Zhen-An Qiao

Rapid and substrate-independent layer-by-layer fabrication of antireflection- and antifogging-integrated coatings

The antireflection- and antifogging-integrated coatings are widely useful in daily life because they can effectively enhance the transmission of light and meanwhile considerably prevent water condensation. Herein, we present a rapid, straightforward and substrate-independent method for the fabrication of antireflection- and antifogging-integrated coatings by layer-by-layer deposition of mesoporous silica (MSiO2) nanoparticles and poly(diallyldimethylammonium chloride) (PDDA). Quartz substrates covered with (MSiO2/PDDA)*3 coatings exhibit both antireflection and antifogging properties because the highly porous MSiO2 nanoparticles and their loose stacking in MSiO2/PDDA coatings enable the fabrication of superhydrophilic porous coatings with a low refractive index. A maximum transmittance of 99.9% in the visible spectral range is achieved for the (MSiO2/PDDA)*3 coatings deposited on quartz substrates. The antireflection and antifogging coatings can be conveniently deposited on daily used plastic substrates such as polycarbonate and Columbia resin CR-39. The rapid fabrication of the antireflection and antifogging (MSiO2/PDDA)*3 coatings is benefited from the large dimension and the fast adsorption kinetics of MSiO2 nanoparticles.

Highly ordered periodic mesoporous organosilica nanoparticles with controllable pore structures

A general synthetic procedure for highly ordered and well-dispersed periodic mesoporous organosilica (PMO) nanoparticles is reported based on a single cationic surfactant cetyltrimethylammonium bromide (CTAB) and simple silica sources with organic bridging groups via an ammonia-catalyzed sol-gel reaction. By changing the bridging group in the silica sources, the pore structures of the as-made particles with three-dimensional hexagonal (P6(3)/mmc), cubic (Pm3n), two-dimensional hexagonal (P6mm), and wormlike structure were evidenced by powder X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The size range of the nanoparticles can be adjusted from 30 nm to 500 nm by variation of the ammonia concentration or the co-solvent content of the reaction medium. The PMO nanoparticles with high concentration of organic groups in the framework offered good thermal stability, good dispersion in low polarity solvent and high adsorption of small hydrophobic molecules. Finally, the dye functionalized PMO nanoparticles show low cytotoxicity and excellent cell permeability, which offers great potential for biomedical applications.

Transition metal complexes on mesoporous silica nanoparticles as highly efficient catalysts for epoxidation of styrene

We have synthesized a series of catalysts for epoxidation of styrene by immobilizing salicylaldimine transition metal (copper, manganese, and cobalt) complexes on mesoporous silica nanoparticles (MSNs) with diameters of 120-150 nm. The prepared catalysts are characterized by infrared (IR) spectra, thermal gravimetric analyses (TGA), inductively coupled plasma (ICP), CHN elemental analysis, nitrogen adsorption-desorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). These catalysts possess excellent catalytic efficiency in epoxidation of styrene when using tert-BuOOH (TBHP) as oxidant. Styrene shows a high conversion (∼99%) as well as epoxide selectivity (∼80%) over Cu-MSN catalysts, and high conversion (∼99%) and moderate epoxide selectivity (∼65%) over Mn-MSN and Co-MSN catalysts. The recycling experiment results indicate that these catalysts maintain catalytic activity even after being used for three cycles. Our results indicate that MSNs can serve as better catalyst supports.

Cooperative adsorbent based on mesoporous SiO2 for organic pollutants in water

Cooperative adsorbents, designed on the basis of molecular structural features of targeted pollutant, were made by simultaneous grafting of two different organic functional groups on mesoporous SiO2 material SBA-15 for removal of low concentration organic pollutants in water. In this study, eosin, 4-nonylphenol (4-NP) and di-n-butyl-phthalate (DBP) were chosen as model compounds. For molecule-specific adsorption, we synthesized three corresponding cooperative adsorbents: diamine/phenyl-SBA-15, diamine/cetyl-SBA-15 and phenyl/cetyl-SBA-15, respectively. These bifunctionalized adsorbents were prepared using two appropriate organosilanes among N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-phenoxypropyldimethylchlorosilane and n-hexadecyltriethoxysilane to modify the surface of SAB-15. The XRD, TEM, IR, N2 adsorption, 29Si MAS NMR and CHN elemental analysis measurements reveal that all cooperative adsorbents not only maintain ordered mesopores of SBA-15, but also possess characteristics of the two organic functional groups. Compared with the monofunctionalized adsorbents and their physical mixtures, the cooperative adsorbents show much higher adsorption capacity and efficiency for model pollutants at low concentration. The maximal adsorption amounts of eosin, 4-NP and DBP are 0.59, 1.49 and 1.56 mmol g−1 on corresponding cooperative adsorbents, respectively. Especially, 99.95% of eosin can be removed from low concentration aqueous solution. The experimental results confirm that the cooperative effect of two functional groups on the same solid surface leads to excellent adsorption performance of bifunctionalized adsorbents.

Mesoporous silica nanoparticles immobilized salicylaldimine cobalt complexes as high efficient catalysts for polymerization of 1,3-butadiene

We have synthesized a series of nanocatalysts with different sizes (50-200 nm) for polymerization of 1,3-butadiene (Bd) by immobilizing salicylaldimine cobalt complexes on the mesoporous silica nanoparticles (MSNs). The prepared catalysts have been characterized by infrared (IR) spectra, thermal gravimetric analyses (TGAs), chemical composition analysis, nitrogen adsorption-desorption, scanning electron microscope (SEM), and transmission electron microscope (TEM). The nanocatalysts in combination with methylaluminoxane (MAO) show excellent catalytic efficiency in polymerization of 1,3-butadiene. The results reveal that these nanocatalysts also show higher activity than the homogeneous analog of cobalt complex and the same catalyst on bulky mesoporous silica supporting materials. The yield and the molecular weight of the poly-butadiene product depend on the particle size of the catalyst support. This catalysis process is also a facile way to directly synthesize the polymer/silica composite materials.

Mesostructured TiO2 Gated Periodic Mesoporous Organosilica‐Based Nanotablets for Multistimuli‐responsive Drug Release

A multistimuli-responsive drug carrier is designed and successfully synthesized by self-assembly of thiol-modified periodic mesoporous organosilica (PMO) nanoparticles, coated gold nanoparticles (AuNPs), and mesostructured titanium dioxide (TiO2). Dye-loaded PMO-Au@TiO2 nanotablets are shown to respond to environmental changes (pH, temperature, and light) to achieve controlled release.

Facile synthesis for colloid silica cross-linked threadlike micelles based on block copolymer self-assembly.

A new class of silica cross-linked threadlike micelles has been successfully synthesized in the form of stable colloidal suspensions by using block copolymer P123 (EO(20)PO(70)EO(20)) as template, tetramethyl orthosilicate as silica source, and 3-aminopropyltriethoxysilane as stabilizing agent. The aggregation of threadlike hybrid micelles is suppressed by electrostatic repulsion from the positive -NH(3)(+) on the surfaces of threadlike hybrid micelles in strong acidic media. Compared with P123 micelles, the threadlike hybrid micelles have significantly improved stability against dilution. Furthermore, the threadlike hybrid micelles are potential drug carrier and have a higher loading capacity and a slower release rate.

Mesoporous Carbon Nanospheres as a Multifunctional Carrier for Cancer Theranostics

Optical nanomaterials with intense absorption in near-infrared (NIR) region hold great promise for biomedical applications such as photothermal therapy (PTT) and photoacoustic imaging (PAI). In this work, we report mesoporous carbon nanospheres (Meso-CNs) with broadband and intense absorption in the UV-Vis-NIR region (300-1400 nm) and explore their potential as a multifunctional platform for photoacoustic imaging and chemo-photothermal therapy. Methods: Meso-CNs were prepared by a “silica-assisted” synthesis strategy and characterized by transmission electron microscope and optical spectroscopy. We investigated the photothermal conversion and photoacoustic imaging of Meso-CNs in comparison with single-walled carbon nanotubes (SWCNTs), graphene and gold nanorods (GNRs). In vitro cellular assays and in vivo chemo-photothermal combination therapy were performed. Results: The absorption coefficients of Meso-CNs are 1.5-2 times higher than those of SWCNTs and graphene and are comparable to those of GNRs in both the first and the second near-infrared optical windows (NIR-I and NIR-II) of tissues. When exposed to an NIR laser, the photothermal and photoacoustic signal generation of Meso-CNs are also stronger than those of SWCNTs, graphene, and GNRs. DOX was loaded into Meso-CNs with a high efficiency (35 wt%) owing to the unique mesoporous structure. Particularly, the drug release from Meso-CNs is sensitive to both pH and NIR light stimulation. In vivo chemo-photothermal combination therapy demonstrates a remarkable inhibition effect on tumor growth under NIR laser treatment. Conclusions: We have developed Meso-CNs for photothermal conversion and photoacoustic imaging. The porous structure also serves as a drug carrier and the drug release can be controlled by pH and external light. The high drug loading capacity, superior photothermal and photoacoustic generation, together with the apparent chemo-photothermal therapeutic effect, make Meso-CNs a promising platform for cancer theranostics.

Co-entrapped, N-doped mesoporous carbons prepared from melamine formaldehyde resins with CoCl 2 as template for hydrogen evolution

Cobalt-entrapped, nitrogen-doped mesoporous carbon materials have been prepared using melamine formaldehyde resin (MF resin) as precursor and CoCl2 as template. A fraction of CoCl2 can be reduced to Co nanoparticles and wrapped by the nitrogen doped carbon. Meanwhile, the ratio of MF resin to CoCl2 is an important parameter determining the mesoporous structures of the final products. The surface area of the obtained material decreases with the increase in the ratio of MF resin to CoCl2. Electrocatalytic tests show that the obtained catalysts are highly active for hydrogen evolution reaction in both acidic and basic media, achieving a current density of 10 mA cm-2 at 171 and 186 mV under acidic and alkaline conditions, respectively. Additionally, these catalysts also show good long-term stabilities.

Sprout-like Growth of Mesoporous Mo2C/NC Nanonetworks as Efficient Electrocatalyst for Hydrogen Evolution

Owing to their high surface areas, porous networks, nanosized walls, and unique electronic structure, mesoporous metal carbides with tailored nanoarchitectures are of particular interest for their prominent potential applications in various fields, including energy storage, fuel cells, and catalysis. Herein, we report a sprout‐like growth strategy for the preparation of a mesoporous β‐Mo2C nanonetwork embedded in a nitrogen‐rich carbon matrix. The nanoarchitecture can be tailored from a mesoporous Mo2C nanonetwork film into Mo2C nanoparticles embedded into the carbon layer. The as‐prepared β‐Mo2C material was demonstrated to drive a current density of 10 mA cm−2 at a low overpotential of 140 mV for the hydrogen evolution reaction (HER) in acidic conditions and to remain stable for at least 120 h. The excellent electrocatalytic performance may be from (1) mesoporous Mo2C frameworks offering numerous accessible active sites; (2) a carbon layer that protects the Mo2C from accumulation and favors electron transportation; and (3) shortened diffusion paths and ultrafine crystallinity that benefit its catalytic performance.