Reversible light-controlled fluorescence switch of block polymer-grafted carbon dots and cellular imaging.

A novel type of aggregation-induced emission (AIE) nanoparticles, which are carbon dots (CDs) grafted with block polymer of tetraphenylethylene, spiropyran and N-isopropylacrylamide (CD-g-poly((TPE-co-SPA)-block-NIPAM)), was synthesized. The CD-g-poly((TPE-co-SPA)-block-NIPAM) nanoparticles can emit weak cyan fluorescence in tetrahydrofuran, while showing AIE-enhanced cyan fluorescence in water and solid film. The fluorescence of the CD-g-poly((TPE-co-SPA)-block-NIPAM) nanoparticles can reversibly transform cyan to red with UV/visible light irradiation, and functioned as a reversible fluorescence photoswitch. Importantly, the CD-g-poly((TPE-co-SPA)-block-NIPAM) nanoparticles have low cytotoxicity and, therefore, can be used for imaging in living cells.

Ultrasensitive determination of copper in complex biological media based on modulation of plasmonic properties of gold nanorods.

Accurate determination of copper in complex biological media such as cells is quite difficult, and an analytical strategy based on copper-modulated formation of core-shell gold nanorods is described. Selective and label-free sensing can be achieved by measuring the change in the localized surface plasmon resonance absorption. The technique can determine trace amounts of copper in human serum, urine, and red blood cells without or with minimal sample pretreatment. The Cu detection limits are 20.67 µM in human serum, 0.193 µM in human urine, and 3.09 × 10(-16) g in a single cell. The advantages of the technique are the high selectivity, simple or no sample pretreatment, and label free. Boasting a practical detection limit down to 2 fM, only 10(3) red blood cells are needed to conduct the analysis and the technique may be extended to the detection of trace amounts of copper in a single cell.

Multiplex plasmonic sensor for detection of different metal ions based on a single type of gold nanorod.

In this paper, a label-free multiplex plasmonic sensor has been developed to selectively determine different metal ions including Fe(3+), Hg(2+), Cu(2+), and Ag(+) ions based on a single type of gold nanorod (GNR). Under proper conditions, these metal ions can react with GNRs, resulting in changes of nanostructure and composition. The determination of Fe(3+), Hg(2+), Cu(2+), and Ag(+) ions is therefore readily implemented due to changes of longitudinal plasmon wavelength (LPW) of nanorods. Moreover, the GNR-based assay can not only determine all four kinds of metal ions successively but also can detect which of any one or several kinds of metal ions. This assay is sensitive to detect Fe(3+), Hg(2+), Cu(2+), and Ag(+) as low as 10(-6), 10(-8), 10(-10), and 10(-8) M, respectively. Importantly, the special nanostructure and composition of the nanorods are induced by these metal ions, which allow this sensor to maintain high selectivity to determine these metal ions. This nanosensor abrogates the need for complicated chemosensors or sophisticated equipment, providing a simple and highly selective detection platform.

A novel method for aqueous synthesis of CdTe duantum dots.

We have developed a simple and an economical one-pot method to synthesize water-soluble CdTe quantum dots (QDs) using hydroxylamine hydrochloride (HAH) as reduction and l-cysteine (CYS) as the ligand. The size of the CdTe QDs could easily be controlled by the duration of reflux and monitored by absorption and photoluminescence spectra. The factors influencing the photoluminescence quantum yields (PL QYs) on the QYs of CdTe NCs were investigated and the optimum conditions were determined. Under the optimum conditions (pH=11.0, the concentration of Cd(2+) was 1.0mmolL(-1) and the molar ratio of Cd(2+):Te(2)(-):CYS:HAH was 1:0.05:2.4:5), photoluminescence quantum yields of the CdTe QDs have been improved significantly and the maximum QYs of the QDs can achieve to 47%. The QDs were characterized by Fourier transform infrared spectrometry (FTIR), transmission-electron microscopy (TEM) and X-ray powder diffraction (XRD). The XRD patterns indicated that CdS was formed in the preparation process of CdTe QDs. This CdS shell could effectively passivate the surface trap states, and enhance the PL QY and stability of the CdTe QDs.

An ultrasensitive method for the determination of melamine using cadmium telluride quantum dots as fluorescence probes.

An ultrasensitive and simple method for the determination of melamine was developed based on the fluorescence quenching of thioglycolic acid (TGA) capped CdTe quantum dots (QDs) at pH 11.0. In strong alkaline aqueous solution, the selectivity of the method has been greatly improved due to most heavy metal ions show no interference as they are in the precipitation form or in their anion form. Furthermore, CdTe quantum dots have higher quantum yields at higher pH. The method has a wider concentration range and lower detection limit. The influence factors on the determination of melamine were investigated and the optimum conditions were determined. Under optimum conditions, the fluorescence intensity change of TGA coated CdTe quantum dots was linearly proportional to melamine over a concentration range from 1.0×10(-11) to 1.0×10(-5) mol L(-1) with a correlation coefficient of 0.9943 and a detection limit of 5×10(-12) mol L(-1). The mechanism of fluorescence quenching of the QDs has been proposed based on the infrared spectroscopy information and electrophoresis experiments in presence of melamine under alkaline condition. The proposed method was employed to detect trace melamine in milk powder and pet feeds with satisfactory results.

Sensitive and simultaneous detection of different disease markers using multiplexed gold nanorods.

A multiplexed bioanalytical assay is produced by incorporating two types of gold nanorods (GNRs). Besides retaining the desirable features of common GNRs LSPR sensors, this sensor is easy to fabricate and requires only a visible-NIR spectrometer for detection. This assay can simultaneously detect different acceptor-ligand pairs by choosing the proper GNRs possessing various LPWs in a wide detection wavelength range and can be developed into a high-throughput detection method. This bioanalytical assay allows easy detection of human serum specimens infected by S. japonicum and tuberculosis (TB) from human serum specimens (human serum/Tris-HCl buffer ratio=1:10(4)) without the need for sample pretreatment. The technique is very sensitive compared to other standard methods such as indirect hemagglutination assays (IHA) that require a serum concentration ratio of larger than 1:20 and enzyme-linked immunosorbent assays (ELISA) requiring a ratio larger than 1:100. This methodology can be readily extended to other immunoassays to realize wider diagnostic applications.