Self-assembly of carbon based nanoparticles films by Langmuir-Blodgett method

Carbon nanoparticles are a class of materials with extraordinary properties. In the past three decades, four major types of carbon nanoparticles were synthesized and investigated: fullerenes, carbon nanotubes, graphene and carbon quantum dots. One of the main properties of such materials is their hydrophobic nature. At the same time, Langmuir–Blodgett (LB) method the for deposition of thin films of hydrophobic materials provides the possibility to design thin films of different carbon-based nanoparticles with special architectures and features enabling their usage in various fields, particularly in electronics and biomedicine. In this review, the state of art of LB thin films of four types of carbon-based nanoparticles and their application in electronics and biomedicine are presented. The breakthrough in this field was finally achieved by application of carbon quantum dots soluble in solvents optimized for LB deposition

Phloroglucinol-Based Carbon Quantum Dots/Polyurethane Composite Films: How Structure of Carbon Quantum Dots Affects Antibacterial and Antibiofouling Efficiency of Composite Films

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

Antibacterial and Antibiofouling Activities of Carbon Polymerized Dots/Polyurethane and C60/Polyurethane Composite Films

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

Ab Initio Study of Structural, Electronic and Optical Properties of Edge-Functionalized Graphene Quantum Dots

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 wide variety of applications.29th International Symposium on Analytical and Environmental Problems : Proceedings; November 13-14, 2023; Szeged, Hungary

The Influence of Carbonized Polymer Dots on Mechanical Properties of Polyurethane Foil

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 %).29th International Symposium on Analytical and Environmental Problems : Proceedings; November 13-14, 2023; Szeged, Hungary

Comparative Analysis of Different Methods for Graphene Nanoribbon Synthesis

Graphene nanoribbons (GNRs) are thin strips of graphene that have captured the interest of scientists due to their unique structure and promising applications in electronics. This paper presents the results of a comparative analysis of morphological properties of graphene nanoribbons synthesized by different methods. Various methods have been reported for graphene nanoribons synthesis. Lithography methods usually include electron-beam (e-beam) lithography, atomic force microscopy (AFM) lithography, and scanning tunnelling microscopy (STM) lithography. Sonochemical and chemical methods exist as well, namely chemical vapour deposition (CVD) and anisotropic etching. Graphene nanoribbons can also be fabricated from unzipping carbon nanotubes (CNTs). We propose a new highly efficient method for graphene nanoribbons production by gamma irradiation of graphene dispersed in cyclopentanone (CPO). Surface morphology of graphene nanoribbons was visualized with atomic force and transmission electron microscopy. It was determined that dimensions of graphene nanoribbons are inversely proportional to applied gamma irradiation dose. It was established that the narrowest nanoribbons were 10-20 nm wide and 1 nm high with regular and smooth edges. In comparison to other synthesis methods, dimensions of graphene nanoribbons synthesized by gamma irradiation are slightly larger, but the yield of nanoribbons is much higher. Fourier transform infrared spectroscopy was used for structural analysis of graphene nanoribbons. Results of photoluminescence spectroscopy revealed for the first time that synthesized nanoribbons showed photoluminescence in the blue region of visible light in contrast to graphene nanoribbons synthesized by other methods. Based on disclosed facts, we believe that our synthesis method has good prospects for potential future mass production of graphene nanoribbons with uniform size, as well as for future investigations of carbon nanomaterials for applications in optoelectronics and biological labeling

Reduction in Pathogenic Biofilms by the Photoactive Composite of Bacterial Cellulose and Nanochitosan Dots under Blue and Green Light

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

Facile synthesis of water-soluble curcumin nanocrystals

In this paper, a facile synthesis of water-soluble curcumin nanocrystals is reported. Solvent exchange method was applied to synthesize curcumin nanocrystals. Different techniques were used to characterize the structural and photophysical properties of the curcumin nanocrystals. It was found that the nanocurcumin prepared by this method had good chemical and physical stability, could be stored in the powder form at room temperature, and was freely dispersible in water. It was established that the size of curcumin nanocrystals varied in the range of 20-500 nm. Fourier transform infrared spectroscopy and UV-Vis analyses showed the presence of tetrahydrofuran inside the curcumin nanocrystals. Furthermore, it was found that the nanocurcumin emitted photoluminescence with a yellow green color

Singlet oxygen generation by higher fullerene-based colloids

In this paper, the results of the synthesis and characterization of higher fullerene-based colloids is presented. The generation of singlet oxygen (1)O2 ((1)Delta g) by fullerenc water-based colloids (nC60, nC70 and nC84) was investigated. It was found by electron paramagnetic resonance spectroscopy that the generation of singlet oxygen was the highest by the nC84 colloid. The amplitude of the electron paramagnetic resonance (EPR) signal was two orders of magnitude higher than the amplitude of the EPR signals which originated from nC60 and nC70. The surface morphology and the structure of the particles of the water-based colloids were investigated by atomic force microscopy (AFM). The AFM study showed that the average size of the nC60, nC70 and nC84 were 200, 80 and 70 nm, respectively. In addition, the particle size distribution of the nC60, nC70 and nC84 colloids was determined by dynamic light scattering (DLS) measurements

Gamma ray assisted modification of carbon quantum dot/polyurethane nanocomposites: structural, mechanical and photocatalytic study

In recent years, water pollution and contamination had become a major threat to the ecosystem. However, the use of nanostructured materials has been proven as a very promising approach in the treatment of polluted water. The present study reports the results of the gamma ray-assisted modification of hydrophobic carbon quantum dot (hCQD)/polyurethane nanocomposites for photocatalytic degradation of organic dyes. Different characterization methods were applied to investigate the influence of the different doses of gamma irradiation (1, 10 and 200 kGy) on the physical and chemical properties of nanocomposites (morphology, chemical content, mechanical properties, wettability, and potential for singlet oxygen generation). Surface morphology and mechanical properties analyses showed that gamma rays induced insignificant changes in the structure of nanocomposites, but the potential for singlet oxygen generation increased significantly. Here we also explore, in detail, the photocatalytic properties of gamma-ray modified hCQDs/polyurethane nanocomposites. UV-vis analysis showed that the removal efficiency of the rose bengal dye reached up to 97% for the nanocomposite irradiated with the dose of 200 kGy