Germanium quantum dots (GeQDs) show unique advantages in fluorescence applications due to their large quantum confinement effect and excellent biocompatibility. However, GeQDs are confronted with difficulty in accurately controlling the fluorescence emission. This defect brings challenges to understanding the fluorescence mechanism and limits the potential applications of GeQDs. In this paper, a series of GeQDs with the average diameter of about 2.6 nm modified with different ligands were synthesized by the chemical reduction method. The fluorescence emission of GeQDs can be changed from blue to yellow-green through adjusting the surface ligands. The influence of surface ligands on the fluorescence emission of GeQDs was thoroughly investigated by experimental and theoretical calculations. Furthermore, the synthesized GeQDs exhibit good biocompatibility and photostability and can act as high-performance fluorescence probes for long-term fluorescent bioimaging. This work provides a good and deep understanding of the fluorescence mechanism of GeQDs and will facilitate diverse promising applications of GeQDs in the near future.
Wei Wei,Yongya Zhang,Lei Liang,Kefeng Wang,Qingfeng Zhou,Yanli Zhou,Hua Wang
Metal germanium (Ge) with a high theoretical capacity of 590 mA h g−1 is regarded as a promising anode material for sodium ion batteries, but it suffers from a fast capacity decay problem due to the serious agglomeration of Ge particles caused by the drastic volume change during the sodiation/desodiation process. Constructing highly dispersed ultrafine Ge nanoparticles is a possible way to address this problem. However, reported methods to obtain highly dispersed metal nanoparticles encountered problems of poor electrochemical activity or non-uniform particle size. In this work, we proposed a new in situ confined polymerization method for preparing highly dispersed Ge quantum dots (QDs). Due to the high dispersion of Ge QDs in carbon frameworks derived from poly(ionic liquid) networks, the obtained Ge@C nanocomposite could effectively avoid the agglomeration of Ge particles. When applied as the anode material for sodium ion batteries, the Ge@C nanocomposite shows ultra-long cycle life and high rate capability. At a current density of 1500 mA g−1, the Ge@C electrode could display a high capacity of 201 mA h g−1 after 5000 cycles. This method could be extended to prepare other highly dispersed metal nanoparticles and achieve fairly efficient electrode materials for new-type secondary batteries.
The optoelectronic tunability and solution processability of colloidal germanium quantum dots (GeQDs) make them highly attractive as active materials for thin film optoelectronics. However, while long-chain aliphatic ligands can effectively protect GeQD surfaces from oxidation and enhance colloidal stability, their insulating nature severely impedes charge carrier transport within the GeQD active layer. In this study, we introduce a solid-state ligand exchange (SSLE) approach using methylammonium iodide (MAI) to replace the insulating oleylamine ligands, thereby enhancing charge carrier mobilities in the GeQD thin film. We demonstrate that a low concentration of MAI effectively substitutes for OAm on GeQD surfaces while preserving the structural integrity of the crystalline core. The resulting MAI-passivated GeQD films exhibit significantly reduced trap densities and enhanced hole and electron mobilities compared with their OAm-passivated counterparts. Furthermore, we fabricate solar cells using a layer-by-layer SSLE process to construct a multilayered GeQD active layer, achieving a power conversion efficiency of up to 1.64 × 10–3 %, a significant improvement over previously reported GeQD photovoltaics.
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