Electrogenerated chemiluminescence (ECL) of semiconductor quantum dots in aqueous solutions and its first sensing application were studied by depositing CdSe nanocrystals (NCs) on a paraffin-impregnated graphite electrode (PIGE). The CdSe nanocrystal thin film exhibited two ECL peaks at -1.20 (ECL-1) and -1.50 V (ECL-2) in pH 9.3, 0.1 M PBS during the cyclic sweep between 0 and -1.8 V at 20 mV s(-1). The electron-transfer reaction between individual electrochemically reduced nanocrystal species and oxidant coreactants such as H(2)O(2) and reduced dissolved oxygen led to ECL-1. When mass NCs packed densely in the film were reduced electrochemically, assembly of reduced nanocrystal species could react with coreactants to produce another ECL signal, ECL-2. ECL-1 showed higher sensitivity to the concentration of oxidant coreactants than ECL-2 and thus was used for ECL detection of coreactant, H(2)O(2). A linear response of ECL-1 to H(2)O(2) was observed in the concentration range of 2.5 x 10(-7)-6 x 10(-5) M with a detection limit of 1.0 x10(-7) M. The fabrication of 10 CdSe nanocrystal thin-film modified PIGEs displayed an acceptable reproducibility with a RSD of 1.18% obtained at H(2)O(2) level of 10 microM.

Small size molybdenum disulfide (MoS2) quantum dots (QDs) with desired optical properties were controllably synthesized by using tetrabutylammonium-assisted ultrasonication of multilayered MoS2 powder via OH-mediated chain-like Mo-S bond cleavage mode. The tunable up-bottom approach of precise fabrication of MoS2 QDs finally enables detailed experimental investigations of their optical properties. The synthesized MoS2 QDs present good down-conversion photoluminescence behaviors and exhibit remarkable up-conversion photoluminescence for bioimaging. The mechanism of the emerging photoluminescence was investigated. Furthermore, superior (1)O2 production ability of MoS2 QDs to commercial photosensitizer PpIX was demonstrated, which has great potential application for photodynamic therapy. These early affording results of tunable synthesis of MoS2 QDs with desired photo properties can lead to application in fields of biomedical and optoelectronics.

This work investigates the interaction of carbon nitride nanosheet (CNNS), a recently developed two-dimensional nanomaterial, with DNA and its fluorescence quenching mechanism on fluorophore labeled single-stranded DNA probes. The static quenching through the photoinduced electron transfer (PET) from the excited fluorophore to the conductive band of CNNS is identified. Utilizing the affinity change of CNNS to DNA probes upon their recognition to targets and the PET-based fluorescence quenching effect, a universal sensing strategy is proposed for design of several homogeneous fluorescence detection methods with short assay time and high sensitivity. This strategy is versatile and can be combined with different amplification tools for quick fluorescence sensing of DNA and extensive DNA related analytes such as metal cations, small molecules, and proteins. As examples, two simple fluorescence detection methods for DNA and Hg(2+), one facile detection method coupled with Exo III-mediated target recycling for sensitive DNA analysis, and a ratiometric fluorescence protocol for DNA detection are proposed. This work provides an avenue for understanding the interaction between two-dimensional nanomaterials and biomolecules and designing novel sensing strategies for extending the applications of nanomaterials in bioanalysis.

This work designs a telomerase-responsive mesoporous silica nanoparticle (MSN) to realize in situ "off-on" imaging of intracellular telomerase activity. In the wrapping DNA (O1) sealed MSN probe, a black hole fluorescence quencher is covalently immobilized on the inner walls of the mesopores, while fluorescein is loaded in the mesopores. In the presence of telomerase and dNTPs, the designed O1 can be extended and then moves away from the MSN surface via forming a rigid hairpin-like DNA structure. Thus the O1 can act as a "biogate" to block and release fluorescein for "off-on" switchable fluorescent imaging. The MSN probe exhibits good performance for sensitive in situ tracking of telomerase activity in living cells. The practicality of this protocol has been verified by monitoring the change of cellular telomerase activity in response to telomerase-related drugs.

A trifunctional photosensitizer was designed to achieve highly selective near-infrared tumor imaging, efficient photodynamic therapy and therapeutic self-monitoring.