Synthesis of Fluorescent and Water-Dispersed Germanium Nanoparticles and Their Cellular Imaging Applications

Abstract

In recent years, Ge nanomaterials have aroused a great deal of attention because of their unique physical and chemical properties. However, the current synthesis methods bear some disadvantages, such as high reaction temperature, dangerous reagents, and inert atmospheres. In this paper, we developed a facile one-step route for preparing fluorescent and water-dispersed germanium nanoparticles (Ge NPs) by utilizing organogermanes as the precursor, operated at mild reactive conditions. The as-synthesized Ge NPs have an average diameter of 2.6 ± 0.5 nm and intense blue-green fluorescence (FL). Furthermore, the as-synthesized Ge NPs show remarkable water dispersibility, favorable biocompatibility, outstanding photostability, excellent storage stability, and low cytotoxicity. More importantly, these Ge NPs can act as a satisfactory FL probe and successfully be applied to cellular imaging of HeLa. The present study offers a simple and moderate strategy for the preparation of Ge NPs and expedites Ge NPs for bioimaging applications.

Morphological and Surface-State Challenges in Ge Nanoparticle Applications

“…Of the known NIR-emitting NPs, Ge is one of the only materials that enables targeted applications in both the NIR-II and NIR-III biological windows at sizes appropriate for renal clearance while maintaining low toxicity, making quantum confined Ge an ideal candidate for future biomedical applications. This has prompted large scientific efforts to improve the quality, reproducibility, and surface control of these materials in order to exploit their favorable properties for bioimaging and medicine. ,,,,,,,− …”

“…Besides their size-dependent absorption and emission, fluorescent NPs show high resistance against photobleaching, making them suitable for long-term and multicolor labeling . Hu et al developed a water-based reduction of organogermanium precursors with NaBH 4 to produce fluorescent c-Ge NPs with remarkable photostability . Within this study, the researchers developed a relatively mild and simple one-pot synthesis with different organogermanium compounds.…”

“…(b) Merged image of a confocal fluorescent image with an image acquired with 405 nm excitation of Ge NPs in HeLa cells. Reproduced from ref . Copyright 2018 American Chemical Society.…”

Bacterial Toxicity of Germanium Nanocrystals Induced by Doping with Boron and Phosphorus

“…Recently, fluorescent materials that are made of group IV elements (e.g., C, Si, and Ge) are gaining interest as they are conventionally regarded as inert and nontoxic elements presenting minimal environmental burden and negligible influence on human health. − Among this group, germanium nanocrystals (Ge NCs) are attracting attention due to their favorable features. Specifically, like traditional Cd/Pb-based QDs, the optical properties of Ge NCs are tunable; however, because of the relatively large Bohr exciton radius (∼24 nm), Ge NCs are more sensitive to quantum confinement effects and thus are expected to exhibit quantum confinement at even larger particle sizes than Cd- or Pb-based QDs. , In addition, compared to silicon nanocrystals (Si NCs), the narrower bandgap of Ge NCs grants them the capability to absorb in the visible range of the electromagnetic spectrum; after appropriate surface passivation and size control, the emission of Ge NCs (>1600 nm) can reach the far end of the near-infrared (NIR) II biological transparency window (1000–1700 nm), while most Si NCs emit in the NIR I region (700–950 nm). ,, This optical range makes Ge NCs excellent candidates for bioimaging applications. − …”

“…22,24,25 This optical range makes Ge NCs excellent candidates for bioimaging applications. 26 Over the past two decades, a wide array of methods have been developed to fabricate Ge NCs, including laser ablation, 29 solution phase synthesis, 28,30 reductive thermal processing, 31 and electrochemical etching. 32 Compared to those approaches, nonthermal plasma methods are exemplified by high purity products, narrow particle size distributions, and efficient incorporation of dopants.…”