Nanoscale Infrared Spectroscopy: Improving the Spectral Range of the Photothermal Induced Resonance Technique
Nanoscale Infrared Spectroscopy: Improving the Spectral Range of the Photothermal Induced Resonance Technique
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DOI：
10.1021/ac303620y
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发表时间：
2013-02-19
影响因子：
7.4
通讯作者：
Centrone, Andrea
中科院分区：
文献类型：
--
作者：
Katzenmeyer, Aaron M.;Aksyuk, Vladimir;Centrone, Andrea
光热诱导共振（PTIR）是一种结合了红外光谱的化学特性和原子力显微镜（AFM）的横向分辨能力的新技术。PTIR需要用于样品激发的脉冲可调谐激光器和用于测量由光吸收引起的样品膨胀的AFM针尖。通常可用的激光源的有限的可调谐性限制了PTIR技术对IR光谱的一部分的应用。在这项工作中，一个广泛的可调谐脉冲激光器依赖于差频产生方案在GaSe晶体发射光可调谐从1.55 μ m到16 μ m（从6450 cm（-1）到625 cm（-1））与商业PTIR仪器接口。其结果是一个能够进行化学成像的材料表征平台，与原子力图像注册，其空间分辨率在整个中红外光谱范围内明显超过光衍射极限。PTIR纳米级光谱和图像允许识别成分和光学相似但不同的材料;有机，无机和复合材料样品可以用这种纳米级的红外光谱模拟进行研究，这表明了广泛的适用性。此外，我们比较了两个可调谐激光器，具有不同的脉冲长度，实验评估最近开发的理论PTIR信号产生的结果。
Photothermal induced resonance (PTIR) is a new technique which combines the chemical specificity of infrared (IR) spectroscopy with the lateral resolution of atomic force microscopy (AFM). PTIR requires a pulsed tunable laser for sample excitation and an AFM tip to measure the sample expansion induced by light absorption. The limited tunability of commonly available laser sources constrains the application of the PTIR technique to a portion of the IR spectrum. In this work, a broadly tunable pulsed laser relying on a difference frequency generation scheme in a GaSe crystal to emit light tunable from 1.55 mu m to 16 mu m (from 6450 cm(-1) to 625 cm(-1)) was interfaced with a commercial PTIR instrument. The result is a materials characterization platform capable of chemical imaging, in registry with atomic force images, with a spatial resolution that notably surpasses the light diffraction limit throughout the entire mid-IR spectral range. PTIR nanoscale spectra and images allow the identification of compositionally and optically similar yet distinct materials; organic, inorganic, and composite samples can be studied with this nanoscale analog of infrared spectroscopy, suggesting broad applicability. Additionally, we compare the results obtained with the two tunable lasers, which have different pulse lengths, to experimentally assess the recently developed theory of PTIR signal generation.