Molecular dynamics investigation on synthesis of a pH- and temperature-sensitive carbon nanotube loaded with doxorubicin.

The many exotic properties of carbon nanotubes (CNTs) make them a powerful attraction in the field of drug delivery systems (DDS). In this work, based on quantum chemical calculation and molecular simulation techniques, polyacrylic acid (PAA) and N-isopropyl acrylamide (NIP) are selected and acted simultaneously on the CNT to form a stable system (FCNT). As a potential DDS, FCNT captures the dispersed doxorubicin (DOX) molecules around it and maintains a stable configuration. In these processes, electrostatic and van der Waals forces act synergistically, with van der Waals forces dominating. Compared to NIP, PAA molecules exhibit stronger adhesion and encapsulation efficiency to CNT and stronger adsorption capacity to DOX. This study reveals the mechanism of action among PAA, NIP, CNT, and DOX, providing feasibility verification and prospective guidance for the experimental synthesis of PAA-NIP-CNT-type multifunctional DDS, and also broadening the idea for exploring more efficient DDS suitable for DOX.

Study on crystal growth of Ge/Si quantum dots at different Ge deposition by using magnetron sputtering technique.

We investigated the growth and evolution of Si-based Ge quantum dots (Ge/Si QDs) under low Ge deposition (1.2-4.4 nm thick) using magnetron sputtering. The morphology and structure of QDs were analyzed with the help of an atomic force microscope (AFM), scanning electron microscope, transmission electron microscope, Raman, surface energy theory and dynamics theory, the photoelectric properties of QDs were characterized by photoluminescence (PL) spectra. The results showed that the growth mechanism of QDs conformed to Stranski-Krastanow mode, but the typical thickness of the wetting layer was nearly three times higher than those derived from conventional technologies such as molecular beam epitaxy, chemical vapor deposition, solid phase epitaxy and so on. Meanwhile, the shape evolution of QDs was very different from existing reports. The specific internal causes of these novel phenomena were analyzed and confirmed and reported in this paper. In addition, the AFM, Raman, and PL tests all indicated that the QDs grown when 3.4 nm Ge was deposited have the most excellent morphology, structure, and optoelectronic performance. Our work lays a foundation for further exploration of the controllable growth of QDs at high deposition rates, which is a new way to realize the industrialization of QDs used for future devices.

Controllable Fabrication of Non-Close-Packed Colloidal Nanoparticle Arrays by Ion Beam Etching.

Polystyrene (PS) nanoparticle films with non-close-packed arrays were prepared by using ion beam etching technology. The effects of etching time, beam current, and voltage on the size reduction of PS particles were well investigated. A slow etching rate, about 9.2 nm/min, is obtained for the nanospheres with the diameter of 100 nm. The rate does not maintain constant with increasing the etching time. This may result from the thermal energy accumulated gradually in a long-time bombardment of ion beam. The etching rate increases nonlinearly with the increase of beam current, while it increases firstly then reach its saturation with the increase of beam voltage. The diameter of PS nanoparticles can be controlled in the range from 34 to 88 nm. Based on the non-close-packed arrays of PS nanoparticles, the ordered silicon (Si) nanopillars with their average diameter of 54 nm are fabricated by employing metal-assisted chemical etching technique. Our results pave an effective way to fabricate the ordered nanostructures with the size less than 100 nm.

Microstructure and optical response optimization of Ge/Si quantum dots transformed from the sputtering-grown Ge thin film by manipulating the thermal annealing.

A series of zero-dimensional Ge/Si quantum dots (QDs) samples are fabricated by inducing the transformation from the two-dimensional Ge thin film, which is grown by the traditional direct current (DC) magnetron sputtering, via regulating the annealing process. The QD density increases sharply after the post rapid thermal annealing (PRTA). The observations of atomic force microscopy (AFM) and Raman spectroscopy suggest that the good morphology of Ge QDs results from an appropriate thermodynamics and kinetics surrounding shaped by the cooperative interaction of the Ge-Si lattice mismatch, the film's surface temperature, and the difference in thermal expansion coefficients between Ge and Si. The photoluminescence (PL) peaks of Ge QDs are detected in monolayer Ge QDs with ultrahigh density at 17 K. The Metal-Ge/Si QDs-Metal (MGM) photodetector fabricated from the ultrahigh-density QDs sample exhibits a relatively high current gain, absolute photoelectric responsivity, and internal quantum efficiency (IQE). Our results demonstrate that the high-quality Ge QDs with strong light absorption and quantum confinement effect can be realized by modulating DC magnetron sputtering and the PRTA process. This paves the way for realizing silicon-based optoelectronic devices with high performance by the traditional, relatively low-cost, and large-scale production nanomaterial fabricating method.