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1. Plasmon-enhanced Quantum Emission from Spin Defects in Two-dimensional Hexagonal Boron Nitride

   https://doi.org/10.1364/CLEO_QELS.2022.FF3C.3  

   Xu, Xiaohui; Solanki, Abhishek. B.; Sychev, Demid; Gao, Xingyu; Martin, Zachariah O.; Baburin, Alexander S.; Chen, Yong P.; Rodionov, Ilya A.; Kildishev, Alexander; Li, Tongcang; et al (January 2022, CLEO: QELS_Fundamental Science 2022)

   We demonstrate 120-fold photoluminescence enhancement of V_B^-spin defects in hBN by coupling them to nanopatch antennas. Since the laser spot is 6.25 times larger than the antenna area, the actual enhancement is 750-fold. 

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2. SABRE-SHEATH hyperpolarized ¹⁵ N ₂ -imidazole for Zn ²⁺ sensing

   https://doi.org/10.1039/D5CC02890F  

   Dhali, Brojo_Kishor Shachib; Abdurraheem, Abubakar; Abdulmojeed, Mustapha; Samoilenko, Anna; Pike, Megan; Harrison, Rielly J; Theiss, Franziska; Goodson, Boyd M; Chekmenev, Eduard Y; Theis, Thomas (August 2025, Chemical Communications)

   SABRE-SHEATH hyperpolarized¹⁵N₂-imidazole is introduced as a novel¹⁵N NMR probe for Zn²⁺sensing. The method achieves 45 700 fold signal enhancement and a detection limit of 1.3 mM, enabling chemical sensing without penetration-depth limitations. 

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3. Impurity Band Formation as a Route to Thermoelectric Power Factor Enhancement in n‐type XNiSn Half‐Heuslers

   https://doi.org/10.1002/apxr.202400179  

   Quinn, Robert J; Go, Yuji; Naden, Aaron B; Bojtor, Andras; Paráda, Gabor; Shawon, Ashiq_K_M A; Domosud, Kamil; Refson, Keith; Zevalkink, Alexandra; Neophytou, Neophytos; et al (January 2025, Advanced Physics Research)

   Abstract Bandstructure engineering is a key route for thermoelectric performance enhancement. Here, 20–50% Seebeck (S) enhancement is reported for XNiCu_ySn half‐Heusler samples based onX= Ti. This novel electronic effect is attributed to the emergence of impurity bands of finite extent, due to the Cu dopants. Depending on the dispersion, extent, and offset with respect to the parent material, these bands are shown to enhanceSto different degrees. Experimentally, this effect is controllable by the Ti content of the samples, with the addition of Zr/Hf gradually removing the enhancement. At the same time, the mobility remains largely intact, enabling power factors ≥3 mW m⁻¹K⁻²near room temperature, increasing to ≥5 mW m⁻¹K⁻²at high temperature. Combined with reduced thermal conductivity due to the Cu interstitials, this enables high averagezT= 0.67–0.72 between 320 and 793 K for XNiCu_ySn compositions with ≥70% Ti. This work reveals the existence of a new route for electronic performance enhancement in n‐type XNiSn materials that are normally limited by their single carrier pocket. In principle, impurity bands can be applied to other materials and provide a new direction for further development. 

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4. Optical characterization of potassium barium borate glasses embedded with Er ³⁺ and silver nanoparticles

   https://doi.org/10.1364/JOSAB.600109  

   Talewar, Rupesh A; Johnson, Aaron; Palmer-Tesema, Yannik; Reddy, B Rami (June 2026, Journal of the Optical Society of America B)

   In this work, the effect of silver (Ag) nanoparticles (NPs) on thespectroscopic properties ofEr³⁺ions embedded in a potassium barium borate glass (KBB) matrix wassystematically investigated. Glass samples were prepared using themelt-quenching technique with varying Ag concentrations. Opticalabsorption and emission studies revealed notable modifications in spectralfeatures due to the surface plasmon resonance (SPR) of Ag NPs. Apronounced enhancement ofEr³⁺luminescence is observed after annealing of Ag containing glasses, arisingfrom annealing-assisted Ag NPs formation and modification of the localglass environment. Fluorescence lifetime measurements further confirmedstrong interactions betweenEr³⁺ions and Ag NPs. The Judd–Ofelt (J–O) analysis was performed to assesschanges in the local field environment ofEr³⁺ions induced by Ag incorporation. The calculated intensity parameters(Ω₂,Ω₄,andΩ₆)exhibited systematic variations with Ag content, indicating modificationsin site symmetry and ligand field strength. The derived radiativeparameters are consistent with the observed luminescence enhancement,demonstrating that Ag NPs effectively modified both emission behavior andfundamental spectroscopic characteristics ofEr³⁺-dopedpotassium barium borate glasses. 

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5. Raman enhancement induced by exciton hybridization in molecules and 2D materials

   https://doi.org/10.1038/s41699-024-00446-z  

   Kitadai, Hikari; Tan, Qishuo; Ping, Lu; Ling, Xi (December 2024, npj 2D Materials and Applications)

   Abstract Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for trace-level fingerprinting. Recently, layered two-dimensional (2D) materials have gained significant interest as SERS substrates for providing stable, uniform, and reproducible Raman enhancement with the potential for trace-level detection. Yet, the development of effective 2D SERS substrates is still hindered by the lack of fundamental understanding of the coupling mechanism between target molecules and substrates. Here, we report a systematic excitation-dependent Raman spectroscopy investigation on the coupling between 2D materials such as SnS₂, MoS₂, WSe₂, and graphene and small organic molecules like rhodamine 6G (Rh 6G). Strong coupling between SnS₂and Rh 6G is found due to their degenerate excitons through Raman excitation profiles (REP), leading to the enhancement of Rh 6G vibrational modes that are observable down to 10⁻¹³M. Our study shows that exciton coupling in the substrate-adsorbate complex plays a vital role in the Raman enhancement effect, opening a new route for designing SERS substrates for high sensitivity. 

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