Synthesis of Organic Nanoparticles and their Applications in Drug Delivery and Food Nanotechnology: A Review
Organic nanoparticles, nanocrystals and nanobeads are of major interest in material and life sciences. Biopolymer nanoparticles are offering numerous advantages that embrace the simplicity of their preparation from well-understood biodegradable, biocompatible polymers and their high stability in biological fluids during storage. Several types of polymers have been tested as potential drug delivery systems; including nanoparticles, dendrimers, capsosomes and micelles. In the present review, synthetic methods for the preparation of organic nanoparticles, types and significant applications of organic nanoparticles have been reviewed with suitable examples.
Electronic Theory of Ultrafast Spin Dynamics in NiO
NiO is a good candidate for ultrafast magnetic switching because of its large spin density, antiferromagnetic order, and clearly separated intragap states. In order to detect and monitor the switching dynamics, we develop a systematic approach to study optical second harmonic generation (SHG) in NiO, both at the (001) surface and in the bulk. In our calculations NiO is modeled as a doubly embedded cluster. All intragap d-states of the bulk and the (001) surface are obtained with highly-correlational quantum chemistry and propagated in time under the influence of a static magnetic field and a laser pulse. We find that demagnetization and switching can be best achieved in a subpicosecond regime with linearly rather than circularly polarized light. We also show the importance of including an external magnetic field in order to distinguish spin-up and spin-down states and the necessity of including magnetic-dipole transitions in order to realize the process in the centrosymmetric bulk. Having already shown the effects of phonons in the SHG for the bulk NiO within the frozen-phonon approximation, and following the same trail of thoughts, we discuss the role of phonons in a fully quantized picture as a symmetrylowering mechanism in the switching scenario and investigate the electronic and lattice temperature effects.
Hierarchical ZnO Nanostructures Derived from Zn-Al Layered Double Hydroxides and their Photocatalytic Activity
In this work, Zn-Al layered double hydroxide (LDH) nanocrystals were used as a single precursor to fabricate ZnO/Zn-Al LDH nanocomposite based on the dissolution of aluminium hydroxide in NaOH. The newly formed ZnO nanorods vertically align on two sides of thinned LDH nanosheet to form “sandwich-like” nanostructure. The following calcination of these ZnO/Zn-Al LDH nanostructures at moderate temperature provided ZnO-Al2O3 mixed metal oxide nanocomposites. Both of ZnO/Zn-Al LDH and ZnO-Al2O3 samples were investigated as photocatalysts and showed selective activity for the photolysis of different dyes under low-Watt UV irradiation. Such photocatalytic mixed metal hydroxide/oxide nanocomposites should facilitate the decontamination of industrial wastewater and be helpful to environmental remediation.
Field Emission Simulations of Carbon Nanotubes and Graphene with an Atomic Model
Most models of field emission from carbon nanotubes (CNTs) and graphene sheets consider the geometry of the emitter tip as a smooth spherical surface. In these models, indicated with the terms simplified geometry (SG), the electronic distribution is not taken into account. However, the electronic distribution is concentrated around the atoms nuclei and their bonds forming hexagonal patterns that affect the field enhancement and largely determines the field emission. In this paper we evaluate the field emission in a SG-model and compare it with the emission in a ball-stick model that better represents the atomic structure at the surface of the emitter. We found that the emission current from open and capped carbon nanotubes and for graphene sheets is typically 10 times larger in the ball-stick geometry than in the SG. Furthermore, different morphologies of the CNT highlight the sensitivity of the emission current.