Charge Transfer Doping Modulated Raman Scattering and Enhanced Stability of Black Phosphorus Quantum Dots on a ZnO Nanorod

Abstract

multiple capabilities in transistors, [2] biomedicine, [3] energy storage and conversion applications. [4] Thanks to its thicknessdependent band structure and anisotropic feature, explorations for basic optical properties of BP have recently been extensively performed, including layer-dependent optical absorption, [5] excitonic transition, [6] fluorescent engineering, [7] and polarized Raman behaviors, [8] which provide a lightmatter interaction platform to access novel electron-phonon phenomena. [9] Nevertheless, few methodologies have been developed to tune Raman scattering intensity of few-layer BP. In general, solvent exfoliated BP possess the damaged interlayer structure and abundant trap states, which suppress the extraction of Raman scattering signals as compared with mechanically cleaved ones. [10] Noble metal nanoparticles are often used to enhance Raman scattering of small molecules through a classic electromagnetic enhancement mechanism. Very recently, several attempts on noble metals loaded on few-layer BP have shown very limited effect, [11] indicating a strong near-field electron-phonon coupling is not so easy to obtain for BP. Inspired by charge transfer Black phosphorus (BP) has recently triggered an unprecedented interest in the 2D community. However, many of its unique properties are not exploited and the well-known environmental vulnerability is not conquered. Herein, a type-I mixed-dimensional (0D-1D) van der Waals heterojunction is developed, where three-atomic-layer BP quantum dots (QDs) are assembled on a single ZnO nanorod (NR). By adjusting the indium (In) content in ZnO NRs, the degree and even the direction of surface charge transfer doping within the heterojunction can be tuned, which result in selective Raman scattering enhancements between ZnO and BP. The maximal enhancement factor is determined as 4340 for BP QDs with sub-ppm level. Furthermore, an unexpected long-term ambient stability (more than six months) of BP QDs is revealed, which is ascribed to the electron doping from ZnO:In NRs. The first demonstration of selective Raman enhancements between two inorganic semiconductors as well as the improved stability of BP shed light on this emerging 2D material. Raman Modulation

Surface Enhanced Raman Scattering Revealed by Interfacial Charge-Transfer Transitions

“…The dramatically enhanced PICT processes in the heterojunction were believed to responsible for the SERS, based on the promoted charge-carrier separation and exciton resonance induced by the heterojunctions. As an interesting example reported by Hu and coworkers, 94 few-layered black phosphorus (BP) quantum dots (QDs) were utilized to construct vdW heterojunctions with a ZnO nanorod. In the hybrid, the degree and even direction of the CT could be modulated by adjusting the indium content in the ZnO nanorod, leading to mutual enhancements in Raman scattering between ZnO and BP.…”

Layer‐Dependent Optoelectronic Properties of 2D van der Waals SnS Grown by Pulsed Laser Deposition

“…The critical size of field effect transistors (FETs) is aggressively scaled down to the nanometer regime to acquire higher chip density, higher speed, and lower power consumption 3,4. Among the low‐dimensional materials, 2D layered materials5 such as graphene,6 black phosphorus (BP),7–9 and transition metal dichalcogenides (TMDCs)10 have been widely investigated for their potential development in future electronics and optoelectronics technology due to their unique physical, chemical, optical, and electronic properties. As carrier transport is confined in plane, 2D layered materials are considered as promising candidates for high‐mobility “tunnel‐electronic” devices.…”

2D Black Phosphorus–Based Biomedical Applications

“…Therefore, the PPT effect of the BP–Au NS‐based in vivo is also monitored by using SERS analysis. Hu et al prepared a BP heterojunction by assembling both three‐atomic‐layer BPQD and a single ZnO nanorod (NR). By modulating the content of indium in ZnO NRs, selective Raman scattering between ZnO and BP could be enhanced due to the adjustment of the surface charge transfer of heterojunction.…”