Label-free and non-enzymatic detection of DNA based on hybridization chain reaction amplification and dsDNA-templated copper nanoparticles

A label-free and non-enzymatic amplification fluorescent method for detection of DNA has been developed by using hybridization chain reaction (HCR) and dsDNA-templated copper nanoparticles (CuNPs). First, the biotinylated capture DNA probes were immobilized on the streptavidin-modified beads through the interaction of biotin and streptavidin. Then, target DNA hybridized with the capture DNA probes, which formed a hybridized DNA with sticky end. The sticky end triggered the HCR process and formation of dsDNA polymers while two hairpin probes coexisted. Subsequently, the dsDNA polymers were employed as template for synthesis of CuNPs with excellent fluorescent properties, which provided a label-free, non-enzymatic signal response. Meanwhile, the fluorescence sensing depended on the target DNA triggered HCR, which render this method a high selectivity against single-base mismatch sequences. The concept and methodology developed in this work show great promise in the quantitative detection of DNA in biological and medical applications.     

基于碳量子点-银纳米簇荧光共振能量转移纳米探针的荧光传感器检测转基因成分CaMV35S

利用荧光共振能量转移(FRET)纳米探针结合催化发夹组装(CHA)无酶扩增信号放大途径建立了一种可用于转基因成分的荧光检测方法。首先为CaMV35S目标序列(tDNA)设计了可诱导的CHA循环的两个发夹结构序列HP1和HP2。当单链DNA标记碳点(sDNA-CDs)和DNA模板化银纳米团簇(Ts-AgNCs)杂交后,AgNCs和碳量子点(CDs)靠近,形成FRET效应,得到sDNA-CDs/Ts-AgNCs荧光猝灭的比率荧光探针。当tDNA存在时,通过杂交反应打开HP1发夹,形成HP1-tDNA双链结构;该结构可将HP2的发夹结构打开,从而形成HP1-HP2双链结构,同时释放出tDNA进入下一轮杂交,触发CHA循环。由于HP1-HP2中HP1的部分序列与Ts部分序列间的亲和性较sDNA强,因此,加入sDNA-CDs/Ts-AgNCs后,sDNA-CDs从探针中释放,使CDs(λ_em=464 nm)的荧光得以增强。而AgNCs仍在双链结构中,其荧光强度(λ_em=560 nm)基本保持不变。以I_F464/I_F560...     

Magnetic endohedral transition-metal-doped semiconducting-nanoclusters

Endohedral first-row transition-metal-doped TM@Zn(i)S(i) nanoclusters, in which TM stands for the first-row transition-metals from Sc to Zn, and i=12, 16, have been characterized. In these structures the dopant metals are trapped inside spheroidal hollow semiconducting nanoclusters. It is observed that some of the transition metals are trapped in the center of mass of the cluster, whereas others are found to be displaced from that center, leading to structures in which the transition metals display a complex dynamical behavior upon encapsulation. This fact was confirmed by quantum molecular dynamics calculations, which further confirmed the thermal stability of endohedral compounds. In the endohedrally-doped nanoclusters in which the transition-metal atom sits on the center of mass, the host hollow cluster structure remains undistorted after dopant encapsulation. Conversely, if the encapsulated transition-metal atom is displaced from the center of mass, the host hollow cluster structure suffers a very tiny distortion. Additionally, it is found that there is negligible charge transfer between the dopant transition-metal atom and its hollow cluster host and, after encapsulation, the spin densities remain localized on the transition-metal atom. This allows for the atomic-like behavior of the trapped transition-metal atom, which gives rise to their atomic-like magnetic properties. The encapsulation free energies are negative, suggesting that these compounds are thermodynamically stable.     

离子液体与绿色化学：为了今天还是为了未来？

离子液体因绿色化学的兴起而成名。本文结合作者自己8年来的研究工作评述了离子液体特别是在化学合成、化学反应领域的最新进展。主要分4个方面：离子液体改变了载体/模版的概念;离子液体研究促进了液相反应的研究;离子液体推动了相分离技术的进步;离子液体推动了绿色化学的发展。     

Gap site-specific rapid formation of fluorescent silver nanoclusters for label-free DNA nucleobase recognition

Silver nanoclusters (Ag NCs) templated with DNAs have attracted much attention as novel fluorophores because of their convenient emission tunability by the sequence and length of the template DNAs. However, the precise production of Ag NCs in a site-specific manner still remains a challenge to attain highly selective and label-free DNA recognition. Here we exploited the availability of a gap site in DNA duplexes as a new scaffold for the synthesis of Ag NCs. Compared to the commonly used DNA templates for the creation of Ag NCs, the gap site in DNA duplexes was found to facilitate the rapid formation of the fluorescent Ag NCs without sacrifice of their bright emission and excellent stability. We found that fluorescent Ag NCs were highly selectively formed when cytosine faced toward the gap site in DNA duplexes, and they were in situ utilized as readout by signal-on manner for the DNA mutation assays. This base-selective growth of the fluorescent Ag NCs at the gap site would find promising applications in practical detection of single nucleotide polymorphism (SNP) and construction of DNA-based functional sensors with label-free and cost-effective merits.     

Low temperature synthesis of thiol‐functionalized CdTe nanoclusters with different tellurium contents

In recent years thiol‐functionalized cadmium telluride nanoparticles act as a core layers for obtaining high photovoltaic efficiency in conjugated polymer/inorganic nanocrystal solar cells and also provide easy tuning of quantum size effect by varying thiol groups and processing temperature. In this work, thiol functionalized CdTe nanoclusters were prepared for different tellurium concentrations at low temperature and its impact has been discussed. Structural parameters estimated by X‐ray diffraction revealed hexagonal phases at lower tellurium concentration and cubic phase at higher tellurium concentrations. Surface morphology of the samples analyzed by transmission electron microscopy, exhibited cluster type of morphology. Optical band gap energy estimated by diffused electron microscopy showed an increase with Te content and band edge emission has been observed in the photoluminescence spectra of CdTe nanoclusters around 620 nm. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

铜纳米簇的制备、聚集诱导荧光增强性能及应用研究进展

铜纳米簇不仅具有金属纳米簇的特异性,还有前驱体价格便宜等优点,因此有广泛的应用前景。从配体辅助法、模板法、微波法、电化学法和刻蚀法等综述了铜纳米簇的制备方法。从离子诱导聚集、pH诱导聚集、组装诱导聚集和溶剂诱导聚集增强发射等方面综述了铜纳米簇聚集诱导荧光发射增强性能。从离子检测、小分子检测、酶活性检测、生物大分子检测和生物成像等方面综述了铜纳米簇的应用,并对铜纳米簇的制备、性能优化和应用等方面作了展望。     

Coherent Vibrational Dynamics of [Au25(SR)18]- Nanoclusters?

Coherent vibrational dynamics can be observed in atomically precise gold nanoclusters using femtosecond time-resolved pump-probe spectroscopy. It can not only reveal the coupling between electrons and vibrations, but also reflect the mechanical and electronic properties of metal nanoclusters, which holds potential applications in biological sensing and mass detection. Here, we investigated the coherent vibrational dynamics of [Au₂₅(SR)₁₈]^- nanoclusters by ultrafast spectroscopy and revealed the origins of these coherent vibrations by analyzing their frequency, phase and probe wavelength distributions. Strong coherent oscillations with frequency of 40 cm^-1 and 80 cm^-1 can be reproduced in the excited state dynamics of [Au₂₅(SR)₁₈]^-, which should originate from acoustic vibrations of the Au₁₃ metal core. Phase analysis on the oscillations indicates that the 80 cm^-1 mode should arise from the frequency modulation of the electronic states while the 40 cm^-1 mode should originate from the amplitude modulation of the dynamic spectrum. Moreover, it is found that the vibration frequencies of [Au₂₅(SR)₁₈]^- obtained in pump-probe measurements are independent of the surface ligands so that they are intrinsic properties of the metal core. These results are of great value to understand the electron-vibration coupling of metal nanoclusters.     

金属纳米簇在CO2光催化还原中的研究进展

化石燃料的大量燃烧不仅造成能源危机，而且排放的二氧化碳（CO2）会使气候变暖。以清洁、储量丰富的太阳光作为能量来源，将CO2光催化还原为高附加值的化学产品是缓解当前环境问题和能源问题的主要方法之一。然而，CO2在常温常压下非常的稳定，因此需要设计并构筑高效光催化剂来捕捉和转化CO2，以达到高效光催化CO2还原的目的。在众多研究的光催化剂中，金属纳米簇因其具有独特的结构特点、优异的物理和化学性质，所以在光催化CO2还原领域得到了广泛的应用。基于此，我们首先对金属纳米簇进行了分类，将其分为贵金属纳米簇和非贵金属纳米簇；然后分别对贵金属和非贵金属纳米簇在光催化CO2还原中的研究进展进行了归纳与总结。本文通过及时全面概述近几年该领域的研究进展，从而为未来研究方向提供新思路。     

Molecularly controlled blending of metals and organic metals with polyolefins for the preparation of materials with modulated optical properties

In this paper, after revisiting previous data on terthiophene molecules, several attempts are described to use metal containing species such as nanoclusters and molecular complexes as dispersed chromophores in the same ethylene polymer matrix in order to extend an approach to new classes of molecules and improve some specific optical responses including fluorescence dichroism and behaviour as linear optical polarizers is evaluated. Comparison with typical linear polarizers from the same polymer and terthiophenes of innovative gold clusters is discussed as well as transition metal complexes.