3C-SiC nanocrystals as fluorescent biological labels
3C-SiC nanocrystals as fluorescent biological labels
复制标题
DOI：
10.1002/smll.200800080
复制
发表时间：
2008-08-01
期刊：
影响因子：
13.3
通讯作者：
Chu, Paul K.
中科院分区：
文献类型：
--
作者：
Fan, Jiyang;Li, Hongxia;Chu, Paul K.
量子点在荧光尺寸可调和抗光漂白等方面上级染料分子，因此作为荧光探针在生物学中得到了广泛的应用。[1，2]然而，一些量子点的细胞毒性限制了它们在生物系统中的应用，[3，4]并且开发具有低细胞毒性的绿色纳米颗粒已经成为该领域的一个主要关注点。[5-8]碳化硅是一种著名的电力电子半导体材料，被认为是最好的生物相容性材料之一，尤其是对血液。[9]此外，它还具有优良的上级性能，如低密度、高硬度、高强度和化学惰性。近年来，人们在纳米SiC的制备及其光致发光特性的研究方面做了大量的工作。[10-16]一些合成的SiC纳米结构显示出在蓝色到UV范围内的发射，其性质敏感地取决于制造方法，甚至取决于特定的实验。虽然已经报道了一些变化，但一般来说，所观察到的发射可以归因于SiC纳米结构中的一些表面或缺陷状态。然而，由于它们相对较大的尺寸，低发射强度，缺乏可控合成，以及可变的光学性质，这些互连的SiC纳米结构很难用作有效的生物标记物。Kassiba及其同事通过激光热解程序合成了直径为数十纳米的SiC纳米颗粒以及相应的纳米复合材料，并广泛研究了它们的光学性质。[1 - 7 -19]事实上，最近的一篇论文报道了直径在1- 7 nm之间的高度分散的超小胶体3C-SiC纳米颗粒。[20已经从悬浮的6 H-SiC纳米颗粒中观察到类似的发射。[22]在这篇文章中，我们首次报道了3C-SiC纳米晶体在细胞成像中作为生物标记的用途。我们分析了纳米颗粒的荧光动力学和表面化学，这对它们的生物用途至关重要，以了解尺寸小到几纳米的SiC微晶的电子和光学性质。纳米晶体是无毒的和高度抗光漂白。我们的研究结果表明，3C-SiC纳米晶是合适的有效的生物探针。3C-SiC纳米晶体通过将电化学蚀刻的n型多晶3C-SiC（Nd 1/4 5 016 cm 3）分散到水（纯水）溶液中来制备。[21]颗粒的尺寸近似正态分布，最可能的直径为3.9 × 1.1 nm（图1和2）。如图3所示，通过分析UV/维斯和时间分辨的PL光谱，获得了对3C-SiC纳米颗粒的生物物理性质的洞察，包括它们在生物成像中的应用潜力。纳米颗粒显示出单调增加的UV/维斯光谱，起始于约2.8 eV（图3a），其相对于体3C-SiC的带隙（2.2 eV，如图3a所示）蓝移，如从量子限制效应所预期的。低能侧的长吸收尾反映了带隙的间接性质。[23]随着光子能量的增加，从5.3eV开始，吸收的急剧上升可能与第二次间接跃迁有关，因为它的能量低于体3C-SiC的直接带隙。图3b示出了来自荧光3C-SiC纳米晶体的时间分辨PL衰减（插图显示了相应的PL光谱）。PL衰减可以满意地拟合两个指数：一个快速的组件与t% 4.3 ns（84%）和一个缓慢的组件与t% 10.9 ns（16%）。那个...
Quantum dots are superior to dye molecules in many aspects from size-tunable ffuorescence and resistance to photobleaching and they have thus been widely used in biology as ffuorescent probes.[1, 2] However, the cytotoxicity of some quantum dots limits their use in biological systems,[3, 4] and exploiting green nanoparticles with low cytotoxicity has become one major concern in this field.[5–8] Silicon carbide, one well-known power electronic semiconductor material, is considered one of the best biocompatible materials, especially to blood.[9] In addition, it has superior properties such as low density, high hardness, high strength, and chemical inertness. In recent years, much effort has been made to synthesize nanocrystalline SiC and study its photoluminescence (PL) properties.[10–16] Some synthesized SiC nanostructures showed emission in the blue-to-UV range with their properties depending sensitively on the fabrication method and even on specific experiments. Although some variations have been reported, in general the observed emissions can be ascribed to some surface or defect states in the SiC nanostructures. However, owing to their relatively large size, low emission intensity, lack of controlled synthesis, and variable optical properties, these interconnected SiC nanostructures can hardly be used as ffuorescent biological labels. Kassiba and co-workers synthesized SiC nanoparticles with diameters of tens of nanometers as well as the corresponding nanocomposites by a laser pyrolysis procedure and extensively investigated their optical properties.[17–19] Indeed, one recent paper reported highly ffuorescent, ultrasmall colloidal 3C–SiC nanoparticles with diameters of between 1-7nm.[20, 21] Similar emissions have been observed from suspended 6H–SiC nanoparticles.[22] In this Communication, we report for the first time the use of 3C–SiC nanocrystals as biological labels in cell imaging. We analyzed the ffuorescence dynamics and surface chemistry of the nanoparticles, which are crucial to their biological use, in order to fathom the electronic and optical properties of SiC crystallites with sizes down to a few nanometers. The nanocrystals are nontoxic and highly resistant against photobleaching. Our results suggest that 3C–SiC nanocrystals are suitable ffuorescent biological probes. 3C–SiC nanocrystals were prepared by dispersing electrochemically etched n-type polycrystalline 3C–SiC (Nd ¼ 5 Â 016 cmÀ3) into an aqueous (pure water) solution.[21] The size of the particles has an approximately normal distribution with the most probable diameter being 3.9 Æ 1.1 nm (Figure 1 and 2). Insight into the photophysical properties of 3C–SiC nanoparticles involving their application potential in bioimaging was obtained by analyzing the UV/Vis and time-resolved PL spectra, as shown in Figure 3. The nanoparticles show a monotonically increasing UV/Vis spectrum with an onset at around 2.8 eV (Figure 3a), which is blue shifted with respect to the bandgap of bulk 3C–SiC (2.2 eV, as indicated in Figure 3a), as expected from quantum-confinement effects. The long absorption tail on the lower-energy side reffects the indirect nature of the bandgap.[23] The sharper rise in absorption with increasing photon energies, starting from% 5.3 eV, may be associated with a second indirect transition because it is lower in energy than the direct bandgap of bulk 3C–SiC. Figure 3b shows the time-resolved PL decay from ffuorescent 3C–SiC nanocrystals (the inset displays the corresponding PL spectrum). The PL decay can be satisfactorily fitted by two exponentials: a fast component with t% 4.3 ns (84%) and a slow component with t% 10.9 ns (16%). The …