Vimolvan Pimpan

Green synthesis of silver nanoparticles for ammonia sensing.

Silver nanoparticles synthesized by a reagent less method involving only UV radiation have been used in colorimetric assay for the detection of ammonia in solution. The silver nanoparticles were synthesized by the exposure of a silver nitrate solution to a low-power UV source in the presence of poly(methacrylic acid) (PMA), which acted both as reducing and capping agent. The synthesis of the silver nanoparticles was studied by monitoring the changes in position and amplitude of the localized plasmon resonance (LSPR) band using UV-vis spectroscopy. The morphology of the particles was studied using transmission electron microscopy which confirmed the formation of spherical particles with an average particle size around 8 nm. Interestingly, the silver nanoparticles solution was found to display a strong color shift from purple to yellow upon mixing with increasing concentration of ammonia ranging from 5 to 100 ppm. Hence, the nanoparticles prepared with this method could be used as colorimetric assay for sensing applications of ammonia in water.

Alkaline Stability of Polyaniline Synthesized Using Pulsed Inductively Coupled Plasma Device

The stability of polyaniline synthesized using pulsed inductively coupled plasma device was studied in alkaline media. Polyaniline was exposed to potassium hydroxide at 25°C and 90°C for various time intervals up to 4 months. An increase in %mass loss, the decreases in the absorbance intensities of polyaniline characteristic bands in FT-IR and UV-Visible spectra and the reduction of the conductivity with increasing exposure time to alkaline solution and/or temperature indicated the increases in the conversion of polyaniline into its base form and the degradation of its structure. The results also suggested that the temperature was the main factor affecting its conductivity in alkaline stability since exposing at 25°C and 90°C caused the conductivity to decrease from 4.53x10-8 S.cm-1 to 1.74x10-8 S.cm-1 and 8.15x10-9 S.cm-1 in 4 months, respectively. Therefore, this polyaniline synthesized via this system may be suitable for the applications at room temperature where alkaline stability is needed.

pH Effect on Characteristics and Ammonia Sensing of Silver Nanoparticles Synthesized in the Presence of Tannic Acid

Silver nanoparticles were synthesized using silver nitrate as a silver precursor in the presence of tannic acid under UV radiation for 60 minutes. Various pH conditions were employed in the synthesis in order to study its effect on characteristics and ammonia sensing of the synthesized nanoparticles. The images obtained from transmission electron microscope revealed the formation of the spherical particles with average diameters in the range of 10-40 nm depending on pH conditions. It was found that using acidic condition resulted in yellow silver nanoparticles colloids with bigger particles and exhibiting a UV-visible absorbance peak at around 435 nm whereas using other conditions yielded greenish-yellow colloids with smaller particles and having two absorbance peaks at around 370 and 430 nm. After adding 100 ppm of ammonia, TEM images revealed the aggregation and the changes in size and shape of the silver nanoparticles. The color of the silver nanoparticles colloids synthesized using acidic condition changed to orange-yellow color. However, other pH conditions caused the color of the colloids became darker. These color changes were observed by the naked eyes.

Quality Assurance Information System of Chulalongkorn University

Data management is one of the necessary processes in quality management. Chulalongkorn University has developed the tool for this process called Quality Assurance Information System (QAIS). This system was originally developed based on “Lotus Notes” software. Currently, its system consists of the processes of data input, reference input, data checking and correction, data evaluation, and report preparation. By using this system, the data collection process changes from “Offline” to “Online via Intranet.” It has been used to support internal and external quality assessments according to national quality standards of Thailand since this system can connect and transfer data to the national database called CHE QA Online (Commission on Higher Education Quality Assessment online system). Chulalongkorn University was nationally awarded by the Office of the Public Sector Development Commission in the category of Servicing Innovation for implementing this system. Therefore, Chulalongkorn University would like to share and exchange the concept and the operation of this system for further improvement.

Effects of UV Radiation and pH of Tannic Acid Solution in the Synthesis of Silver Nanoparticles

The reductions of silver nitrate by tannic acid at various pH with and without UV radiation at room temperature were done in order to study the effects of UV radiation and pH of tannic acid solution in the synthesis of silver nanoparticles. The results from UV-Visible spectroscopy, dynamic light scattering method and transmission electron microscopy indicated that using UV radiation resulted in silver nanoparticles with smaller particles and narrower size distribution at every pH. The results also revealed that smallest particles without agglomeration were obtained when alkali condition was applied. Therefore, the suitable condition for synthesizing silver nanoparticles in this research was to use UV radiation and tannic acid solution having pH of 8.0.

Synthesis of Polyaniline by Pulsed Plasma Polymerization Using Theta-Pinch Device

Polyaniline was synthesized by pulsed plasma polymerization using a theta-pinch device. The process was done using oxygen plasma at a voltage of 20 kV, a pressure of 2 Pa and a discharging current of 125 kA. The number of the plasma shots was varied from 10, 15, 20, 25, to 30 shots. This parameter significantly affected the chemical structures of the synthesized polyanilines as revealed by FTIR spectra. While all synthesized polyaniline exhibited the characteristic peaks of quinoid ring and benzenoid group, the peaks corresponding to the formation of oxygen containing groups was found when high numbers of plasma shots were employed. This also caused the difference in UV-VIS absorption of these polyanilines. The highest conductivity of polyaniline was obtained when 20 shots of oxygen plasma were used. At this condition, polyaniline had a semi-crystalline structure and the thermal decomposition temperature at 262oC.

Synthesis and Characterization of Fluorescent Acrylamide Water Soluble Macromer

Fluorescent acrylamide water soluble macromer was synthesized from dimethylaminopropylmethacrylamide-9-(chloromethyl)anthracene quaternary ammonium salt monomer using an inverse emulsion polymerization method. It was initiated by benzoylperoxide and stabilized by a co-emulsifier system consisting of Span®80 and Tween®60 dispersed in a continuous phase of cyclohexane with HLB value of 6.42. The polymerization was done at 80°C for 4 hours. The obtained macromer exhibited similar functional groups, ultraviolet-visible absorption and fluorescent emission but different solubility when compared to the monomer. Further analyses by proton nuclear magnetic resonance spectroscopy and mass spectrometry revealed the chemical structure of the macromer as a dimer of the monomer containing carcon-carbon double bonds.