More Like this

1. Ultrahigh Piezoelectric Performance through Synergistic Compositional and Microstructural Engineering

   https://doi.org/10.1002/advs.202105715  

   Yan, Yongke ; Geng, Liwei D. ; Zhu, Li‐Feng ; Leng, Haoyang ; Li, Xiaotian ; Liu, Hairui ; Lin, Dabin ; Wang, Ke ; Wang, Yu U. ; Priya, Shashank ( March 2022 , Advanced Science)

   Piezoelectric materials enable the conversion of mechanical energy into electrical energy and vice‐versa. Ultrahigh piezoelectricity has been only observed in single crystals. Realization of piezoelectric ceramics with longitudinal piezoelectric constant (d₃₃) close to 2000 pC N^–1, which combines single crystal‐like high properties and ceramic‐like cost effectiveness, large‐scale manufacturing, and machinability will be a milestone in advancement of piezoelectric ceramic materials. Here, guided by phenomenological models and phase‐field simulations that provide conditions for flattening the energy landscape of polarization, a synergistic design strategy is demonstrated that exploits compositionally driven local structural heterogeneity and microstructural grain orientation/texturing to provide record piezoelectricity in ceramics. This strategy is demonstrated on [001]_PC‐textured and Eu³⁺‐doped Pb(Mg_1/3Nb_2/3)O₃‐PbTiO₃(PMN‐PT) ceramics that exhibit the highest piezoelectric coefficient (small‐signald₃₃of up to 1950 pC N^–1and large‐signald₃₃* of ≈2100 pm V^–1) among all the reported piezoelectric ceramics. Extensive characterization conducted using high‐resolution microscopy and diffraction techniques in conjunction with the computational models reveals the underlying mechanisms governing the piezoelectric performance. Further, the impact of losses on the electromechanical coupling is identified, which plays major role in suppressing the percentage of piezoelectricity enhancement, and the fundamental understanding of loss in this study sheds light on further enhancement of piezoelectricity. These results on cost‐effective and record performance piezoelectric ceramics will launch a new generation of piezoelectric applications.

    

   more » « less
2. 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)

   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.

    

   more » « less
3. Coupling Spin Defects in a Layered Material to Nanoscale Plasmonic Cavities

   https://doi.org/10.1002/adma.202106046  

   Mendelson, Noah ; Ritika, Ritika ; Kianinia, Mehran ; Scott, John ; Kim, Sejeong ; Fröch, Johannes E. ; Gazzana, Camilla ; Westerhausen, Mika ; Xiao, Licheng ; Mohajerani, Seyed Sepehr ; et al ( October 2021 , Advanced Materials)

   Spin defects in hexagonal boron nitride, and specifically the negatively charged boron vacancy (V_B^‐) centers, are emerging candidates for quantum sensing. However, the V_B^‐defects suffer from low quantum efficiency and, as a result, exhibit weak photoluminescence. In this work, a scalable approach is demonstrated to dramatically enhance the V_B^‐emission by coupling to a plasmonic gap cavity. The plasmonic cavity is composed of a flat gold surface and a silver cube, with few‐layer hBN flakes positioned in between. Employing these plasmonic cavities, two orders of magnitude are extracted in photoluminescence enhancement associated with a corresponding twofold enhancement in optically detected magnetic resonance contrast. The work will be pivotal to progress in quantum sensing employing 2D materials, and in realization of nanophotonic devices with spin defects in hexagonal boron nitride.

    

   more » « less
4. 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)

   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.

    

   more » « less
5. Extraordinary Sensitivity of Surface‐Enhanced Raman Spectroscopy of Molecules on MoS 2 (WS 2 ) Nanodomes/Graphene van der Waals Heterostructure Substrates

   https://doi.org/10.1002/adom.201801249  

   Ghopry, Samar A. ; Alamri, Mohammed A. ; Goul, Ryan ; Sakidja, Ridwan ; Wu, Judy Z. ( February 2019 , Advanced Optical Materials)

   Two‐dimensional transition metal dichalcogenides (TMDs)/graphene van der Waals (vdW) heterostructures integrate the superior light–solid interaction in TMDs and charge mobility in graphene, and therefore are promising for surface‐enhanced Raman spectroscopy (SERS). Herein, a novel TMD (MoS₂and WS₂) nanodome/graphene vdW heterostructure SERS substrate, on which an extraordinary SERS sensitivity is achieved, is reported. Using fluorescent Rhodamine 6G (R6G) as probe molecules, the SERS sensitivity is in the range of 10⁻¹¹to 10⁻¹²mon the TMD nanodomes/graphene vdW heterostructure substrates using 532 nm Raman excitation, which is comparable to the best sensitivity reported so far using plasmonic metal nanostructures/graphene SERS substrates, and is more than three orders of magnitude higher than that on single‐layer TMD and graphene substrates. Density functional theory simulation reveals enhanced electric dipole moments and dipole–dipole interaction at the TMD/graphene vdW interface, yielding an effective means to facilitate an external electrostatic perturbation on the graphene surface and charge transfer. This not only promotes chemical enhancement on SERS, but also enables electromagnetic enhancement of SERS through the excitation of localized surface plasmonic resonance on the TMD nanodomes. This TMD nanodome/graphene vdW heterostructure is therefore promising for commercial applications in high‐performance optoelectronics and sensing.

    

   more » « less