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.

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.

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.

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...

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Size-dependent luminescence is one of the most promising properties in semiconductor nanocrystals.1 -3 Such sizedependent luminescence is also found in various metal nanocrystals like the gold nanoclusters.4 -6 For example, blue luminescence was observed from Au 8 , which was stabilized and encapsulated by dendrimers. The color of the luminescence was extended to near-IR, as the size of the gold nanoclusters increased, 7,8 which was attributed to the confinement of the cluster sizes comparable to the Fermi wavelength of electrons (approximately 0.7 nm). 9 We recently studied the luminescence of the gold nanoclusters, especially the blue luminescence of Au 8 , 10 which provided a clue to the origin of luminescence in the gold nanoclusters. 11 -13 In this work, we examined the electronic transitions of Au 8 to elucidate the photoluminescence spectrum of the gold nanoclusters in more detail. The calculated geometries and energies of the isomers in Au 8 indicated that one isomer was more stable than the others, implying that a single isomer was the main contributor to the photoluminescence spectrum of Au 8 . The calculated spectrum of the most stable isomer agreed with the experimental spectrum, suggesting that several excited states of the single isomer contributed to the photoluminescence spectrum, whose shape was broad and asymmetric.The photoluminescence of the gold nanoclusters encapsulated by dendrimers was previously reported. 10 The emission maximum at 460 nm (2.7 eV) matched the emission energy of Au 8 (2.75 eV) in the spherical jellium approximation (Figure 1 (a)).8 On the other hand, the photoluminescence band was broad and asymmetric, which was ascribed to the spectral overlapping of emission bands.10 Indeed, the photoluminescence spectrum could be deconvoluted by two Gaussian functions. The low-energy band at 535 nm (2.32 eV) happened to agree with the emission energy of Au 13 (2.34 eV) in the spherical jellium model. 8 In this regard, another nanocluster was previously assigned as Au 13 , 10 because Au 13 was also the stable size of the gold nanoclusters. 8 For better understanding of the broad and asymmetric shape, the electronic transitions of Au 8 were calculated using the GAUSSIAN program.14 At first, the stable geometries and energies of Au 8 were obtained, by analytical gradients with full optimization using ab initio method such as the Møller-Plesset perturbation theory (MP2) and the density functional theory (DFT) such as Becke three-parameter Lee-Yang-Parr (B3LYP) and Perdew-Wang 1991 (B3PW91) gradient corrected exchange and correlation functional at two basis sets (CEP-4G and LANL2DZ). These levels of calculation have been frequently employed to obtain the stable geometries and energies of small gold nanoclusters. 15 -17 Since the emission energy of the dendrimer-encapsulated Au 8 matched the spherical jellium model, three-dimensional geometries were mainly examined, although the most stable geometry was known to be two-dimensional in the gas phase.15 -17 Among the optimized three-dimensio...

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.

An electrochemical approach for single base-specific detection of label-free target single-strand DNA (ssDNA) was demonstrated. The approach was based on the high ligation selectivity of Taq DNA ligase coupled with ferrocenated gold nanoparticle/streptavidin conjugate-based voltammetric detection method. The ferrocene (Fc) moieties of Fc-capped gold nanoparticle/streptavidin conjugates, which were selectively bound to the biotinylated DNA layer, were found to be close enough to the underlying electrode surface for facile electron transfer. The proposed electrochemical method was evaluated with label-free target DNA strands making all possible base pair combinations at the 3'-OH side of capture probe, and showed significant voltammetric signals only with a perfect match target strand. Here, we demonstrate an approach for single base-specific detection of label-free target single-strand DNA (ssDNA). The approach is based on the high ligation selectivity of Taq DNA ligase coupled with ferrocenated nanoparticle-based electrochemical detection method. Taq DNA ligases have been reported to show high selectivity for joining DNA strands that have complementary base pairs at the nick site [1]. The high ligation selectivity of DNA ligases has allowed the development of various ligase-based biotechnologies, but we noticed that there are only a few recent publications on electrochemical techniques based on DNA ligases [2]. The use of ferrocenated nanoparticles has been applied for signal amplification of electrochemical analysis of biomolecules [3]. Owing to the large number of ferrocene (Fc) moieties present on each nanoparticle, the electrochemical signals can be amplified, resulting in high sensitivity for biomolecular analysis.Details of the suggested approach are illustrated in Scheme 1. We first start with allele-discriminating capture probe 1 (P1) immobilized on gold electrode. The P1-immobilized gold surface is then treated with a biotinylated ligation probe 2 (P2) and a target ssDNA to assemble the ternary complex that is a substrate for the subsequent surface ligation reaction with the high fidelity Taq DNA ligase. Only matched DNA substrate resulted in ligation of biotinylated P2 to immobilized P1 on gold surface. After a stringent dehybridization treatment, ligated (and thus immobilized) biotinylated P2 is voltammetrically detected after incubation with ferrocenylhexanethiol(Fc)-capped gold nanoparticle/streptavidin conjugates.We investigated the voltammetric behavior of Fccapped gold nanoparticle/streptavidin conjugates linked to surface-confined biotinylated probe since the distance between the redox Fc moieties and the underlying electrode might prevent facile electron transfer to occur. Specifically, we performed key experiments illustrated in Figure 1 (parts A and B) in order to verify the electron transfer between the surface-confined ferrocenated gold nanoparticle and the underlying electrode. We first immobilized biotinylated long probe (Table 1), which corresponds to the ligated probes (P1 and P2...