Ultra-narrow-bandwidth graphene quantum dots for superresolved spectral and spatial sensing

Abstract

Narrow-bandwidth luminescent materials are already used in optoelectronic devices, superresolution, lasers, imaging, and sensing. The new-generation carbon fluorescence nanomaterials—carbon dots—have attracted considerable attention due to their advantages, such as simple operation, environmental friendliness, and good photoelectric performance. In this work, two narrower-bandwidth (21 and 30\u2009nm) emission graphene quantum dots with long-wavelength fluorescence were successfully prepared by a one-step method, and their photoluminescence (PL) peaks were at 683 and 667\u2009nm, respectively. These red-emitting graphene quantum dots were characterized by excitation wavelength dependence of the fluorescence lifetimes, and they were successfully applied to spectral and spatial superresolved sensing. Here, we proposed to develop an infrared spectroscopic sensing configuration based on two narrow-bandwidth-emission graphene quantum dots. The advantage of the method used is that spectroscopic information was extracted without using a spectrometer, and two narrow-bandwidth-emission graphene quantum dots were simultaneously excited to achieve spatial separation through the unique temporal “signatures” of the two types of graphene quantum dots. The spatial separation localization errors of the graphene quantum dots (GQDs-Sn and GQDs-OH) were 1 pixel (10\u2009nm) and 3 pixels (30\u2009nm), respectively. The method could also be adjusted for nanoscope-related applications in which spatial superresolved sensing was achieved. Graphene nanoparticles useful for high-resolution spectroscopy and imaging have been fabricated by scientists in China and Israel. Quantum dots are nanoparticles of semiconductor that can trap electrons and their positively charged counterparts, ‘holes’. The light emitted when the electron and hole combine is notable for its high spectral purity, i.e., its very narrow range of frequencies, or colors. Zheng Xie from the Technical Institute of Physics and Chemistry in Beijing, Zeev Zalevsky from Bar-Ilan University, Ramat-Gan, and their colleagues used a simple one-pot method to synthesize graphene quantum dots that emit ultranarrow frequency light in two different shades of red. The team proposed unique configurations for using those nanoparticles for spatial and spectral superresolved sensing specifically for field called nanoscopy, to create images at a resolution beyond that achievable with a microscope. Infrared spectral and spatial imaging configurations were developed based on near-infrared graphene quantum dots with ultranarrow half-width (FWHM\u2009=\u200921\u2009nm). The spectral imaging is obtained without a spectrometer and the spatial imaging exceeds the limits of resolution (superresolved imaging). The superresolved sensing is obtained due to the unique temporal and spectral properties of the quantum dot.