Blue luminescence of dendrimer-encapsulated gold nanoclusters.

Direct evidence for the blue luminescence of gold nanoclusters encapsulated inside hydroxyl-terminated polyamidoamine (PAMAM) dendrimers was provided by spectroscopic studies as well as by theoretical calculations. Steady-state and time-resolved spectroscopic studies showed that the luminescence of the gold nanoclusters consisted largely of two electronic transitions. Theoretical calculations indicate that the two transitions are attributed to the different sizes of the gold nanoclusters (Au8 and Au13). The luminescence of the gold nanoclusters was clearly distinguished from that of the dendrimers.

Distinctive optical transitions of tunable multicolor carbon dots.

Three types of carbon dots (CDs) are synthesized from isomers of phenylenediamine to develop multicolor nanomaterials with low toxicity, high stability, and high quantum yield. The distinctive electronic structures of CDs lead to the characteristic optical transitions, such as three colors of blue, green, and red, which are primarily attributed to the difference in configurations, despite the similar basic structures of conjugated systems. The excitation-independent emission and the single exponential decay of CDs indicate the single chromophore-like nature in each type of CD. In addition, the two-photon luminescence of CDs exhibits a comparable shape and time profile to the typical photoluminescence with high photostability. Although the surface-related defect states are observed by intragap excitation, the contribution of defect states is barely observed in the emission profile upon band gap excitation. Consequently, the controllability of optical transitions in CDs enhances the potential of tunable multicolor nanomaterials for various applications as alternatives to quantum dots containing toxic elements.

Near-infrared electrochemiluminescence from orange fluorescent Au nanoclusters in water.

We report the unusual generation of near-infrared (near-IR) electrochemiluminescence (ECL) from water-soluble Au nanoclusters (NCs), of which the photoluminescence is primarily within the visible wavelength region. The near-IR ECL is ascribed to the Au(0)-glutathione motif in the Au NCs stabilized by glutathione in water.

Electrochemical discrimination of phthalic acid among three phthalic acid isomers based on an N-butylaminomethyl-ferrocene derivative.

A chemosensor compound (1) consisting of a central ferrocene with two butylaminomethyl arms showed unexpected facile electrochemical oxidation of the secondary amines in proximity to the ferrocene, which was utilized for electrochemical discrimination of phthalic acid selectively over two other isomers, isophthalic acid and terephthalic acid.

Covalent decoration of graphene oxide with dendrimer-encapsulated nanoparticles for universal attachment of multiple nanoparticles on chemically converted graphene.

We report a method for universal assembly of multiple nanoparticles with different sizes and compositions on a single chemically converted graphene sheet with good control over particle sizes in the range of 1 to 2 nm through the covalent immobilization of dendrimer-encapsulated nanoparticles.

Changes of Telomerase Activity and Proliferation by Inhibition of Reverse Transcriptase Activity in Human Cancer Cell.

PURPOSE: Activation of telomerase is proposed to be an essential step in cancer cell immortalization and cancer progression. 3'-azido-2',3'-dideoxythymidine (AZT), a reverse transcriptase inhibitor, was reported to be incorporated in telomeric sequences of immortalized cells in culture and to suppress the activity of telomerase and the cell proliferation. In this study, after induction of cancer cell senescence with long-term treatment of AZT, we investigated the dynamics of telomerase subunits (hTERT, hTR, TEP), transcription factors (c-Myc, Mad1), telomerase activity, and finally, telomere length in a human breast cancer cell line. MATERIALS AND METGODS: Human breast cancer cell (MDA-MB-231) was treated with AZT. Senescence was measured by senescence-associated beta-gal staining and apoptosis was counted by dTd enzyme assay. Telomerase activity (by TRAP assay), expression of telomerase subunit genes (by RT-PCR and real-time PCR) and telomere length (by Southern blot analysis) were measured after the AZT treatment. RESULTS: We found evidences of senescence, apoptosis and growth delay after AZT treatment. In addition, AZT- treated cancer cells showed inhibition of telomerase activity and shortening of telomere length in a dose- and duration-dependent way. Among the telomerase subunits, hTERT and c-Myc were the first factors to change after AZT treatment, subsequently, followed by the changes of hTR, Mad1 and TEP. CONCLUSION: The suppression of hTERT and c-Myc by AZT treatment was the initial genetic phenomenon, subsequently followed by the changes of hTR, Mad1 and TEP.