Surface- and tip-enhanced resonant Raman scattering from CdSe nanocrystals.
Surface- and tip-enhanced resonant Raman scattering from CdSe nanocrystals.
复制标题
DOI：
10.1039/c4cp05087h
复制
发表时间：
2015-08
期刊：
影响因子：
--
通讯作者：
E. Sheremet;A. Milekhin;Raul D. Rodriguez;Thomas Weiss;Maxim Nesterov;E. Rodyakina;O. Gordan;L. S
中科院分区：
文献类型：
--
作者：
E. Sheremet;A. Milekhin;Raul D. Rodriguez;Thomas Weiss;Maxim Nesterov;E. Rodyakina;O. Gordan;L. S
研究了单层CdSe量子点中光学声子的表面和针尖增强共振拉曼散射（共振SERS和TERS）。SERS增强是通过采用由电子束光刻制备的具有不同纳米团簇直径的金阵列组成的等离子体活性基底来实现的。SERS增强的幅度取决于局域表面等离子体共振（LSPR）能量，这是由结构参数决定的。的LSPR位置作为纳米团簇直径的函数，实验确定从光谱显微椭圆偏振，并比较数值模拟显示良好的定性协议。采用LB技术在SERS基底上制备了单层的CdSe量子点。通过调节激发能使其接近于量子点的带隙和LSPR能，实现了由量子点的纵光学声子引起的共振SERS。SERS增强因子达到2 × 10（3）。这允许检测CdSe QD的更高阶LO模式，证明QD的高结晶质量。LO声子模强度与Au纳米团簇尺寸的关系显示出共振特性，表明SERS增强的电磁机制占主导地位。最后，使用电化学蚀刻的金尖端获得了来自CdSe量子点的共振TERS光谱，提供了10（4）量级的增强。这是从单个量子点检测声子谱的重要一步。
Surface- and tip-enhanced resonant Raman scattering (resonant SERS and TERS) by optical phonons in a monolayer of CdSe quantum dots (QDs) is demonstrated. The SERS enhancement was achieved by employing plasmonically active substrates consisting of gold arrays with varying nanocluster diameters prepared by electron-beam lithography. The magnitude of the SERS enhancement depends on the localized surface plasmon resonance (LSPR) energy, which is determined by the structural parameters. The LSPR positions as a function of nanocluster diameter were experimentally determined from spectroscopic micro-ellipsometry, and compared to numerical simulations showing good qualitative agreement. The monolayer of CdSe QDs was deposited by the Langmuir-Blodgett-based technique on the SERS substrates. By tuning the excitation energy close to the band gap of the CdSe QDs and to the LSPR energy, resonant SERS by longitudinal optical (LO) phonons of CdSe QDs was realized. A SERS enhancement factor of 2 × 10(3) was achieved. This allowed the detection of higher order LO modes of CdSe QDs, evidencing the high crystalline quality of QDs. The dependence of LO phonon mode intensity on the size of Au nanoclusters reveals a resonant character, suggesting that the electromagnetic mechanism of the SERS enhancement is dominant. Finally, the resonant TERS spectrum from CdSe QDs was obtained using electrochemically etched gold tips providing an enhancement on the order of 10(4). This is an important step towards the detection of the phonon spectrum from a single QD.