Novel Strategy for Synthesis of High Quality CdTe Nanocrystals in Aqueous Solution

A novel aqueous route for the synthesis of high-quality CdTe nanocrystals（NCs） is presented in this article. With both glutathione（GSH） and cysteine[n（GSH）：n（cysteine）=1：3] as stabilizers, high-quality CdTe NCs with controllable photoluminescence（PL） wavelength from 500 to 630 nm can be prepared within 4 h. As-prepared CdTe NCs show higher photoluminescence quantum yields（PLQY） compared with CdTe NCs prepared via other aqueous methods. When the fluorescent emission peak appeared in orange-red window, the PLQY reaches 70% or above at room temperature without any post-preparative treatment.

Iodine Determination by Microwave Plasma Torch Atomic Emission Spectrometer Coupled with Online Preconcentration Vapor Generation Technique

This article focuses on iodine determination by microwave plasma torch atomic emission spectrometry （MPT-AES） coupled with online preconcentration vapor generation method. A new desolvation device, multistrand Nafion dryer, was used as the substitute for condenser desolvation system. Some experimental conditions, such as preconcentration time, acidity of sample solution, rinsing solution acidity and dynamic linear range were investigated and optimized. The new desolvation system eliminates the problem of decreasing emission intensity of I（I） 206.238 nm line with the increase of working time on a conventional condenser desolvation system, thus greatly improving the reproducibility.

Simple, Selective, and Sensitive Spectrophotometric Method for Determination of Trace Amounts of Nickel(Ⅱ), Copper (Ⅱ), Cobalt (Ⅱ), and Iron (Ⅲ) with a Novel Reagent 2-Pyridine Carboxaldehyde Isonicotinyl Hydrazone

A selective and sensitive reagent of 2-pyridine carboxaldehyde isonicotinyl hydrazone（2-PYAINH） was synthesized and studied for the spectrophotometric determination of nickel, copper, cobalt, and iron in detail. At a pH value of 7.0, 9,0, 9.0, and 8.0, respectively, which greatly increased the selectivity; nickel, copper, cobalt, and iron reacted with 2-PYAINH to form a 1：2 yellow-orange, 1：2 yellow-green, 1：2 yellow and 1：1 yellow complexes, with absorption peaks at 363, 352, 346, and 359 nm, respectively. Under the optimal conditions, Beer＇s law was obeyed over the ranges of 0.01-1.4, 0.01-1.5, 0.01-2.7, and 0.01-5.4 mg/L respectively. The apparent molar absorptivity and Sandell＇s sensitivities were 8.4×10^4, 5.2×10^4, 7.1×10^4, and 3.9×10^4 L·mol^-l·cm^-1, respectively, and 0.00069, 0.0012, 0.00078, and 0.0014 μg·cm2, respectively. The detection limits were found to be 0.001, 0.002, 0.003, and 0.01 mg/L, respectively. The detailed study of various interfering ions to make the method more sensitive was carried out and selective and several real samples were analyzed with satisfactory results.

Studies on Excitation and Rotational Temperatures of an Oxygen-shielded Argon Microwave Plasma Torch Source

Excitation（ Texc ） and rotation（ Trot ） temperatures were determined under different conditions for an oxygen-shielded argon microwave plasmsa torch source（OS-Ar-MPT）. The Texc value, which was shown to be between 4300 and 5250 K under different operating conditions, was calculated from the slope of the Boltzmann plot with Fe as the thermometric species. The Trot value, which was in the range of 2100-2500 K, was measured with OH molecular spectra. The influences of microwave power, flow rates of the support gas, cartier gas, and shielding gas, as well as the observation height on Texc and Trot were investigated and discussed. The detailed results of Texc and Trot provided a better understanding of the performance of an OS-ArMPT as a source for atomic emission spectrometry.

Detection of Serine Octamer by Desorption Electrospray Ionization Mass Spectrometry in Resultant Mixture of Aspartic Acid Exposed to Sunshine Under Natural Conditions

Serine, one of the nonessential amino acids, is of principal interest because of its capability to form magic-number ionic clusters, which provide a remarkable preference for homochirality. With L-aspartic acid as the precursor, this study provides experimental evidence for serine formation in weak acidified aqueous solutions in the presence of iron, with exposure to sunlight, which simulates the natural conditions of the prebiotic aqueous environment. The resultant mixture is directly analyzed via desorption electrospray ionization mass spectrometry（ DESI-MS）, without any sample preseparation. The serine monomer is successfully detected as protonated molecules, giving a peak at m/z 106, which is confirmed by the MS/MS fragments. Protonated serine octamer（ m/z 841 ） is also observed with significant abundance in the MS spectra and is confirmed by the MS/MS data, which shows the formation of the serine octamer by a synthesized serine in the resultant mixture. It is also found that the serine octamer yielded equivalent abundance in the DESI mass spectra in a wide pH range（pH = 1-5 ）, and that existence of ferrous salt and sunshine are essential for the conversion of aspartic acid to serine in the acidic water solution.

Immunosensor Based on Surface Plasmon Resonance for Antigen Recognition

A novel immunosensor based on surface plasmon resonance（SPR） has been developed for the recognition of antigen. The sensor was designed on the basis of the fixed angle of incidence and measuring the reflected intensities in a wavelength range of 430--750 nm in real-time. An ultra-bright white light-emitting diode（LED） was used as the light source. Molecular self-assembling in solution was used to form the sensing membrane on gold substrate. It has been seen that the sensitivity of the SPR sensor with 3-mercaptopropionic acid（MPA）/protein A（SPA） sensing membrane is considerably higher than that with MPA or SPA modified sensing membrane. The kinetic processes on the sensing membrane were studied. The human B factor（Bf）, an activator of complement 3（C3）, was recognized among the other antigens. This sensor can also be used for other antigen/antibody or adaptor/receptor recognition. Under optimized experimental conditions, the sensor has good selectivity, repeatability, and reversibility.

Detection of Penicillin via Surface Plasmon Resonance Biosensor

A method of using Au colloid to capture the decomposed product of penicillin, penicillamine, on a surface plasmon resonance（SPR） biosensor for the quantitative determination of penicillin was developed. Based on the de-composition of penicillin to generate penicillamine and penilloaldehyde, a high sensitive biosensor for detecting penicillin was also developed. In our experiment, it was penicillamine rather than penicillin that has been measured. This is because penicillamine contains a functional group that makes it self-assembling on Au colloid to increase the molecular weight so as to improve the surface plasmon resonance signal. On a UV-Vis spectrophotometer, a high concentration of penicilliamine-Au complex was determined, indicating that penicillamine was already well combined with Au colloid. The method, using the combination of Au colloid with penicillamine, proved to detect penicillin.

Determination of Cd,Pb and Sr by Microwave Plasma Torch Atomic Emision Spectrometry Using an Electrothermal Vaporization Sample Introduction System

A method for the determination of Cd,Pb and Sr by microwave plasma torch(MPT)atomic emission spectrometry(AES)was developed.Th e samples were introduced into the MPT with an elec trothermal vaporization(ETV)device.The effects of some experimental conditions on the de-termination of Cd,Pb and Sr were examined.The effects of easily ionized elements on the emis-sion intensity of Cd,Pb and Sr were studied in detail.The detection limits for Cd,Pb and Sr are 2.4,4.0 and 1.3 ng/mL,respectively.

Gold Nanoparticles Based Colorimetric Detection of Target DNA After Loop-mediated Isothermal Amplification

We have developed a rapid, simple and label-free colorimetric method for the identification of target DNA It is based on loop-mediated isothermal amplification（LAMP）. Plain gold nanoparticles（AuNPs） are used to indicate the occurrence of LAME The amplified product is mixed with AuNPs in an optimized ratio, at which the deoxyribonucleotides（dNTPs） bind to the AuNPs via ligand-metal interactions and thus enhance AuNPs stability. If a target DNA is amplified, the dramatic reduction of the dNTPs leads to the aggregation of AuNPs and a color change from red to blue. The success of the method strongly depends on the ionic strength of the solution and the initial concentration of dNTPs. Unlike other methods for the identification of isothermal products, this method is simple and can be readily applied on site where instrumentation is inadequate or even lacking.