Search

Carbon-based nanomaterials, such as carbon nanotubes, fullerenes, nanodiamonds, and graphene, have been investigated for various biomedical applications, including biological imaging, photothermal therapy, drug/gene delivery, cancer therapy, biosensors, and electrochemical sensors. Graphene oxide (GO) has unique physicochemical properties and can be used to restore conductivity through oxidation. In this study, we developed poly(N-isopropylacrylamide) (PNIPAM)-based nanogel systems containing GO for controlled in vitro drug delivery. The photothermal effects of the PNIPAM/GO- and PNIPAMAAM/GO-based nanogel systems were enhanced. The release of DOX from the PNIPAM/GO-based nanogel was achieved using the photothermal effect of near-infrared irradiation. Using a Cell Counting Kit-8 assay, the cytotoxicity of all conditions demonstrated that the PNIPAM composite-based nanogels were biocompatible with no significance. [ABSTRACT FROM AUTHOR]

A nuclear environment, including decommissioning activity contains various radioactive nuclides such as pure beta emitters. These radionuclides should be monitored to ensure radiological safety. In particular, beta radionuclides, such as 3H and 14C, can cause internal exposures and should be managed more strictly in terms of health physics. For beta radionuclides, the measurement is carried out in a laboratory through sampling rather than on-site because of the short range. This method is time consuming, laborious, and costly and can also generate secondary waste. In this study, a system for the in situ monitoring of beta radionuclides in water samples is proposed for nuclear facilities and decommissioned environments. A plastic scintillator with low sensitivity to gamma rays and good reactivity with beta radionuclides was used. The detection efficiency was increased by using a detection part, whereby the water sample is made to directly contact the scintillator by utilizing the characteristic of plastic scintillators (i.e., they do not react with water). A coincidence circuit was constructed by using multiple photomultiplier tubes (PMTs) and applied to gross beta activity measurements. The values obtained from a single PMT were used in the spectral analysis to determine the effect of each beta radionuclide. Beta radionuclides in water samples in the field can be monitored by using plastic scintillators and multiple PMTs. [ABSTRACT FROM AUTHOR]

Stimuli-responsive nanoparticles are favorable for improving the selective delivery and rational vocation that easily avoids the undesirable barriers or side effects, leading to a further improved therapeutic efficiency. Furthermore, multifunctional nanomaterials have been extensively developed as attractive candidates for theranostic reagents for cancer treatment. In this article, we developed reversibly pH-responsive gold nanoparticles (AuNPs) with an enhanced Raman scattering signal as well as an efficient photothermal effect and demonstrated their applications as a theranostic reagent for cancer treatment. Surfaces of these AuNPs were modified with mixed layers of Cy3-modified single-stranded DNA (ssDNA-Cy3) for Raman probing and a negative charge supply and cytochrome C (Cyt C) for pH-responsive charge inversion. This combination of pH-responsive ligands and Raman probes played an important role in inducing the assembly or disassembly of AuNPs corresponding to the neighboring pH, accompanied by an additional highly distinguished Raman signal intensity. An operative reversible response of the AuNPs to pH is endowed with the characteristic behavior of AuNPs with the cancerous cell's acidic microenvironment of low pH. The responsive aggregation of AuNPs in a lower pH medium provides highly amplified signals attributed to well-formed hot spots between the particle surfaces that deliver better Raman scattering signals. The acidic pH-responsive aggregation of the particles also provided efficient photothermal treatments using a long-wavelength laser light with the benefit of deeper penetration for cancer cells. In vitro experiments employing cancer cells and control normal cells well-demonstrated the specificity of the particles to cancer cells in terms of highly enhanced Raman imaging and therapeutic efficiency.

The enhanced growth of Cu oxides underneath graphene grown on a Cu substrate has been of great interest to many groups. In this work, the strain and doping status of graphene, based on the gradual growth of Cu oxides from underneath, were systematically studied using time evolution Raman spectroscopy. The compressive strain to graphene, due to the thermal expansion coefficient difference between graphene and the Cu substrate, was almost released by the nonuniform Cu 2 O growth; however, slight tensile strain was exerted. This induced p-doping in the graphene with a carrier density up to 1.7 × 10 13 cm -2 when it was exposed to air for up to 30 days. With longer exposure to ambient conditions (>1 year), we observed that graphene/Cu 2 O hybrid structures significantly slow down the oxidation compared to that using a bare Cu substrate. The thickness of the CuO layer on the bare Cu substrate was increased to approximately 270 nm. These findings were confirmed through white light interference measurements and scanning electron microscopy.

In heavy water reactors, radionuclides are generated, then removed and treated by ion exchange resin. The disposal cost of spent resin is expected to increase because of the saturation of the existing storage capacity. In this study, a spent resin treatment process using microwaves is proposed, and a radiological safety assessment and cost evaluation of the spent resin treatment process are performed. A dose assessment was conducted by using the established exposure scenarios and the RESRAD-Build software. A sensitivity analysis was conducted to identify the main contributory radionuclide of the dose according to each exposure pathway because a spent resin consists of various radionuclides. The main exposure pathway was identified, and sensitivity analysis was applied to the working time and radioactivity concentrations of 14 C, 60 Co and 137 Cs to confirm their effect on the dose. Finally, an optimal shielding system for a safe work environment was proposed. The disposal cost of the spent resin is reduced by lowering its radioactivity level via a treatment process using microwaves. The treatment process can reduce the radioactivity level through the desorption of 14 C and can also recycle the 14 C nuclide. These characteristics have great economic advantages from the viewpoint of the entire nuclear energy cycle. Thus, this study evaluates the radiological safety of the spent resin treatment process for actual application in a heavy water reactor power plant.

The metal/graphene interface has been one of the most important research topics with regard to charge screening, charge transfer, contact resistance, and solar cells. Chemical bond formation of metal and graphene can be deduced from the defect induced D-band and its second-order mode, 2D band, measured by Raman spectroscopy, as a simple and nondestructive method. However, a phonon mode located at ∼1350 cm -1 , which is normally known as the defect-induced D-band, is intriguing for graphene deposited with noble metals (Ag, Au, and Cu). We observe anomalous K-point phonons in nonreactive noble metal/graphene heterostructures. The intensity ratio of the midfrequency mode at ∼1350 cm -1 over G-band (∼1590 cm -1 ) exhibits nonlinear but resonant behavior with the excitation laser wavelength, and more importantly, the phonon frequency-laser energy dispersion is ∼10-17 cm -1 eV -1 , which is much less than the conventional range. These phonon modes of graphene at nonzero phonon wave vector (q ≠ 0) around K points are activated by localized surface plasmon resonance and not by the defects due to chemical bond formation of metal/graphene. This hypothesis is supported by density functional theory (DFT) calculations for noble metals and Cr along with the measured contact resistances.