Search

A ratiometric nanosensor for the selective detection and intracellular imaging of highly reactive oxygen species (hROS) is developed. Benzoperylene probe and Mn-ZnS quantum dots based nanoparticles were fabricated through cost effective and simple procedures. The nanoparticles exhibit distinct excimer emission and long-lived room-temperature phosphorescence (RTP) emission at the same time under single wavelength excitation. The nanosensor shows highly sensitive and selective ratiometric response towards hROS over other ROS. The dual emission property also endows the nanoparticles the capability for sensitive live cell imaging of hROS, and the potential for real time monitoring of intracellular hROS.

A novel and efficient approach has been established for the synthesis of silver nanoclusters capped silica nanoparticles (SiO 2 @AgNCs). These nanoclusters (AgNCs) capped silica nanoparticles were utilized as a novel ratiometric photoluminescence (PL) nanosensor for extremely sensitive and selective detection of I − and S 2− ions. The AgNCs were prepared in situ on the silica nanoparticles through polyethyleneimine (PEI) template approach. While dual PL emissions of AgNCs (at 500 nm) and luminescent silica nanoparticles (at 602 nm) formed the basis for the ratiometric sensing. The PL emission of AgNCs was strongly quenched by I − (or S 2− ), while that of luminescent silica nanoparticles was hardly affected. The PL emission intensity ratio of AgNCs and the luminescent silica nanoparticles was defined as I 500 /I 602 . A good linear relationship between the I 500 /I 602 value and the concentration of I − (or S 2− ) was observed, and the limit of detection (LOD) was estimated to be 57 nM for I − and 62 nM for S 2− . In addition, the fluorescence images of the SiO 2 @AgNCs nanosensor changed from white to orange upon exposure to different concentrations of I − (or S 2− ) (0–250 μM), which could be clearly distinguished by the naked eye. The SiO 2 @AgNCs nanosensor exhibited good selectivity against other analytes, and I − or S 2− ions could be separately detected via the introduction of proper masking agents. Furthermore, the detection of I − and S 2− in real water samples was also demonstrated.

A fluorescence turn-on assay for alkaline phosphatase (ALP) activity is developed through the controlled release of polyethyleneimine-capped copper nanoclusters (PEI-capped CuNCs) from the MnO2 nanosheets. In an aqueous solution, the positively charged PEI-capped CuNCs could be adsorbed onto the surface of the negatively charged MnO2 nanosheets. Such adsorption through favorable electrostatic interactions could efficiently quench the nanocluster fluorescence emission via resonance energy transfer from the PEI-capped CuNCs to the MnO2 nanosheets. 2-Phospho-l-ascorbic acid (AAP) could be hydrolyzed to l-ascorbic acid (AA) in the presence of ALP. AA could reduce MnO2 into Mn2+ and trigger the disintegration of the MnO2 nanosheets. As a result, the CuNCs were released and the quenched fluorescence was recovered efficiently. The detection strategy is simple, inexpensive, sensitive, selective, with low toxicity, and has better biocompatibility. The newly fabricated biosensor for ALP activity will potentially make it a robust candidate for numerous biological and biomedical applications.

A sensitive and selective luminescent nanoprobe (referred to as DEPN) is designed for the determination of Cu(II) ions. DEPN shows two emission peaks, one at 602 nm and caused by [Ru(bpy)3]2+, the other (peaking at 500 nm) caused by silver nanoclusters (AgNCs). The luminescence of the ruthenium complex is inert and acts as the internal reference signal, while that of the AgNCs is quenched by Cu(II) ions. Under 350 nm photoexcitation, a linear relationship is found between the ratio of emission intensity (I500/I602) and the concentration of Cu(II) ions in the 0.1–16 μM range. The detection limit of Cu(II) ions is estimated to be 50 nM. The DEPN was applied to the determination of Cu(II) ions in (spiked) water samples, and to intracellular imaging of Cu(II) in HeLa cells using confocal fluorescence microscopy.

Three pairs of new spirocyclic alkaloid enantiomers eurotinoids A-C (1-3), as well as a known biogenetically related racemate dihydrocryptoechinulin D (4) were isolated from a marine-derived fungus Eurotium sp. SCSIO F452. Their structures were determined by spectroscopic analyses and electronic circular dichroism (ECD) calculations. Compounds 1 and 2 represent the first two "meta" products from a non-stereoselective [4 + 2] Diels-Alder cycloaddition presumably between an enone group of a diketopiperazine alkaloid and a diene group of a benzaldehyde derivative via a new head-to-tail coupling mode biosynthetically, while 3 and 4 were "ortho" products. Their enantiomers exhibited different antioxidative and cytotoxic activities. The modes of action were investigated by a preliminary molecular docking study.

A bright white light emitting benzoperylene probe-polyethyleneimine capped quantum dot nanocomposite has been synthesized for the first time. The negatively charged benzoperylene probe with a carboxylic acid functional group tends to self-assemble in the presence of a polycation, and exhibits distinct induced excimer fluorescence. Phosphorescence emitting manganese doped zinc sulfide quantum dots (Mn-ZnS QDs) were capped with polyethyleneimine (PEI). The PEI capped Mn-ZnS QDs were used to induce the benzoperylene probe self-assembly. A bright white light emitting nanocomposite was obtained both in solution and in solid state. The white emission has Commission Internationale de l'Eclairage (CIE) coordinates of (0.33, 0.32), a color-rendering index (CRI) of 72.61 and correlated color temperature (CCT) of 5697 K. Multiple color emissions from blue to orange could also be obtained in a controllable manner via simple adjustment of the ratio of the PEI capped Mn-ZnS QDs and the benzoperylene probe. The nanocomposite displays good photo, chemical and long-term stability. A strong white light emitting LED device based on the nanocomposite was demonstrated.

In this work, we report a novel sensor for colorimetric and fluorometric H2O2 sensing which is based on silver nanoparticles decorated and tetraphenylethene probe doped silica nanoparticles (Ag@TPE-SiO2 NPs). A positively charged tetraphenylethene (TPE) probe is doped into silica nanoparticles, and the nanoparticles exhibit strong fluorescence emission due to aggregation-induced emission (AIE) of the TPE probe. Ag nanoparticles (AgNPs) are prepared in situ on the surface of the silica nanoparticles. AgNPs serve as a nanoquencher which can quench the AIE emission of the TPE-SiO2 NPs efficiently. However, AgNPs can be oxidized to Ag+ by H2O2, which leads to fluorescence recovery and color fading of the Ag@TPE-SiO2 NPs. The dual-readout strategy allows sensitive analysis of H2O2. The detection limit of the fluorometric and colorimetric assay is 0.28 and 2.1 μM, respectively. And the nanosensor also shows good selectivity. In addition, analysis of H2O2 in human serum and intracellular imaging of H2O2 are both demonstrated. With the good analytical properties of merit, the proposed nanoprobe has a promising potential for H2O2 related bioanalysis and biomedical applications.