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.
Nowadays, bacteria resistance to many antibiotics is a huge problem, especially in clinics and other parts of the healthcare system. This critical health issue requires a dynamic approach to produce ...new types of antibacterial coatings to combat various pathogen microbes. In this research, we prepared a new type of carbon quantum dots based on phloroglucinol using the bottom-up method. Polyurethane composite films were produced using the swell–encapsulation–shrink method. Detailed electrostatic force and viscoelastic microscopy of carbon quantum dots revealed inhomogeneous structure characterized by electron-rich/soft and electron-poor/hard regions. The uncommon photoluminescence spectrum of carbon quantum dots core had a multipeak structure. Several tests confirmed that carbon quantum dots and composite films produced singlet oxygen. Antibacterial and antibiofouling efficiency of composite films was tested on eight bacteria strains and three bacteria biofilms.
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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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.
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.
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Electrochemically exfoliated graphene is functionalized graphene with potential application in biomedicine. Two most relevant biological features of this material are its electrical ...conductivity and excellent water dispersibility. In this study we have tried to establish the correlation between graphene structure and its antibacterial properties. The exfoliation process was performed in a two electrode-highly oriented pyrolytic graphite electrochemical cell. Solution of ammonium persulfate was used as an electrolyte. Exfoliated graphene sheets were dispersed in aqueous media and characterized by atomic force microscopy, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X photoelectron spectroscopy, X-ray diffraction, electron paramagnetic resonance, zeta potential, contact angle measurements and surface energy. Antibacterial assays have shown lack of the significant antibacterial activity. Major effect on bacteria was slight change of bacteria morphology. Membrane remained intact despite significant change of chemical content of membrane components.
The cost of treatment of antibiotic-resistant pathogens is on the level of tens of billions of dollars at the moment. It is of special interest to reduce or solve this problem using antimicrobial ...coatings, especially in hospitals or other healthcare facilities. The bacteria can transfer from medical staff or contaminated surfaces to patients. In this paper, we focused our attention on the antibacterial and antibiofouling activities of two types of photodynamic polyurethane composite films doped with carbon polymerized dots (CPDs) and fullerene C60. Detailed atomic force, electrostatic force and viscoelastic microscopy revealed topology, nanoelectrical and nanomechanical properties of used fillers and composites. A relationship between the electronic structure of the nanocarbon fillers and the antibacterial and antibiofouling activities of the composites was established. Thorough spectroscopic analysis of reactive oxygen species (ROS) generation was conducted for both composite films, and it was found that both of them were potent antibacterial agents against nosocomial bacteria (Klebsiela pneumoniae, Proteus mirabilis, Salmonela enterica, Enterococcus faecalis, Enterococcus epidermis and Pseudomonas aeruginosa). Antibiofouling testing of composite films indicated that the CPDs/PU composite films eradicated almost completely the biofilms of Pseudomonas aeruginosa and Staphylococcus aureus and about 50% of Escherichia coli biofilms.
Due to their unique structural properties bacterial cellulose (BC) hydrogels find possible usage in many fields such as cosmetology, food industry, or medicine. In this study, photoactive BC ...hydrogels are investigated through modifications of their structural, mechanical, and pro‐oxidant properties resulting from graphene quantum dots (GQDs) encapsulation. Detailed structural analysis is conducted by atomic force microscopy, transmission electron microscopy and scanning electron microscopy, X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction method. Dynamic mechanical analysis is performed to study the changes in storage modulus, loss modulus and tan δ. Pro‐oxidative properties of new designed composites are tested by electron paramagnetic resonance (EPR). Structural and mechanical analyses show successful encapsulation of GQDs into BC whereas EPR measurements indicate high potential of these composites for singlet oxygen production.
Photoactive GQDs‐BC composite hydrogels are produced by immersing BC in GQDs acetone solution. Detailed structural, chemical and mechanical analyses show that photoactive GQDs are encapsulated into BC polymer matrix. Porosity test shows significant pore enlargement of GQDs‐BC composite hydrogels. Composite hydrogels are highly potent oxygen radical generator and present advanced material for wound dressing application.
In this study, nanochitosan dots (ChiDs) were synthesized using gamma rays and encapsulated in bacterial cellulose (BC) polymer matrix for antibiofilm potential in photodynamic therapy. The ...composites were analyzed for structural changes using SEM, AFM, FTIR, XRD, EPR, and porosity measurements. Additionally, ChiD release was assessed. The results showed that the chemical composition remained unaltered, but ChiD agglomerates embedded in BC changed shape (1.5-2.5 µm). Bacterial cellulose fibers became deformed and interconnected, with increased surface roughness and porosity and decreased crystallinity. No singlet oxygen formation was observed, and the total amount of released ChiD was up to 16.10%. Antibiofilm activity was higher under green light, with reductions ranging from 48 to 57% under blue light and 78 to 85% under green light. Methicillin-resistant
was the most sensitive strain. The new photoactive composite hydrogels show promising potential for combating biofilm-related infections.
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