Self-assembled Mesoporous Silica Research Articles

Self-assembled mesoporous silica decorated with biogenic carbon dot nanospheres hybrid nanomaterial for efficient removal of aqueous Methoxy-DDT via a Short-Bed Adsorption column technique

Methoxy-DDT is an organochlorine pesticide extensively used in agricultural practices as a DDT substitute. Methoxy-DDT has been found and quantified in several investigations in groundwater, drinking water, sediment, and various biota. Therefore, designing efficient and cost-effective adsorbents for removing methoxy-DDT is vital. In this work, we embedded Ficus benghalensis L. derived carbon dots (CDs) in mesoporous silica (MS) to fabricate MS-CDs nanohybrid material. MS-CDs nanohybrid exhibited remarkable selectivity and removal efficiency towards methoxy-DDT, outperforming other endocrine disruptors. Parameters for industrial-scale fixed-bed adsorption columns, such as bed capacity, length, and breakthrough times, were analyzed. The kinetic study revealed that pseudo-second-order (PSO) adsorption and isotherm analysis confirmed the Langmuir model as the best fit. Small bed adsorption (SBA) column analysis was carried out using spiked Yamuna river water, and the breakthrough curves were demonstrated by varying MS-CDs bed height. The maximum adsorption capacity obtained for methoxy-DDT was 17.16 mg/g at breakthrough and 49.98 mg/g at exhaustion. The adsorbent showed 86.53% removal efficiency in the 5th cycle, demonstrating good reusability. These results indicate that the developed material MS-CDs-based organic sphere is an effective adsorbent for aqueous methoxy-DDT adsorption and can be applied to wastewater treatment.

Dual response to pH and chiral microenvironments for the release of a flurbiprofen-loaded chiral self-assembled mesoporous silica drug delivery system

This study examined the effects of pH and chirality on the release of flurbiprofen (FP)-loaded chiral (L/D) self-assembled mesoporous silica nanoparticles (CSA-L/D-MSNs), which were synthesized using cationic cetyltrimethyl ammonium bromide (CTAB) as a template and chiral modified using L/D-tartaric acids. The morphology and physicochemical properties of the CSA-L/D-MSNs were systemically determined and compared with those of non-functionalized mesoporous silica nanoparticles (MSN). The results showed that the CSA-L/D-MSNs were spherical nanoparticles, and the chirality in the L/D-tartaric acids was successfully imparted to the CSA-L/D-MSNs. FP could be loaded into the CSA-L/D-MSNs and was effectively transformed from the crystalline state to an amorphous state after drug loading due to the finite size effect. The release of FP@CSA-L/D-MSNs was faster than that of FP in a pH 1.2 medium and slower in a pH 6.8 medium, and it was better than that of FP@MSNs in both release mediums. Meanwhile, the FP@CSA-L/D-MSNs exhibited a clearly enhanced pH response because the negatively charged carboxyl groups on their surface induced stronger electrostatic repulsion between FP and CSA-L/D-MSNs. Moreover, the effect of the chiral environment on the release of FP@CSA-L/D-MSNs was further studied by introducing small-molecule chiral additives (L/D-alanine). It was found that the release of FP was inhibited in a chiral environment. Particularly, the CSA-L/D-MSNs began to exert the chiral recognition function, in which the CSA-L-MSN responded to chiral stimuli and enhanced the cumulative release amount from 84.25 %–89.11 % in a pH 6.8-L medium, while the CSA-D-MSN showed a suppressed release in the pH 6.8-L medium. Notably, the CSA-L/D-MSNs exhibited intelligent drug release by both chirality response and pH response, and will provide valuable guidance for the design of drug delivery systems.

N-Doped Hierarchical Continuous Hollow Thin Porous Carbon Nanostructure for High-Performance Flexible Gel-Type Symmetric Supercapacitors

A N-doped hierarchical porous carbon nanostructure (NHPCN) was created on a carbon cloth (CC), through a templating process using self-assembled mesoporous silica spheres as the template, to fabric...

Porous N-doped carbon nanostructure integrated with mesh current collector for Li-ion based energy storage

A self-assembled mesoporous silica sphere templating process was developed to create hierarchical continuous porous coral reef like N-doped carbon nanostructures on stainless steel meshes as bifunctional electrodes for ultrahigh performance lithium ion based energy storage devices. The coral reef like carbon nanostructure achieved a high specific surface area of 1229 m2 g−1 and a large specific pore volume of 2.21 cm3 g−1, without application of chemical activations. The electrode, when serving as an anode for lithium ion batteries (LIB) or lithium ion capacitors (LIC), delivered an ultrahigh specific capacity of 2058 mAh g−1 at 0.2 A g−1. If used as a cathode for LICs, it generated a high specific capacity of 125 mAh g−1 at 0.1 A g−1. The LICs assembled from using the electrode as both the cathode and anode, exhibited a high energy density of 145 Wh kg−1 at a power density of 1.4 kW kg−1 and maintained an energy density of 58 Wh kg−1 under an ultrahigh power density of 27.3 kW kg−1, among the top tie of the state-of-the-art LICs. The cycling stability of the LIC was outstanding with a 85% capacity retention after 5000 cycle operations at 5 A g−1. The hierarchical continuous porous coral reef like N-doped carbonaceous nanostructure provides micropores as micro-reservoirs of Li ions for local and fast Li ion intercalation/de-intercalation, edge N-doping for additional redox pseudo-capacitances, and large pore volumes to accommodate the volume expansion/shrinkage at the charge/discharge cycles and to offer fast mass transfer path for electrolyte ions, altogether leading to the successful applications as bifunctional electrodes for Li ion based energy storage devices.

Percolation Diffusion into Self-Assembled Mesoporous Silica Microfibres.

Percolation diffusion into long (11.5 cm) self-assembled, ordered mesoporous microfibres is studied using optical transmission and laser ablation inductive coupled mass spectrometry (LA-ICP-MS). Optical transmission based diffusion studies reveal rapid penetration (<5 s, D > 80 μm2∙s−1) of Rhodamine B with very little percolation of larger molecules such as zinc tetraphenylporphyrin (ZnTPP) observed under similar loading conditions. The failure of ZnTPP to enter the microfibre was confirmed, in higher resolution, using LA-ICP-MS. In the latter case, LA-ICP-MS was used to determine the diffusion of zinc acetate dihydrate, D~3 × 10−4 nm2∙s−1. The large differences between the molecules are accounted for by proposing ordered solvent and structure assisted accelerated diffusion of the Rhodamine B based on its hydrophilicity relative to the zinc compounds. The broader implications and applications for filtration, molecular sieves and a range of devices and uses are described.

Self-Assembled Mesoporous Silica Nanoparticles in Controlled Patterns Produced by Soft-Lithography and Ink-Jet Printing

This study demonstrate assembly of mesoporous silica nanoparticles (MSNs) into various patterns by soft-lithography and ink-jet printing techniques. A clear suspension containing MSNs with a particle size around 58 nm is firstly synthesized. Then, soft-lithographic techniques (i.e., MIMIC, impression with PDMS) and an ink-jet printing technique are applied to create various patterns assembled by MSNs. The MIMIC method results in a high density of MSNs, but is limited to linear patterns due to the capillary principle. The impression method led to MSN colloids in various patterns, but the MSNs assembled in low density due to the lack of the colloidal supplements. The ink-jet technique can create various patterns more conveniently, and the final patterns are generated after a de-wetting process. During the de-wetting process, the MSN concentrations and the jetted times are related only to the final number of particles dispersed in patterns. Comparison of different patterning techniques will be helpful towards creation of patterned assembly with MSNs.

Analysis of dip coating processing parameters by double optical monitoring

Double optical monitoring is applied to determine the influence of main process parameters on the formation of sulfated zirconia and self-assembled mesoporous silica solgel films by dip coating. In addition, we analyze, for the first time to the best of our knowledge, the influence of withdrawal speed, temperature, and relative humidity on refractive-index and physical thickness variations (uncertainties of +/-0.005 and +/-7 nm) during the process. Results provide insight into controlled production of single and multilayer films from complex fluids by dip coating.

Physical and electrical properties of low dielectric constant self-assembled mesoporous silica thin films

The physical and electrical properties of self-assembled mesoporous silica thin films with defined 2D hexagonal porous architectures have been evaluated in the following study. Self-assembled mesoporous silica thin (MPS) films have been prepared by evaporation-induced self-assembly (EISA) methods using the triblock copolymer (C 2H 2) 106(C 3H 3) 70(C 2H 2) 106 (Pluronic F127 ®). The MPS films exhibit remarkably low level leakage currents (1 × 10 −8–1 × 10 −7 A/cm 2 at 1 MV/cm 1) and high breakdown voltages (>3 MV/cm 1). The films have dielectric constants of approximately 2.3, low dielectric loss factors of 0.01–0.03 and exhibit negligible frequency dispersion of dielectric constant between 100 kHz and 1 MHz. The effect of physisorbed water (humidity) upon the electrical properties of the films is also investigated using capacitance–voltage techniques.

Nanometer-Thick Conformal Pore Sealing of Self-Assembled Mesoporous Silica by Plasma-Assisted Atomic Layer Deposition

On a porous substrate, regular atomic layer deposition (ALD) not only takes place on top of the substrate but also penetrates into the internal porosity. Here we report a plasma-assisted process in which the ALD precursors are chosen to be nonreactive unless triggered by plasma, so that ALD can be spatially defined by the supply of plasma irradiation. Since plasma cannot penetrate within the internal porosity, ALD has been successfully confined to the immediate surface. This not only gives a possible solution for sealing of porous low dielectric constant films with a conformal layer of nm-scale thickness but also enables us to progressively reduce the pore size of mesoporous materials in a sub-A/cycle fashion for membrane formation.

Rapid Thermal Processing of Mesoporous Silica Films: A Simple Method to Fabricate Films Micrometers Thick for Microelectromechanical Systems (MEMS) Applications

We are interested in constructing self-assembled mesoporous silica films several micrometers thick in a cost-effective way, for use as ionic conductors, membranes, and sensors for microelectromechanical systems (MEMS) applications. One way to construct films of micrometer thickness is to repeat the coating processes with each step, followed by calcination of the surfactants. However, conventional furnace calcination requires hours, which makes it impractical. In this paper, we report the use of a lamp-based rapid thermal processing (RTP) as a simple and fast way to remove surfactants and stiffen the silica framework. The RTP enabled us to save processing time (by an order of magnitude, in comparison to the time required for conventional furnace processing). Mesoporous silica films ∼2.5 μm thick were fabricated within an hour. Using microfabrication techniques, self-supporting mesoporous films were subsequently fabricated on patterned silicon wafers.