Photoluminescence Of Carbon Nanodots Research Articles

The luminescence photostability of carbon nanodots synthesized by the plasma method from a glucose solution after UV radiation

Carbon nanodots (CNDs) were synthesized by the microplasma method using a glucose solution as a precursor. The photoluminescence of CNDs before and after UV irradiation was studied. The spectral and kinetic properties of the synthesized CNDs were studied using a MicroTime 200 confocal scanning luminescence microscope. It was experimentally demonstrated that the short component (tau1) of luminescence refers to C=O bonds on the CND surface. A significant decrease in the luminescence intensity of CNDs after UV irradiation due to a decrease in oxygen-containing groups on the surface of carbon dots was found. Keywords: Luminescence, carbon nanodots, photostability, time-correlated photon counting.

Фотостабильность люминесценции углеродных наноточек, синтезированных плазменным методом из раствора глюкозы, под воздействием УФ-излучения

Carbon nanodots (CNTs) were synthesized by the microplasma method using a glucose solution as a precursor. The photoluminescence of CNTs before and after UV irradiation was studied. The spectral and kinetic properties of the synthesized CNTs were studied using a MicroTime 200 confocal scanning luminescence microscope. It was experimentally demonstrated that the short component (τ1) of luminescence refers to C=O bonds on the CNT surface. A significant decrease in the luminescence intensity of CNT’s after UV irradiation due to a decrease in oxygen-containing groups on the surface of carbon dots was found.

Carbon nano-dot for cancer studies as dual nano-sensor for imaging intracellular temperature or pH variation

Cellular temperature and pH govern many cellular physiologies, especially of cancer cells. Besides, attaining higher cellular temperature plays key role in therapeutic efficacy of hyperthermia treatment of cancer. This requires bio-compatible, non-toxic and sensitive probe with dual sensing ability to detect temperature and pH variations. In this regard, fluorescence based nano-sensors for cancer studies play an important role. Therefore, a facile green synthesis of orange carbon nano-dots (CND) with high quantum yield of 90% was achieved and its application as dual nano-sensor for imaging intracellular temperature and pH was explored. CND was synthesized from readily available, bio-compatible citric acid and rhodamine 6G hydrazide using solvent-free and simple heating technique requiring purification by dialysis. Although the particle size of 19 nm (which is quite large for CND) was observed yet CND exhibits no surface defects leading to decrease in photoluminescence (PL). On the contrary, very high fluorescence was observed along with good photo-stability. Temperature and pH dependent fluorescence studies show linearity in fluorescence intensity which was replicated in breast cancer cells. In addition, molecular nature of PL of CND was established using pH dependent fluorescence study. Together, the current investigation showed synthesis of highly fluorescent orange CND, which acts as a sensitive bio-imaging probe: an optical nano-thermal or nano-pH sensor for cancer-related studies.

Luminescent Plasmonic Structures Based on Gold Nanoparticles and Carbon Nanodots in Mesoporous Silica Particles

Composite plasmonic structures consisting of gold nanoparticles and carbon nanodots (CDs) in mesoporous silica particles have been synthesized. It has been established that the visible photoluminescence of CDs in these structures is three times more intense than that in analogous structures free of gold nanoparticles.

Evolution from UV emission of phenyl groups to visible emission of pyrolytic nanocarbons dispersed in fumed silica: Alternative insight into photoluminescence of carbon nanodots

SiO2:C nanopowder, luminescent in ultraviolet and visible spectral ranges, was synthesised using fumed silica as morphological matrix (specific surface of 295 m2/g) and phenyltrimethoxysilane (PhTMS) as carbon precursor. Fumed silica was impregnated by toluene solution of PhTMS followed by drying and annealing at 600 °C. Two series of SiO2:C nanocomposites with different carbon concentration were synthesised and studied. The main idea of the study was to explore the correlation of structural reconstruction and evolution of photoluminescent properties of carbon moieties. Chemically modified fumed silica exhibited ultraviolet (UV) photoluminescence band at about 330 nm originated from phenyl groups. After calcinations at 600 °C two overlapped emission bands were found at about 380 nm and 420 nm in “low-carbon” SiO2:C, while “high-carbon” series exhibited broad but homogeneous emission band peaked at about 440–450 nm. One more characteristic emission band at 495 nm in SiO2:C appeared and developed under intense ultraviolet radiation. Evolution of light emission from ultraviolet to visible was analysed in correlation with structural reconstruction of carbon examined by FTIR spectroscopy, X-ray photoelectron spectroscopy, high resolution scanning transmission electron microscopy, and electron energy loss spectroscopy. The nature of light emission of pyrolytic carbon moieties in SiO2:C nanopowder was discussed in frame of the concepts of polycyclic carbon clusters and their aggregates based on the analogy with polycyclic organic molecules and luminescent carbon nanodots.

Assisted Surface-state Recombination of Orange-peel Carbon Nanodots in Various Matrices

The contentious origin of the luminescence of carbon nanodots (CDs) has attracted considerable attention. In this work, we synthesized CDs from orange peel by using a microwave-assisted technique. We investigated the optical properties of the synthesized CDs. Moreover, we studied the effect of matrix addition on the optical properties of CDs. We found that matrix addition significantly influences the absorbance and photoluminescence of CDs. Shifts in absorbance peak intensity and emission peak wavelength indicated that the bonding of matrix molecules on the surfaces of the CDs has changed the structures of CDs. This finding is supported by the extended half-life of CDs after matrix addition. Our results will expand research on the use of CDs as phosphorescent materials.

Chlorine triggered de-alloying of AuAg@Carbon nanodots: Towards fabrication of a dual signalling assay combining the plasmonic property of bimetallic alloy nanoparticles and photoluminescence of carbon nanodots

Integration of Au-Ag alloy and fluorescent carbon nanodots (C-dots) into a single platform resulted in a new dual sensing assay for chlorine. Selective etching of Ag from AuAg@C-dots was transformed into: (i) colorimetric signal by surface plasmon resonance (SPR) tuning of the alloy and (ii) fluorimetric signal by perturbation of fluorescence energy transfer between C-dots and alloy nanoparticles. Fast oxidizing of silver atoms incorporated in the bimetallic structure induced by chlorine resulted in selective de-alloying of bimetallic hybrid nanoparticles and an intense visible change of the colloidal dispersion color. On the other hand, the systematic change in Au/Ag ratio strongly affected the emission intensity of C-dots in the hybrid structure leading to an enhancement in the fluorescence signal. Thus, the assay enables the detection of chlorine both under visible and UV lights with high sensitivity. The detection limit (DL) values were calculated as 6.2 × 10−7 M and 5.1 × 10−7 M through colorimetric and fluorimetric pathways, respectively. Most importantly, it was demonstrated to be selective over common cations, anions and some reactive oxygen species (ROS). This assay was successfully applied to the determination of chlorine concentration in bleach solution and tap water. It is robust and is suitable for cost effective chlorine measurement in environmental samples.

Photoluminescence-tunable carbon nanodots: surface-state energy-gap tuning.

The photoluminescence of carbon nanodots (C-dots) can be tuned by changing their surface chemistry or size because the photoluminescence is a function of the surface-state electronic transitions. Increasing the degree of surface oxidation leads to a narrowing of the energy gap of the surface; meanwhile, larger C-dots with an extensive π-electron system, which can couple with surface electronic states, can also lead to a narrowing of the energy gap of the surface states.