Search

We observed a unique interpillar gap-related surface-enhanced Raman scattering (SERS) behavior of p -aminothiophenol (PATP) molecules from periodic TiO2 nanopillar arrays with three gap sizes of 191, 297 and 401 nm, which is completely different from that on Ag and Ni nanopillar arrays. Especially, the gap-size-dependent charge-transfer (CT) resonance enhancement from TiO2/Ni has been indicated through comparisons of variation trend of SERS intensities with inter-pillar gap size between TiO2/Ni and Ag/TiO2/Ni as well as Ni nanoarrays, and been confirmed by spectra of ultraviolet–visible absorption and photoluminescence. Results demonstrate that the CT resonance enhancement is more susceptible to the change of the gap size compared with the surface plasmon resonance (SPR) enhancement in TiO2/Ni nanoarrays. Hence, SPR and CT enhancement showing different variation trend and rate with the gap size that leads to a different relative contribution of CT resonance to the overall SERS enhancement as gap size changes, and consequently results in a unique gap-related SERS behavior for TiO2/Ni nanoarrays. The present study is not only helpful for investigating SERS mechanism for semiconductors but also providing a method to design and optimize periodic metal/semiconductor SERS substrates in a controllable way. [ABSTRACT FROM AUTHOR]

The realization of large-scale and high-density gaps with sizes as small as possible is crucial for designing ultra-sensitive surface-enhanced Raman scattering (SERS) substrates. As known, the ultrathin alumina mask (UTAM) surface nanopatterning technique allows the fabrication of periodic nanoparticle (NP) arrays with 5 nm gaps among the NPs, however, it still faces a significant challenge in realizing the reliable distribution of nanogaps over a large area, because of the unavoidable collapse of the UTAM pore wall during the traditional one-step homothermal pore-widening process. Herein, an efficient two-step poikilothermal pore-widening process was developed to precisely control the pore wall etching of a UTAM, enabling effectively avoiding the fragmentation of the UTAM and finally obtaining a large-scale UTAM with a pore wall thickness of about 5 nm. As a result, large-scale NP arrays with high-density sub-5 nm and even smaller gaps between the neighboring NPs have been realized through applying the as-prepared UTAM as the nanopatterning template. These NP arrays with sub-5 nm gaps show ultrahigh SERS sensitivity (signal enhancement improved by an order of magnitude compared with NP arrays with 5 nm gaps) and good reproducibility, which demonstrates the practical feasibility of this promising two-step pore-widening UTAM technique for the fabrication of high-performance active SERS substrates with large-scale ultra-small nanogaps. [ABSTRACT FROM AUTHOR]

We observed a unique interpillar gap-related surface-enhanced Raman scattering (SERS) behavior of p -aminothiophenol (PATP) molecules from periodic TiO 2 nanopillar arrays with three gap sizes of 191, 297 and 401 nm, which is completely different from that on Ag and Ni nanopillar arrays. Especially, the gap-size-dependent charge-transfer (CT) resonance enhancement from TiO 2 /Ni has been indicated through comparisons of variation trend of SERS intensities with inter-pillar gap size between TiO 2 /Ni and Ag/TiO 2 /Ni as well as Ni nanoarrays, and been confirmed by spectra of ultraviolet-visible absorption and photoluminescence. Results demonstrate that the CT resonance enhancement is more susceptible to the change of the gap size compared with the surface plasmon resonance (SPR) enhancement in TiO 2 /Ni nanoarrays. Hence, SPR and CT enhancement showing different variation trend and rate with the gap size that leads to a different relative contribution of CT resonance to the overall SERS enhancement as gap size changes, and consequently results in a unique gap-related SERS behavior for TiO 2 /Ni nanoarrays. The present study is not only helpful for investigating SERS mechanism for semiconductors but also providing a method to design and optimize periodic metal/semiconductor SERS substrates in a controllable way., (© 2024 IOP Publishing Ltd.)

Van der Waals heterostructures based on the combination of 2D transition metal dichalcogenides and conventional semiconductors offer new opportunities for the next generation of optoelectronics. In this work, the sulfurization of Mo film is used to synthesize vertically-aligned MoS 2 nanofilm (V-MoS 2 ) with wafer-size and layer controllability. The V-MoS 2 /n-Si heterojunction was fabricated by using a 20 nm thickness V-MoS 2 , and the self-powered broadband photodetectors covering from deep ultraviolet to near infrared is achieved. The device shows superior responsivity (5.06 mA W -1 ), good photodetectivity (5.36 × 10 11 Jones) and high on/off ratio I on / I off (8.31 × 10 3 at 254 nm). Furthermore, the V-MoS 2 /n-Si heterojunction device presents a fast response speed with the rise time and fall time being 54.53 ms and 97.83 ms, respectively. The high photoelectric performances could be attributed to the high-quality heterojunction between the V-MoS 2 and n-Si. These findings suggest that the V-MoS 2 /n-Si heterojunction has great potential applications in the deep ultraviolet-near infrared detection field, and might be used as a part of the construction of integrated optoelectronic systems., (© 2021 IOP Publishing Ltd.)

The full utilization of incident light is vitally important for boosting the photoelectrochemical activity of photoelectrodes. Herein, we introduce Ni-BiVO 4 nanoarrays for mediating the photoelectrochemical water splitting by optimizing the optical modes. Highly ordered Ni-BiVO 4 nanoarrays were fabricated using a nanoimprinted AAO templating technique. By controlling the thickness of BiVO 4 , we efficiently regulate the photoelectrochemical activity, and the photocurrent was up to 0.91 mA cm -2 at 1.4 V versus Ag/AgCl under 100 mW cm -2 in the visible light, which is 3.25 times that of a flat Ni-BiVO 4 electrode with the same deposition cycles of BiVO 4 . The optimal efficiency of a Ni-BiVO 4 nanoarrray-based photoelectrode can be attributed to the optimal morphology, which has the lowest reflection, the strongest scattering and the induced strongest absorption for the incident light among the nanoarrays samples with different thickness of BiVO 4 . This work demonstrates the importance of the optimization of optical modes in the nanoarray photoelectrode in order to boost photoelectrochemical activity.