Teerakiat Kerdcharoen

Detection and Classification of Human Body Odor Using an Electronic Nose

An electronic nose (E-nose) has been designed and equipped with software that can detect and classify human armpit body odor. An array of metal oxide sensors was used for detecting volatile organic compounds. The measurement circuit employs a voltage divider resistor to measure the sensitivity of each sensor. This E-nose was controlled by in-house developed software through a portable USB data acquisition card with a principle component analysis (PCA) algorithm implemented for pattern recognition and classification. Because gas sensor sensitivity in the detection of armpit odor samples is affected by humidity, we propose a new method and algorithms combining hardware/software for the correction of the humidity noise. After the humidity correction, the E-nose showed the capability of detecting human body odor and distinguishing the body odors from two persons in a relative manner. The E-nose is still able to recognize people, even after application of deodorant. In conclusion, this is the first report of the application of an E-nose for armpit odor recognition.

High loading fragrance encapsulation based on a polymer-blend: preparation and release behavior.

The six fragrances, camphor, citronellal, eucalyptol, limonene, menthol and 4-tert-butylcyclohexyl acetate, which represent different chemical functionalities, were encapsulated with a polymer-blend of ethylcellulose (EC), hydroxypropyl methylcellulose (HPMC) and poly(vinyl alcohol) (PV(OH)) using solvent displacement (ethanol displaced by water). The process gave >or=40% fragrance loading capacity with >or=80% encapsulation efficiency at the fragrance to polymer weight ratio of 1:1 and at initial polymer concentrations of 2000-16,000 ppm and the obtained fragrance-encapsulated spheres showed hydrodynamic diameters of less than 450 nm. The release profile of the encapsulated fragrances, evaluated by both thermal gravimetric and electronic nose techniques, indicated different release characteristics amongst the six encapsulated fragrances. Limonene showed the fastest release with essentially no retention by the nanoparticles, while eucalyptol and menthol showed the slowest release.

Multi-Walled Carbon Nanotube-Doped Tungsten Oxide Thin Films for Hydrogen Gas Sensing

In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO3) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO3 thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO3 hydrogen sensor prepared by the E-beam method.

A Novel Wearable Electronic Nose for Healthcare Based on Flexible Printed Chemical Sensor Array

A novel wearable electronic nose for armpit odor analysis is proposed by using a low-cost chemical sensor array integrated in a ZigBee wireless communication system. We report the development of a carbon nanotubes (CNTs)/polymer sensor array based on inkjet printing technology. With this technique both composite-like layer and actual composite film of CNTs/polymer were prepared as sensing layers for the chemical sensor array. The sensor array can response to a variety of complex odors and is installed in a prototype of wearable e-nose for monitoring the axillary odor released from human body. The wearable e-nose allows the classification of different armpit odors and the amount of the volatiles released as a function of level of skin hygiene upon different activities.

Facile preparation of graphene–metal phthalocyanine hybrid material by electrolytic exfoliation

In this article, we present a new, facile and efficient electrochemical method for the production of a stable aqueous dispersion of a graphene–metal phthalocyanine hybrid material. The material has been prepared by electrolytic exfoliation of graphite in an electrolyte containing copper phthalocyanine-3,4′,4′′,4′′′-tetrasulfonic acid tetrasodium salt (TSCuPc). Single- and few-layer graphene sheets, decorated with metal phthalocyanine molecules, are generated during the electrolysis and stably dispersed in the electrolyte with no further chemical treatment. Scanning electron/atomic force microscopic characterization shows that the TSCuPc–graphene hybrid structure has a sharp-edged particle morphology with thicknesses ranging from 2 nm to 6 nm, corresponding to 1 to 6 graphene-stacked layers and largely varied lateral dimensions from a few tens to several hundreds of nanometers. In addition, Raman/FTIR/UV-Vis spectra and X-ray diffraction reveal characteristic peaks that suggest that the TSCuPc–graphene hybrid is formed by non-covalent π–π interactions between graphene sheets and metal phthalocyanine and indicate a high quality graphene hybrid structure that can potentially be used in practical applications.

Au-doped zinc oxide nanostructure sensors for detection and discrimination of volatile organic compounds

Abstract Pure and 10% w/w Au-doped zinc oxide (ZnO) nanostructure sensors were produced and used as sensing devices in a portable electronic nose (E-nose). The nanosensors were prepared using thermal oxidation technique with sintering temperature at 700°C under oxygen atmosphere at a flow rate of 500 mL min–1. The sensors were demonstrated to be sensitive to various volatile organic compounds (VOCs), especially ethanol vapour. The E-nose even with only two sensors was efficient to discriminate a number of selected VOCs. The Au-doped sensor shows a significant improvement of sensitivity. The portable E-nose can detect the difference between alcohol beverages and alcohol solutions and can distinguish the difference of white and red wines having the same percentage of alcohol.

Combined quantum mechanics and molecular mechanics simulation of Ca2+/ammonia solution based on the ONIOM-XS method: Octahedral coordination and implication to biology

An extension of the ONIOM (Own N-layered Integrated molecular Orbital and molecular Mechanics) method [M. Svensson, S. Humbel, R. D. J. Froese, T. Mutsubara, S. Sieber, and K. Morokuma, J. Phys. Chem. 100, 19357 (1996)] for simulation in the condensed phase, called ONIOM-XS (XS=eXtension to Solvation) [T. Kerdcharoen and K. Morokuma, Chem. Phys. Lett. 355, 257 (2002)], was applied to investigate the coordination of Ca2+ in liquid ammonia. A coordination number of 6 is found. Previous simulations based on pair potential or pair potential plus three-body correction gave values of 9 and 8.2, respectively. The new value is the same as the coordination number most frequently listed in the Cambridge Structural Database (CSD) and Protein Data Bank (PDB). N–Ca–N angular distribution reveals a near-octahedral coordination structure. Inclusion of many-body interactions (which amounts to 25% of the pair interactions) into the potential energy surface is essential for obtaining reasonable coordination number. Analyse...

Development of Fabric-Based Chemical Gas Sensors for Use as Wearable Electronic Noses

Novel gas sensors embroidered into fabric substrates based on polymers/ SWNT-COOH nanocomposites were proposed in this paper, aiming for their use as a wearable electronic nose (e-nose). The fabric-based chemical gas sensors were fabricated by two main processes: drop coating and embroidery. Four potential polymers (PVC, cumene-PSMA, PSE and PVP)/functionalized-SWCNT sensing materials were deposited onto interdigitated electrodes previously prepared by embroidering conductive thread on a fabric substrate to make an optimal set of sensors. After preliminary trials of the obtained sensors, it was found that the sensors yielded a electrical resistance in the region of a few kilo-Ohms. The sensors were tested with various volatile compounds such as ammonium hydroxide, ethanol, pyridine, triethylamine, methanol and acetone, which are commonly found in the wastes released from the human body. These sensors were used to detect and discriminate between the body odors of different regions and exist in various forms such as the urine, armpit and exhaled breath odor. Based on a simple pattern recognition technique, we have shown that the proposed fabric-based chemical gas sensors can discriminate the human body odor from two persons.

Inkjet printing PEDOT:PSS using desktop inkjet printer

PEDOT:PSS has been used recently into many organic-based devices in order to help charge transfer and improve efficiency of the devices. PEDOT:PSS exhibit various interesting properties. It posses relatively good electrochemical, ambient, and thermal stability of its electrical properties as compared with the other polythiophenes. One aim of manufacturing organic-based device is to lowering the fabrication cost. Due to PEDOT:PSSs stability , it is possible to pattern PEDOT:PSS using inkjet printing. We found that using the CANON IP4500 desktop inkjet printer, the structure of 150 micron could be patterned on PET substrate. By modifying the surface properties of the substrate , the structure of 20 micron could be achieved. The conductivity of inkjet printed PEDOT:PSS could be further enhanced by annealing at 80 C. The conductivity could be 3 times improved. The morphology of the annealed PEDOT:PSS was further investigated using atomic force microscopy(AFM) and the cause for conductivity enhancement could be explained via localization length extension in variable range hopping theory.

Microclimate real-time monitoring based on ZigBee sensor network

Monitoring microenvironment at the farm level has recently become one of the hottest topics in precision agriculture. Zigbee technology is then the most prospective candidate for wirelessly networking those field sensors due to its low cost and power consumption and flexible architecture. The microclimate monitoring system in this research is a suit of equipments based on Zigbee networking to measure the air temperature and humidity in a vast area. Every sensor node works on a cluster tree topology which extends the point-to-point distance up to 1 mile (line of sight), allowing this system to cover large farm using less sensor nodes. A sensor node consists of a micro-controller unit connected with air temperature and humidity sensor chips which are packed in a cylindrical louvered housing to prevent fault air temperature and humidity data from solar radiation. Every sensor node uses energy from a solar cell charged by a charger circuit to a battery package that stores power for use during night time. An energy management scheme was implemented to optimize power use for sending and receiving data. The data from every node were sent to the receiver every 8–30 minutes, depending on backup energy status at each node. The humidity and temperature data are stored on a data-logging PC and only current data are displayed on website