Sort:
Show:
Page Size:
Topic review
Updated time: 09 Sep 2021
Submitted by: Marcelo I. Guzman
Definition: Atmospheric organic aerosols play a major role in climate, demanding a better understanding of their formation mechanisms by contributing multiphase chemical reactions with the participation of water. The sunlight driven aqueous photochemistry of small 2-oxocarboxylic acids is a potential major source of organic aerosol, which prompted the investigations into the mechanisms of glyoxylic acid and pyruvic acid photochemistry reviewed here. While 2-oxocarboxylic acids can be contained or directly created in the particles, the majorities of these abundant and available molecules are in the gas phase and must first undergo the surface uptake process to react in, and on the surface, of aqueous particles. Thus, the work also reviews the acid-base reaction that occurs when gaseous pyruvic acid meets the interface of aqueous microdroplets, which is contrasted with the same process for acetic acid.
Entry Collection : Environmental Sciences
Unfold
Topic review
Updated time: 15 Jul 2020
Submitted by: Luigi Monsù Scolaro
Definition: The zinc(II) metal derivative of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4) is quite labile and readily demetallates under acidic conditions, affording the parent diacid porphyrin in a monomeric form. The rate of this process is first order on [ZnTPPS4] and second order on [H+], allowing a precise control of the monomer release in solution. Under high ionic strength, this latter species is able to self-assemble into J-aggregates, whose kinetics of growth are largely modulated by pH. The aggregation kinetics have been treated according to a well-established model, in which the formation of an initial nucleus is the rate determining step preceding the autocatalytic growth of the whole assembly. The extinction spectra of the aggregates suggest the occurrence of a dipolar coupling mechanism very similar to that operating in metal nanoparticles. Spontaneous symmetry breaking takes place in these aggregates as evidenced by unusual circular dichroism spectra. The intensity and sign of the effect is controlled by the aggregation rate and therefore can be tuned through a proper choice of initial conditions.
Unfold
Topic review
Updated time: 27 Apr 2021
Submitted by: Łukasz Szeleszczuk
Definition: Molecular dynamics (MD) simulation is a well-established technique used for the study of various chemical substances and mixtures in any state of matter and almost at any temperature and pressure conditions. Its combination with QM NMR calculations can significantly increase the accuracy of the results.
Unfold
Biography
Updated time: 28 Oct 2020
Submitted by: Ajaya Bhattarai
Abstract: I am Dr. Ajaya Bhattarai, an Assistant Professor of Chemistry at Tribhuvan University, Nepal. I have received my M.Sc. degree in Physical Chemistry from Tribhuvan University in 1998 and a Ph.D. degree in Polymer Chemistry from North Bengal University, India in 2010. I have also received the "TWAS Young Scientist Award" in 2008 for Chemistry. I have visited the University of Warsaw, Poland for Post-doctorate research in Nanomaterials as well as Surface Chemistry in 2013 under Erasmus Mundus post-doctoral fellowship of European Commission for nine months. I was at Boston College, the USA for Post-doctorate research in “Theoretical studies of Glass-Forming liquids” under Fulbright fellowship for the year 2018-2019. I have published more than 100 articles in reputed journals. My current research interest is in Polymer Chemistry, Surface Chemistry, and Nanomaterials as well as theoretical studies of Glass-Forming liquids.
Unfold
Biography
Updated time: 29 Oct 2020
Submitted by: Anan Yaghmur
Abstract: Anan Yaghmur is associate professor at the Department of Pharmacy, Faculty of Health & Medical Sciences, University of Copenhagen. He is also serving as a referee for at least 12 prominent journals including ACS NANO & ACS Applied Materials and Interfaces, Soft Matter, PLoS ONE, PCCP, Chemical Communications, Journal of Physical Chemistry B, and Langmuir. In addition to the evaluation of grant applications for scientific funding bodies. Anan Yaghmur has extensive expertise and know-how in formulation and nanostructural characterization of safe and efficient drug nanocarriers based on self-assembled lyotropic liquid crystalline systems and their dispersions (cubosomes and hexosomes).
Unfold
Topic review
Updated time: 09 Apr 2021
Definition: Atmospheric plasma treatment is an effective and economical surface treatment technique. The main advantage of this technique is that the bulk properties of the material remain unchanged while the surface properties and biocompatibility are enhanced.
Unfold
Topic review
Updated time: 30 Jul 2021
Submitted by: Zhi Li
Definition: The barrier layer in Cu technology is essential to prevent Cu from diffusing into the dielectric layer at high temperatures; therefore, it must have a high stability and good adhesion to both Cu and the dielectric layer. In the past three decades, tantalum/tantalum nitride (Ta/TaN) has been widely used as an inter-layer to separate the dielectric layer and the Cu. However, to fulfill the demand for continuous down-scaling of the Cu technology node, traditional materials and technical processes are being challenged. Direct electrochemical deposition of Cu on top of Ta/TaN is not realistic, due to its high resistivity. Therefore, pre-deposition of a Cu seed layer by physical vapor deposition (PVD) or chemical vapor deposition (CVD) is necessary, but the non-uniformity of the Cu seed layer has a devastating effect on the defect-free fill of modern sub-20 or even sub-10 nm Cu technology nodes. New Cu diffusion barrier materials having ultra-thin size, high resistivity and stability are needed for the successful super-fill of trenches at the nanometer scale. In this review, we briefly summarize recent advances in the development of Cu diffusion-proof materials, including metals, metal alloys, self-assembled molecular layers (SAMs), two-dimensional (2D) materials and high-entropy alloys (HEAs). Also, challenges are highlighted and future research directions are suggested.
Unfold
Topic review
Updated time: 27 Mar 2021
Submitted by: Bengu Ozturk
Definition: Bioactive lipids, such as fat-soluble vitamins, omega-3 fatty acids, conjugated linoleic acids, carotenoids and phytosterols play an important role in boosting human health and wellbeing. These lipophilic substances cannot be synthesized within the human body, and so people must include them in their diet. There is increasing interest in incorporating these bioactive lipids into functional foods designed to produce certain health benefits, such as anti-inflammatory, antioxidant, anticancer and cholesterol-lowering properties. However, many of these lipids have poor compatibility with food matrices and low bioavailability because of their extremely low water solubility. Nanotechnology is a promising technology that can be used to overcome many of these limitations. Different kinds of nanoscale delivery systems have been designed to encapsulate and protect bioactive lipids, thereby facilitating their handling, stability, food matrix compatibility, and bioavailability.
Unfold
Topic review
Updated time: 12 May 2021
Submitted by: Valentijn De Coster
Definition: Supported nanoparticles are commonly applied in heterogeneous catalysis. The catalytic performance of these solid catalysts is, for a given support, dependent on the nanoparticle size, shape, and composition, thus necessitating synthesis techniques that allow for preparing these materials with fine control over those properties. Such control can be exploited to deconvolute their effects on the catalyst’s performance, which is the basis for knowledge-driven catalyst design. In this regard, bottom-up synthesis procedures based on colloidal chemistry have proven successful in achieving the desired level of control for a variety of fundamental studies. This article aims to give an overview of recent progress made in this synthesis technique for the application of controlled catalytic materials in gas-phase catalysis. The focus goes to mono- and bimetallic materials, as well as to recent efforts in enhancing their performance by embedding colloidal templates in porous oxide phases.
Unfold
Topic review
Updated time: 01 Feb 2021
Submitted by: Junkai Ren
Definition: Carbon Dots (CDs) are a kind of 0-D emissive spheroidal carbon-based nanostructures with a size smaller than 20 nm. The CDs, in fact, stand in between organic (polymers) and inorganic materials (black carbon), macromolecules, and nanoparticle, between bottom-up (polycyclic aromatic compounds) and top-down synthesis (laser ablation of graphene, etc.).
Unfold
  • Page
  • of
  • 5