The addition of heteroatoms to pristine carbon quantum dots (CQDs) change their structure and optical properties. In this study, fluorine (F)- and chlorine (Cl)-doped CQDs are prepared by the ...one-step green hydrothermal route from sodium fluoride, sodium chloride, urea, and citric acid as the starting precursors. Microscopy analysis reveals that the average size of these quantum dots is 5 ± 2 nm, whereas the chemical study shows the existence of C–F and C–Cl bonds. The produced F- and Cl-doped CQDs have fluorescence quantum yields of 0.151 and 0.284, respectively, at an excitation wavelength of 450 nm. Charge transfer resistance of F- and Cl-doped CQDs films is 2 orders of magnitude higher than in the pristine CQD films. Transport band gap of the doped CQDs is 2 eV bigger than that of pristine CQDs. Radical scavenging activity shows very good antioxidant activity of doped CQDs. Antibacterial testing reveals poor antibacterial activity against Staphylococcus aureus and Escherichia coli. The F- and Cl-doped CQDs are successfully used as fluorescent probes for cell imaging as shown by confocal microscopy.
Herein, the ability of gamma irradiation to enhance the photoluminescence properties of graphene quantum dots (GQDs) was investigated. Different doses of γ-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. The main outcome was that the GQDs irradiated at lower doses act as better photoproducers than the ones irradiated at higher doses. These results corroborate that the structural changes caused by gamma irradiation have a direct impact on GQD ability to produce singlet oxygen and their photostability under prolonged UV illumination. This makes low-dose irradiated GQDs promising candidates for photodynamic therapy.
Due to controversial reports concerning antibacterial activity of different graphene based materials it is very important to investigate their antibacterial action on a wide range of Gram-positive ...and Gram-negative bacteria. In this paper we have investigated the structure induced phototoxic antibacterial activity of four types of graphene based materials: graphene oxide (GO), graphene quantum dots (GQDs), carbon quantum dots (CQDs) and nitrogen doped carbon quantum dots (N-CQDs). Antibacterial activity was tested on 19 types of bacteria. It is found that nanometer-size CQDs and N-CQDs are the most potent agents whereas micrometer-size GO has very poor antibacterial activity. Electron paramagnetic resonance measurements confirmed photodynamic production of singlet oxygen for all types of used quantum dots. Detailed analysis has shown that N-CQDs are an excellent photodynamic antibacterial agent for treatment of bacterial infections induced by
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Development of new types of antibacterial coatings or nanocomposites is of great importance due to widespread multidrug-resistant infections including bacterial infections. Herein, we investigated ...biocompatibility as well as structural, photocatalytic, and antibacterial properties of photoactive hydrophobic carbon quantum dots/polyurethane nanocomposite. The swell-encapsulation-shrink method was applied for production of these nanocomposites. Hydrophobic carbon quantum dots/polyurethane nanocomposites were found to be highly effective generator of singlet oxygen upon irradiation by low-power blue light. Analysis of conducted antibacterial tests on Staphyloccocus aureus and Escherichia coli showed 5-log bactericidal effect of these nanocomposites within 60 min of irradiation. Very powerful degradation of dye (rose bengal) was observed within 180 min of blue light irradiation of the nanocomposites. Biocompatibility studies revealed that nanocomposites were not cytotoxic against mouse embryonic fibroblast cell line, whereas they showed moderate cytotoxicity toward adenocarcinomic human epithelial cell line. Minor hemolytic effect of these nanocomposites toward red blood cells was revealed.
Photoactive materials called photosensitizers can be used for treatment of different types of cancer in combination with light source. In this paper, we have investigated pro-oxidant and antioxidant ...potentials of four graphene based nanomaterials (graphene oxide-GO, graphene quantum dots-GQDs, carbon quantum dots-CQDs and N-doped carbon quantum dots-N-CQDs) depending on the presence/absence of visible light source. Structural and optical properties of these materials and their potentials for reactive oxygen species generation/quenching are investigated by applying different microscopy and spectroscopy techniques (transmission electron microscopy, FTIR, UV–Vis, photoluminescence, electron paramagnetic resonance). Results show that all types of quantum dots has pro-oxidant and antioxidant potentials whereas GO demonstrated only moderate antioxidant effect. The best free radical scavenger is CQDs sample in the absence of light. CQDs are the best singlet oxygen generator under blue light irradiation as well. To check photo-cytotoxicity of these materials, photo-cytotoxic concentrations of the GO, GQDs, CQDs and N-CQDs were determined for three cellular lines: human rhabdomyosarcoma (RD), cell line derived from human cervix carcinoma Hep2c (HeLa) and fibroblast cell line from murine (L2OB). Cytotoxicity test has indicated that all samples are much less photocytotoxic than cis-diamminedichloroplatinum (cis-DPP). The production method and doping of quantum dots affect the photodynamic activity of tested samples very much.
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•Graphene oxide size and structure materials.•Crossover between pro-oxidant and antioxidant activities.•Fullerene like structure affects ROS generation/quenching.•Blue light dependent cytotoxicity toward cancer cells.
Carbon quantum dots as a novel type of carbon nanomaterials have attracted the attention of many researchers because of their unique optical, antibacterial, and anticancer properties as well as their ...biocompatibility. In this study, for the first time, carbon quantum dots were prepared from
-phenylenediamine dissolved in toluene by a solvothermal route. Subsequently, the prepared carbon quantum dots were encapsulated into polyurethane films by a swelling-encapsulation-shrink method. Analyses of the results obtained by different characterization methods (AFM, TEM, EDS, FTIR, photoluminescence, and EPR) indicate the significant influence of the precursor on structural, chemical, and optical properties. Antibacterial and cytotoxicity tests showed that these dots did not have any antibacterial potential, because of the low extent of reactive oxygen species production, and showed low dark cytotoxicity. By investigating the cellular uptake, it was established that these dots penetrated the HeLa cells and could be used as probes for bioimaging.
Inimitable properties of carbon quantum dots as well as a cheap production contribute to their possible application in biomedicine especially as antibacterial and antibiofouling coatings. Fluorescent ...hydrophobic carbon quantum dots are synthesized by bottom-up condensation method and used for deposition of uniform and homogeneous Langmuir–Blodgett thin films on different substrates. It is found that this kind of quantum dots generates singlet oxygen under blue light irradiation. Antibacterial and antibiofouling testing on four different bacteria strains (Escherichia coli, Staphylococcus aureus, Bacillus cereus, and Pseudomonas aeruginosa) reveals enhanced antibacterial and antibiofouling activity of hydrophobic carbon dots thin films under blue light irradiation. Moreover, hydrophobic quantum dots show noncytotoxic effect on mouse fibroblast cell line. These properties enable potential usage of hydrophobic carbon quantum dots thin films as excellent antibacterial and antibiofouling coatings for different biomedical applications.
Determination of sarcopenia is crucial in identifying patients at high risk of adverse health outcomes. Recent studies reported a significant decline in masticatory muscle (MM) function in patients ...with sarcopenia. This study aimed to analyze the cross-sectional area (CSA) of MMs on computed tomography (CT) images and to explore their potential to predict sarcopenia. The study included 149 adult subjects retrospectively (59 males, 90 females, mean age 57.4 ± 14.8 years) who underwent head and neck CT examination for diagnostic purposes. Sarcopenia was diagnosed on CT by measuring CSA of neck muscles at the C3 vertebral level and estimating skeletal muscle index. CSA of MMs (temporal, masseter, medial pterygoid, and lateral pterygoid) were measured bilaterally on reference CT slices. Sarcopenia was diagnosed in 67 (45%) patients. Univariate logistic regression analysis demonstrated a significant association between CSA of all MMs and sarcopenia. In the multivariate logistic regression model, only masseter CSA, lateral pterygoid CSA, age, and gender were marked as predictors of sarcopenia. These parameters were combined in a regression equation, which showed excellent sensitivity and specificity in predicting sarcopenia. The masseter and lateral pterygoid CSA can be used to predict sarcopenia in healthy aging subjects with a high accuracy.
Industrialization today leads to a significant increase in the environmental pollution, with number of phenols, pesticides, paints, solvents and other organic pollutants with potentially carcinogenic ...effect in natural resources. Investigation of some new semiconductor materials and their photocatalytic properties for removal of pollutants is a challenging work. However, limited usage of photoactive materials still requires the testing of new materials with photoactive properties. The current work introduces the swift and easy approach for synthesis of (metal–free) N–doped carbon quantum dots in water using microwave reactor. Synthesis was performed from glucose water solution by heating in microwave reactor for only 1 min, at low temperature and applied microwave power. The synthesized N–doped carbon quantum dots show remarkable photocatalytic activity for removal of toxic organic dye (Rose Bengal) under visible light irradiation. Almost 93% of the dye degradation is achieved after only 30 min of radiation. The uninspected result, that the pH of the medium has a significant effect on the performance of the synthesized material in the presence of organic dye, indicates that dots show dual behavior. In the neutral and basic conditions, they have the ability to degrade organic dye, whereas, by shifting the medium pH into acidic medium, they form a stable conjugate with Rose Bengal.
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•New type of photoactive antibacterial surface.•Simple route to fabricate hCQDs/PDMS nanocomposites.•hCQDs/PDMS nanocomposites eradicate bacteria under blue light efficiently.
Despite ...great efforts, the design of antibacterial surfaces is still a challenge. In this work, results of structural, mechanical, cytotoxic and antibacterial activities of hydrophobic carbon quantum dots/polydimethylsiloxane surfaces are presented. Antibacterial action of this surface is based on the generation of reactive oxygen species which cause bacteria damage by oxidative stress. At the same time, this surface was not cytotoxic towards the NIH/3T3 cells. Swelling-encapsulation-shrink method is applied for encapsulation of hydrophobic carbon quantum dots in medical grade silicone-polydimethylsiloxane. XPS and photoluminescence spectroscopy analyses confirm that hydrophobic carbon quantum dots have been encapsulated successfully into polydimethylsiloxane polymer matrix. Based on stress-strain test the improvement of mechanical properties of these nanocomposites is established. It is shown by electron paramagnetic resonance spectroscopy and luminescence method that nanocomposite generates singlet oxygen initiated by 470 nm blue light irradiation. Antibacterial testing shows the nanocomposite in the form of foil kills Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae and is very effective after only a 15 min irradiation.
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