Singlet fission (SF) is an effective multi-exciton generation process. The photoelectric conversion efficiency of photovoltaic devices can be improved by absorbing a high-energy photon and converting it into multiple excitons. Among the known SF materials, crystal materials with high SF efficiency have attracted extensive attention because of their long triplet exciton diffusion length; however, their limited absorption wavelength range and low triplet state energy limit their application. Perylenediimide (PDI) and its derivatives are SF materials with good photostability. However, most studies on their SF remain in solutions and amorphous or polycrystalline films. In this study, we fabricate solutions, polycrystalline films, and nanocrystal films of several PDI derivatives, and analyze their SF processes. The results of the steady-state spectra, time-resolved emission kinetics, and transient absorption spectra indicate that SF exists in nanocrystals; additionally, the charge-transfer (CT) state, which plays a mediating role in the SF process of materials, is found. The SF rates (k SF ) of nanocrystal films are considerably higher than those of polycrystalline films, particularly, PTCDI-C5 (C5) nanocrystal film, which can reach 2.69 ns −1 . The triplet yield of C5 nanocrystals can still reach 103%, even in the case of exciton annihilation. Our results reveal the SF mechanism in PDI derivative nanocrystals, which not only proves that PDI derivative crystals are prospective SF materials, but also indicates that a reasonable design of the molecular structure can help improve the SF efficiency of materials.

At present, the use of efficient and cost-effective methods to construct plasmonic surface-enhanced Raman scattering (SERS) substrates of high sensitivity, uniformity and reproducibility is still crucial to satisfy the practical application of SERS technology. In this paper, a localized surface plasmonic resonance (LSPR) tunable flexible Ag@PDMS substrate was successfully constructed by the low-cost bio-template-stripping method and magnetron sputtering technology. The theory proves that the local electromagnetic field enhancement and “hot spot” distribution is adjustable by modifying the size of the optical cavity unit in the periodicity nanocavity array structure. Experimentally, using rhodamine 6G (R6G) as the target analyte, the SERS performance of optimal Ag@PDMS substrate (Ag film thickness for 315 nm) was researched in detail, which the minimum detection limit was 10−11 M and the enhancement factor was calculated as 8.03 × 108, indicating its high sensitivity. The relative standard deviation (RSD) was calculated as 10.38%, showing that the prepared substrate had excellent electromagnetic field enhancement uniformity. At last, the trace detection of Crystal violet (CV, LOD = 10−9 M) and the simultaneous detection of three common dyes (R6G, CV and Methylene blue (MB) mixture) were also realized. This result suggests that the SERS substrate has a good application prospect in the quantitative and qualitative detection of dye molecules.

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Plasmonic tweezers based on periodic nanostructures have been used to manipulate particles through multiple and uniform local surface plasmon (LSP) fields. However, the coverage area of periodic nanostructures is limited, which restricts the range of trapping and manipulation. In this paper, we present a novel approach to achieve large-scale manipulation and trapping of microspheres by uniformly coupled LSP fields on a short-range disordered self-assembled Ag nanoplates (DSNP) film. The DSNP film is prepared by simple and low-cost methods�chemical growth and self-assembly technique, which overcome the challenges of preparing periodic nanostructures with a large coverage area. The uniform and coupled plasmon fields generated by this film provide enhanced electrodynamic interactions with particles, enabling the non-invasive and repeatable trapping of particles in solution. Utilizing sensitive LSPRs, dynamic manipulating particles was achieved by controlling the laser position. This large-scale platform of stable manipulation enabled by the DSNP film opens up new possibilities for the trapping and manipulation of nanoparticles in a variety of applications.