Nongnit Morakot

A reversible Em-FRET rhodamine-based chemosensor for carboxylate anions using a ditopic receptor strategy

A reversible rhodamine-based sensor (L1) capable of undergoing excimer-fluorescent resonance energy transfer (Em-FRET) was designed and synthesized using a ditopic receptor strategy. Addition of Cu2+ ions to a solution of L1 induced a ring-open conformation of spirolactam (Em-FRET ON), whilst ring closure was induced upon addition of CH3COO− (Em-FRET OFF).

Optical chemosensors for Hg2+ from terthiophene appended rhodamine derivatives: FRET based molecular and in situ hybrid gold nanoparticle sensors

A multifunction sensor based on rhodamine B with a terthiophene substituent has been developed as a highly sensitive chemosensor for Hg2+. This method is mainly based on Hg2+-induced spirocycle opening leading to fluorescence and colorimetric enhancement. The binding properties of a terthiophene appended rhodamine based fluorescence chemosensor (RhoT) was studied using the fluorescence resonance energy transfer (FRET) process, and RhoT displayed highly selective fluorescence enhancement and a color change in the presence of Hg2+. Moreover, the in situ formation of gold nanoparticle/conducting polymer nanocomposite based-chemosensors (AuNPs-RhoT) was achieved to explore the sensitive and selective detection of Hg2+ in aqueous solution over 12 other metal ions using a colorimetric technique. The hybrid sensor became aggregated in solution in the presence of Hg2+ by an ion-templated chelation process, which caused an easily measurable change in the emission spectrum of the particles and provided an inherently sensitive method for Hg2+ detection in aqueous solution.

Preparation and Morphology Study of Biodegradable Chitosan/Methoxy Poly(ethylene glycol)-b-Poly(ϵ-caprolactone) Nanocomposite Films

Abstract Nanocomposite chitosan-based films containing nanoparticles of methoxy poly(ethylene glycol)-b-poly(ϵ-caprolactone) (MPEG-b-PCL) diblock copolymer were prepared by forming nanoparticles in chitosan solution before suspension-solution casting. Films with chitosan/MPEG-b-PCL composite ratios of 90/10, 80/20, and 70/30 (w/w) were prepared and investigated. From FT-IR analysis, it was found that intermolecular bonds exist between chitosan and MPEG-b-PCL. The film surface and cross section of the nanocomposite films was studied by scanning electron microscopy (SEM). The surfaces of the nanocomposite films were found to be rougher than those observed for the chitosan film. Nanoparticles of approximately 200 nm in size with spherical shape were dispersed in the nanocomposite films. In addition, the nanopores were found at the film and cross section surface. The thermal properties of the nanocomposite films were determined by differential scanning calorimetry and found to be strongly dependent upon the composite ratios. Film transparency of the nanocomposite films was lower than that obtained for the chitosan film. It was found that the film transparency decreased as the MPEG-b-PCL ratios increased.

Fluorescent sensors based on BODIPY derivatives for aluminium ion recognition: an experimental and theoretical study.

AbstractTwo BODIPY derivative sensors for metal ion recognition containing 10-(4-hydroxyphenyl) (L1) and 10-(3,4-dihydroxyphenyl) (L2) were synthesized in a one-pot reaction of benzaldehyde derivative and 2,4-dimethylpyrrole in the presence of trifluoroacetic acid as catalyst. The binding abilities between these sensors and 50 equivalents of Na+, K+, Ag+, Ca2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+, Al3+ and Cr3+ ions were studied using UV–vis and fluorescent spectroscopic methods. Of all the metal ions tested, Al3+ ion showed the greatest decrease in intensity in the spectra of the sensors, and therefore Al3+ ion forms the strongest complex. The binding abilities of BODIPY receptors with Na+, Ag+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+ and Al3+ ions were also investigated using density functional theory (DFT) calculations at B3LYP/LanL2DZ theoretical level. The calculated results point to the same conclusion. DFT calculations also provided the HOMO–LUMO energy levels, which can explain the spectrum change upon complexation. FigureGraphical structure, fluorescent spectra, frontier orbital energy diagrams and electron-transfer paths in sensor L1, and after attachment with Al3+ ion.

Optical chemosensors for Cu(II) ion based on BODIPY derivatives: an experimental and theoretical study

AbstractTwo BODIPY derivatives for Cu2+ ion chemosensors containing 4-[2-(diethylamino)-2-oxoethoxy]phenyl (BDP1) and 3,4-bis[2-(diethylamino)-2-oxoethoxy]phenyl (BDP2) were synthesized by coupling appropriate N,N-diethyl-2-(4-formylphenoxy)acetamide and 2,4-dimethylpyrrole moieties in the presence of trifluoroacetic acid and anhydrous dichloromethane at room temperature. The binding abilities between these chemosensors and 50 equivalents of Na+, K+, Ag+, Ca2+, Fe2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions were studied using UV-vis and fluorescence spectrophotometry. The results show that, compared to other ions, both the UV-vis absorption and fluorescence emission intensity of BDP2 decreased dramatically when Cu2+ ion was added. To explain this behavior, ab initio quantum chemical calculations were performed using correlated second-order Møller-Plesset perturbation theory (MP2/LanL2DZ). The calculated orbital energies indicated that the decrease in UV-vis absorption intensity and the quenching of fluorescene emission were due to the single-electron reduction of Cu2+ to Cu+ ion. FigureOptimized structure, fluorescent spectra, frontier orbital energy diagrams and electron-transfer paths in receptor BDP2 before and after attachment to Cu2+ ion

Novel selective and sensitive optical chemosensor based on phenylfluorone derivative for detection of Ge(IV) ion in aqueous solution

A water soluble chemosensor for Ge4+ ion based on fluorone derivative containing 3,4-bis(2-(diethylamino)-2-oxoethoxy)phenyl (R8) has been synthesized. The binding abilities between R8 and 10 equiv. of Na+, K+, Ca2+, Fe2+, Cu2+, Cd2+, Hg2+, Pb2+, Al3+, Cr3+, Fe3+ and Ge4+ ions in 1% v/v EtOH-water (tris-buffer pH 7.0) were studied using UV-vis and fluorescence spectrophotometry. When observed by naked-eyes, the color of R8 changed from yellow-orange to pink and the fluorescent color changed from green to non-fluorescence when complexed with Ge4+ ion. The spectral analysis showed that UV-vis absorption and fluorescence emission intensity of R8 decreased dramatically when Ge4+ ion was added comparing with other ions. To explain this behavior, the quantum calculation was performed using the hybrid density functional at B3LYP /LanL2DZ level of theory. The calculated orbital energies indicated that the decreasing of UV-vis absorption and the quenching of fluorescence were due to the complexation induced metal to ligand charge transfer. The association constants (Ka) of R8-Ge4+ complexes calculated from Benesi-Hildebrand equation was 6.21 × 105 M-1. The UV-vis detection limit for Ge4+ was 4.40 × 10-7 M which was three orders of magnitude lower than those of Al3+, Cd2+, Cu2+ and Na+ ion.

Mechanical properties and hydrolytic degradation of methoxy poly(ethylene glycol)-b-poly(DL-lactide-coglycolide- co--caprolactone) diblock copolymer films

Abstract Biodegradable films of methoxy poly(ethylene glycol)-b-poly(DL-lactideco- glycolide-co-ε-caprolactone) diblock copolymers (MPEG-b-PDLLGCL) were prepared by solution casting method. Effects of MPEG block length and DLL:G:CL ratio of the MPEG-b-PDLLGCL films on their mechanical properties and hydrolytic degradation were studied and discussed. It was found that the mechanical properties of films were strongly dependent on glass transition temperatures (Tg) of the diblock copolymers. The hydrolytic degradation was investigated in phosphatebuffered solution at 37°C. The degraded films were characterized using gravimetry (%water uptake and %weight loss), 1H-NMR spectroscopy, differential scanning calorimetry and size exclusion chromatography. The %weight loss of the degraded films increased and molecular weight decreased on increasing the MPEG block length and incorporating the G and CL units, according to their %water uptakes. The MPEG content of the degraded film decreased and the Tg increased with hydrolytic degradation time.