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1. Hot carrier transfer from plasmon decay in Ag ₂₀ at H–Si(111) surface: real-time TDDFT simulation in Wannier gauge

   https://doi.org/10.1088/1361-648X/ad8b8e  

   Bost, John L; Shepard, Christopher; Kanai, Yosuke (November 2024, Journal of Physics: Condensed Matter)

   Abstract Plasmon decay is believed to play an essential role in inducing hot carrier transfer at the interfaces between plasmonic nanoparticles and semiconductor surfaces. In this work, we employ real-time time-dependent density functional theory (RT-TDDFT) simulation in the Wannier gauge to gain quantum-mechanical insights into the nonlinear dynamics of the plasmon decay in the Ag₂₀nanoparticle at a semiconductor surface. The first-principles simulations show that the plasmon decay is more than two times faster when the Ag₂₀nanoparticle is adsorbed on a hydrogen-terminated Si(111) surface, taking place within 100 femtoseconds of the plasmon excitation. Hot carrier transfer across the interface is observed as the plasmon decay takes place, and nearly 30% of holes are generated deep in the valence band of the semiconductor surface. The use of Wannier gauge in RT-TDDFT simulation is particularly convenient for gaining quantum-mechanical insights into non-equilibrium electron dynamics in complex heterogeneous systems. 

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2. Wide‐Bandgap R Ba ₃ (B ₃ O ₆ ) ₃ ( R = Nd, Sm, Tb, Dy, and Er) Single Crystals for Ultraviolet Nonlinear Optics

   https://doi.org/10.1002/adom.202401437  

   Sarker, Saugata; Wang, Yu; Benyacko, Caeli; Guan, Yingdong; Yoshida, Suguru; Yennawar, Hemant; He, Jingyang; Mao, Zhiqiang; Gopalan, Venkatraman (August 2024, Advanced Optical Materials)

   Abstract Discovery of new materials with enhanced optical properties in the visible and UV‐C range can impact applications in lasers, nonlinear optics, and quantum optics. Here, the optical floating zone growth of a family of rare earth borates,RBa₃(B₃O₆)₃(R= Nd, Sm, Tb, Dy, and Er), with promising linear and nonlinear optical (NLO) properties is reported. Although previously identified to be centrosymmetric, the X‐ray analysis combined with optical second harmonic generation (SHG) assigns the noncentrosymmetricPspace group to these crystals. Characterization of linear optical properties reveals a direct bandgap of ≈5.61–5.72 eV and strong photoluminescence in both the visible and mid‐IR regions. Anisotropic linear and nonlinear optical characterization reveals both Type‐I and Type‐II SHG phase matchability, with the highest effective phase‐matched SHG coefficient of 1.2 pm V⁻¹at 800‐nm fundamental wavelength (for DyBa₃(B₃O₆)₃), comparable to β‐BaB₂O₄(phase‐matchedd₂₂≈ 1.9 pm V⁻¹). Laser‐induced surface damage threshold for these environmentally stable crystals is 650–900 GW cm⁻², which is four to five times higher than that of β‐BaB₂O₄, thus providing an opportunity to pump with significantly higher power to generate about six to seven times stronger SHG light. Since the SHG arises from disorder on the Ba‐site, significantly larger SHG coefficients may be realized by “poling” the crystals to align the Ba displacements. These properties motivate further development of this crystal family for laser and wide bandgap NLO applications. 

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3. On the role of wall thickness in determining the plasmonic properties of silver-gold nanocages

   https://doi.org/10.1039/D3CC02068A  

   Shao, Shikuan; Wang, Ankai; Gupta, Ria; Zou, Shengli; Xia, Xiaohu (June 2023, Chemical Communications)

   Understanding the roles played by wall thickness in determining the plasmonic properties of Ag–Au nanocages from both experimental and theoretical perspectives. 

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4. High-Precision Biochemical Sensing with Resonant Monocrystalline Plasmonic Ag Microcubes in the Mid-Infrared Spectrum

   https://doi.org/10.1021/acsnano.5c00624  

   Beisenova, Aidana; Adi, Wihan; Kang, Shinwon; Germanson, Kenzie B; Nam, Simon; Rosas, Samir; Biswas, Shovasis Kumar; Patankar, Manish S; Jeon, Seog-Jin; Yesilkoy, Filiz (March 2025, ACS Nano)

   Infrared (IR) spectroscopic fingerprinting is a powerful analytical tool for characterizing molecular compositions across biological, environmental, and industrial samples through their vibrational modes. Specifically, when the sample is characterized in resonant plasmonic cavities, as in the surface-enhanced mid-IR absorption spectroscopy (SEIRAS), highly sensitive and specific molecular detection can be achieved. However, current SEIRAS techniques rely on nanofabricated sub-wavelength antennas, limited by low-throughput lithographic processes, lacking scalability to address broad biochemical sensing applications. To address this, we present an on-resonance SEIRAS method utilizing silver (Ag) cubic microparticles (Ag-CMPs) with robust mid-IR plasmonic resonances. These monocrystalline Ag-CMPs, featuring sharp edges and vertices, are synthesized via a high-throughput, wet-chemical process. When dispersed on gold mirror substrates with an aluminum oxide spacer, Ag-CMPs support enhanced near-field light-matter interactions in nanocavities while enabling far-field imaging-based optical interrogation due to their strong extinction cross-sections. We demonstrate the detection of polydimethylsiloxane (PDMS) and bovine serum albumin (BSA) monolayers by simply probing individual Ag-CMPs, enabled by the resonant amplification of the characteristic vibrational absorptions. Furthermore, our single-particle SEIRAS (SP-SEIRAS) approach effectively analyzes complex human peritoneal fluid (PF) samples, eliminating the challenges of standard bulk sample measurements. This scalable and efficient SP-SEIRAS method addresses key limitations of IR spectroscopic fingerprinting techniques, unlocking possibilities for their widespread adoption in real-world biochemical sensing applications. 

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5. Ultrathin-shell epitaxial Ag@Au core-shell nanowires for high-performance and chemically-stable electronic, optical, and mechanical devices

   https://doi.org/10.1007/s12274-021-3718-z  

   Zhu, Yangzhi; Kim, Sanggon; Ma, Xuezhi; Byrley, Peter; Yu, Ning; Liu, Qiushi; Sun, Xiaoming; Xu, Da; Peng, Sangshan; Hartel, Martin C.; et al (November 2021, Nano Research)

   Abstract Silver nanowires (AgNWs) hold great promise for applications in wearable electronics, flexible solar cells, chemical and biological sensors, photonic/plasmonic circuits, and scanning probe microscopy (SPM) due to their unique plasmonic, mechanical, and electronic properties. However, the lifetime, reliability, and operating conditions of AgNW-based devices are significantly restricted by their poor chemical stability, limiting their commercial potentials. Therefore, it is crucial to create a reliable oxidation barrier on AgNWs that provides long-term chemical stability to various optical, electrical, and mechanical devices while maintaining their high performance. Here we report a room-temperature solution-phase approach to grow an ultra-thin, epitaxial gold coating on AgNWs to effectively shield the Ag surface from environmental oxidation. The Ag@Au core-shell nanowires (Ag@Au NWs) remain stable in air for over six months, under elevated temperature and humidity (80 °C and 100% humidity) for twelve weeks, in physiological buffer solutions for three weeks, and can survive overnight treatment of an oxidative solution (2% H 2 O 2 ). The Ag@Au core-shell NWs demonstrated comparable performance as pristine AgNWs in various electronic, optical, and mechanical devices, such as transparent mesh electrodes, surface-enhanced Raman spectroscopy (SERS) substrates, plasmonic waveguides, plasmonic nanofocusing probes, and high-aspect-ratio, high-resolution atomic force microscopy (AFM) probes. These Au@Ag core-shell NWs offer a universal solution towards chemically-stable AgNW-based devices without compromising material property or device performance. 

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