5 research outputs found
Controlling Nanorod Oligomer Aggregation in Solutions
Controlling the size of ordered nanorod
aggregates in colloidal
dispersions is a challenge. Here, we employ Brownian dynamics to explore
the dependence of the nanorod aggregate size and structure on the
molecular weight of a polyelectrolyte attached to one end of the nanorod
and on the nature of the solvent. Upon increasing the polyelectrolyte
molecular weight (the length of the polyelectrolyte), the size of
the aggregates decreases because of increasing electrostatic repulsion.
The critical van der Waals interaction strength for transition from
individual nanorods to nanorod dimers/trimers+ (trimers and larger
aggregates) increases with increasing polyelectrolyte molecular weight.
In a medium with a dielectric constant of 1.0, upon increasing the
van der Waals interaction between nanorods, the individual nanorods
aggregate as dimers and trimers+, with approximately 50% of individual
nanorods forming dimers. In a solvent with a sufficiently large dielectric
constant (e.g., ≥10.0), upon increasing the van der Waals interaction
between nanorods, most nanorods aggregate into trimers or larger aggregates;
few dimers are generated. A lower solvent dielectric constant and
a higher polyelectrolyte molecular weight favor formation of more
uniform aggregates. As the charge of the segments of the polyelectrolyte
increases, the fraction of nanorod dimers increases and the fraction
of nanorod trimers+ decreases. In media with the dielectric constant
of water, aggregation was insensitive to the temperature. In low dielectric
constant media, aggregate formation was sensitive to the temperature
for high molecular weight polyelectrolytes, but insensitive to the
temperature for low molecular weight polyelectrolytes
Micellar Structures in Nanoparticle-Multiblock Copolymer Complexes
Brownian dynamics simulation is employed
to examine the structure
changes of complexes composed of a hydrophobic nanoparticle and a
multiblock copolymer molecule (MCP). The dependence of the structure
transitions on the radius of the nanoparticle, on the interactions
between the hydrophobic segments of the MCP, and on the interactions
between the hydrophobic segments and hydrophobic nanoparticle is examined.
It is shown that the multiblock copolymer adsorbed on a nanoparticle
can acquire the structure of a micelle.To better characterize the
micelle generated and the structure changes in the nanoparticle–MCP
complex, the mass dipole moment of the complex [the distance between
the center of mass of MCP and the center of the nanoparticle minus
the radius of the nanoparticle (DCC)], the density profiles of MCP
segments around its center of mass and around the nanoparticle, the
radius of gyration of the MCP, and the thickness of the micelle around
the nanoparticle are determined. It was found that, when structural
transition of the complex occurs, the above quantities change dramatically.
The present simulation may provide new insights regarding the drug-loaded
micelle interacting with a virus represented by a nanoparticle
Tunable Primary and Secondary Encapsulation of a Charged Nonspherical Nanoparticle: Insights from Brownian Dynamics Simulations
Surface
properties of encapsulated nanoparticles play a central
role in colloidal stability and in diverse applications of colloidal
nanomaterials. In this paper, by employing Brownian dynamics simulations,
we simulate the environment-dependent primary encapsulation of a charged
nonspherical nanoparticle (NSNP) by Janus particles (JPs). We propose
and determine, for the first time, the secondary encapsulation (i.e.,
reconfiguration of encapsulants on the surface of the NSNP), which
also depends on the environment. The adsorption phase behavior and
configuration transformation are strongly correlated with temperature
and Bjerrum length. Bjerrum-length-induced order–order structural
transitions and temperature-induced disorder–order/order–order
structural transitions are found. Interestingly, electric double layers
on the surfaces of the NSNP can form upon changing the environment.
Our detailed results of primary encapsulation and secondary reconfiguration
of encapsulants on the surface of the NSNP indicate that the surface
properties of the charged NSNP are tunable and reversible. Such transformations
should be readily detected experimentally by techniques such as zeta
potential measurement. We also find that the primary encapsulation
occurred via sequential adsorption and assembly of JPs, whereas the
secondary encapsulation process involved adsorption/desorption of
JPs and rotation of their configurations as well as their reassembly.
These new insights may provide useful information in design and modulation
of nanomaterials with surface properties that respond to their environment,
for applications such as drug or gene delivery
Highly Selective Ethylene Production from Solar-Driven CO<sub>2</sub> Reduction on the Bi<sub>2</sub>S<sub>3</sub>@In<sub>2</sub>S<sub>3</sub> Catalyst with In–S<sub>V</sub>–Bi Active Sites
Photothermal
catalysis that utilizes solar energy to
not only generate
charge carriers but also supply heat input represents a potentially
sustainable strategy for the efficient conversion of CO2 to valuable chemicals. It is highly desirable to develop photothermal
catalysts with broadband light absorption across the whole solar spectrum,
efficient photothermal conversion, and appropriate active sites. In
this work, the Bi2S3@In2S3 heterostructure catalyst is fabricated via one-step
solvothermal synthesis, where Bi2S3 serves as
a photothermal material and synchronously affords photoexcited charge
carriers. Experimental results indicate that the photoinduced charge
carriers trigger H2O-assisted CO2 reduction
and the elevated temperature kinetically accelerates the reaction.
Furthermore, the tightly bonded heterointerfaces provide unique In–SV–Bi active centers consisting of adjacent Bi and In
atoms coupled with sulfur vacancies, which reduces the energy barriers
of CO2 activation and C–C coupling, facilitating
the generation and dimerization of CO intermediates for highly selective
C2H4 production. The integration of In–SV–Bi active sites and the photothermal effect into the
Bi2S3@In2S3 catalyst induces
a high rate of 11.81 μmol gcat–1 h–1 and near 90% selectivity for CO2 conversion to C2H4 under simulated sunlight
without extra heat input. The catalytic mechanism is expounded by in situ characterizations and theoretical calculations.
This work would provide some enlightening guidance to construct efficient
photothermal catalysts for the direct transformation of CO2 to multicarbon (C2+) products with solar energy
Capture of pure toxic gases through porous materials from molecular simulations
<p>In the last three decades, the air pollution is the main problem to affect human health and the environment in China and its contaminants include SO<sub>2,</sub> NH<sub>3,</sub> H<sub>2</sub>S, NO<sub>2</sub>, NO and CO. In this work, we employed grand canonical Monte Carlo simulations to investigate the adsorption capability of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) for these toxic gases. Eighty-nine MOFs and COFs were studied, and top-10 adsorption materials were screened for each toxic gas at room temperature. Dependence of the adsorption performance on the geometry and constructed element of MOFs/COFs was determined and the adsorption conditions were optimised. The open metal sites have mainly influenced the adsorption of NH<sub>3</sub>, H<sub>2</sub>S, NO<sub>2</sub> and NO. Especially, the X-DOBDC and XMOF-74 (X = Mg, Co, Ni, Zn) series of materials containing open metal sites are all best performance for adsorption of NH<sub>3</sub> to illustrate the importance of electrostatic interaction. Our simulation results also showed that ZnBDC and IRMOF-13 are good candidates to capture the toxic gases NH<sub>3,</sub> H<sub>2</sub>S, NO<sub>2</sub>, NO and CO. This work provides important insights in screening MOF and COF materials with satisfactory performance for toxic gas removal.</p