Facile synthesis of nitrogen-doped carbon dots for Fe sensing and cellular imaging

A fast and facile approach to synthesize highly nitrogen (N)-doped carbon dots (N-CDs) by microwave-assisted pyrolysis of chitosan, acetic acid and 1,2-ethylenediamine as the carbon source, condensation agent and N-dopant, respectively, is reported. The obtained N-CDs are fully characterized by elemental analysis, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction pattern, X-ray photoelectron spectroscopy, UV–vis absorption, and photoluminescence spectroscopy. Doping N heteroatoms benefits the generation of N-CDs with stronger fluorescence emission. As the emission of N-CDs is efficiently quenched by Fe³⁺, the as-prepared N-CDs are employed as a highly sensitive and selective probe for Fe³⁺ detection. The detection limit can reach as low as 10 ppb, and the linear range is 0.010–1.8 ppm Fe³⁺. The as-synthesized N-CDs have been successfully applied for cell imaging and detecting Fe³⁺ in biosystem.     

One Pot Phase Transfer Synthesis of Trithiocarbonates from Carbon Bisulphide and Alkyl Halides

Symmetrical and cyclic alkyl trithiocarbonates were synthesized by reacting CS₂ and 33% aqueous NaOH with alkyl hal-ides under phase transfer catalysis conditions     

Experimental study of enhanced emission of the laser-ablated plume in backing gas

The effects of background gases on the optical emission of the excimer-laser-ablated plume from a brass target have been studied experimentally. It is found that the plume emission can be enhanced significantly in a proper gas ambient. In hydrogen, the highest peak intensity is detected, and in argon, there is a distinctive difference in the pressure-dependent emission between in He and in the other three gases, Ar, N₂ and H₂. Moreover, the monitored line peak intensity remains unchanged in Ar and N₂ and increases in H₂ within a distance above the target surface; but in He, the observed peak intensity decreases with distance like in vacuum. Furthermore, the emissions of several more atomic lines of Cu and Zn atoms from the plume are also found to be enhanced in the same manner in gas ambient. Some physical processes involved in the plume expansion and the possible mechanisms for the enhanced emission of the plume in backing gas are discussed.     

Electrogenerated chemiluminescence of anatase TiO₂ nanotubes film

Highly ordered titanium dioxide (TiO₂) nanotubes film was successfully synthesized via anodic oxidation of a Ti foil in an ammonium fluoride-based ethylene glycol solution. The electrogenerated chemiluminescence (ECL) behavior of the resulting TiO₂ nanotubes film was subsequently studied. Strong ECL emission was observed at −1.40 V (vs. Ag/AgCl) and the ECL spectrum displayed three emission peaks which were bathochromatically shifted by ca. 140 nm as compared to its corresponding photoluminescence (PL) emission peaks, indicating that the surface state plays an important role in the emission process. The ECL emission can also occur in a deareated solution attributing to the surface adsorbed O₂ molecules. The ECL emission intensity was quenched by dopamine and greatly enhanced in the presence of dissolved O₂ and H₂O₂, making it possible to detect these analytes. The TiO₂ nanotubes film has been successfully applied to determine the dissolved O₂ content in river and pond water samples, the H₂O₂ concentration in commercial disinfectant samples and the dopamine concentration in commercial dopamine injections with satisfactory results. The plausible ECL mechanisms of TiO₂ nanotubes film in aqueous solution are discussed.     

Computer graphics-assisted applications of first-order chemical kinetics in the determination of inorganic complexes complexes

Computer graphics-assisted applications of first-order chemical kinetics are applied to absorbance data from spectrophotometric measurements of the decomposition of di-μ-hydroxobis[dioxalatocobaltate(III)] (at pH 4.0) and trioxalatocobaltate(III) (in 1.0 M perchloric acid) in order to estimate the purity of the complexes. A program called KINFIR is used.     

Toward a UV-visible-near-infrared hyperspectral imaging platform for fast multiplex reflection spectroscopy

A reflection hyperspectral imaging system covering a 350-1000nm spectral range is realized by a UV-visible-near-IR Fourier transform imaging spectrometer. The system has a simple design and good spectral and spatial resolving performance. Accurate and fast microspectroscopic measurement results on novel colloidal crystal beads demonstrate the system has practical potential for high-throughput molecular multiplex assays.     

Underwater cytometer for in situ measurement of marine phytoplankton by a technique combining laser-induced fluorescence and laser Doppler velocimetry

We present a new type of flow cytometer that can operate underwater for a long time, as long as days, for measuring the size distribution, concentration, and biomass of marine phytoplankton. The major improvement of the instrument over existing techniques is the elimination of sample preparation, which is achieved with a laser Doppler crossed-beam arrangement for both defining a measurement volume and measuring the speed of the particle traversing it. By simultaneously sampling the laser-induced fluorescence signal and the Doppler signals, the technique can discriminate sizes of phytoplankton.     

Fourier transform ultraviolet-visible spectrometer based on a beam-folding technique

A beam-folding technique in optical interferometry, where the number of beam folds used can be very large, is reported. This technique can be used as a low-cost position-tracking method in a Fourier transform spectrometer (FTS) to cover the broad spectral range from UV to IR. The main advantage gained is the simple position-tracking algorithm used in sampling the interferogram. We have developed a UV-visible FTS, whose wavelength coverage is limited only by the optical elements (350 nm(-1) microm with off-the-shelf components). Preliminary results show that it can achieve a resolution of approximately 4 cm(-1) even with a ball-bearing translation stage.     

Electrospray ionization tandem mass spectrometric characterization of DNA adducts formed by bromobenzoquinones

Bromobenzoquinones (BBQs) represent a class of reactive metabolites of various aromatic contaminants with bromine-containing substituents, including bromobenzene, bromophenols, polybrominated diphenyl ethers (PBDEs). Recently, 2,6-dibromobenzoquinone also has been detected directly from drinking water. The alternation of the genome caused by covalent binding of chemicals or their metabolites to DNA provides a viable mechanism for carcinogenicity. In the present study, electrospray ionization coupled with ion trap mass spectrometry (ITMS), triple quadrupole MS or quadrupole time-of-flight MS was applied for the analysis of DNA adducts formed by BBQs. The study demonstrated 2-monobromobenzoquinone and 2,6-dibromobenzoquinone could covalently bind to deoxyguanosine (dG) and DNA in vitro. The chemical structures of the DNA adducts were confirmed by accurate mass values, collision-induced fragmentation tandem mass spectra as well as isotopic patterns. Generally, the reaction mechanism for the DNA adduction involved Michael addition between the electron-deficient carbon from the quinone and the nucleophilic exocyclic nitrogen from the dG followed by reductive cyclization with loss of a small molecule such as H(2)O, or HBrO. It was of particular interest to note that some adducts were generated from the reaction of one dG molecule with two BBQ molecules. The obtained results provided new information for assessing the potential cancer risk associated with bromobenzene, bromophenols, PBDEs and BBQs.     

Ion-selective electrodes in organic analysis-determination of xanthate

A PVC membrane xanthate-selective electrode has been developed for the direct determination of xanthates of primary and secondary alcohols. The xanthate electrode is highly selective and exhibits a Nernstian response in the range 5.0 x 10(-2)-7.1 x 10(-5)M xanthate with a slope of 58.6 mV per concentration decade. The electrode has a wide working pH range (5.0-11.5), a fast response time (less than 30 sec) and is stable for at least two months.