Ultraviolet Photoluminescence of Carbon Nanospheres and its Surface Plasmon‐Induced Enhancement

Abstract

Ultraviolet (UV) light can be used in versatile applications ranging from photoelectronic devices to biomedical imaging. In the development of new UV light sources, in this study, stable UV emission at ≈350 nm is unprecedentedly obtained from carbon nanospheres (CNSs). The origin of the UV fluorescence is comprehensively investigated via various characterization methods, including Raman and Fourier transform infrared analyses, with comparison to the visible emission of carbon nanodots. Based on the density functional calculations, the UV fluorescence is assigned to the carbon nanostructures bonded to bridging O atoms and dangling -OH groups. Moreover, a twofold enhancement in the UV emission is acquired for Au-carbon core-shell nanospheres (Au-CNSs). This remarkable modification of the UV emission is primarily ascribed to charge transfer between the CNSs and the Au surface.

Deep-Ultraviolet Emissive Carbon Nanodots

“…Fluorescent carbon nanodots (CNDs) have attracted broad scientific interest in recent years because of their high efficiency, high chemical stability, antiphotobleaching, biocompatibility, low toxicity, etc. − The above characters make CNDs a burgeoning luminescent nanomaterial that may be applied in many fields, such as biosensing, − bioimaging, , photothermal conversion therapy, drug delivery, , optoelectronic devices, − etc. To date, CNDs with an emission peak in visible regions have been reported extensively. − Especially, blue CNDs with a photoluminescence (PL) quantum yield (QY) over 90%, green luminescent CNDs with PL QY higher than 70%, and red luminescent with PL QY higher than 86%, and UV emissive graphene quantum dots (GQDs) with PL QY of 11%, , have been demonstrated. However, CNDs with emission in the DUV region have not been reported yet.…”

“…To date, CNDs with an emission peak in visible regions have been reported extensively. 23−30 Especially, blue CNDs with a photoluminescence (PL) quantum yield (QY) over 90%, 31 green luminescent CNDs with PL QY higher than 70%, 32 and red luminescent with PL QY higher than 86%, 33 and UV emissive graphene quantum dots (GQDs) with PL QY of 11%, 34,35 have been demonstrated. However, CNDs with emission in the DUV region have not been reported yet.…”

Preparation of Carbon Nanodots with Ultraviolet Emission by Pulsed Laser Ablation

“…UV emission can only be observed from the CNDs upon suppression of the defect state and radiative surface state. [32] As confirmed by the HRTEM, XRD, and Raman results, the cores of the CNDs prepared by the PLA method are crystalline with negligible defects. Thus, UV emission is expected from the CNDs prepared by our PLA method.…”

“…The two optical absorption bands at 285 and 318 nm are attributed to π – σ * transitions of oxygen‐related groups and π–π* transitions of the graphitic cores, respectively. [ 32,35,45–47 ] The three UV emission bands at 305 nm, 325 nm, and 335 nm are ascribed to transitions of σ *π, π*π, and π* n , respectively. As the electronic states are independent on excitation wavelength, the UV bands are unshifted when the CNDs are excited at different wavelengths.…”

Ultraviolet Carbon Nanodots Providing a Dual-Mode Spectral Matching Platform for Synergistic Enhancement of the Fluorescent Sensing

“…Meanwhile, various kinds of element doping could be expected, owing to the abundant chemical groups in the protein. It has been reported that the hybridization of N [21] or O [27] atoms into the aromatic sp 2 structure resulted in a widening of the energy gap and blue shift of the emission wavelength. The excitation-independent 304, 360 and 435 nm peaks might either originate from different kinds of element doping in the sp 2 domains, or from molecular states generated from fluorophores.…”