Shedding Light on Graphene Quantum Dots: Key Synthetic Strategies, Characterization Tools, and Cutting-Edge Applications

During the last 20 years, the scientific community has shown growing interest towards carbonaceous nanomaterials due to their appealing mechanical, thermal, and optical features, depending on the specific nanoforms. Among these, graphene quantum dots (GQDs) recently emerged as one of the most promising nanomaterials due to their outstanding electrical properties, chemical stability, and intense and tunable photoluminescence, as it is witnessed by a booming number of reported applications, ranging from the biological field to the photovoltaic market. To date, a plethora of synthetic protocols have been investigated to modulate the portfolio of features that GQDs possess and to facilitate the…

Gel permeation chromatography, calibration, and distributions of cellulose trinitrates

The effect of annealing temperature and time on synthesis of graphene thin films by rapid thermal annealing

In this paper, we performed synthesis of graphene thin films by rapid thermal annealing (RTA) of thin nickel copper (Ni/Cu) layers deposited on spectroscopic graphite as a carbon source. Furthermore, we investigated the effect of annealing temperature and annealing time on formation and quality of synthesized graphene films. Raman spectroscopy study showed that annealing at lower temperatures results in formation of monolayer graphene films, while annealing at higher temperatures results in formation of multilayer graphene films. We used Raman mapping to determine the distribution of graphene sheets. Surface morphology of graphene thin films was investigated by atomic force microscopy and s…

Gamma irradiation of graphene quantum dots with ethylenediamine: Antioxidant for ion sensing

Due to the low consumption of chemicals, the absence of toxic residual side products, the procedure simplicity and time-saving aspects, gamma irradiation offers advantages over the classical chemical protocols. We successfully employed gamma irradiation in order to introduce N-atoms in Graphene Quantum Dots (GQDs). By irradiating GQDs water dispersions in the presence of isopropyl alcohol and ethylenediamine, at doses of 25, 50 and 200 kGy, we attached amino groups onto GQDs in a single synthetic step. At the same time, a chemical reduction is achieved, too. Selected conditions induced incorporation of N-atoms within GDQs atomic lattice (around 3 at%), at all applied doses. Additionally, th…

Modification of Structural and Luminescence Properties of Graphene Quantum Dots by Gamma Irradiation and Their Application in a Photodynamic Therapy

Herein, the ability of gamma irradiation to enhance the photoluminescence properties of graphene quantum dots (GQDs) was investigated. Different doses of gamma-irradiation were used on GQDs to examine the way in which their structure and optical properties can be affected. The photoluminescence quantum yield was increased six times for the GQDs irradiated with high doses compared to the nonirradiated material. Both photoluminescence lifetime and values of optical band gap were increased with the dose of applied gamma irradiation. In addition, the exploitation of the gamma-irradiated GQDs as photosensitizers was examined by monitoring the production of singlet oxygen under UV illumination. T…

Blue luminescent amino-functionalized graphene quantum dots as a responsive material for potential detection of metal ions and malathion

Large amounts of hazardous and toxic substances in the environment require non-toxic, cheap, easy, rapid, and sensitive methods for their detection. Blue luminescent graphene quantum dots (GQDs) were produced by electrochemical cleavage of graphite electrodes followed by gamma irradiation in the presence of ethylenediamine (EDA). Modified dots were able to detect metal ions (Co2+, Pd2+, Fe3+) due to photoluminescence quenching. The highest sensitivity was detected for the sample irradiated at a dose of 25 kGy. The limits of detection (LODs) were 1.79, 2.55, and 0.66 μmol L−1 for Co2+, Fe3+, and Pd2+, respectively. It was observed that GQDs irradiated at 200 kGy act as an ultra-sensitive tur…

Gamma-Ray-Induced Structural Transformation of GQDs towards the Improvement of Their Optical Properties, Monitoring of Selected Toxic Compounds, and Photo-Induced Effects on Bacterial Strains.

Structural modification of different carbon-based nanomaterials is often necessary to improve their morphology and optical properties, particularly the incorporation of N-atoms in graphene quantum dots (GQDs). Here, a clean, simple, one-step, and eco-friendly method for N-doping of GQDs using gamma irradiation is reported. GQDs were irradiated in the presence of the different ethylenediamine (EDA) amounts (1 g, 5 g, and 10 g) and the highest % of N was detected in the presence of 10 g. N-doped GQDs emitted strong, blue photoluminescence (PL). Photoluminescence quantum yield was increased from 1.45, as obtained for non-irradiated dots, to 7.24% for those irradiated in the presence of 1 g of …

Antioxidative and Photo-Induced Effects of Different Types of N-Doped Graphene Quantum Dots.

Due to the increasing number of bacterial infections and the development of resistivity toward antibiotics, new materials and approaches for treatments must be urgently developed. The production of new materials should be ecologically friendly considering overall pollution with chemicals and economically acceptable and accessible to the wide population. Thus, the possibility of using biocompatible graphene quantum dots (GQDs) as an agent in photodynamic therapy was studied. First, dots were obtained using electrochemical cutting of graphite. In only one synthetic step using gamma irradiation, GQDs were doped with N atoms without any reagent. Obtained dots showed blue photoluminescence, with…

Facile synthesis of L-cysteine functionalized graphene quantum dots as a bioimaging and photosensitive agent

Nowadays, a larger number of aggressive and corrosive chemical reagents as well as toxic solvents are used to achieve structural modification and cleaning of the final products. These lead to the production of residual, waste chemicals, which are often reactive, cancerogenic, and toxic to the environment. This study shows a new approach to the modification of graphene quantum dots (GQDs) using gamma irradiation where the usage of reagents was avoided. We achieved the incorporation of S and N atoms in the GQD structure by selecting an aqueous solution of L-cysteine as an irradiation medium. GQDs were exposed to gamma-irradiation at doses of 25, 50 and 200 kGy. After irradiation, the optical,…