Gamolwan Tumcharern

A-D-A Sensors Based on Naphthoimidazoledione and Boronic Acid as Turn-On Cyanide Probes in Water

Three fluorescence sensors based on naphthoquinoneimidazole and boronic acid (A-D-A system) have been developed with high selectivity for cyanide in water. The fluorescence band at 460 nm was switched on upon substitution of cyanide on sensors in the CTAB micelle.

Electronic absorption spectroscopy probed side-chain movement in chromic transitions of polydiacetylene vesicles.

Thermochromism, solvatochromism, and alkalinochromism of a poly-10,12-pentacosadiynoic acid (poly(PCDA)) vesicle solution are studied by electronic absorption spectroscopy. The spectroscopic profiles reveal different sequences of side-chain movement during the chromic transitions. The gradual hypsochromic shift and reversibility of the purple solution at low temperature in the thermochromic transition indicates that the transition starts with reversible conformational alteration of methylene side chains leading to metastable purple vesicles. Further heating to 80 degrees C or higher eventually causes the hydrogen bonds at the carboxylic head groups to break and turns the vesicle solution to red. The irreversibility of the red vesicles indicates that it is the most thermodynamically stable form. In the ethanolochromism and alkalinochromism, the processes are however induced at the vesicle-media interface, directly bringing about the hydrogen bond breaking. The purple solutions observed in the ethanolochromism and alkalinochromism cannot reverse back to the blue one. The absorption spectra clearly demonstrate that they are mixtures of the blue and red vesicles.

Aqueous sols of oligo(ethylene glycol) surface decorated polydiacetylene vesicles for colorimetric detection of Pb2

A series of ethylene glycol (EG), triethylene glycol (3EG) and pentaethylene glycol (5EG) esters of 10,12-pentacosadiynoic acid (PCDA) are synthesized. The glycol ester lipids can be hydrated and well dispersed in water but they cannot form polydiacetylenes upon UV irradiation. They however can be mixed with PCDA up to 30 mol% and polymerized to form blue sols. The mixed polydiacetylene sols show blue to red thermochromic transition with two-stepped transition temperatures. The first transition temperature decreases with the increase of the glycol ester content as well as the length of their chains indicating greater fluidity of the self-assembled structure due to less collaborative hydrogen bonding among the lipid head groups. These mixed polydiacetylene sol prepared from 30 mol% of the penta(ethylene glycol) ester show linear colorimetric response selectively to Pb(2+) in the range of 5-30 μM.

Colorimetric detection of dichlorvos using polydiacetylene vesicles with acetylcholinesterase and cationic surfactants.

Widespread use of dichlorvos in agriculture has posed serious concern for food and water contamination. A new colorimetric method for the detection of dichlorvos based on polydiacethylene and acetylcholinesterase inhibition is developed. The blue-to-red color transition of poly(10,12-pentacosadynoic acid) vesicles can be induced by myristoylcholine which is enzymatically hydrolyzed by acetylcholinesterase to myristic acid and choline to prevent the color transition. In the presence of dichlorvos, the hydrolytic activity of the enzyme is inhibited that the blue-to-red color transition is restored with a linear correlation to the dichlorvos concentration. Using UV-vis absorption spectrometer, the limit of dichlorvos detection is 6.7 ppb. A naked eye detection of 50 ppb dichlorvos is achievable by using dimiristoylphosphatidylcholine to the diacetylene mixed lipid vesicles.

Synthesis and characterisation of polyaza crown ether derivatives of calix[4]arene and their role as anion receptors

Abstract Novel compounds of polyaza crown ether derivatives of calix[4]arene have been synthesised. Both the ammonium and methyl ammonium derivatives, 25,27-2,2′-[2,2′-((2,5,8-triammonium)nonyl)diphenoxyl]diethyl-p-tert-butylcalix[4]arene trichloride, 1b and 25,27-2,2′-[2,2′-((2,5,8-dimethyl ammonium)nonyl)diphenoxy]dipthyl-p-tert-butylcalix[4] arene, 1d , were studied complexation with a series of anions by 1 H NMR spectroscopy. The ammonium derivatives, 1b , was found to form complexes with Cl − , NO 3 − , AsO 2 − and CO 3 2− ions in which the selectivity for anions varies as CO 3 2− > NO 3 − > AsO 2 − > Cl − . The methylammonium derivative, 1d , however, does not show any sign of anion complexation.

Polydiacetylenes carrying amino groups for colorimetric detection and identification of anionic surfactants

A series of diacetylene lipids carrying primary amine, secondary amine or ammonium head groups are prepared and converted to blue polydiacetylene (PDA) sols by UV irradiation. The blue to pink colorimetric transition of polymerized diacetylenes in the presence of anionic surfactants such as sodium dodecanoate (SDC), sodium docecyl sulphate (SDS), and sodium dodecyl benzene sulphate (SDBS) are observed by the naked eye at the micromolar concentration level while there is no change with cationic surfactants and little response with nonionic surfactants. An identification of common anionic surfactants can be accomplished based on a combination of the colorimetric pattern of structurally diverse PDAs using the principal component analysis technique. Moreover, PDA was successfully fabricated on filter paper and the colorimetric response of PDA embedded on the paper was investigated which allowed the direct colorimetric detection of anionic surfactants.

Fluorescence sensor array for identification of commercial milk samples according to their thermal treatments

Identification of processed milk is of importance for commercial and legal concerns. The fluorescence response patterns induced by fluorophore/protein interactions allow a possible discrimination of processed milk samples corresponding to their thermal treatment. The fluorescence responses of 4 fluorophores upon addition of commercial milk samples in 96-well plate are measured in the range of 400-600 nm using the excitation wavelength at 375 nm. The pattern recognition of the 53,126 fluorescence responses (4 fluorophores×41 wavelengths×4 thermally processed milks×3 brands×3 lots×3 bottles×3 repeats) are analyzed by multivariate statistical methods. Linear discriminant analysis (LDA) successfully recognizes the milk samples according to their thermal processing, i.e. pasteurized milk, sterilized milk, UHT fresh milk and recombined milk (UHT milk having milk powder), with 100% classification accuracy in a cross validation using a leave-one-out technique.

Highly sensitive salicylic fluorophore for visual detection of picomole amounts of Cu2

Four new fluorophores containing multiple fluorogenic branches of phenylene-ethynylene and salicylic acid Cu2+ binding sites are synthesized and evaluated as Cu2+ sensors in aqueous media. The fluorophore, F4, having a triphenylamine core and three fluorogenic branches, possesses superior sensitivity, selectivity and emission properties for fluorescence quenching detection of Cu2+. This fluorophore exhibits the highest Cu2+ quenching sensitivity in aqueous solution; Ksv = 5.79 × 106 M−1. The relatively high fluorescence emission of this fluorophore provides excellent visual contrast in a solid state paper-based sensor that enables naked eye detection of Cu2+ at the picomole level.

Self-assembled coordination nanoparticles from nucleotides and lanthanide ions with doped-boronic acid-fluorescein for detection of cyanide in the presence of Cu2+ in water

The sensor molecule, F-oBOH, containing boronic acid-linked hydrazide and fluorescein moieties was synthesized. For anion sensing applications, F-oBOH was studied in aqueous media. Unfortunately, F-oBOH was found to be hydrolyzed in water. Therefore, a new strategy was developed to prevent the hydrolysis of F-oBOH by applying self-assembly coordination nanoparticles network (F-oBOH-AMP/Gd(3+) CNPs). Interestingly, the nanoparticles network displayed the enhancement of fluorescent signal after adding Cu(2+) following by CN(-). The network, therefore, possessed a high selectivity for detection of CN(-) compared to other competitive anions in the presence of Cu(2+). Cyanide ion could promote the Cu(2+) binding to F-oBOH incorporated in AMP/Gd(3+) CNPs to give the opened-ring form of spirolactam resulting in the fourfold of fluorescence enhancement compared to Cu(2+) complexation without CN(-). Additionally, the log K value of F-oBOH-AMP/Gd(3+) CNPs⊂Cu(2+) toward CN(-) was 3.97 and the detection limits obtained from naked-eye and spectrofluorometry detections were 20μM and 4.03μM, respectively. The proposed method was demonstrated to detect CN(-) in drinking water with high accuracy.

Multifunctional metal and metal oxide hybrid nanomaterials for solar light photocatalyst and antibacterial applications

Abstract While simple mixing of the multiple nanostructural components might not necessarily satisfy the multiple functional requirements, this research work showed that such structural complexity demanded both strategic structural design and deliberate fabrication methods. As such, nanosilver-hybridized WO3 nanofibers incorporating paramagnetic CoFe2O4 nanoparticles were for the first time fabricated following three aspects of morphological control–bulk crystallinity, fiber chemical compositions, and surface modifications. Experimentally, co-precipitation, eletrospinning, and photodeposition were employed to synthesize CoFe2O4 nanoparticles, generate magnetically recoverable solar light-active photocatalyst nanofibers, and decorate them with nanosilver, respectively. The successful synthetic steps represented a facile and scalable route to multifunctional nanocatalyst against waterborne pollutants with organic and microbial constituents via WO3 photocatalytic system. The work extended to nanofiber fabrication using the NS LAB 500 Nanospider machine which allowed for the pilot-scale hybrid nanofibrous catalyst effective under natural sunlight towards elimination of a model waterborne pollutant.Graphical Abstract