Radchada Buntem

Facile synthesis of silica monolith doped with meso-tetra(p-carboxyphenyl)porphyrin as a novel metal ion sensor.

A novel metal ion sensor was prepared using silica monolith doped with meso-tetra(p-carboxyphenyl)porphyrin. The doped material was prepared using TEOS:EtOH:H(2)O:HCl:porphyrin molar ratios of 1:5:7:3.1 x 10(-2):2.3 x 10(-5), respectively. The mixture was kept 16 days for the gelation process and then the wet gel was dried at 55-60 degrees C for 3 days. The porphyrin-doped monolith obtained was kept in 1 M metal salt solution for 2 days. The visible spectrum of the metal-coordinated porphyrin-doped monolith was compared with the uncoordinated porphyrin-doped monolith. The spectra show the characteristic maxima for Cu(2+) at 543 nm, for Zn(2+) at 522, 559, and 596 nm, for Pb(2+) at 531 and 559 nm, and for Ni(2+) at 522 and 551 nm. The metal coordinated to the silica monolith could be removed by washing with 1 M HNO(3). However the Cu(2+) could not be eluted by acidic solution due to its strong bonding to the porphyrin. The results show that this porphyrin-doped monolithic biomaterial is a promising sensor for metal ions in wastewater and other harsh environments.

Volatile organic compound sensor arrays based on zinc phthalocyanine and zinc porphyrin thin films

In this paper, organic thin films based on two types of metal-macromolecules, i.e., zinc-2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (ZnTTBPc) and zinc-5,10,15,20-tetra-phenyl-21H,23H-porphyrin (ZnTPP), were demonstrated to discriminate among diverse volatile organic compounds (VOCs) even if they have very similar functional group. The ZnTTBPc and the ZnTPP thin films have been prepared by spin coating technique and then were tested for their optical response to VOCs, which share a similar carbonyl (C = O) group, namely acetone, formaldehyde (in a mixture form with methanol) and acetic acid, based on UV-Vis absorption. The transduction employs the optical response of selected spectral ranges arranged in an array configuration, which is then subjected to the principal component analysis (PCA). The PCA results have shown successful discrimination of these VOCs. Density functional theory (DFT) calculation was employed to study the interactions between these VOCs and the sensing materials. The calculation yields different degrees of interactions for each VOC, in compliment with the experimental results. This work supports the prospects of this organic sensor for beverage industry where VOCs are abundant in their products.

Fluoride and Antimony-Doped Tin Oxide Film by Spray Pyrolysis

Thin films of undoped, fluoride- and antimony- doped tin oxide on glass were prepared by spray pyrolysis technique. The aerosols were atomized from precursor solution by a commercial ultrasonic generator. Tin chloride(SnCl2.2H2O), ammonium fluoride (NH4F), and antimony chloride (SbCl3) were used as a source for tin, fluoride, and antimony respectively. For the undoped tin oxide film, the solution of 0.8 M tin chloride was used as a precursor solution. While fluoride-doped tin oxide films (FTO), the solution of 0.8 M SnCl2.2H2O in ethanol and varying amounts of NH4F dissolved in 0.2 M HCl (0.6 mL) were used as a precursor solution. The doping concentrations of NH4F were 0, 0.2, 0.3, 0.4, 0.5 and 0.6 M. For the antimony- doped tin oxide films (ATO), the doping concentrations of SbCl3 dissolved in butanol (10 mL) are 0, 0.016, 0.032, 0.048, 0.064 and 0.080 M. The aerosols were sprayed on the hot glass substrates by air at a flow rate of 1 L/minute through a PVC and glass tubing for 20 minutes for every solution. Substrate temperature was kept at 320 ± 15 °C for undoped and fluoride-doped tin oxide films and at 390 ± 20 °C for antimony- doped tin oxide films. The electrical and optical properties of the films were characterized by four-point probe measurement and UV/VIS spectrophotometer. The best FTO film exhibits the resistivity of 53.83 W-cm and the light transmission of 88.18%. While the best ATO exhibits the resistivity of 61.03 W-cm and the light transmission of 86.45%.

Studies on the Deterioration of Ancient Thai Manuscripts

Various Thai manuscripts, commonly made from Khoi, suffer the severe deterioration primarily from the degradation of cellulose. Temperature, light, humidity, oxygen, pollution, and microorganisms are the main environmental factors for the conditions of manuscript collections. The degree of the cellulose deterioration can be studied by scanning electron microscopy (SEM), attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD). The morphology of the sample was revealed by Scanning Electron Microscopy. The fiber disintegration and the presence of inorganic particles can be found on the paper surface. The ATR-FTIR results showed the characteristic functional groups of cellulose as follows: nOH (3650–3100 cm-1), nCH (3000–2850 cm-1), dOH (~1640 cm-1), dCH (1420-1300 cm-1), nC-O-C of the b-glucosidic linkage (~1100 cm-1), and dCO or CC (~910 cm cm-1). The presence of inorganic filling, CO32- salt (~1400 cm-1) could not be determined explicitly due to the signal overlap with dCH. The relative intensities of the absorption peaks in dCH of the ancient paper samples are different to those of the new khoi paper. The X-ray diffraction of each sample showed the characteristic peaks of crystalline fraction at 2q between 22.0º and 23.0º and the amorphous fraction at 2q between 15.0º and 16.0º. However, the intensity ratio of the crystalline and amorphous phases for the ancient paper is less than that of the new paper.

XANES Studies on the Oxidation States of Copper Ion in Silicate Glass

The silicate glass was prepared using rice husk as the source of silica. The base glass formula is composed of SiO2 (from rice husk ash), Na2CO3, K2CO3, ZnO, H3BO3, CaO and Al2O3 or Al. CuO was used as the colorant in the glass matrix in the absence and presence of reducing agent. The color of the glass obtained was varied from dark blue to blue depending on the amount of CuO and reducing agent. The expansion coefficients of copper doped glass are in the range of 12.43 x 10-6 - 14.35 x 10-6 (°C-1) which is common for the silicate glass. The finger prints of the bond vibrations were studied using IR spectroscopy. While the oxidation state and the coordination information of the copper ion in the glass matrix were investigated using X-ray absorption spectroscopy. In the absence and presence of reducing agent, Cu+ and Cu2+ exist in the glass matrix. However, in the presence of reducing agent, the amount of Cu+ in the glass matrix is higher.

Studies on the Deterioration of the Cordon of the Most Illustrious Order of Chulachomklao

The Cordon of the Most Illustrious Order of Chulachomklao was one of the insignia that King Rama the fifth gave to the ladies of the court to present their goodness. One component of this object was made from silk and decorated by needled the silvered and golden thread as the laurel and the initial of King’s royal name. This ancient silk suffers from discoloration, low strength and severe deterioration. Amino acids in fibroin were photo-degraded under UV-irradiation and heat. Three silk samples, S-Raw, S-White and S-Ancient, were selected for ATR-FTIR and XRD analyses. FTIR spectroscopy can be used for the determination of the molecular structure of silk fibroin. The characteristic bands of silk fibroin corresponding to amide I, II, and III were found in all silk samples. The skeletal vibrations were also observed. Two degradation estimators, EAmideI/II and EcC=O2 were calculated and used to qualitatively estimate the degree of degradation due to oxidation and crystallinity of silk fibroin respectively. The results showed the higher degree of degradation and lower crystallinity of A-Ancient. The X-ray diffraction of S-Ancient showed the broader and weaker characteristic peaks at 2 theta of ∼ 20o indicating the lower crystallinity.

Morphological Studies on Microstructure of Thai Ancient Glass Beads

Various ancient glass beads in prehistorical - historical period (around 2500-1200 BP) from the collection of the Banraiprachasawan local museum (A. Pisalee, Nakhon Sawan) were studied to determine elemental compositions and morphologies using electron probe microanalysis (EPMA) and scanning electron microscopy/energy dispersive x-ray analysis (SEM/EDX). The colors of the beads range from blue to red brown. From the EPMA data, all beads contain copper in the glass matrices. The SEM/EDX showed differences in the microstructures of the glass beads. The transparent blue, greenish blue and light green beads contain small particles of tin oxide while the opaque orange or red brown beads contain both copper oxide and tin oxide particles. The forms of copper oxide in the orange and red brown beads were proposed from previous work: Cu2O in the orange glass and copper metal in the red brown glass.