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Lead is highly toxic. The detection of lead in the environmental bodies is difficult, because it is colourless and odourless. Herein, we report the synthesis of gold nanoparticles (AuNPs) using the interdigitized vesicles formed by N-decanoyltromethamine (NDTM). AuNPs stabilized by NDTM was pink in colour with spherical shape and the size is 29 ± 7 nm. The optical property of the NDTM-AuNPs was explored for the first time to detect toxic chemical, Pb2+. The addition of toxic metal ion Pb2+ to NDTM-AuNPs rapidly ( less then 1 min) alters the colour from pink to violet due to aggregation, which was confirmed by particle size analyser and TEM. The aggregation induced colour changes were realized via broad spectra in UV-Vis spectroscopy. NDTM-AuNPs showed a selective and sensitive spectrophotometric signal with Pb2+ when compared with other metal ions. The colorimetric change as a function of Pb2+ concentration gave a linear response in the range of 0-30 μM (R2 = 0.9942). The detection limit was found at 10 μM by naked eye and 0.35 μM by spectrophotometry. The proposed method was successfully applied for the determination of Pb2+ ions in tap water and sewage water. Moreover, as a proof of concept, the NDTM-AuNPs sensor system was applied for the detection of lead in commercial paints. The results of the quantitative estimation of lead in paints by NDTM-AuNPs colorimetric sensor were as good as the standard method, atomic absorption spectroscopy.Asenapine maleate was approved by the FDA for the treatment of schizophrenia and mania or mixed episodes with bipolar I disorder. In the present article, two spectroscopic methods were developed and validated for the determination of asenapine. Both methods depend on association complex formation between xanthine based dye (eosin Y) and the cited drug in acetate buffer pH = 3.8. In the spectrophotometric method (method I), the absorbance of the formed complex was estimated at maximum wavelength of 545 nm and Beer's law was obeyed in the range of 1-12 μg mL-1. The spectrofluorimetric method (method II) depends on measuring the quenching effect of the drug on the native fluorescence of eosin Y at 545 nm after excitation at 303 nm. The linearity range of method II was 0.4-3.2 μg mL-1. The limits of detection were 0.24 and 0.08 μg mL-1 for method I and II, respectively. The instructions of ICH were followed to fully validate the developed analytical procedures. The formation constant of the reaction was 3.93 × 104 while its Gibb's free energy was -2.6 × 104 J mol-1. Finally, the methods were applied for the analysis of pharmaceutical tablets and for evaluation of their content uniformity.The influence of furo-, thieno-, and benzo-fused structures at the b bonds in the BODIPY frame on the optical properties is investigated by TD-CAM-B3LYP and RI-CC2 calculations. The most important result is that substituents at the b bond of the BODIPY core affect strongly the S1-S2 gaps. In contrast to the S1 (local excited (LE-type)) state, energy of which is nearly the same for all the substituents at the b bond, energy of the S2 (charge transfer (CT-type)) state depends strongly on the nature of the substituent and decreases in the following order furo-fused > thieno-fused > benzo-fused. In the last case the inversion of S1 and S2 levels occurs. No red shift of the main long-wave absorption transition and no substantial changes in its intensity can be predicted by the calculations for benzo[b]-derivative (vertical energy (Ev) is 2.95 eV, oscillator strength (f) is 0.80) relative to furo- (Ev = 2.97 eV, f = 0.69) and thieno-derivatives (Ev = 2.95 eV, f = 0.65). However, the dramatic decrease of the fluorescence quantum yield is expected owing to positions of their LE-type (Ev = 2.95 eV, f = 0.80) and CT-type (Ev = 2.79 eV, f = 0.01) transitions. In the case of thieno-fused BODIPY, owing to the approach of the energy levels of the vertical S2 and S1 states, the energy equilibrium of the [1]CT-type state becomes lower than that of the [1]LE state, and Φf of the thieno-derivative may be substantially lower than Φf of the furo-derivative.A naturally fluorescent cyanobacterial protein C-phycoerythrin (CPE) was investigated as a fluorescent probe for biologically and environmentally important hydrosulphide (HS-) ion. It was selective for HS amongst a large anion screen and the optical response was rapid. Sequential UV-visible titration showed considerable peak shift and attenuation with increasing [HS-] while fluorescence titration proved that HS- quenched CPE fluorescence in a concentration dependent manner. The linear response range was 0-2 mM HS- while the Stern Volmer curve was non-linear and the limit of detection was 185.12 μM. Except bicarbonate and glycine, no anion or biomolecule interfered with the detection even at 10 times the concentration of HS-. It was also free of influences from other sulphur forms like sulphite, sulphate and thiosulphate. CPE reliably detected HS- in freshwater and effluent samples, though some under- and over - estimation was evident. The % recovery ranged from ~96 to 105% (RSD ~ 0.035-0.188%). FTIR analysis showed significant changes in the amide I and II regions of CPE, along with minor modifications in the amide III region as well, showing that HS- was able to influence the protein secondary structure at higher concentrations.A simple and green approach for the synthesis of photoluminescent N,S-carbon dots (N,S-CDs) has been proposed using a single natural source precursor (bamboo leaf) as raw materials. The as-synthesized N,S-CDs exhibited a highly stable, excitation wavelength-dependent emission, excellent photobleaching, alkali, and salt tolerance. Here, the mechanism of N,S-CDs luminescence was studied via the UV-vis absorption spectrum and photoluminescence spectroscopy. Based on the quenching properties of nitrophenol compounds on the fluorescence of N,S-CDs, the interaction between N,S-CDs and nitrophenol compounds was investigated on detail in aqueous solution. learn more More importantly, the study on photophysical properties of the N,S-CDs may provide the basis for the development of the N,S-CDs for the fluorescent probe of nitrophenol compounds.