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Microfluidic magnetic switching valves based on aggregates of magnetic nanoparticles: Effects of aggregate length and nanoparticle sizes
(2017-01-15)
Jiemsakul, Thanakorn
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Manakasettharn, Supone
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Kanharattanachai, Sivakorn
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Wanna, Yongyuth
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Wangsuya, Sujint
We demonstrate microfluidic switching valves using magnetic nanoparticles blended within the working fluid as an alternative microfluidic flow control in microchannels. Y-shaped microchannels have been fabricated by using a CO<inf>2</inf> laser cutter to pattern microchannels on transparent poly(methyl methacrylate) (PMMA) sheets covered with thermally bonded transparent polyvinyl chloride (PVC) sheets. To examine the performance of the microfluidic magnetic switching valves, an aqueous magnetic nanoparticle suspension was injected into the microchannels by a syringe pump. Neodymium magnets were then employed to attract magnetic nanoparticles and form an aggregate that blocked the microchannels at a required position. We have found that the maximum volumetric flow rate of the syringe pump that the magnetic nanoparticle aggregate can withstand scales with the square of the external magnetic flux density. The viscosity of the fluid exhibits dependent on the aggregate length and the size of the magnetic nanoparticles. This microfluidic switching valve based on aggregates of magnetic nanoparticles has strong potentials as an on-demand flow control, which may help simplifying microfluidic channel designs.
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TiO2/Pt/TiO2 Sandwich Nanostructures: Towards Alcohol Sensing and UV Irradiation-Assisted Recovery
(2017-01-01)
Maolanon, Rungroj
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Wongwiriyapan, Winadda
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Pratontep, Sirapat
The TiO<inf>2</inf>/Pt/TiO<inf>2</inf> sandwich nanostructures were synthesized by RF magnetron sputtering and demonstrated as an alcohol sensor at room-temperature operation with a fast recovery by UV irradiation. The TiO<inf>2</inf>/Pt/TiO<inf>2</inf> layers on SiO<inf>2</inf>/Si substrate were confirmed by Auger electron spectroscopy with the interdiffusion of each layer. The TiO<inf>2</inf>/Pt/TiO<inf>2</inf> layers on printed circuit board show the superior sensor response to alcohol in terms of the sensitivity and stability compared to the nonsandwich structure, that is, the only Pt layer or the TiO<inf>2</inf>/Pt structures. Moreover, the recovery time of the TiO<inf>2</inf>/Pt/TiO<inf>2</inf> was improved by UV irradiation-assisted recovery. The optimum TiO<inf>2</inf>/Pt/TiO<inf>2</inf> with thicknesses of the undermost TiO<inf>2</inf> layer, a Pt layer, and the topmost TiO<inf>2</inf> layer being 50 nm, 6 nm, and 5 nm, respectively, showed the highest response to ethanol down to 10 ppm. Additionally, TiO<inf>2</inf>/Pt/TiO<inf>2</inf> shows an excellent sensing stability and exhibits different sensing selectivity among ethanol, methanol, and 2-propanol. The sensing mechanism could be attributed to the change of Pt work function during vapor adsorption. The TiO<inf>2</inf> layer plays an important role in UV-assisted recovery by photocatalytic activity and the topmost TiO<inf>2</inf> acts as protective layer for Pt.
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Photoresponse of composites of zinc oxide and poly(3-hexythiophene) under selective UV and white-light illumination
(2016-12-01)
Pattamang, Pattaraluck
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Jiramitmonkon, Kanpitcha
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Piyakulawat, Phimwipha
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Asawapirom, Udom
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Tantisantisom, Kittitpong
We investigate charge transport in UV sensing devices based on organic-inorganic semiconductor composites with the metal-semiconductor-metal (MSM) structure. Composite materials of zinc oxide (ZnO) nanoparticles and poly(3-hexylthiophene) (P3HT) were prepared by drop-casting their colloidal mixture in chloroform onto low-cost interdigitated copper electrodes. The current-voltage characteristics of the devices were investigated under both dark and illuminated conditions in the UV–visible range. The highest photoresponse was observed for an optimal P3HT:ZnO ratio of 1:8 w/w in the wavelength range between 310 and 380 nm. The dynamic response was investigated by pulsing a 365 nm UV light with a long period to reveal the response time of 4 s and the recovery time of less than 1 s. The photoresponse of the materials was also investigated for a shorter period of UV pulsing, using a rotating chopper. The response time and recovery time for the short UV pulse were found to be approximately 20 m and 25 m, respectively. The dual response times should stem from the presence of two types of semiconductor materials, namely ZnO with a high electron mobility and P3HT with a moderate hole mobility. To probe the charge generation and transport mechanisms, we further investigate the photoresponse using UV pulsing under background white light of different intensities, and vice versa. The background white light was found to deteriorate the UV photoresponse of the materials. On the other hand, the background UV illumination produced an anomalous photoresponse pattern with the white light pulsing. Understanding the charge transport mechanisms for composite materials is highly important for future applications in low-cost UV sensors and tunable optoelectronic devices.
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Efficiency of SPIONs functionalized with polyethylene glycol bis(amine) for heavy metal removal
(2016-09-15)
Wanna, Yongyuth
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Chindaduang, Anon
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Tumcharern, Gamolwan
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Phromyothin, Darinee
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Porntheerapat, Supanit
Hybrid magnetic nanoparticles based on poly(methylmethacrylate) (PMMA) and super-paramagnetic iron oxide nanopaticles (SPIONs) with selective surface modification has been developed for heavy metal removal by applying external magnetic fields. The nanoparticles were prepared by the emulsion polymerization technique in an aqueous suspension of SPIONs. The hydrolysis of carboxyl functional group was then applied for grafting polyethylene glycol bis(amine)(PEG-bis(amine)) onto the PMMA-coated SPIONs. The morphology, the chemical structure and the magnetic properties of the grafted nanoparticles were investigated. The efficiency of the hybrid nanoparticles for heavy metal removal were conducted on Pb(II), Hg(II), Cu(II) and Co(II) in aqueous solutions.The metal concentration in the solutions after separation by the hybrid nanoparticles was determined by inductively coupled plasma optical emission spectrometer (ICP-OES). The results show the heavy metal uptake ratios of 0.08, 0.04, 0.03, and 0.01 mM per gramme of the grafted SPIONs for Pb(II), Hg(II), Cu(II), and Co(II), respectively. A competitive removal of Cu(II), Pb(II), Co(II) and Hg(II) ions in mixed metal salt solutions has also been studied.The heavy metal removal efficiency of the hybrid nanoparitcles was found to depend on the cation radius, in accordance with capture of metal ions by the amine group.
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Relationship between overall difference decision and electronic tongue: Discrimination of civet coffee
(2016-07-01)
Lopetcharat, Kannapon
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Kulapichitr, Fareeya
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Suppavorasatit, Inthawoot
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Chodjarusawad, Thanawee
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Phatthara-Aneksin, Anat
This paper demonstrates a new approach to relate electronic tongue (E-tongue) to human perception for fine quality of beverage. Six civet, one weasel and one non-civet coffees were chosen as the testing platform. The sensory test based on the overall difference method by pair comparison followed by sureness-rating tasks was divided into three experiments. In each, 12-14 consumers were asked to express differences in six pairs of hot brew coffee samples on a four-point scale. The results were analyzed by the Multi-Dimensional Scaling (MDS) analysis. An in-house electronic tongue based on cyclic voltammetry and the Principal Component Analysis (PCA) was applied to measure the coffee samples, alongside the panel test. The relationship between PCA and MDS solutions was obtained by Generalized Procrustes Analysis (GPA), which reveals a strong correlation between E-tongue and human perception. Both were able to identify differences between all coffee samples from different sources.
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Hybrid gas sensor based on platinum nanoparticles/poly(methyl methacrylate)-coated single-walled carbon nanotubes for dichloromethane detection with a high response magnitude
(2016-05-01)
Muangrat, Worawut
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Yordsri, Visittapong
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Maolanon, Rungroj
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Pratontep, Sirapat
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Porntheeraphat, Supanit
A dichloromethane (DCM) sensor with a high response magnitude was successfully fabricated using the integration of single-walled carbon nanotubes (SWNTs), poly(methyl methacrylate) (PMMA) and platinum nanoparticles (Pt NPs). A pristine SWNT network was first formed by drop-casting onto printed circuit board (PCB) substrates. Next, PMMA was coated onto the pre-dropped SWNT network by spin coating using a PMMA-toluene solution, followed by the deposition of Pt NPs by electron-beam evaporation (hereafter referred to as Pt/PMMA/SWNT). The Pt/PMMA/SWNT enabled an approximately 69-fold improvement in DCM detection compared to pristine SWNT. The high response magnitude of the Pt/PMMA/SWNT was successfully achieved because of the incorporation of PMMA and Pt functions. Swelling of the PMMA matrix as a result of DCM adsorption leads to PMMA volume expansion, thereby increasing the SWNT-SWNT distance, which results in an increase in the resistance. Pt NPs promote the dissociation of DCM to CO, and consequently the CO oxidation on the Pt NPs catalyst and electron donation from Pt NPs to SWNTs, resulting in an increase in the resistance. Moreover, a linear relationship was obtained between the sensor response of the Pt/PMMA/SWNT and the concentration of DCM. These results suggest that the integration of SWNTs with PMMA and Pt NPs is a promising approach for improving DCM detection at room temperature.
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Preparation and characterization of PEG bis(amine) grafted PMMA/SPION composite nanoparticles
(2016-03-01)
Wanna, Yongyuth
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Pui-ngam, Rachineewan
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Nukeaw, Jitti
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Chindaduang, Anon
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Tumcharern, Gamolwan
We report novel magnetic composite nanoparticles for heavy metal ion separation. Superparamagnetic iron oxide nanoparticles (SPIONs) and were coated with poly(methylmethacrylate) (PMMA) by emulsion polymerization process in the aqueous suspension of SPIONs. In addition, the hydrolysis of carboxylic functional groups onto the PMMA-coated SPIONs was grafted with Polyethylene glycol bis(amine). Then, the functional group structures were investigated by Fourier transforms infrared spectroscopy (FTIR). The morphology of PMMA/SPIONs was determined by transmission electron microscopy (TEM) and atomic force microscope (AFM). The magnetic property was investigated by the vibrating sample magnetometer (VSM). The metal concentration in the solution after separation using the nanoparticles was determined by inductivity coupled plasma optical emission spectrometer (ICP-OES). Furthermore, we demonstrate that the efficiencies of the heavy metal ion removal for Cu(II), Mn(II), Zn(II), Cd(II), Pb(II), Co(II) and Ni(II) are 80.0%, 57.7%, 54.3%, 40.0%, 34.8%, 32.5% and 30.2% by weight, respectively. The nanoparticles also exhibit some selectivity for copper, manganese and zinc. The results show that the composite nanoparticles are extremely promising for heavy metal ion separation.
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Poly(methyl methacrylate) and thiophene-coated single-walled carbon nanotubes for volatile organic compound discrimination
(2016-02-01)
Muangrat, Worawut
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Chodjarusawad, Thanawee
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Maolanon, Rungroj
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Pratontep, Sirapat
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Porntheeraphat, Supanit
Poly(methyl methacrylate) (PMMA) and thiophene-coated single-walled carbon nanotubes (SWNTs) were fabricated for use in volatile organic compound (VOC) detection. Pristine SWNTs were separately coated with PMMA (PMMA/SWNTs) and thiophene (thiophene/SWNTs) by spincoating. Pristine SWNTs showed the highest response to methanol, while PMMA/SWNTs enabled 5.4-fold improved dichloromethane detection and thiophene/SWNTs enabled 1.4-fold improved acetone detection compared with pristine SWNTs. The sensor response of PMMA/SWNTs to dichloromethane and that of thiophene/SWNTs to acetone can be attributed to the Hildebrand solubility parameter (HSP). The more similar the HSP, the higher the sensor response. The sensor response of pristine SWNTs to methanol is related to the diffusion coefficient and molecular size. The relationships between the vapor concentration and sensor response of PMMA/SWNTs to dichloromethane and thiophene/SWNTs to acetone are based on Henry's adsorption isotherm, while that of pristine SWNTs to methanol is based on the Henry-clustering model. Principal component analysis (PCA) results show that dichloromethane, acetone, and methanol were successfully discriminated.
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Surfactant effect on the physicochemical characteristics of γ-oryanol-containing solid lipid nanoparticles
(2016-01-05)
Karn-orachai, Kullavadee
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Smith, Siwaporn Meejoo
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Saesoo, Somsak
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Treethong, Alongkot
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Puttipipatkhachorn, Satit
Surfactants employed in production of solid lipid nanoparticles (SLNs) play a major role on physical stability of nanoparticles, and the extent of drug dissolution and permeability into cells. In this study, cationic (cetyl pyridinium chloride), anionic (sodium dodecyl sulfate) and non-ionic (Tween 80) surfactants, as well as its combinations, were employed to formulate compritol based SLNs using γ-oryzanol as a model drug. The physicochemical properties of drug-loaded SLNs are influenced by the surfactant composition systems. Surfactant blend systems gave SLNs with superior stability compared with single surfactant systems due to enhanced incorporation of the drug within the solid lipid matrix. This may be due to synergic effects arising from electrostatic repulsion of the surfactant charges (ionic), the steric hindrance of surfactant structure (non-ionic), and ion-pairing effects between cationic and anionic ones. The cytotoxicity results demonstrated that positively charged SLNs can be uptaken into cells to a high extent. Nevertheless, the mixed surfactant systems (cationic/non-ionic and cationic/anionic/non-ionic), have remarkable advantages providing SLNs with high cell internalization capability, however, low cytotoxicity. This systematic investigation may give an insight into the practical integration of multi-surfactant systems to achieve non-toxic and highly effective drug delivery systems.
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A study and characterization of photophysical properties of fluorene derivative thin flim
(2016-01-01)
Sirijarutus, Wattanaruk
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Charoensuwan, Sittan
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Thanakit, Prawonwan
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Pratontep, Sirapat
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Phromyothin, Darinee Sae Tang
An emissive layer, fluorene derivative, was performed for organic light-emitting device properties. The preparation of fluorene derivative thin film by spin coating and convective technique was studied the band diagram of thin films which its properties out as the energy gap (Eg). UV-Visible spectrophotometer has been used to investigate the thin film properties. The results indicate spectacular property which occurs in the optical properties, fluorescence in thin film and luminescence as a green light in device that it could be applied as emissive layer for organic light-emitting diodes (OLEDs) due to the appropriate work function with cathode and anode, aluminum metal and indium tin oxide layer (ITO), respectively.

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