Herein, we report the successful application of hybrid Au-Ag nanoparticles (NPs) and nanochains (NCs) in the harvesting of visible light energy for selective hydrogenation reactions. For individual Au@Ag NPs with Au25 cores, the conversion and turnover frequency (TOF) are approximately 8 and 10 times higher than those of Au25 NPs, respectively. Notably, after the self-assembly of the Au@Ag NPs, the conversion and TOF of 1D NCs were approximately 2.5 and 2 times higher than those of isolated Au@Ag NPs, respectively, owing to the coupling of surface plasmon and the increase in the rate at which hot (energetic) electrons are generated with the formation of plasmonic hot spots between NPs. Furthermore, the surface-enhanced Raman scattering (SERS) activity of 1D Au@Ag NCs was strengthened by nearly 2 orders of magnitude.

Achieving strong coupling between plasmonic oscillators can significantly modulate their intrinsic optical properties. Here, we report the direct observation of ultrafast plasmonic hot electron transfer from an Au grating array to an MoS2 monolayer in the strong coupling regime between localized surface plasmons (LSPs) and surface plasmon polaritons (SPPs). By means of femtosecond pump-probe spectroscopy, the measured hot electron transfer time is approximately 40 fs with a maximum external quantum yield of 1.65%. Our results suggest that strong coupling between LSPs and SPPs has synergetic effects on the generation of plasmonic hot carriers, where SPPs with a unique nonradiative feature can act as an ‘energy recycle bin’ to reuse the radiative energy of LSPs and contribute to hot carrier generation. Coherent energy exchange between plasmonic modes in the strong coupling regime can further enhance the vertical electric field and promote the transfer of hot electrons between the Au grating and the MoS2 monolayer. Our proposed plasmonic strong coupling configuration overcomes the challenge associated with utilizing hot carriers and is instructive in terms of improving the performance of plasmonic opto-electronic devices.

Transition metal dichalcogenides with intrinsic spin-valley degrees of freedom hold great potentials for applications in spintronic and valleytronic devices. MoS monolayer possesses two inequivalent valleys in the Brillouin zone, with each valley coupling selectively with circularly polarized photons. The degree of valley polarization (DVP) is a parameter to characterize the purity of valley-polarized photoluminescence (PL) of MoS monolayer. Usually, the detected values of DVP in MoS monolayer show achiral property under optical excitation of opposite helicities due to reciprocal phonon-assisted intervalley scattering process. Here, it is reported that valley-polarized PL of MoS can be tailored through near-field interaction with plasmonic chiral metasurface. The resonant field of the chiral metasurface couples with valley-polarized excitons, and tailors the measured PL spectra in the far-field, resulting in observation of chiral DVP of MoS -metasurface under opposite helicities excitations. Valley-contrast PL in the chiral heterostructure is also observed when illuminated by linearly polarized light. The manipulation of valley-polarized PL in 2D materials using chiral metasurface represents a viable route toward valley-polaritonic devices.

Ag nanowire with the receiving and transmitting Ag bow tie antenna pairs at its incident and emission ends was patterned on the SiO(2) substrate to realize an enhanced surface plasmon emission with a factor of 45 compared to the single Ag nanowire without antenna pairs. The receiving and transmitting bow tie antenna pairs enhanced the plasmon coupling and emission efficiencies of the Ag nanowire. And the maximum plasmon emission sensitively depended on the length of Ag nanowire, the arm length of bow tie antennas, and the incident angle of optical excitation. This enhanced plasmon emission was confirmed by finite-difference time-domain simulations and explored with analytical calculations using the impedance matching theory at optical frequency.

Photodetectors that capture light and convert it into electricity have been used in many applications, such as imaging systems, environmental surveillance, communications, and biological sensing. [1][2][3] UV detectors play an important role in practical applications, many devices have been prepared with wide bandgap semiconductors, such as ZnO, NiO, and TiO 2 etc. [4][5][6][7][8][9] However, these heterojunction self-powered detectors often exhibit low responsivity and slow response times.

Shape-directed self-assembly of unique gold nanoarrows into supercrystals with unprecedented architectures is realized.

The dangling-bond-free surfaces of van der Waals (vdW) materials make it possible to build ultrathin junctions. Fundamentally, the interfacial phenomena and related optoelectronic properties of vdW junctions are modulated by the interlayer coupling effect. However, the weak interlayer coupling of vdW heterostructures limits the interlayer charge transfer efficiency, resulting in low photoresponsivity. Here, a bilayer MoS2 homogeneous junction is constructed by stacking the as-grown onto the self-healed monolayer MoS2. The homojunction barrier of ∼165 meV is obtained by the electronic structure modulation of defect self-healing. This homojunction reveals the stronger interlayer coupling effect in comparison with vdW heterostructures. This ultrastrong interlayer coupling effect is experimentally verified by Raman spectra and angle-resolved photoemission spectroscopy. The ultrafast interlayer charge transfer takes place within ∼447 fs, which is faster than those of most vdW heterostructures. Furthermore, the homojunction photodiode manifests outstanding rectifying behavior with an ideal factor of ∼1.6, perfect air stability over 12 months, and high responsivity of ∼54.6 mA/W. Moreover, the interlayer exciton peak of ∼1.66 eV is found in vdW homojunctions. This work offers an uncommon vdW junction with strong interlayer coupling and perfects the relevance of interlayer coupling and interlayer charge transfer.

of these perovskite-based photodetectors decreases to almost zero when the incident light wavelength is in the nearinfrared range due to the threshold of the material bandgap width at 760 nm. To improve the optical response of the perovskites in the near-infrared range, many chemical processings were explored, such as mixing of different perovskites [19][20][21][22] and doping of other materials. [23][24][25] Unfortunately, these chemical methods might induce the distortion of perovskite lattice and damage the device performance. [26] Metal nanostructures under light illumination can give rise to localized surface plasmon resonance (LSPR), [27,28] which induces strong light scattering and absorption. [29][30][31][32][33] Randomly inserting metal nanostructures into perovskite-based devices, such as solar cells [34][35][36][37] and photodetectors, [38,39] can improve photoresponse ability at the visible range. However, the response of these perovskite-based devices at the near-infrared range is still very weak.Here, we report a perovskite-based photodetector with high photoresponsivity in the near-infrared range that was fabricated on a well-defined plasmonic-functionalized multilayer substrate that was composed of arrays of Au nanosquares/SiO 2 spacer/ Au film. Due to the strong plasmonic coupling between the substrate and the incident light, a great amount of free carriers are generated in the perovskite film. As a consequence, a wider optical spectrum response and a better external quantum efficiency (EQE) in the near-infrared range were achieved, compared with the perovskite film on a usual Si/SiO 2 substrate. In addition, a sequentially tunable spectral response range of our device can be realized by varying the size of Au nanosquares.The schematic of our photodetector device is shown in Figure 1a, where the plasmonic substrate was designed to consist of three functional layers, arrays of Au nanosquares at the top, a SiO 2 dielectric spacer in the middle, and an Au film at the bottom. The perovskite (CH 3 NH 3 PbI 3 ) and hole-transporting medium (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4 -TCNQ)-doped poly [bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) solution, abbreviated as HTM) were spin-coated onto the substrate. The HTM layer, incorporated between the substrate and CH 3 NH 3 PbI 3 layer, serves two functions: harvesting holes from the CH 3 NH 3 PbI 3 layer and insulating the transfer of hot electrons from the decay of LSPR. The incident Organic-inorganic hybrid perovskite photodetectors have been reported to possess superior optoelectronic properties, such as high sensitivity, ultrafast response, and capability of strongly absorbing the light in the visible range. While in the near-infrared range, the performances of these photodetectors deteriorate seriously, originating from the weak coupling of infrared light to the perovskites. In this study, an organic-inorganic hybrid perovskite photodetector on arrays of Au nanostructures is fabricated, which exhibits a remarkable photocur...