMR) media and heat-assisted magnetic recording (HAMR). PMR and HAMR can attain storage densities in excess of 1 Tb/in2 (> 10 times more than the bit density of present hard-disks) and are expected to be the dominant storage media for the next 10-15 years. Magnetic nanoparticles are also increasingly being used in biomedical applications such as bead-array counters and targeted drug delivery.

Nano-entities have a great impact on living cells. A typical example is the entry of viruses into a host cell, followed by the viral replication and virions exit. The entry and exit involve cell membrane wrapping and budding, thereby leading to a substantial deformation of the lipid bilayer membrane, depending on the entity size and the interaction with the membrane. Due to the complex nature of living cells, the underlying biophysics is not easy to resolve and remains a challenge to date. Computer simulations are a powerful tool that has been widely used in polymer science and appears promising to study the interactions, dynamics and kinetics for nano-entities in the vicinity of a living cell. Coarse-grained Monte Carlo and Brownian dynamic simulations will be applied to investigate the particle (to model a virus, for instance) induced cell fusion and fission, and the corresponding morphological changes of the membrane. It is aimed to gain a better understanding of underlying physics for biological processes.

The primary goal of this project is to conduct a systematic study to understand, predict and control the effects of nano-scale changes in the synthetic ECM on cell morphology and functions. Hence, this research will directly test the underlying hypothesis that the interplay between cells and nano-scale synthetic ECM is critical to the morphological and functional development of cells. Although it is well characterized that gross changes in ECM impact on cell behavior, little is know on how cell morphology and functions would be affected by fine changes (at the nanometer scale) in the synthetic ECM. An in-depth understanding of the molecular effects of synthetic nanofiber ECM on cell behavior will aid in designing superior biomaterials for tissue engineering with specific applications.

Bone grafting and tissue engineering is a subject of intensive investigation in human health care as it directly affects the quality and length of the human life. Need for the development of biomaterials for bone grafting and tissue engineering is continuously stimulated by the unsatisfactory performance of available materials and, of course, lacking appropriate technique to fabricate bone-resembling substitutes. Reconstruction of bone tissue using biomaterials having structure, composition, and biological features that mimic the natural bone is a goal to be pursued.

Main supervisor: A/Prof Anjam Kursheed (Dept of Electrical & Computing Engrg, FOE)

Due to recent interest in nano-technology, electron microscopy techniques have received greater attention. This is because electron microscopy not only provides a way of imaging surface features on the nano-scale, it can also obtain structural and chemical information through the use of energy spectral techniques. In the department of Electrical and Computer Engineering at the NUS, there are a variety of graduate research projects aimed at developing electron microscopy analytical instrumentation to improve the study of nano-structures. These projects typically aim to combine the high resolution imaging capability of electron microscopy to energy spectroscopic methods.

Students will receive the chance to work on challenging areas relating to electron microscopy and surface science. They will also gain experience in operating various electron optical columns such as the scanning electron microscope and designing novel columns of their own. Candidates applying for these projects should have a good grasp of the fundamental principles of electricity and magnetism.

Our main goal is to fabricate and develop rapid, sensitive and less expensive nanofiber based sensors to detect biomolecules, gases and to trace chemical compounds. As we are know, sensors comprises of two elements, a detection element coupled to a physical element, converting the sensed signal into meaningful information. The project is still in the initial planning and conceptualization stage; we have successfully spun nanofibers and also functionalized their surface. Investigation is now on study of the binding properties of these polymer nanofibers with biological molecules like proteins and enzymes.

Please use the application forms of the Faculty of Engineering.

We are developing a new kind of affinity membrane using electrospun polymeric nanofibers. Affinity membrane is also called molecular filtration membrane or adsorptive membrane and is widely used for affinity separation. The rationale of our idea is that the 2-D non-woven polymer nanofiber sheet has properties necessary for affinity membrane such as high surface area to volume ratio, micro scaled interstitial space with high interconnectivity, good morphology stability, and easily controllable fiber diameter and the sheet thickness. These properties make the electrospun polymer nanofiber sheet a potential candidate material for affinity membrane.

Please use the application forms of the Faculty of Engineering.

Main Supervisor: Dr Teo Kie Leong (Dept of Electrical & Computer Engineering, FOE)

Co-supervisor(s): Dr Mansoor Bin Abdul Jalil (Dept of Electrical & Computer Engrg, FOE),
                         Dr Liew Yun Fook Thomas (DSI),
                         Prof Chong Tow Chong (Dept of Electrical & Computer Engrg & DSI),
                        A/P Wu Yihong (Dept of Electrical & Computer Engineering & DSI),
                        A/P Shen Ze Xiang (Dept of Physics, FOS)

The recent success in spin injection from magnetic metals, from dilute magnetic semiconductors, and from non-magnetic semiconductor, and the transport of the spin-polarized current in semiconductors at room temperature promises the possibility of integrating spin transport devices (e.g. spin transistors, spin switches, and spin-based magnetic random access memory) in standard microelectronics at higher density, ultrafast speed, non-volatility, more logic and memory functionalities, and lower power consumption than the conventional charge-based microelectronic devices. The objectives of this research are (a) growth and characterization of ferromagnetic metals and semiconductor materials for spintronic application, (b) design and fabrication of thin films and spintronic prototype devices using different injector materials and nanostructures and (c) development of theoretical models and computation for magnetic and transport properties of magnetic semiconductors and hybrid ferromagnetic-semiconductor heterostructures. Techniques that will be employed include (a) the growth of materials using molecular beam epitaxy, (b) nanofabrication and nanolithography, (c) optical and structural characterization, (d) RKKY and tight-binding models for calculating magnetic properties, and (e) free-electron quantum model (ballistic and tunneling) and modified Boltzmann model (diffusive) for calculating transport properties.

Please use the application forms of the Faculty of Engineering.

Nano-biotechnology has emerged as one of the scientific and technological areas combining the innovative potential of nanotechnology and biotechnology, requiring close collaboration between researchers from different disciplines. As current research in genomics and proteomics produces more sequence data, there is a strong need for new technologies that can screen a large number of genes and proteins. Our research is to focus on developing luminescent nanomaterials as biological nano-probes and revolutionary biochips for the multiplexed bio-analysis. It will play an important role in solving biological and biomedical problems at molecular and cellular levels. Quantitatively multi-parameter analysis at single cell level will provide a direct way to identify sets of genes correlating with certain diseases, such as cancer.

Interaction Between Polymeric Nanoparticles & Biological Cell Membrane
(Experimental & Theoretical, suitable for PhD students ONLY)

Main supervisor: Dr Yu Liya (Department of Chemical & Biomolecular Engineering, FOE)

Co-supervisor(s): A/P Feng Si-Shen (Division of Bioengineering and Department of
Chemical & Biomolecular Engineering, FOE)

Polymeric nanoparticles have great potentials in medical application such as cancer chemotherapy, gene delivery and tissue repair. However, our understanding of interactions between nanoparticles and biological cells are quite limited. This project proposes application of lipid monolayers at the air-water or oil-water interface and lipid bilayer vesicles (liposomes) as model cell membranes to conduct quantitative investigation on interactions between polymeric nanoparticles and the lipid membrane, which include nanoparticle adhesion to, penetration into, and interaction with the lipid membrane. Cell line experiment will also be conducted. Emphasis will be given to the effects of nanoparticles size, surface charge and surface coating on the amount and rate of nanoparticle penetration. Various state-of-the-art techniques will be employed for nanoparticle preparation, characterization and penetration/interaction investigation, which may include laser light scattering, scanning electron microscopy (SEM), atomic force microscopy (AFM), tunnel electron microscopy (TEM), and confocal laser scanning microscopy (CLSM). Molecular thermodynamics and mechanics will be applied to interpret the measured data. The information obtained can provide general guidance for nanoparticle technology to be applied in medicine.

Growth of Nanocrystalline Diamond Films & Boron Nitride/Carbon Nanotubes Using Microwave Plasma Enhanced Chemical Vapore Deposition

Co-supervisor(s): A/Prof Andrew Wee T S (Dept of Physics, FOS),
A/Prof Thong, John (Dept of Electrical & Computer Engineering, FOE)

Attachment of biomolecules (eg. neural cells, DNA etc.) on polymer-functionalised diamond electrode for examining the suitability of diamond electrode for use as prosthetic devices in brain tissue study.

Developing molecular machines and components such as motors, valves etc. is an emerging area of research in nanotechnolgoy. Recently, Sow et. al developed a mechanism to control the rotation of polymeric spheres using lasers. Here, we are interested in using surface fucntionalized polymer spheres to control the rotation of the spheres as well as develop novel applications in microfluidics or other areas. The project will focus on optimization of the surface morphology of the spheres through chemical functionalization as well as to optimize the environmental conditions such as viscosity of the medium, temperature etc. to develop molecular components using such modified polymer spheres.

The project will be involving the studies of the mechanism of the formation of 3D colloidal crystal. Project includes looking at the influence of external influences of the formation of the crystal and the feasibility of using the assembly as Micro/Nano Template.

Enzyme immobilization for biocatalysis and biosensor applications
(Students with background in chemistry or chemical engineering are desired)

Main supervisor: Dr Zhao X. S., George (Dept of Chemical & Biomolecular Engineering, FOE)

The application of an enzyme as a biocatalyst is greatly hampered by its reusability. This is because free enzyme lacks of long-term stability under process conditions and difficult to recover from the reaction mixture. Hence the idea of immobilizing the enzyme on a rigid solid support to enable easy separation and reuse, and the possibility of operation in a packed-bed has been of great industrial interest. This project aims to immobilize enzyme on porous solids. The immobilized enzymes will be evaluated in terms of their enzymatic activity. The use of immobilized enzyme for biosensor application will be explored as well.

Co-supervisor(s): Dr Xie Xianning (NUSNNI),
A/Prof Thong, John (Dept of Electrical & Computer Engineering, FOE)

Understanding electron transport through single molecule is of significant importance in molecular electronics. Metal-molecule-metal junctions formed by self-assembly can display useful electrical behavior such as rectification, negative differential resistance and electrochemical switching. This project addresses the fundamental science of electron transport properties in molecules. Basically, it has the following objectives:

1) To measure the conductivity for various molecules including saturated and unsaturated hydrocarbon chains, conjugated molecular rings.

2) To investigate the dependence of I-V curves on the number of molecules bridging the electrodes, extract the conductivity for a single molecule, and further examine the coupling effects among molecules.

The approach is based on mixed self-assembly and conducting atomic force microscopy (CAFM). The formation of homogeneous binary self-assembled monolayers is used to control the number of molecules contacting the electrodes. Conducting AFM is utilized to form metal-molecule-metal junctions, and perform the I-V curve measurements.

In this project, we make use of atomic force microscopy (AFM) for surface nanopatterning, nanofabrication and nanocharacterization. AFM offers a site-selective, size-controllable and one-step methodology for surface patterning. The sharp AFM probe (20-50 nm radius of curvature) can induce various localized chemical reactions and surface modifications under different conditions. We explore the application of AFM nanolithography on bare and functionalized semiconductor surfaces such as silicon (Si) and silicon carbide (SiC) etc. For example, we investigate probe induced local oxidation for gate oxide growth for metal-oxide-semiconductor (MOS) devices. We also use conducting AFM (c-AFM) and thermal AFM (t-AFM) to examine the electrical and thermal characteristics of nanostructures.

1. X.N. Xie, H.J. Chung, H. Xu, X. Xu, C.H. Sow, and A.T.S. Wee, J. Am. Chem. Soc. 126 (2004) 7665
2. X.N. Xie, H.J. Chung, C.H. Sow, and A.T.S. Wee, Appl. Phys. Lett. 84 (2004) 4914
3. X.N. Xie, H.J. Chung, C.H. Sow, and A.T.S. Wee, Chem. Phys. Lett. 388 (2004) 446

Please use the application forms of the Faculty of Science.

Co-supervisor(s): Dr Wu Ping (Institute of High Performance Computing),
Dr Chen Xian Tong (Institute of Microelectronics)

While ULSI performances have seen great improvements with the scaling down of transistor dimensions, a new set of challenges need to be surmounted before there can be further advances. The interconnect transmission time of new generation nano-transistors is now governed by interconnect resistances and parasitic capacitance because of their small dimensions. The integration of Cu/low-k materials with lower RC delay has therefore become an important issue for current and future ULSI. Integration and reliability issues such as loss of adhesion during process integration, chemical interactions (especially those which may occur during photolithography, etch/clean and dielectric/metal deposition) and surface/bulk diffusion of Cu have impeded implementation of low-k dielectrics. All these issues are strongly dependent on the properties of low-k materials and their interaction with unit processes. Fundamental understanding of adhesion and diffusion of low-k materials and their physical/chemical interaction at material interfaces is critical for successful integration of an insulating material with dielectric constant 1<k<3. This project will study the properties of low-k materials and related process parameters pertaining to 2 critical issues – Cu/Ta adhesion and diffusion of Cu - through theoretical simulation and process evaluation to understand the reaction mechanism.

Polymer nanofibers made by electrospinning method have potential applications in environmental engineering & biotechnology, bioengineering, energy and defense & security fields. Hence, scientific interest about electrospun polymer nanofibers has been growing steadily. Typical electrospinning setup reported in open literature consists of a single syringe filled with polymer solution, high voltage generating apparatus and fiber collecting plate.

Co-supervisor(s): Dr Xu Hai (Institute of Engineering Science)
A/P Feng Yuan Ping (Dept of Physics, FOS)

We investigate methods of creating nanometer-scale structures on surfaces to form one- and two-dimensional ordered patterns using in-situ UHV-STM. When adatoms are nucleated into ordered arrays of sufficiently small dimensions, quantum mechanical effects determine their properties, for example in quantum dots or quantum wires. Such formation of ordered nanostructures on surfaces is indeed a challenge in both fundamental and applied science research. Fabrication of uniform-size clusters in the 1-2 nm size regime is challenging because fluctuation in size of a few atoms could substantially alter their electronic properties. For a complete understanding of the physical properties of nanostructures, the structure of the surface must be determined. The surfaces of nanostructures are likely to vary significantly from the well-characterized bulk structures. Hence, the ability to measure and systematically control the surface is an important field of research. Furthermore, the imaging and measurement of electronic transport properties of single molecule will also be performed in a cryogenic STM.

Please use the application forms of the Faculty of Science.

The blood brain barrier (BBB) is a physiological mechanism that alters the permeability of brain capillaries so that some substances such as toxins and drugs are prevented from entering brain tissue while necessary nutrition is allowed to enter freely. The BBB plays important physiological function to protect brain from harmful chemicals and helps maintain a homeostatic environment for a healthy and efficient brain. The BBB, however, constitutes a main obstacle of sensitizers and drugs for diagnosis and treatment of brain diseases, especially brain cancer, as well as other brain-related diseases such as AIDS. This project proposes to use nanoparticles of biodegradable polymers with coatings of phospholipids, cholesterol, molecularly modified vitamin E to deliver therapeutic agents such as paclitaxel across the BBB. The emphasis will be given to the manufacture and characterization of paclitaxel loaded nanoparticles of biodegradable polymers with a focus on coating techniques. Rat brain capillary endothelial cell lines and brain tumor cell lines will be used to quantitatively measure the cell uptake of the drug loaded nanoparticles. Effects of particles size and surface coating on cell uptake of nanoparticles will be closely investigated. Animal model will also be pursued.

Paclitaxel is one of the best anticancer drugs found from nature in the past decades, which has excellent effects against a wide spectrum of cancers including ovarian, breast, brain, colon, neck, small cell/non-small cell lung cancers. Paclitaxel is also commercially the most successful drug with its world sale of US$1.5 billions in 1999. Due to its high hydrophobicity, however, adjuvant such as Cremophor EL has to be used in its current clinical administration, which has been found to be responsible for most of the side effects such as hypersensitivity reactions, nephrotoxicity, neurotoxicity and cardiotoxicity. Nanoparticles of biodegradable polymers could be an alternative administration system to eliminate Cremophor EL and to have better interaction with cancer cells. Controlled and targeted delivery can also be realized. This project will use a modified solvent extraction/evaporation technique in preparation of paclitaxel loaded nanoparticles of various FDA approved biodegradable polymers. Nanoparticles produced under various conditions will be characterized by state-of-the-art techniques including laser light scattering (LLS), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transformation infrared spectroscopy (FTIR), X-ray electron spectroscopy (XPS), differential scanning calorimetry (DSC), etc. In vitro release will be measured by high performance liquid chromatography (HPLC). The emphasis will be given to cell line experiment, in which Caco-2 cells (colon cells with cancer) will be used to quantitatively measure the cell uptake of the drug loaded nanoparticles. Animal model will also be pursued.

Co-supervisor(s): Dr Teo Kie Leong (Dept of Electrical & Computer Engineering, FOE)

Pressure just like temperature is a thermodynamical variable that can induce major changes in the structural, electronic and magnetic properties of all materials. We investigate the following nanostructured materials using high pressure technique using diamond anvil cells.

Ge/Si nanostructures (quantum dots and nanocrystals) have recently received considerable attention for their applications in optoelectronic and electronic devices. Considering the large interface-to-volume ratio in nanocrystal-matrix systems the interface strain plays an important role in deciding the physical and thermodynamic properties of nanocrystals. One of the most powerful methods to access information on strain in embedded nanostructures is Raman scattering spectroscopy. With the application of pressure, the biaxial strain between the Ge and Si layers can be tuned. Such information provides an insight in understanding the formation mechanism of nanocrystallite Ge embedded in SiO2.

Colloidal semiconductor nanocrystals form an important category of nanoscience and nanotechnology. Among them, II-VI semiconductors such as CdS and CdSe quantum dots are the most studied because of their potential industrial and biomedical applications due to its tunable emission in the visible region. II-VI semiconductor nanorods with precisely controlled diameter and length are of particular interests. This project investigates the high-pressure effects on the optical and structural properties and the phase stability and transition of II-VI semiconductor nanorods of different sizes.

Nanosphere lithography for surface patterning
(students with background in colloidal chemistry and solid-state physics are preferred)

Main supervisor: Dr Zhao X. S., George (Dept of Chemical & Biomolecular Engineering, FOE)

Co-supervisor: Dr Loh Kian Ping (Dept of Chemistry, FOS)
Prof Chua Soo Jin (Dept of Electrical & Computer Engineering / IMRE)

Surface patterning on substrates is of great importance in many technological areas such as photonics, data storage, and biosensors. However, conventional techniques for creating surface patterning such as electron-beam lithography are time-consuming and costly. Nanosphere lithography carries a number of advantages over traditional lithography techniques such as simplicity, lost cost and precise control of surface patterning at nanometer scale. This project aims to create surface nanostructures using nanosphere lithography techniques. Application potentials in photonics or catalysis or sensor will be exploited.

Co-supervisor(s): Dr Xie Xianning (NUSNNI),
A/Prof Thong, John (Dept of Electrical & Computer Engineering, FOE)

The ability to fabricate microscopic structures is a key element for creating nanoscale electronic devices. This project focuses on the constructive fabrication of nanodevices using self-assembly and AFM lithography. We adopt the template-controlled self-assembly strategy to fabricate spatially defined metal structures on organic monolayer templates. Basically, the procedure includes: (1) localized in-situ electrochemical modification of a preassembled monolayer through AFM nanomanipulation and nanolithography; (2) selective attachment of metal nanoparticles/clusters on the modified monolayer via wet chemistry or tip-induced reaction; and (3) further development of 3D nanostructures on the monolayer template by introducing functional molecules.

As the basic unit of life, the cell is a biologically complex system. It requires a combination of various approaches including biomechanics in order to understand the cell. With the recent progress in cell and molecular biology, the field of cell mechanics has grown rapidly over the last few years. This research seeks to study the response of cells to mechanical forces, and to understand the biomechanics and kinetics of cell adhesion (eg. cell-cell or cell-substrate interactions) at the cellular as well as molecular levels. A quantitative approach using cutting-edge techniques such as optical trapping and atomic force microscopy will be used.

Please use the application forms of the Faculty of Engineering.

Recent developments of optical and mechanical probes that are sensitive enough to make measurements on single biological molecules has ushered in a new era of biomechanical studies. Not only can we do such measurements and be able to characterize molecules, we can also investigate into the properties of molecules whose roles and functions are yet unknown. Our goal in biomolecular mechanics is to be able to mechanically characterize the behaviour of single molecules. We want to address questions such as: How does a protein respond to applied force? How does it move, fold and unfold? How does it generate a force? Biomolecules that is of interest include DNA strands, biopolymers, cytoskeletal structures, molecular motors such as myosins, etc. Techniques that will be employed include optical trapping using laser tweezers, micromanipulation and atomic force microscopy.

Please use the application forms of the Faculty of Engineering.

SAMs are an important class of surface coating materials that have extensive application in the area of micro and nano devices. Initial results have shown that SAMs, when used as protective coating on a substrate, provide wear resistance and low friction. In this project a number of SAMs will be deposited on surfaces such as silicone wafer and magnetic hard disk and studied for their friction and wear properties. Molecules with appropriate functional groups will be deposited on these surfaces and a structure-property correlation studies will be carried out. Most importantly a systematic study of polar and nonpolar interactions between two surfaces will be fine tuned to optimize the performance of an interface during this project. The molecular orientation effect, diffusion and stability of molecules at the interface during sliding that gives low friction will also be investigated. The project aims to design a new nano-tribotester which will help us in carrying out extensive nano-tribological work on new materials with potential applications to nanotechnology.

Co-supervisor(s): A/Prof Thong, John (Dept of Electrical & Computer Engineering, FOE)

The synthesis of metal chalcogenides has received much attention due to their important non-linear properties, luminescent properties, quantum size effects, and other important physical and chemical properties.

In this project, we are interested in the solvothermal as well as metal-organic chemical vapor deposition routes to the synthesis of CdS, ZnO, MoS2 nanowires which can show quantum-confinement. The functionalisation of these nanomaterials with organic ligands in order to enhance the assembly and charge transfer properties will be researched upon. TEM and selected area electron diffraction (SAED) will be used to study the microstructure of these nanomaterials. The current transport as well as optical properties of these nanomaterials will be studied using I/V spectroscopy as well as photoluminescence techniques.

Co-supervisor(s): A/P Lim Chwee Teck (Dept of Mechanical Engineering, FOE)

Calcium rich biocomposites are abundant in nature. However, understanding the molecular mechanism of formation of such tough materials is not well developed. We have been working on this theme for the last 4 to 5 years with considerable success. Currently we have acquired enough knowledge to control the crystal morphology of the calcium salts using polymers and macrotemplates and to develop composites of interesting structure. This proposed project will focus on developing novel calcium salt – biopolymer composites and testing the mechanical and morphological properties using various techniques (AFM, nanointender, TEM, SEM etc).

Synthesis of Molecular Building Blocks & Development of Characterization Methods for
Fabrication of Components for Molecular Electronics

Molecular electronics is an emerging area of research started in the last couple of years. Various approaches to develop components for molecular electronics such as molecular transistors were employed using single atom, molecule and recently, spin states of electrons (spintronic transistor). Other approaches are also underway to develop devices such as molecular motors, diodes etc.. In most cases, the critical issue is the interface between the molecule and conducting surface. In the past, the research efforts were focused on understanding the properties of this interface using individual or layers of molecules. However, a full understanding via systematic study of molecular structures and the nature of the conducting surface has not yet established in literature. We plan to design novel molecular structures and conducting surfaces to understand the communication between the electronic structure of the individual molecule and the continuous electronic band structure of the bulk material of the electrode or conducting materials.

Co-supervisor(s): A/Prof Andrew Wee T S (Department of Physics, FOS)
A/P Alfred Huan (Department of Physics / IMRE)
Dr Xu Hai (Institute of Engineering Science)

The SINS (Surface, Interface & Nanostructure Science) synchrotron beamline supports a multifunctional synchrotron experimental station by upgrading the existing equipment for three related projects on ultrathin films (molecular, magnetic, and dielectric). In addition to photoelectron spectroscopy (PES), X-ray absorption (XAS) including Near-edge Extended X-ray Absorption Fine Structure (NEXAFS), PEEM and STM/AFM, magnetic dichroism in XAS (XMCD) is a quantitative tool for magnetic information. Furthermore MOKE (magneto-optical Kerr effect) at IMRE will give important parameters to describe the magnetic properties. PEEM and XMCD provide mainly "static" magnetic domains/properties, whilst MOKE provides the whole magnetization B-H loop curves. These new tools will give us a deeper understanding of the growth and properties of the ultrathin magnetic films, facilitating future technology development in nanomagnetics and data storage.

Please use the application forms of the Faculty of Science.

Co-supervisor(s): Dr Peter Ho (Department of Materials Science)
Dr Gao Xingyu (Department of Physics)

The SINS (Surface, Interface & Nanostructure Science) synchrotron beamline offers a tunable monochromatized light source (50-1000 eV) with high resolution (DE/E better than 10-3), high intensity (1010-1011 photons/s), and tunable polarization. Photoelectron spectroscopy (PES) is a powerful tool for obtaining electronic and surface chemical information. X-ray absorption (XAS), including Near-edge Extended X-ray Absorption Fine Structure (NEXAFS) offers local information on chemical and electronic states, and can be used to determine nearest neighbor distance even though the material does not have long-range order, such as organic thin films. STM/AFM (scanning tunneling microscopy/atomic force microscopy) at the end station enables in-situ atomic scale imaging of nanostructures and defects. These new tools will give us a deeper understanding of the growth and properties of the ultrathin organic films, facilitating future technology development in organic nanodevices.

Co-supervisor(s): A/Prof Andrew Wee T S (Dept of Physics, FOS),
A/Prof Thong, John (Dept of Electrical & Computer Engineering, FOE)

Recently, the remarkable field emission characteristics of carbon nanotubes (CNTs) have generated considerable interest in their application for vacuum microelectronic devices. This project looks at the macroscopic as well as localized field emission characteristics of CNTs in micron/nano scale. Using the technique of scanning field emission microscope, we will investigate the localized field emission properties of various CNTs. This includes the dependence of field emission on the density, distribution and local morphology of CNTs, etc. Together with various fabrication techniques to achieve patterning of the CNTs array, we will also be investigating the individual and collective field emission properties of unique array and/or structures made of CNTs.

Co-supervisor(s): Dr Zhao X. S., George (Dept of Chemical & Biomolecular Engr, FOE),
A/Prof Andrew Wee T S (Dept of Physics, FOS)

Nanoparticles, including clusters, wires, dots and crystallites, are an important family of nano-materials possessing novel properties that can find applications in microelectronics, optoelectronics, and catalysis. This project aims to fabricate various nanoparticles (including Au, Ag, Pt, Pd, Co, Si, Ge) by depositing atoms on inert substrates (such as graphite, SiO2, SiNx, CeO2, ZrO2) followed by self-assembly of the atoms in ultrahigh vacuum and other well-controlled conditions. In-situ scanning probe microscopy and electron diffraction will be employed to examine the size, surface atomic structures, morphology and electronic properties of these nanoparticles. Chemical properties of the nanoparticles will be analyzed by using photoelectron spectroscopy and adsorption/desorption techniques. The correlations between the growth conditions, nanoparticle morphology, and their functional properties will be established through systematic studies.

Main supervisor: Dr Zhao X. S., George (Dept of Chemical & Biomolecular Engineering, FOE)

Optics based on photonic crystals has been deemed the 21st century revolutionary technology that would create as significant impact as electronics did in the 20th Century. According to the Singapore Economic Development Board, Singapore aims to be the centre of excellence in photonics and is well poised to enter into the photonics era. Already, it is tapping about $2 billions of the photonics market in terms of output. Photonic bandgap materials are spatially structured macroporous materials with a high refractive index. When the structure is in 3D periodicity, they can control lights in the same way as semiconductor does for electrons. The traditional lithography technique has trouble making 3D photonic crystals. Thus, it has been a great challenge to fabricate 3D periodic structures in a controllable way, in copious quantities, and at an acceptable cost. This project aims to fabricate 3D photonic crystals by using self-assembled colloidal systems as the template.