<h3>Title</h3>
<h3><span style="font-size: 12.16px;">Interface-selective Nonlinear Spectroscopy at Aqueous Interface</span></h3>
<p><strong><span style="font-size: 12.16px;"><span style="text-decoration: underline;">Abstract</span> :</span></strong></p>
<p class="MsoNormal" style="line-height: 115%; text-align: justify;"><span style="font-size: 12.0pt; line-height: 115%; font-family: 'Times New Roman',serif; color: black; mso-themecolor: text1; mso-no-proof: yes;" lang="EN-US">Aqueous interfaces are ubiquitous and play vital roles in a variety of processes relevant to heterogeneous catalysis, electrochemistry, atmospheric, environmental chemistry, and biological self-assembly. </span><span style="font-size: 12.0pt; line-height: 115%; font-family: 'Times New Roman',serif; mso-bidi-theme-font: minor-bidi; color: black; mso-themecolor: text1;" lang="EN-US">Nevertheless, molecular-level understanding of aqueous interfaces is very limited compared to that of the corresponding bulk media. A huge challenge in investigating the aqueous interface is to selectively observe few molecular layer thick interface in the presence of surrounding more plentiful bulk. Due to lack of interface-selectivity, most of the spectroscopic techniques are inadequate for probing aqueous interfaces. Moreover, unlike a solid, water has substantial vapor pressure, which makes it difficult to probe the water surface by conventional spectroscopy such as X-ray photoelectron spectroscopy (XPS). Thus, it is essential to utilize </span><span style="font-size: 12.0pt; line-height: 115%; font-family: 'Times New Roman',serif; color: black; mso-themecolor: text1;" lang="EN-US">spectroscopic techniques that can selectively detect interfacial molecules and directly reveal the structure and properties of the interface at the molecular level. </span></p>
<p class="MsoNormal" style="text-indent: 36pt; line-height: 115%; text-align: justify;"><span style="font-size: 12.0pt; line-height: 115%; font-family: 'Times New Roman',serif; color: black; mso-themecolor: text1;" lang="EN-US">In this seminar, I will introduce interface-selective nonlinear spectroscopy technique called heterodyne-detected vibrational sum frequency generation (HD-VSFG)</span><span style="font-size: 12.0pt; line-height: 115%; font-family: 'Times New Roman',serif; mso-bidi-theme-font: minor-bidi; color: black; mso-themecolor: text1;" lang="EN-US">, which I have been actively developing during my PhD and postdoctoral research. </span><span style="font-size: 12.0pt; line-height: 115%; font-family: 'Times New Roman',serif; color: black; mso-themecolor: text1;" lang="EN-US">HD-VSFG can selectively probe the </span><span style="font-size: 12.0pt; line-height: 115%; font-family: 'Times New Roman',serif; mso-bidi-theme-font: minor-bidi; color: black; mso-themecolor: text1;" lang="EN-US">aqueous interfaces via the vibration of the interfacial molecules<sup>1</sup>. In fact, HD-VSFG </span><span style="font-size: 12.0pt; line-height: 115%; font-family: 'Times New Roman',serif; color: black; mso-themecolor: text1;" lang="EN-US">provides the accurate vibrational spectra of interfacial molecules that are comparable to the IR/Raman spectra for the bulk. Moreover, the sign of HD-VSFG spectrum (i.e., positive or negative amplitude of the signal) reveals the absolute orientation of interfacial molecules. As typical examples, </span><span style="font-size: 12.0pt; line-height: 115%; font-family: 'Times New Roman',serif; mso-bidi-theme-font: minor-bidi; color: black; mso-themecolor: text1;" lang="EN-US">I will discuss the application of HD-VSFG that addresses the hydrogen bonding and orientation of water molecules at the air/water interface<sup>2</sup>, properties of osmolyte and denaturant at water surface<sup>3</sup>. Furthermore, I will discuss my recent HD-VSFG study that resolved the controversy on the origin of SFG signal for the bend vibration of interfacial water<sup>4</sup>. The presented results highlight the importance of interface-selective molecular information obtainable with HD-VSFG and its potential application to explore interfacial phenomena in more complex chemical and biological systems.</span></p>
<p class="MsoNormal" style="text-indent: 36pt; line-height: 115%;"><span style="font-size: 12.0pt; line-height: 115%; font-family: 'Times New Roman',serif; mso-bidi-theme-font: minor-bidi; color: black; mso-themecolor: text1;" lang="EN-US"> </span></p>
<p class="MsoNormal" style="line-height: 115%;"><span style="font-size: 10.5pt; line-height: 115%; font-family: 'Times New Roman',serif; mso-bidi-theme-font: minor-bidi; color: black; mso-themecolor: text1;" lang="EN-US">1 S. Nihonyanagi, J. A. Mondal, S. Yamaguchi, and T. Tahara, Annu. Rev. Phys. Chem. 64, 579 (2013).</span></p>
<p class="MsoNormal" style="line-height: 115%;"><span style="font-size: 10.5pt; line-height: 115%; font-family: 'Times New Roman',serif; mso-bidi-theme-font: minor-bidi; color: black; mso-themecolor: text1;" lang="EN-US">2 M. Ahmed, Y. Nojima, S. Nihonyanagi, S. Yamaguchi, and T. Tahara, ‎J. Chem. Phys. 152, 237101 (2020).</span></p>
<p class="MsoNormal" style="line-height: 115%;"><span style="font-size: 10.5pt; line-height: 115%; font-family: 'Times New Roman',serif; mso-bidi-theme-font: minor-bidi; color: black; mso-themecolor: text1;" lang="EN-US">3 M. Ahmed, V. Namboodiri, P. Mathi, A. K. Singh, and J. A. Mondal, ‎J. Phys. Chem. C 120, 10252 (2016).</span></p>
<p><span style="font-size: 10.5pt; line-height: 107%; font-family: 'Times New Roman',serif; mso-fareast-font-family: 'MS Mincho'; mso-fareast-theme-font: minor-fareast; mso-bidi-theme-font: minor-bidi; color: black; mso-themecolor: text1; mso-ansi-language: EN-US; mso-fareast-language: JA; mso-bidi-language: AR-SA;" lang="EN-US">4 M. Ahmed, S. Nihonyanagi, A. Kundu, S. Yamaguchi, and T. Tahara, ‎J. Phys. Chem. Lett. 11, 9123 (2020).</span></p>