 หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : An Alkoxide Free Sol-Gel Synthesis of Nanosized TiO2) ผู้เขียน: Kornvalai Panpae, Suppalak Angkaew, Chiravadee Sritara, Chinda Ngernsuttichaiporn สื่อสิ่งพิมพ์:pdf AbstractNanosized TiO2 with anatase structure has been prepared by a non-alkoxide sol-gel route from an aqueous solution of titanyl sulfate. This paper investigated the influence of stirrer speed on anatase precipitation carried out in batch mode. Stirrer speed was varied between 400 and 1000 rpm. The intensity of stirring determined the final particle size of anatase aggregates in suspension. Changes to primary agglomerate and crystal population due to varying stirrer speed were reported. In our study, the smallest aggregates (mean size of 6-8 nm) were obtained at a stirrer speed of 1000 rpm. It was also found that the anatase to rutile phase transformation began at 800?C of calcination. A calcination treatment, from 400 to 1000?C, was applied. The degree of crystallinity and purity of the synthesized materials were reported. The crystalline anatase particles had an average particle size of 10-20 nm between the calcination temperature 400-600?C. The powders were characterized by powder X-ray diffraction (XRD), the morphology and grain size of the titania particles were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD patterns indicated that the samples were crystalline titania which had very broad and small peaks of anatase phase. The TEM observations showed the vast majority of particles were quasispherical; the average size distribution of particle was about 20 nm. The TEM results supported the conclusions derived from the XRD data. Finally, the amorphous hydrous and crystalline titania particles were characterized by thermogravimetric (TGA) and differential thermal analysis (DTA). |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Development of a Urea Potentiometric Biosensor Based on Gelatin-Immobilized Urease) ผู้เขียน:Kornvalai Panpae, Sutanai Krintrakul, Amornrat Chaiyasit สื่อสิ่งพิมพ์:pdf AbstractUrease (typeIII) purified from Jack bean was immobilized on gelatin beads via cross-linking with glutaraldehyde. The maximum immobilization (70.82%) was observed with a half-life of 385 days and there was practical stability for over a period of 50 days. These beads could be reused more than 10 times (with 24 h intervals) without much loss of enzyme activity (i.e. less than 12%). The immobilized beads were used for the preparation of a new urea biosensor developed from the potentiometric pH glass electrode and the reference calomel electrode with major advantages such as long term operational and storage stability, response time and linear range. The beads, as well as the biosensor, were used to analyse the urea content in clinical samples from the local pathology laboratory. The results obtained with the biosensor were similar to those obtained with the various commonly employed biochemical/ autoanalyzer? methods. These immobilization studies also have a potential role in haemodialysis machines that are used to maintain the urea level in kidney patients and in the construction of a portable or wearable kidney. |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Synthesis of Zn (II)-Oxazoline/Pyridine Derivative Complex as a
Molecular Sensing Ensemble for Aspartate and Histidine) ผู้เขียน:Kornvalai Panpae, Thongthawat Rerkchanchai, Thatree Wongsrichalalai สื่อสิ่งพิมพ์:pdf AbstractSynthetic receptors can readily be converted to optical chemosensors using a displacement
assay and common fluorophores and/or chromophores. Most of them are designed with covalent
attachment between a receptor and a reporter moiety. We now describe the design of spectroscopic
chemosensors bearing Zn (II) chelates with oxazoline/pyridine sites. The current progress of our use of
noncovalently attached indicators to signal binding of analytes are demonstrated. With these systems,
analyte binding which we focus on the selected amino acids, aspartate and histidine, leads to indicator
displacement from the binding cavity, which in turn yields a spectroscopic signal modulation. On the
basis of 1H NMR studies, and preliminary x-ray diffraction analysis, it is clear that Zn (II)-oxazoline/
pyridine derivative receptor cooperatively act to bind a carboxylate site of amino acids. Good agreement
of the binding affinity revealed that our receptor can colorimetrically sense aspartate higher than histidine.
In addition, it is demonstrated that careful choice of a chelating indicator with tuned affinity toward the
receptor, lower than that of the envisaged analyte, higher than that of the interferent, can provide
discrimination in sensing of a desired substrate. |