Duong Vu

We present the research on the fabrication of RuO ₂ and the change in dynamic magnetic properties of RuO ₂ /Co-Fe-B stack films with different thicknesses of the RuO ₂ layer ( t _RuO2 ) and the Co-Fe-B layer ( t _CFB ). The RuO ₂ film with a three-domain structure was oriented in (100) direction with a large strain on the α-Al ₂ O ₃ (0001) substrate. The film formation with an atomically flat surface morphology was observed. Through ferromagnetic resonant measurements on RuO ₂ /CFB samples, we found that the effective magnetization (4π M _{s, eff} ) decreases as t _CFB decreases which could be attributed to the contribution of the interfacial anisotropy energy. In addition, the damping constant (α) increases with the decrease of t _CFB from 0.0056 at t _CFB = 10 nm to 0.022 at t _CFB = 1.2 nm. On the other hand, 4π M _{s, eff} and α are independent of t _RuO2 which would relate to the small spin-orbit coupling in RuO ₂ . The results would be helpful for the ongoing research and application of altermagnet-based spintronics utilizing RuO ₂ .

In this study, 16 seasonal fly ash samples of municipal solid waste incinerator (MSWI) were collected in from waste-to energy power plant Cantho city to analysis the physical properties and heavy metals content. The results showed that the fly ash samples are very alkaline with porous and spherical shape, and the particle size of 1-100 µm. The analytical results disclosed that in these fly ash samples, the Zn, Pb, Al, Fe and Cr metals were found at high content range from 0.36-19.05 mg/kg while the toxic metals Ni and Hg are also found in fly ash, with the content from 0.141 to 0.51 mg/kg. Thus, fly ash is not hazardous waste and can be used for reuse in industries or land reclamation. The analysis results of SEM/EDX and XRF were quite similar with a difference of below 5%, indicating that both methods can be applied to research heavy metals. The findings in this study can guide the management, treatment and reuse of fly ash from MSWI incineration plants in Vietnam.

In recent years, portable Raman spectrometers and commercialized surface-enhanced Raman scattering (SERS) substrates have become increasingly popular. They have turned out to be great tools for both substance detection, identification, and analysis on-site. This work addresses the technique to collect proper Raman spectra using SERS substrates and portable Raman spectrometers. We propose a random sampling technique that gives representative and high-quality spectra with high intensity and good resolution. This technique was tested on a home-built portable Raman spectrometer and SERS substrates based on metal film over nano-sphere (MFON) structure. Experimental results showed that peaks of Raman spectrum collected using random sampling technique are significantly narrower than those of spectra measured in conventional one and prevent samples and SERS substrates from photoinduced degradation. Potentially, this method can promote quantitative SERS and chemical trace analysis using portable Raman spectrometers.

Silica nanoparticles (SiO₂ NPs) synthesized by the Stober method were used as drug delivery vehicles. Doxorubicin hydrochloride (DOX·HCl) is a chemo-drug absorbed onto the SiO₂ NPs surfaces. The DOX·HCl loading onto and release from the SiO₂ NPs was monitored via UV-VIS and fluorescence spectra. Alternatively, the zeta potential was also used to monitor and evaluate the DOX·HCl loading process. The results showed that nearly 98% of DOX·HCl was effectively loaded onto the SiO₂ NPs’ surfaces by electrostatic interaction. The pH-dependence of the process wherein DOX·HCl release out of DOX·HCl-SiO₂ NPs was investigated as well. For comparison, both the free DOX·HCl molecules and DOX·HCl-SiO₂ NPs were used as the labels for cultured cancer cells. Confocal laser scanning microscopy images showed that the DOX·HCl-SiO₂ NPs were better delivered to cancer cells which are more acidic than healthy cells. We propose that engineered DOX·HCl-SiO₂ systems are good candidates for drug delivery and clinical applications.

Nano/micro polystyrene (PS) beads have found many applications in different fields spanning from drug delivery, bio-diagnostics, and hybrid plasmonics to advanced photonics. The sizes of the PS beads are an important parameter, especially in plasmonic and photonic experiments. In this work, we demonstrate a quick and straightforward method to estimate the diameters of sub-microspheres (0.2 μm to 0.8 μm) using the transmission spectra of a close-packed monolayer of polystyrene beads on glass or quartz substrates. Experimental transmission spectra of the PS monolayers were verified against finite-difference time-domain (FDTD) simulation and showed good agreement. The effects of the substrates on the transmission spectra and, hence, the accuracy of the method were also studied by simulation, which showed that common transparent substrates only cause minor deviation of the PS bead sizes calculated by the proposed method.