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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.

Silver nanoparticles (Ag NPs) have been produced by low-dose (1–20 kGy) gamma irradiation of silver nitrate in the presence of graphene-based material (graphene oxide or electrochemically exfoliated graphene). The large surface area of those graphene-based materials combined with the presence of oxygen-containing functional groups on the surface provided successful nucleation and growth of Ag nanoparticles, which resulted in a uniformly covered graphene surface. The obtained Ag nanoparticles were spherical with a predominant size distribution of 10–50 nm for graphene oxide and 10–100 nm for electrochemically exfoliated graphene. The photothermal efficiency measurement showed a temperature increase upon exposure to a 532 nm laser for all samples and the highest photothermal efficiency was measured for the graphene oxide/Ag NP sample prepared at 5 kGy. Electromagnetic interference (EMI) shielding efficiency measurements showed poor shielding for the composites prepared with graphene oxide. On the other hand, all composites prepared with electrochemically exfoliated graphene showed EMI shielding to some extent, and the best performance was measured for the samples prepared at 5 and 20 kGy doses.

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.

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 Staphylococcus aureus was the most sensitive strain. The new photoactive composite hydrogels show promising potential for combating biofilm-related infections.

Graphene quantum dots (GQDs) attract huge scientific attention ever since they were discovered. They are the only 0-dimensional, water-dispersible graphene-based nanomaterial. They show (i) excellent biocompatibility; (ii) stable and tunable photoluminescence in the visible part of the spectrum resistive to photobleaching; (iii) large surface area; (iv) good solubility in water and polar organic solvents. Their astonishing properties stem from the structure: graphene in the core and a vast number of different oxygen-containing functional groups such as carboxyl, carbonyl, epoxy, hydroxyl, and lactone. Their lateral size is below 100 nm, and the height is from 0.5 to a few nm. Thanks to different oxygen groups, they have very reach chemistry; they can be easily processed, modified, and functionalized. GQDs can be modified after their synthesis using different chemical reactions, which lead to changes in oxygen content, the addition of heteroatoms, binding of target molecules. Heteroatoms can be built-in GQDs structure during the process of synthesis and usually, N, S, and P are selected. They can be produced in many different ways and starting materials and all of them are dived into two main groups: bottom-up and top-down methods. Due to a large number of diverse functional groups and high surface area, GQDs create complexes with ions, cations, biomolecules, organic molecules, etc. Thanks to this feature, GQDs are studied for the application in sensing heavy metal ions, selected anions, proteins, metabolites, hormones, enzymes, pesticides, organic colors, etc. Another exciting feature of GQDs is their ability to produce reactive oxygen species under visible light.

Carbon quantum dots (CQDs) have exceptional physical-chemical properties that make them suitable for a wide range of uses, such as the photocatalytic removal of organic contaminants from water. Here, we provide a one-step, ecologically friendly, and economical method for creating iron/nitrogen co-doped (Fe/N-CQD) and nitrogen-doped (N-CQD) quantum dot nanomaterials. The characteristics of the developed nanomaterials were investigated with regard to how surface chemistry impacts their capacity for adsorption and photoactivity in a case study of a specific water pollutant reduction. The influence of the two irradiation sources-operating in the UV and visible ranges-on the photoactivity of materials was highlighted. Finally, their eco-friendliness was examined on four different human tumor cell lines.

Nanocomposites of carbonized polymer dots (CPD) and polyurethane (PU) are promising materials. In order to use a material in a wide range of applications, it is necessary to know its mechanical properties. In this study, two CPD/PU nanocomposites, with different CPD, from citric acid/urea (CAUR) and from phloroglucinol (PHL), as well as the reference PU foil, were mechanically characterized. CAUR-CPD was synthesized by 2.1 g of citric acid and 1.8 g of urea, dissolved in 50 mL of acetone. PHL-CPD was synthesized by 500 mg of PHL mixed in 50 mL of acetone. Both solutions were transferred to a Teflon-lined autoclave for heating. After the condensation reactions, the products of CAUR-CPD and PHL-CPD were filtered and centrifuged to remove the unreacted precursors. The CAUR-CPD/PU and PHL-CPD/PU nanocomposites were prepared by dipping PU foil (0.2 mm thick) in CAUR-CPD or PHL-CPD solution in acetone. The swelling-shrink-encapsulation method was used to encapsulate the CAUR-CPD and PHL- CPD in PU. The samples were dried in a vacuum furnace to eliminate acetone from the composites. The mechanical properties were determined on universal testing machine Shimadzu, AG-X plus 10 kN. The samples were prepared in the form of plates with a width of 8 mm. The distance between the grips was 50 mm. The strain rate was set to 1 mm/min for determination of E modulus and to 50 mm/min until the end. Each sample was measured 5 times and the average values were taken. The reference PU sample showed the highest elastic modulus (33.3 MPa) and tensile strength (25.8 MPa). The nanocomposites, CAUR-CPD/PU and PHL-CPD/PU, showed similar mechanical properties: a lower elastic modulus (18.8 and 18.6 MPa, respectively) and tensile strength (14.6 and 16.9 MPa) but much higher strain at break (650 and 608 %) than the reference PU foil (434 %).

Graphene and its derivatives have become the scientific community's focus due to their remarkable electronic, mechanical, and optical properties. In this work, we prepared two graphene-based materials, graphene oxide (GO) and electrochemically exfoliated graphene (EEG), and performed morphological and structural analysis. Both materials showed good dispersibility in water. GO is composed of mainly single- and few-layer graphene sheets, while EEG is predominately multi-layer graphene. EEG showed better thermal stability under nitrogen flow compared to GO. We also performed ElectroMagnetic Interference (EMI) shielding performance measurements of these materials.

Graphene quantum dots (GQD) are nano-particles small enough to exhibit unique electronic and optical properties that results from quantum confinement and edge effects. Unlike graphene they exhibit opening of the HOMO-LUMO band gap responsible for their unique optoelectronic properties high photoluminescence (PL) quantum yield, excellent photobleaching resistance and photostability, low citotoxicity, good biocompatibility, high solubility in various solvents, exceptional electrochemical activity and physicochemical stability. These characterisics of the GQDs make them suitable for a wide range of applications from biomedical applications such as diagnostics and therapy, to susteanable agricultural and environmental appications. In this respect carbon-based quantum dots such as GQDs, present promising candidates for usage in biosensing and fluorescence bioimaging applications, allowing a fast, more sensitive and more selectable detection and diagnosis. As biocompatible nanoparticles, they also have the potential to revolutionize the prospects of photodynamic therapy (PDT) in clinical treatments of cancer [1] and other diseases, antibacterial [2] and preventive antivirus PDT [3], being applied as photosensitizer agents. In a meanwhile comprehensive biomedical studies should pave the way for safe and efficient use of carbon-based quantum dots in clinical applications. In the present work, we investigate the effects of size and shape variation, as well as edge-functionalization on the structural and optical properties of GQDs, using the first-principles study based on the density functional theory (DFT) and time-dependent density functional theory (TD-DFT). We investigate edge-functionalized GQDs, with oxygen-containing –OH and –COOH groups, different shapes, such as hexagonal, triangular and rectangular and zigzag/armchair edge configuration, as well as variation of size, in tailoring the optoelectronic properties and photoluminescence behaviour of GQDs leading to a wid

Nowadays, it is a great challenge to develop new medicines for treating various infectious diseases. The treatment of these diseases is of utmost interest to further prevent the development of multi-drug resistance in different pathogens. Carbon quantum dots, as a new member of the carbon nanomaterials family, can potentially be used as a highly promising visible-light-triggered antibacterial agent. In this work, the results of antibacterial and cytotoxic activities of gamma-rayirradiated carbon quantum dots are presented. Carbon quantum dots (CQDs) were synthesized from citric acid by a pyrolysis procedure and irradiated by gamma rays at different doses (25, 50, 100 and 200 kGy). Structure, chemical composition and optical properties were investigated by atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, UV-Vis spectrometry and photoluminescence. Structural analysis showed that CQDs have a spherical-like shape and dose-dependent average diameters and heights. Antibacterial tests showed that all irradiated dots had antibacterial activity but CQDs irradiated with dose of 100 kGy had antibacterial activity against all seven pathogenreference bacterial strains. Gamma-ray-modified CQDs did not show any cytotoxicity toward human fetal-originated MRC-5 cells. Moreover, fluorescence microscopy showed excellent cellular uptake of CQDs irradiated with doses of 25 and 200 kGy into MRC-5 cells.

Graphene quantum dots (GQDs) are class of nanoparticles exhibiting unique and tunable electronic, optical, chemical and structural properties owing to their small size and quantum confinement and edge effects. GQDs most prominent characteristics are high photoluminescence, photostability, excellent photobleaching resistance, low citotoxicity, good biocompatibility, exceptional electrochemical activity and physicochemical stability, making them suitable for a wide range of applications, from biosensing and fluorescence bioimaging usage, photodynamic therapy, to optoelectronic, susteanable agricultural and environmental applications. Using density functional theory (DFT) we demonstrate that the optical properties of the GQDs can be sensitively tuned by its size, shape, edge configuration, attached chemical functionalities.

Due to the exponential growth of bacterial infection as well as resistance toward most antibiotics, the development of new materials for treatment is urgently needed. In recent years, graphene quantum dots (GQDs) have been identified as promising carbon nanomaterial for eco-friendly antibacterial applications due to their optical and chemical stability, non-toxicity, and biocompatibility. One of the reported GQD’s antimicrobial mechanisms is the photo-induced production of singlet oxygen (1O2). Under light exposure, GQDs transfer the energy to molecular oxygen from the surrounding medium. Oxygen molecules transform to their excited form 1O2, which causes oxidative stress in bacterial cells and reduces their viability. In this study, pristine GQDs were produced in an easy, one-step electrochemical top-down approach using graphite electrodes as a starting material. Carboxyl groups of GQDs are modified using a carbodiimide coupling reaction catalyzed by 1-ethyl-3- (3-dimethylaminopropyl)carbodiimide (EDC), with ethylenediamine (EDA) as an amine. In the next step, these NH2 terminated dots were decorated with gold nanoparticles (AuNPs) by the same EDC coupling procedure. Abillity of GQDs-AuNP nanocomposite to generate singlet oxygen upon blue light (470 nm) was investigated by UV-Vis spectroscopy and 9,10- anthracenediylbis-(methylene)dimalonic acid (ABDA) as selective 1O2 traping agent. After 2 hours of blue light illumination, the band at 420 nm charachterisic for ABDA was completly disaperided only in the presence of the GQD-AuNPs indicating good prooxidative potential of composite. Photoinduced antibacterial effects of GQD-AuNPs were studied using minimum inhibitory concentration (MIC) test which showed great antibacterial activity against several bacterial strains.