Zhengyu Yan

Surface-modified CdS quantum dots as luminescent probes for sulfadiazine determination.

A novel, sensitive and convenient determine technology based on the quenching of the fluorescence intensity of functionalized CdS quantum dots by sulfadiazine was proposed. Luminescent CdS semiconductor quantum dots (QDs) modified by thioglycollic acid (TGA) were synthesized with the microwave method. The modified CdS QDs are water-soluble, stable and highly luminescent. The possible mechanism for the reaction was also discussed. When sulfadiazine was added into the CdS QDs colloid solution, the surface of CdS QDs generates the electrostatic interaction in aqueous medium, which induces the quenching of fluorescence emission at 489 nm. Under optimum condition, the fluorescence intensity versus sulfadiazine concentration gave a linear response according Stern-Volmer equation with an excellent 0.9981 correlation coefficient. The linearity range of the calibration curve was 1.2 x 10(-5) to 2.13 x 10(-3) mol L(-1). The limit of detection (3delta) is 8.0 micromol L(-1). The relative standard deviation for five determinations of 0.13 x 10(-3)mol L(-1) sulfadiazine is 1.4%. The concentrations of sulfadiazine injections were determined by the proposed method with a satisfactory result.

A novel fluorescent assay for edaravone with aqueous functional CdSe quantum dots

Aqueous thiol-capped CdSe QDs with a narrow, symmetric emission were prepared under a low temperature. Based on the fluorescence enhancement of thiol-stabilized CdSe quantum dots (QDs) caused by edaravone, a simple, rapid and specific quantitative method was proposed to the edaravone determination. The concentration dependence of fluorescence intensity followed the binding of edaravone to surface of the thiol-capped CdSe QDs was effectively described by a modified Langmuir-type binding isotherm. Factors affecting the fluorescence detection for edaravone with thiol-stabilized CdSe QDs were studied, such as the effect of pH, reaction time, the concentration of CdSe QDs and so on. Under the optimal conditions, the calibration plot of C/(I-I(0)) with concentration of edaravone was linear in the range of (1.45-17.42) microg/mL (0.008-0.1 micromol/L) with correlation coefficient of 0.998. The limit of detection (LOD) (3sigma/kappa) was 0.15 microg/mL (0.0009 micromol/mL). Possible interaction mechanism was discussed.

Determination of ciprofloxacin with functionalized cadmium sulfide nanoparticles as a fluorescence probe.

A novel assay of ciprofloxacin with a sensitivity at the microgram level is proposed based on the measurement of enhanced fluorescence intensity signals resulting from the interaction of functionalized nano-CdS with ciprofloxacin. The CdS nanoparticles was synthesized by thioacetamide (TAA) and cadmium nitrate (Cd(NO(3))(2)) in the alkaline solution. At pH 7.4, the fluorescence signals of functionalized nano-CdS were greatly enhanced by ciprofloxacin with the increase concentration of ciprofloxacin. Linear relationship can be established between the enhanced fluorescence intensity and ciprofloxacin concentration in the range of (1.25-8.75)x10(-4) mg mL(-1) ((3.77-26.4) x 10(-4)mmol L(-1)) or (8.75-1200) x 10(-4)mg mL(-1) ((26.4-3625) x 10(-4) mmol L(-1)). The limit of detection is 7.64 x 10(-6) mg mL(-1) (2.31 x 10(-5)mmol L(-1)). Based on this, a new direct quantitative determination method for ciprofloxacin in human serum samples without separation of foreign substances was established. The contents of ciprofloxacin in human serum samples were determined with recovery of 95-105% and relative standard deviation (R.S.D.) of 1.5-2.5%. This method was proved to be very sensitive, rapid, simple and tolerance of most interfering substances.

Green biosynthesis of biocompatible CdSe quantum dots in living Escherichia coli cells

A green and efficient biosynthesis method to prepare fluorescence-tunable biocompatible cadmium selenide quantum dots using Escherichia coli cells as biological matrix was proposed. Decisive factors in biosynthesis of cadmium selenide quantum dots in a designed route in Escherichia coli cells were elaborately investigated, including the influence of the biological matrix growth stage, the working concentration of inorganic reactants, and the co-incubation duration of inorganic metals to biomatrix. Ultraviolet-visible, photoluminescence, and inverted fluorescence microscope analysis confirmed the unique optical properties of the biosynthesized cadmium selenide quantum dots. The size distribution of the nanocrystals extracted from cells and the location of nanocrystals foci in vivo were also detected seriously by transmission electron microscopy. A surface protein capping layer outside the nanocrystals was confirmed by Fourier transform infrared spectroscopy measurements, which were supposed to contribute to reducing cytotoxicity and maintain a high viability of cells when incubating with quantum dots at concentrations as high as 2 μM. Cell morphology observation indicated an effective labeling of living cells by the biosynthesized quantum dots after a 48 h co-incubation. The present work demonstrated an economical and environmentally friendly approach to fabricating highly fluorescent quantum dots which were expected to be an excellent fluorescent dye for broad bio-imaging and labeling.

A green synthesis of highly fluorescent nitrogen-doped graphene quantum dots for the highly sensitive and selective detection of mercury(II) ions and biothiols

A facile and environmentally friendly strategy to prepare nitrogen-doped graphene quantum dots (N-GQDs) with a high quantum yield of 28.10% was reported. The obtained N-GQDs exhibited strong blue fluorescence emission with the maximum emission and excitation at 450 nm and 355 nm, respectively. Taking advantage of the effective quenching effect of Hg2+ on N-GQDs, such N-GQDs were developed for the efficient and sensitive detection of Hg2+ with a relatively low detection limit of 0.032 μM. Based on the selective coordination of biothiols and Hg2+, the fluorescence of the N-GQD/Hg system was recovered with the addition of biothiols. This fluorescent “Off–On” process showed a sensitive response to biothiols with a detection limit of 0.036 μM for cysteine and 0.034 μM for glutathione. Most importantly, the N-GQD-based fluorescence method was successfully used to monitor Hg2+ in real water samples and biothiols in serum samples.

Preparation of carbon quantum dots based on starch and their spectral properties

A simple method for the synthesis of water-soluble carbon quantum dots (CQDs) has been developed based on chemical oxidation of starch. The structures and optical properties of the CQDs were characterized by ultraviolet-visible (UV-Vis) spectroscopy, photoluminescence spectroscopy (PL) and transmission electron microscopy. The CQDs were found to emit bright blue fluorescence and disperse uniformly. The effects of ambient temperature, light and pH on the properties of CQDs were studied. The CQDs exhibited good chemical stability, good photostability and pH sensitivity. Furthermore, the interaction between CQDs and bovine serum albumin (BSA) was investigated.

Occurrence, distribution and risk assessment of suspected endocrine-disrupting chemicals in surface water and suspended particulate matter of Yangtze River (Nanjing section)

The occurrence and distribution of eight selected endocrine-disrupting chemicals were investigated in samples of surface water and suspended particulate matter (SPM) in Nanjing section of Yangtze River over a year (the flow period, the wet period and the dry period). All target compounds were detected at least once in surface water with 4-tert-butylphenol (4-TBP), nonyphenol (NP) and bisphenol A (BPA) as the dominant compounds, with concentrations in the range of 225-1121ng/L, 1.4-858ng/L and 1.7-563ng/L, respectively. Except for December, all selected compounds for the other sampling times were not found in all sampling points. NP (mean concentration 69.8µg/g) and BPA (mean concentration 51.8µg/g) were also the dominant estrogens in SPM. In addition, the highest total compounds concentrations were found in December in both phases, which could be due to the low flow conditions and temperature during this season. Meanwhile, a significant positive correlation was found between the total compounds concentrations in the water phase and those in SPM phase. Risk assessment based on the calculated risk quotients (RQ) showed that low and moderate risk for the aquatic environment from presence of the target compounds at all sampling points with exception of 4-TBP and NP which might pose a high risk to aquatic organisms.

Glycine-functionalized carbon quantum dots as chemiluminescence sensitization for detection of m-phenylenediamine

A novel sensing system has been designed for the detection of m-phenylenediamine based on carbon quantum dots (CQDs)-improved chemiluminescence (CL) in a luminol–potassium permanganate (KMnO4) system. The CQDs were synthesized by pyrolyzing a mixture of citric acid (CA) and glycine (Gly). Under the action of CQDs and KMnO4, the luminol can be oxidized by synergy, which significantly increases the chemiluminescence intensity. In this work, it has been demonstrated that this facile methodology can offer a rapid, sensitive and reliable detection of m-phenylenediamine with a detection limit as low as 1.02 × 10−3 g L−1 and a dynamic range from 2.0 × 10−3 to 3.0 × 10−1 g L−1, which shows a promising application prospect.

Singlet oxygen-generating from fluorescence probes based on denatured bovine serum albumin-conjugated CdTe quantum dots and photosensitizer Chlorin e6

Based on the excellent optical properties of quantum dots (QDs), a simple and efficient method was proposed and established to produce a singlet oxygen activating QDs-denatured Bovine Serum Albumin (dBSA)-Chlorin e6 (Ce6) bioprobe. In this work, a quick synthesis of water-soluble CdTe QDs was accomplished and showed a good linear fit between synthetic heating duration and its maximum fluorescence emission wavelength. Moreover, dBSA which is a convenient and widely used agent was employed as a bridge to conjugate the selective CdTe QDs with a suitable emitting wavelength and photosensitizer Ce6, simply using N-ethyl-N-(3-dimethylaminopropyl) carbodiimide and N-hydroxy succinimide as coupling agents. UV–Vis, fluorescence, and IR spectroscopy confirmed the successful conjugation of QDs and Ce6. The as-produced QDs-dBSA-Ce6 bioconjugates demonstrated an effective fluorescence resonance energy transfer efficiency of as high as 0.90, which also proved to be well conserved of its singlet oxygen-generating in oxidation–extraction photometry tests and might be a potential bioprobe in the research of photo dynamic therapy.

Chemiluminescence determination of potassium bromate in flour based on flow injection analysis.

A novel and highly sensitive flow-injection chemiluminescence method for the determination of potassium bromate (KBrO3) has been developed. This method is based on the luminescence properties of the KBrO3-Na2SO3-quinine sulfate system in acid medium. Optimized experimental conditions and a possible mechanism were investigated. The relative chemiluminescence intensity responded linearly to the concentration of KBrO3 in the range of 7.054 × 10(-6)-1.008 × 10(-4) mol/L with a detection limit of 2.116 × 10(-6) mol/L. The relative standard deviation (RSD) at 5.0 × 10(-5) mol/L KBrO3 (n = 12) was 2.3%. The proposed method was applied successfully to the determination of KBrO3 in flour.