Journal of Nanomaterials

The use of graphene nanocomposites in advanced applications has attracted much attention in recent years. However, in order to substitute traditional epoxy reinforcements with graphene, there are still some issues like dispersion, homogenization, and reaggregation. In this paper, graphene bundles dispersed in two-component epoxy system by bath sonication, dispersion state, and reaggregation behavior of graphene in this system have been studied. Light transmittance in ultraviolet-visible spectroscopy has been used to quantify the reaggregation by a series of controlled experiments. After 18 mins sonication of 0.005 wt% graphene dispersion at 20°C, the light transmittance decreased from 68.92% to 54.88% in liquid epoxy and decreased from 72.80% to 46.42% in hardener; while increasing the temperature from 20°C to 60°C, the light transmittance in liquid epoxy decreased from 65.96% to 53.21% after 6 mins sonication. With the incorporation of 0.3 wt% graphene, the tensile strength of nanocomposites increased from 57.2 MPa to 64.4 MPa and the storage modulus increased from 1.66 GPa to 2.16 GPa. The results showed that the dispersion state depends on the function of sonication time and temperature, and graphene has a significant reinforcement effect on epoxy.

Dung dịch AgNPs đã được tổng hợp qua phương pháp khử hóa học, được đặc trưng và thử nghiệm tác dụng chống lại Candida glabrata, Candida tropicalis, Staphylococcus aureus và Staphylococcus aureus kháng methicillin (MRSA). Nồng độ ức chế tối thiểu (MIC) và nồng độ diệt nấm/diệt khuẩn tối thiểu (MFC/MBC) được xác định trên tế bào thể lơ lửng. Ngoài ra, khối lượng phim sinh học tổng thể được xác định bằng phương pháp nhuộm tinh thể tím (CV) và sự thay đổi hình thái học được quan sát bằng kính hiển vi điện tử quét (SEM). MIC cho C. glabrata, C. tropicalis, S. aureus và MRSA lần lượt là 15.63, 3.91, 1.95 và 1.95 µg/mL. MFC cho C. glabrata là 62.5 µg/mL và cho C. tropicalis là 15.63 µg/mL. MBC giống nhau (3.91 µg/mL) được quan sát cho S. aureus và MRSA. Thí nghiệm CV cho thấy các AgNPs (1000 μg/mL) đã thúc đẩy giảm khối lượng phim sinh học khoảng 60% cho C. glabrata và khoảng 35% cho C. tropicalis. Sự giảm ~20% trong khối lượng sinh khối của C. tropicalis cũng được quan sát thấy ở nồng độ 3.91 µg/mL. Không có tác động đáng kể đến tổng khối lượng sinh khối của S. aureus và MRSA. Hình ảnh SEM cho thấy tế bào phim sinh học của C. glabrata và C. tropicalis, tiếp xúc với các AgNPs (1000 μg/mL), có hình dạng không đều và bị nhăn. Dung dịch AgNPs thể hiện hoạt tính kháng khuẩn đáng kể chống lại các tác nhân gây bệnh nấm và vi khuẩn quan trọng, liên quan đến nhiều bệnh lý đường miệng và hệ thống, và có tiềm năng trở thành một tác nhân kháng khuẩn.

Molybdenum disulfide (MoS₂), an inorganic-layered material similar to structure of graphite, was randomly dispersed onto the surface of functionalized multiwalled carbon nanotubes to synthesized nanocomposite MoS₂/CNT. The as-obtained product was characterized via SEM, TEM, TGA, X-ray diffraction, and Raman spectroscopies. It was confirmed from XRD that MoS₂ layers with interlayer spacing of 0.614 nm were successfully produced. TEM images and Raman spectra indicated a random distribution of 20 nm sized nanoflake MoS₂ on the surface of MWNTs. The electrochemical performance of materials are expected to pave the way for the utilized anode material for lithium-ion batteries.

Early and highly accurate detection of diverse diseases is in urgent demand than ever, especially for cancers and infectious ones. Among possibilities, biosensing by utilizing conjugated nanoparticles is still a method of choice. However, the toxicity of quantum dots remains a big matter of concern in those biooriented applications. In this study, mercaptosuccinic acid-coated cadmium selenide quantum dots of approximately 2.3 nm were synthesized with a simple green method at low temperature and cost-saving chemicals. The influence of synthesis factors was investigated with different spectroscopic methods. The toxicity issue was evaluated on the NIH-3T3 cell line (ATCC® CRL-1658™) and an MTT assay, revealing a secure threshold of 20 μg/ml. Consequently, successful conjugation to the CD3 antibody including an A/G protein bridge was implemented and verified with fluorescent methods. Finally, Jurkat T cell detectability of conjugated CdSe was successfully validated with fluorescent microscopy. The CdSe-based products are accessible for future biosensing applications.

In this study, Fe3O4/ZnO/chitosan magnetic nanoparticles were synthesized by an ultrasound-assisted coprecipitation method. The magnetic nanoparticles were characterized by XRD, FT-IR, FESEM, and VSM techniques. The effects of ultrasonication time and content of chitosan on crystal size and lattice parameters of the nanoparticles were also studied via XRD spectra. FESEM measurements revealed that the coating consists of Fe3O4/ZnO nanoparticles of 15-20 nm in diameter homogeneously dispersed on the surface of chitosan substance. The VSM measurements at room temperature showed that the Fe3O4/ZnO/chitosan nanoparticles had superparamagnetic properties. These results indicated that ultrasonication time and chitosan content had a significant effect on the characteristics of nanoparticles. The antibacterial activities of the Fe3O4/ZnO/chitosan were tested against both gram-positive Saccharomyces cerevisiae and Bacillus subtilis and gram-negative E. coli bacteria using a disk diffusion method.

In this study, C-N-S-tridoped TiO₂ composite was fabricated from TiO₂ prepared from ilmenite ore and thiourea by means of hydrothermal method. The obtained material was characterized by X-ray diffraction, Raman scattering spectroscopy, UV-Vis diffuse reflectance spectroscopy, nitrogen adsorption-desorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). It was found that C-N-S-tridoped TiO₂ material has a large specific surface area, showing good photocatalytic activity on the degradation of antibiotic tetracycline in visible light region. The study on the mechanism of tetracycline photodegradation using the liquid chromatography with mass spectrometry was performed. It was found that tetracycline has been degraded over C-N-S-tridoped TiO₂ catalyst into many different intermediates which can eventually be converted into CO₂ and H₂O. The kinetics of photocatalytic decomposition of tetracycline were investigated. In addition, the obtained material could catalyze well the degradation of other antibiotics (ciprofloxacin and chloramphenicol) and dyes (rhodamine-B, methylene blue, and organe red). The catalyst was stable after five recycles with slight loss of catalytic activity, which indicates great potential for practical application of C-N-S-tridoped TiO₂ catalyst in treatment of wastewater containing tetracycline in particular or antibiotics in general.

A low-cost and simplistic approach for the synthesis of nanosized SO42-/TiO2 photocatalyst was successfully performed using Binh Dinh ilmenite ore and H2SO4 as titanium and sulfur sources, respectively. The experimental results indicate that the obtained material exists in the form of particles with a size of about 22 nm and has a specific surface area of about 49 m2 g-1. Compared with the TiO2 sample, the SO42-/TiO2 sample shows much higher photocatalytic degradation of rhodamine B (RhB) under the sunlight irradiation. In more details, the nanosized SO42-/TiO2 sample obtained is capable of completely decomposing RhB after 9 hours of irradiation by a 60 W LED lamp with a corresponding intensity of 9,500 Lux. However, when the SO42-/TiO2 is irradiated by the sunlight with the intensity of 65,000 Lux, it only takes 2 hours to completely decompose rhodamine B (RhB), facilitating the use of SO42-/TiO2 as a potential photocatalyst for the RhB photodegradation.

MoS2/rGO composites were synthesized by hydrothermal method from the precursors of MoS2 and reduced graphene oxide (rGO) prepared in the former steps. The influence of the synthesis conditions including hydrothermal temperature and mass ratio of MoS2 to rGO on the structure, morphology, and optical absorption capacity of the MoS2/rGO composites was systematically investigated using physicochemical characterizations. The photocatalytic performance of as-prepared samples was investigated on the degradation of Rhodamine B under visible light, in which, the composites obtained at hydrothermal temperature of 180°C and MoS2/rGO mass ratio of 4/1 exhibited the highest photodegradation efficiency of approx. 80% after 4 hours of reaction. This enhancement in photocatalytic behaviour of composites could be assigned to the positive effect of rGO in life time expansion of photoinduced electrons—holes.