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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. Synthesis of a BINOL‐Based C ₃ Symmetric Schiff Base and Its Fluorescence Response to Zn ²⁺

   https://doi.org/10.1002/cplu.202300036  

   Lu, Kai; Guo, Hongyu; Jiang, Yixuan; Yang, Jiaqiao; Yu, Shanshan; Yu, Xiaoqi; Pu, Lin (March 2023, ChemPlusChem)

   Abstract A novelC₃symmetric 1,1’‐bi‐2‐naphthol‐based Schiff base (R,R,R)‐6has been synthesized which shows highly selective fluorescence enhancement with Zn²⁺among 21 metal cations examined. Its sensitivity and selectivity are found to be greater than other relatedC₂(1) andC₁[(R)‐9] symmetric compounds in the fluorescent recognition of Zn²⁺. The mechanistic study reveals that the selective fluorescence enhancement of the probe can be attributed to the formation of a unimolecular multidentate 6‐coordinated Zn²⁺complex. 

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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. 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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5. Nuclear Spin Hyperpolarization of NH ₂ ‐ and CH ₃ ‐Substituted Pyridine and Pyrimidine Moieties by SABRE

   https://doi.org/10.1002/cphc.202000483  

   Mandal, Ratnamala; Pham, Pierce; Hilty, Christian (September 2020, ChemPhysChem)

   Abstract Hyperpolarization of N‐heterocycles with signal amplification by reversible exchange (SABRE) induces NMR sensitivity gains for biological molecules. Substitutions with functional groups, in particular in theortho‐position of the heterocycle, however, result in low polarization using a typical Ir catalyst with a bis‐mesityl N‐heterocyclic carbene ligand for SABRE, presumably due to steric hindrance. With the addition of allylamine or acetonitrile as coligands to the precatalyst chloro(1,5‐cyclooctadiene)[4,5‐dimethyl‐1,3‐bis(2,4,6‐trimethylphenyl)imidazol‐2‐ylidene] iridium, the¹H signal enhancement increased in several substrates withorthoNH₂substitutions. For example, for a proton in 2,4‐diaminopyrimidine, the enhancement factors increased from −7±1 to −210±20 with allylamine or to −160±10 with acetonitrile. CH₃substituted molecules yielded maximum signal enhancements of −25±7 with acetonitrile addition, which is considerably less than the corresponding NH₂substituted molecules, despite exhibiting similar steric size. With the more electron‐donating NH₂substitution resulting in greater enhancement, it is concluded that steric hindrance is not the only dominant factor in determining the polarizability of the CH₃substituted compounds. The addition of allylamine increased the signal enhancement for the 290 Da trimethoprim, a molecule with a 2,4‐diaminopyrimidine moiety serving as an antibacterial agent, to −70. 

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