Research

Due to the interdisciplinary nature of nanotechnology and its horizontal relationships to the academic disciplines and the industrial sectors, our research, as a consequence, is also quite diverse. Ranging from electromagnetic optical physics to self-assembly chemistry to bonding with biomaterials, there is no limit to the types of research that can be conducted in the lab. We do focus on three general areas: 1. Energy, 2. Environment, and 3. Food and Agriculture. Projects from the past included desalinization of sea and brackish waters, dye-sensitized solar cells, chitosan coated NPK fertilizers, ammonia gas sensors with homemade inter-digitated electrodes, and anti-fungal research. Please inspect our publications, theses and dissertations in the Publications section of this website.

Currently, in energy, we are developing solar cells that absorb in the infrared range and investigating catalytic materials and processes that enable recycling of CO2 produced from biogas conversion and combustion by converting into methane. In agriculture, we are studying and developing systems using surface enhanced Raman spectroscopy to measure real-time levels of pesticides in plants and nano-encapsulation of nutrients and growth factors for plant growth enhancement. Environmental projects include gas sensing, heavy metal recovery from mining effluents and in mangrove systems and environment friendly antifouling coatings. We also conduct basic research. Optical simulations, membrane science and carbon nanotube projects are available for students - for cutting edge projects. Please review our Publications section of the website. A brief synopsis of past and current research is provided.

Detection and Sensing Electromagnetic / Optical modeling Chemical Synthesis Superhydrophobic Surfaces Carbon Nanotubes Nanofiltration and Template Synthesis Pesticide Analysis by Laser Spectroscopies Antimicrobial Materials Agriculture Solar and Photocatalytic Research Antifouling Coatings Societal Implications Nanobiotechnology

Detection and Sensing

Sensors made of nanomaterials show enhanced performance in terms of sensitivity and selectivity. Many kinds of nano-scale materials are suitable for sensor applications including carbon nanotubes, zinc oxides and conducting polymers like polythiophene. For example, inexpensive (and many) sensors are required to monitor ammonia gas levels in the paper pulping industry as well as sensors that are able to detect natural gas leaks at home. High surface area materials are required to enhance sensitivity. A microelectrode array and 'bottom-gated OFET' are depicted. Inter-digitated electrodes printed by our homemade printer using nanosilver ink were capable of measuring ammonia gas when either zinc oxide nanorods or carbon nanotubes were used as the sensing element. Images are from the work of Pattamon Teerapanich of Thailand and Tanmoy Goswami of Guwahati, India.

Electromagnetic/Optical Modeling

Our simulation group, in conjunction with our colleagues at Bangkok University, is able to model the optical behavior of nanomaterials in electro-magnetic fields. Classical EM modeling systems are applied to describe the behavior of nanoscale arrays of metals/ insulators with effective medium (EMT) and scattering matrix theories. Raman hotspots are shown (bottom- R). Propagation of light through a zigzag waveguide is shown (bottom-L) and optical expression of a thin film of silver embedded in anodic aluminum oxide (AAO) with a point excitation source of l = 533 nm (bottom-C). At top left, the optical behavior of gold/copper/silver nanoparticle alloys are modeled with EMT and other classical electromagnetic theories. Recently, with our collaborators at Bangkok University, we have submitted papers describing the phenomenon of side-coupling of light to enhance the output signal of a plastic fiber optic waveguide. The configuration can also serve as a new kind of sensor. Images are from the work of Mayur Chaudhari of Pune, India and Saabah bin Mahbub from Bangladesh and Prerona Majumder from Guwahati, India.

Chemical Synthesis

Our lab specializes, most of all, in synthesis of nanoparticles. We make nanoparticles out of anything - metals, semiconductors, ceramics, insulators, and polymers. Pictured are scanning electron micrographs (SEMs) of various structures of zinc oxide - nanoparticles, nanorods, microballs, nanoflowers, nanobelts, nanotubes, tetrapods, branches and a nanoring. Our images are obtained with assistance from our neighbors in Thailand Science Park of The National Science & Technology Development Agency (NSTDA). We employ the 'bottom-up' philosophy of synthesis of nanomaterials - bottom-up from atoms and molecules. Anything that we can make in a beaker or flask is what we do. The focus has been on zinc oxide for several years. Zinc oxide nanorods (b) provide high surface area for gas nanosensors, semiconducting support for dye-sensitized solar cells, high surface area coated fibers for photocatalytic water purification and many more applications. Quantum dots are simple to make from the bottom-up. Quantum dots can be attached to the zinc oxide nanorods to provide selective absorbers for solar radiation, enhancing the interaction. Silica nanoparticles chemically modified with silanes are also a popular synthesis that supports several research projects in the laboratory. Dr. Sunandan Baruah, Ph.D. from COEN, contributed most of these images.

Superhydrophobic Surfaces

The textile industry is important in this region. There are already many products on the market today with nano-enhanced properties. We too can make textiles water resistant and/or antibacterial. Images show cotton and cotton-polyester textiles treated with zinc oxide nano and micron scale rods to produce water contact angle greater than 160° - the requirement for a super-hydrophobic surface. A rose petal shows strong adhesion behavior to water even thought the rose petal is also superhydrophobic. In this case, we showed that the case for the superhydrophobicity for the rose petal is more like the graphic outlined in Figure b in the image. In other words, there are domains of adhesion even though the surface provides a low energy for interaction with water droplets - the case again for superhydrophobicity. Nature again is our teacher as the lotus and rose surfaces show us the way to superhydrophobicity. Textiles are also treated with antibacterial materials. The combination of superhydrophobic cloths that are antibacterial is appealing to the textile industry. Images are found in the thesis of Myo T.Z. Myint of Myanmar.

Carbon Nanotubes

A challenging goal for our laboratory is to fabricate long carbon nanotubes for applications in ballistic electrical conduction and reinforced nanocomposites. Carbon nanotubes are the strongest materials known to science. We have used carbon nanotubes in gas sensors to detect gases such as ammonia. Our chemical vapor deposition apparatus is depicted at the accompanying figure. Methane gas is reduced to carbon atoms on nanoscale iron/nickel catalysts. The diameter of the carbon nanotube depends on the diameter of the catalyst. SEMs of single and multi-walled carbon nanotubes are shown in the accompanying figure. The reactor is capable of reaching temperatures in excess of 600 °C. Aligned growth is accomplished with a template system in which the catalyst particles are embedded. More details are provide in the second image. Images are from the thesis of Kataguna Kanuk Nukulchai of Thailand.

Nanofiltration and Template Synthesis

A challenging goal for our laboratory is to fabricate long carbon nanotubes for applications in ballistic electrical conduction and reinforced nanocomposites. Carbon nanotubes are the strongest materials known to science. We have used carbon nanotubes in gas sensors to detect gases such as ammonia. Our chemical vapor deposition apparatus is depicted at the accompanying figure. Methane gas is reduced to carbon atoms on nanoscale iron/nickel catalysts. The diameter of the carbon nanotube depends on the diameter of the catalyst. SEMs of single and multi-walled carbon nanotubes are shown in the accompanying figure. The reactor is capable of reaching temperatures in excess of 600 °C. Aligned growth is accomplished with a template system in which the catalyst particles are embedded. More details are provide in the second image. Images are from the thesis of Kataguna Kanuk Nukulchai of Thailand.

Pesticide Analysis by Laser Spectroscopies

High levels of pesticide residues in tea and other cash crops are a worldwide issue. COEN has submitted proposals to governmental agencies and private groups that address this issue. The problem is that conventional methods of measuring pesticide levels in crops are expensive, slow and require highly trained operators. These methods are usually based in high end cost instruments such as gas (liquid) chromatography linked to mass spectrometers (Top-left image). We propose the use of Raman and near-IR (infrared) spectroscopies linked to sophisticated databases for data reduction and analysis. Handheld models are already available in the marketplace for numerous applications. We wish to develop our own portable spectrometer linked with the latest information communication technology to Cloud style databases for quick and virtually unlimited response. We work in partnership with our colleagues in NECTEC (National Electronics and Computer Technology Center) in Thailand Science Park. NECTEC has developed surface enhanced Raman spectroscopy substrates (SERS) for analysis of pesticides. COEN will develop the methodology and statistical deconvolution methods by application of principal component analysis (PCA) and other statistical methods. GC-MS systems first separate pesticide components via chromatography, and then components are identified via mass spectrometry (image- top right). In our system, all components are instantly measured simultaneously and then identified via statistical methods grounded in a pesticide library database. A sample SERS spectrum of the pesticide imidacloprid is shown beside.

Antimicrobial Materials

Antibacterial paper and textiles have been developed and tested extensively. Zinc oxide nanorods and silver nanoparticles are important materials in killing bacteria and fungus. The use of such materials in the preservation of foods is in progress. Since ~30% of agriculture products are lost to spoilage, this is quite an important field of study. We work with our Biotechnology Lab and the Pulp & Paper Technology facility to develop antibacterial packaging. 'Zones of inhibition' created by ZnO are clearly visible from the images shown above. Bacteria and fungus are unable to grow within the inhibited zone. Images are from the work of Mayuree Jaisai, a research assistant in COEN.

Silver nanoparticles are the most popular nanomaterial on the market today. All kinds of antibacterial products are available today ranging from odorless socks to antibacterial plastics to medical salves and bandages. Paints too and air purifiers also take advantage of nanoscale silver particles and their incredible bacteria killing properties. Other materials such as titanium dioxide and zinc oxide (as shown above) also show antibacterial properties. Our lab is equipped with a self-contained biotech lab which does not allow contamination within or without. Our work mainly involves the microorganisms Aspergillus niger (the common mold) and Escherichia coli (the intestinal bacterium).

Agriculture

Agriculture is very important to Thailand and the region including the South Asian countries of India, Nepal, Pakistan and Sri Lanka. We support agricultural research in a variety of ways. One area of great interest is in energy crops. Conversion of energy crops like Pak Chong-1 (elephant grass) into biogas has potential to create a renewable source of energy for the region. Converting CO2 into methane is a path to green energy sustainability. CO2 and CH4 are produced during bioconversion into biogas. The CO2 is recycled and converted into methane by catalytic processes mitigated by nanoscale metals. Upon clean and efficient combustion, the CO2 produced is again recycled and converted into methane - equal to carbon neutral! A pipedream? We have submitted proposals to various funding agencies concerning this area of biogas conversion. AIT in particular produces tons of biomass per year. Why not convert that material into recyclable methane fuel.

Solar and Photocatalytic Research

The application of nanoscale materials to solar and photocatalytic research is a major focus of the laboratory. Dye-sensitized solar cells (DSSC) offer an inexpensive means of harvesting solar energy. Although not as efficient as traditional silicon-based solar collectors, the cost of materials and manufacturing is not prohibitive. The lab is equipped with sensitive electronic measurement equipment and a solar simulator good enough to deliver the intensity of one sun onto dye sensitized solar cell samples. An image above shows the path of electrons once excited within the dye cell. Quantum dot decoration of zinc oxide nanorods also demonstrated enhanced solar photocurrent. Quantum dots are fabricated by simple chemical methods (shown here).

Photocatalysis is applied to purify drinking water by removing toxins and killing bacteria. Purification of textile industrial effluents by photocatalytic methods benefits the health of local communities and the environment. SEM of high surface area ZnO nanorods is depicted. The images are from the work of Dr. Tanujjal Bora, a former Ph.D. student at COEN.

Antifouling Coatings

We have projects investigating the development of new coatings that prevent biofouling of marine structure surfaces. One section of the laboratory has been dedicated to this effort. We have also submitted proposals focusing on this are of research. Worldwide, antifouling is a very important process, especially to the shipping industry. Nanotechnology has made great strides in the development of antifouling coatings. There are several strategies that have proven to be effective in retarding the adhesion and colonization of organisms onto submerged surfaces. Surfaces consisting of silica nanoparticles coated with perfluorinated carbons that produce a superhydrophobic effect and some special texture that aids in the prevention of settlement by barnacles.

Societal Implications

Societal implications? Yes, we also study the societal implications of nanotechnology. We have a program right focused on evaluating the opinion of Thai university students on subjects like nanotechnology and nanosafety.

Nanobiotechnology

NANO-Biotechnology is a highly integrated field. Use of nanomaterials in biological systems (and vice versa) opens up many new avenues of research. Since we are made of nanoscale materials, it Is a good idea to understand Nature's nanotechnology. Biomimetics is the study of Nature applied to our technology. Gold nanotubes were formed by template synthesis from the hyphae of Aspergillus niger, a common mold (work produced by former Ph.D. student Dr. Aneeqa Nazir). Nature provides many models for us. A new kind of fingerprint analysis was accomplished by utilizing the sticky properties of chitosan-coated gold nanoparticles. More and more, students are interested in the biotechnological aspects of nanotechnology. To accommodate them, we have divided our curriculum into two tracks— the engineering track and the life sciences track. Makes sense!


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