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gold nanocluster

Mojtaba Shamsipur, Afshin Pashabadi, Fatemeh Molaabasi, Saman Hosseinkhani
It is well known that cytochrome c (Cyt c) is a crucial death regulator that triggers programmed cell death, apoptosis. Here, we report on the successful application of an aptamer bioconjugated nanoclusters for the detection of apoptosis based on release of cytochrome c from mitochondria in lysates human embryonic kidney cells HEK293T. The aptamer-conjugated silver nanoclusters (Apt@AgNCs) were synthesized and immobilized on gold electrode for impedimetric detection of Cyt c over the range of 0.15-375nM. It was found that the presence of Ag(I) ions shell at the surface of prepared NCs could increase their affinity to the donor groups (COO(-) and some amine groups in its deprotonated form, NH2) of cysteine attached on the gold electrode surface...
November 23, 2016: Biosensors & Bioelectronics
Guoxiang Hu, Rongchao Jin, De-En Jiang
Staple motifs in the form of -RS(AuSR)x- (x = 1, 2, 3, etc.) are the most common structural feature at the interface of the thiolate-protected gold nanoclusters, Aun(SR)m. However, the recently solved structure of Au92(SR)44, in which the facets of the Au84 core are protected mainly by the bridging thiolates, challenges the staple hypothesis. Herein, we explore the surface sensitivity of the thiolate-gold interface from first principles density functional theory. We find that the interfacial structures of thiolates on gold are surface sensitive: while a staple motif (such as -RS-Au-SR-) is preferred on Au(111), a bridging motif (-RS-) is preferred on Au(100) and Au(110)...
November 29, 2016: Nanoscale
Alper Kinaci, Badri Narayanan, Fatih G Sen, Michael J Davis, Stephen K Gray, Subramanian K R S Sankaranarayanan, Maria K Y Chan
Au nanoclusters are of technological relevance for catalysis, photonics, sensors, and of fundamental scientific interest owing to planar to globular structural transformation at an anomalously high number of atoms i.e. in the range 12-14. The nature and causes of this transition remain a mystery. In order to unravel this conundrum, high throughput density functional theory (DFT) calculations, coupled with a global structural optimization scheme based on a modified genetic algorithm (GA) are conducted. More than 20,000 Au12, Au13, and Au14 nanoclusters are evaluated...
November 28, 2016: Scientific Reports
Xue Yu, Menglu Li, Tianrui Li, Shuo Zhou, Hongyun Liu
In this work, electrochromic Prussian blue (PB) films were electrodeposited on the surface of indium tin oxide (ITO) electrodes, and a dispersion mixture of glucose oxidase (GOD), chitosan (CS) and gold nanoclusters (AuNCs) was then cast on the PB surface to form CS-AuNC-GOD/PB nanocomposite film electrodes. The blue PB component in the films could be changed into its colourless reduced form of Prussian white (PW) upon application of -0.2 V. The addition of glucose to the solution would produce H2O2 with the help of GOD in the films and oxygen in the solution, which could oxidize PW back to PB...
November 24, 2016: Nanoscale
Qi Li, Anindita Das, Shuxin Wang, Yuxiang Chen, Rongchao Jin
The catalytic potential of atomically precise quantum-sized gold nanoclusters (Au38(SC2H4Ph)24) is explored for the three-component coupling of an aldehyde, an alkyne and an amine to synthesize propargylamines. A high catalytic efficiency with a very low loading (0.01 mol%) is achieved. Furthermore, the synergistic effect of the electron-deficient surface (i.e. Au(δ+), 0 < δ(+) < 1) and the electron-rich Au23 core of the ligand-protected nanoclusters is critical for this catalytic reaction.
November 24, 2016: Chemical Communications: Chem Comm
Nonappa, Tanja Lahtinen, Johannes S Haataja, Tiia-Riikka Tero, Hannu Häkkinen, Olli Ikkala
We report supracolloidal self-assembly of atomically precise and strictly monodisperse gold nanoclusters involving p-mercaptobenzoic acid ligands (Au102 -pMBA44 ) under aqueous conditions into hexagonally packed monolayer-thick two-dimensional facetted colloidal crystals (thickness 2.7 nm) and their bending to closed shells leading to spherical capsids (d ca. 200 nm), as controlled by solvent conditions. The 2D colloidal assembly is driven in template-free manner by the spontaneous patchiness of the pMBA ligands around the Au102 -pMBA44 nanoclusters preferably towards equatorial plane, thus promoting inter-nanocluster hydrogen bonds and high packing to planar sheets...
November 23, 2016: Angewandte Chemie
Dong Wang, Qingyuan Bi, Guoheng Yin, Wenli Zhao, Fuqiang Huang, Xiaoming Xie, Mianheng Jiang
An efficient titania supported Au nanocluster (NC) has been prepared for the direct synthesis of useful EtOH from CO2 and H2. The unique creation of an excellent synergistic effect between Au NCs and the underlying TiO2 support, especially the anatase crystal phase with abundant oxygen vacancies, can achieve the high performance for EtOH synthesis under moderate and practical conditions.
November 22, 2016: Chemical Communications: Chem Comm
Qian Zhao, Huan Yan, Ping Liu, Yingyi Yao, Yudong Wu, Jian Zhang, Hengxuan Li, Xiaoqun Gong, Jin Chang
Here, we report an ultra-sensitive and colorimetric sensor for the detection of Fe(3+) or Cu(2+) successively using glutathione-functionalized Au nanoclusters (GSH-AuNCs). For GSH-AuNCs can catalytically oxidize peroxidase substrates, such as 3, 3', 5, 5'-tetramethylbenzidine (TMB), colored products are formed in the presence of H2O2. While upon the addition of Fe(3+) or Cu(2+) into the GSH-AuNCs-TMB-H2O2 system, diverse color and absorbance of the system was obtained due to the self oxidation of Fe(3+) and the inhibition of peroxidase-like activity of GSH-AuNCs...
December 15, 2016: Analytica Chimica Acta
Karuppuchamy Selvaprakash, Yu-Chie Chen
Ricin produced from the castor oil plant, Ricinus communis, is a well-known toxin. The toxin comprises A and B chains. Ricin A chain can cause toxicity by inhibiting protein synthesis, and ricin B can bind to the galactose ligand on the cell membrane of host cells. Inhalation or ingestion of ricin may even lead to death. Therefore, rapid and convenient sensing methods for detecting ricin in suspicious samples must be developed. In this study, we generated protein encapsulated gold nanoclusters (AuNCs@ew) with bright photoluminescence by using chicken egg white proteins as starting materials to react with aqueous tetrachloroaurate...
November 1, 2016: Biosensors & Bioelectronics
Silvia Varela-Aramburu, Richard Wirth, Chian-Hui Lai, Guillermo Orts-Gil, Peter H Seeberger
Gold nanoclusters are small (1-3 nm) nanoparticles with a high surface area that are useful for biomedical studies and drug delivery. The synthesis of small, surface-functionalized gold nanoclusters is greatly dependent on the reaction conditions. Here, we describe a straightforward, efficient and robust room temperature one-pot synthesis of 2 nm gold nanoclusters using thioglucose as a reducing and stabilizing agent, which was discovered by serendipity. The resultant monodisperse gold nanoclusters are more stable than those generated using some other common methods...
2016: Beilstein Journal of Nanotechnology
Yuchun Qiao, Jizhen Shang, Shuying Li, Luping Feng, Yao Jiang, Zhiqiang Duan, Xiaoxia Lv, Chunxian Zhang, Tiantian Yao, Zhichao Dong, Yu Zhang, Hua Wang
A fluorimetric Hg(2+) test strip has been developed using a lotus-inspired fabrication method for suppressing the "coffee stains" toward the uniform distribution of probe materials through creating a hydrophobic drying pattern for fast solvent evaporation. The test strips were first loaded with the model probes of fluorescent gold-silver nanoclusters and then dried in vacuum on the hydrophobic pattern. On the one hand, here, the hydrophobic constraining forces from the lotus surface-like pattern could control the exterior transport of dispersed nanoclusters on strips leading to the minimized "coffee stains"...
November 4, 2016: Scientific Reports
Yu Wang, Haifeng Su, Liting Ren, Sami Malola, Shuichao Lin, Boon K Teo, Hannu Häkkinen, Nanfeng Zheng
The synthesis, structure, substitution chemistry, and optical properties of the gold-centered cubic monocationic cluster [Au@Ag8 @Au6 (C≡C(t) Bu)12 ](+) are reported. The metal framework of this cluster can be described as a fragment of a body-centered cubic (bcc) lattice with the silver and gold atoms occupying the vertices and the body center of the cube, respectively. The incorporation of alkali metal atoms gave rise to [Mn Ag8-n Au7 (C≡C(t) Bu)12 ](+) clusters (n=1 for M=Na, K, Rb, Cs and n=2 for M=K, Rb), with the alkali metal ion(s) presumably occupying the vertex site(s), whereas the incorporation of copper atoms produced [Cun Ag8 Au7-n (C≡C(t) Bu)12 ](+) clusters (n=1-6), with the Cu atom(s) presumably occupying the capping site(s)...
November 3, 2016: Angewandte Chemie
Seema Pande, Wei Huang, Nan Shao, Lei-Ming Wang, Navneet Singh Khetrapal, Wai-Ning Mei, Tian Jian, Lai-Sheng Wang, Xiao Cheng Zeng
Gold nanoclusters have attracted great attentions in the past decade due to their remarkable size-dependent electronic, optical, and catalytic properties. However, the structures of large gold clusters are still not well known because of the challenges in global structural searches. Here we report a joint photoelectron spectroscopy (PES) and theoretical study of the structural evolution of negatively-charged core-shell gold nanoclusters (Aun-) for n = 42 to 50. Photoelectron spectra of size-selected Aun- clusters are well resolved with distinct spectral features, suggesting a dominating structural type...
October 30, 2016: ACS Nano
Kyunglim Pyo, Viraj Dhanushka Thanthirige, Sook Young Yoon, Guda Ramakrishna, Dongil Lee
We report design strategies for the preparation of highly luminescent Au22(SG)18 clusters, where SG is glutathione, by the functionalization of the cluster shell. In these strategies, the cluster shell was covalently modified with small aromatic molecules and pyrene chromophores that led to a 5-fold PL enhancement by rigidifying the shell-gold. Highly luminescent water-soluble gold clusters with a PL quantum yield of 30% were obtained at room temperature. To further enhance the luminescence, the pyrene chromophores in the functionalized Au22 clusters were photoexcited at 350 nm to induce energy transfer from pyrene to the Au22 cluster...
October 26, 2016: Nanoscale
Yong Li, Pei Li, Rong Zhu, Chao Luo, Hao Li, Shanfang Hu, Zhou Nie, Yan Huang, Shouzhuo Yao
Bio-imaging probes for accurately monitoring apoptosis process have extensive significance for cell biological studies and clinical investigations. Herein, a novel multi-functional peptide-tailored gold nanoclusters (AuNCs) has been developed for real-time imaging of caspase-indicated cell apoptosis. The AuNCs nanoprobe was facilely prepared by a one-step peptide-mediated biomineralization with the dye (TRAMA)-tagged peptides specific to caspase 3 as both template agents and the signal switch. Unlike conventional FRET-based fluorescent probes of caspase activity, these nanoprobes relied on the unique quenching effect of AuNCs through the nanosurface energy transfer (NSET) from dye to AuNCs...
October 25, 2016: Analytical Chemistry
Tong Shu, Jianxing Wang, Lei Su, Xueji Zhang
This study describes a novel ratiometric fluorescent sensor based on chemical etching of gold nanocluster (GNCs) for label-free, separation-free determination of tris(2-carboxyethyl)phosphine (TCEP). TCEP was discovered to exhibit unusual chemical behavior toward fluorescent gold nanoclusters: it quenched the red fluorescent emission of the bovine serum album (BSA)-protected GNCs (GNCs@BSA) and simultaneously restored the blue fluorescent emission of the dityrosine (diTyr) residues of the BSA ligand. The TCEP-induced quenching of the fluorescent GNCs@BSA was investigated with the UV-vis adsorption spectrum, the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MOLDI-TOF-MS), inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray photoelectron spectroscopy (XPS), revealing the chemical etching of the gold(0) core of the GNCs@BSA by TCEP...
October 24, 2016: Analytical Chemistry
Eunkeu Oh, Alan L Huston, Andrew Shabaev, Alexander Efros, Marc Currie, Kimihiro Susumu, Konrad Bussmann, Ramasis Goswami, Fredrik K Fatemi, Igor L Medintz
Luminescent gold nanocrystals (AuNCs) are a recently-developed material with potential optic, electronic and biological applications. They also demonstrate energy transfer (ET) acceptor/sensitization properties which have been ascribed to Förster resonance energy transfer (FRET) and, to a lesser extent, nanosurface energy transfer (NSET). Here, we investigate AuNC acceptor interactions with three structurally/functionally-distinct donor classes including organic dyes, metal chelates and semiconductor quantum dots (QDs)...
October 24, 2016: Scientific Reports
Jing Lan, Hong Yan Zou, Qiang Wang, Ping Zeng, Yuan Fang Li, Cheng Zhi Huang
An ultra-sensitive and selective turn off-on fluorescence detection of heparin based on the energy transfer in the BSA-stabilized gold nanoclusters/amino-functionalized graphene oxide (BSA-AuNCs/NH2-GO) hybrids was successfully realized. The BSA-AuNCs containing amounts of carboxyl groups could be absorbed on the surface of NH2-GO through the electrostatic interaction, which resulted in the fluorescence quenching of BSA-AuNCs with high efficiency. However, heparin, possessing high density of negative charge, could compete with BSA-AuNCs to bind NH2-GO and block the energy transfer from BSA-AuNCs to NH2-GO...
December 1, 2016: Talanta
Taiping Qing, Xiaoxiao He, Dinggeng He, Zhihe Qing, Kemin Wang, Yanli Lei, Ting Liu, Peng Tang, Yue Li
In this work, we developed a simple, rapid and mild strategy for synthesis of DNA-templated fluorescent gold nanoclusters (AuNCs) through association of gold ions to DNA templates and reduction with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES). After systematical investigation on the formation of fluorescent AuNCs by using different DNA templates, C5 DNA was found as the best template for the formation of fluorescent AuNCs in this system. This process could be completed within 5min after the reaction beginning under ambient conditions...
December 1, 2016: Talanta
Zhi Wang, Ravithree Senanayake, Christine M Aikens, Wen-Miao Chen, Chen-Ho Tung, Di Sun
Here we report the single-crystal structure, experimental and theoretical characterization of a 41-metal atom Au-Ag alloy nanocluster [Au3Ag38(SCH2Ph)24X5](2-) (1, X = Cl or Br). The nanocluster 1 is co-protected by thiolate and halogen atoms and features an all-metallic face-fused biicosahedral Au2@AuAg20 rod-like kernel enwrapped by the outermost Ag18(SCH2Ph)24X3 shell. Two sites on the surface of the biicosahedral kernel are partially occupied by Au and Ag atoms. The outer Ag18(SCH2Ph)24X3 shell is composed of two Ag6S6 cycles at the two poles and one Ag6S2X3 arc at the equator with both 2- and 3-coordinated Ag atoms, which has not been observed in gold or silver nanoclusters ever before...
December 7, 2016: Nanoscale
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