Phan Hoa T, Vinson Claire, Haes Amanda J
Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States.
Langmuir. 2021 Apr 27;37(16):4891-4899. doi: 10.1021/acs.langmuir.1c00132. Epub 2021 Apr 16.
The plasmonic properties of carboxylated gold nanostars distributed on amidoximated polyacrylonitrile (AO PAN) electrospun polymer films scale with surface-enhanced Raman scattering (SERS) intensities for coordinated uranium(VI) oxide (uranyl) species. This two-step plasmonic sensor first isolates uranyl from solution using functionalized polymers; then carboxylated gold nanostars are subsequently deposited for SERS. Spatially resolved localized surface plasmon resonance (LSPR) and SERS facilitate correlated nanostar optical density and uranyl quantification. To reduce sampling bias, gold nanostars are deposited in an inverted drop-coating geometry and measurements are conducted inside resulting nanoparticle coffee rings that form on the polymer substrates. This approach naturally preserves the plasmonic properties of gold nanostars while reducing the deposition of nanoparticle aggregates in active sensing regions, thereby maximizing both the accuracy and the precision of SERS measurements. Several advances are made. First, second-derivative analysis of LSPR spectra facilitates the quantification of local nanostar density across large regions of the sensor substrate by reducing background variations caused by the polymeric and gold materials. Second, local nanostar densities ranging from 140 to 200 pM·cm are shown to result in uranyl signals that are independent of nanostar concentration. Third, the Gibbs free energy of uranyl adsorption to carboxylated nanostars is estimated at 8.4 ± 0.2 kcal/mol. Finally, a linear dynamic range from ∼0.3 to 3.4 μg U/mg polymer is demonstrated. Signals vary by 10% or less. As such, the uniformity of the plasmonic activity of distributed gold nanostars and the employment of spatially resolved spectroscopic measurements on the composite nanomaterial sensor interface facilitate the quantitative detection of uranyl while also reducing the dependence on user expertise and the selected sampling region. These important advances are critical for the development of a user-friendly SERS-based sensor for uranyl.
分布在偕胺肟化聚丙烯腈（AO PAN）电纺聚合物薄膜上的羧基化金纳米星的等离子体特性与配位铀酰（六价铀）物种的表面增强拉曼散射（SERS）强度成比例。这种两步等离子体传感器首先使用功能化聚合物从溶液中分离出铀酰；然后沉积羧基化金纳米星用于SERS。空间分辨的局域表面等离子体共振（LSPR）和SERS有助于相关纳米星光密度和铀酰定量。为了减少采样偏差，金纳米星以倒滴涂层几何形状沉积，并在聚合物基板上形成的纳米颗粒咖啡环内部进行测量。这种方法自然地保留了金纳米星的等离子体特性，同时减少了纳米颗粒聚集体在活性传感区域的沉积，从而最大限度地提高了SERS测量的准确性和精度。取得了几项进展。首先，LSPR光谱的二阶导数分析通过减少由聚合物和金材料引起的背景变化，有助于在传感器基板的大区域上定量局部纳米星密度。其次，显示局部纳米星密度在140至200 pM·cm范围内会产生与纳米星浓度无关的铀酰信号。第三，估计铀酰吸附到羧基化纳米星上的吉布斯自由能为8.4±0.2 kcal/mol。最后，展示了约0.3至3.4 μg U/mg聚合物的线性动态范围。信号变化在10%或更小。因此，分布的金纳米星的等离子体活性的均匀性以及在复合纳米材料传感器界面上采用空间分辨光谱测量有助于铀酰的定量检测，同时也减少了对用户专业知识和所选采样区域的依赖。这些重要进展对于开发用户友好的基于SERS的铀酰传感器至关重要。
