Removal of aqueous Hg(ii) by thiol-functionalized nonporous silica microspheres prepared by one-step sol–gel method

It is well known that thiol-functionalized silica (SiO₂-SH) can be used as an effective adsorbent for the removal of Hg(ii) from water. Studies in this field have focused on porous silica gels and mesoporous silicas that have large surface area and pore volume, while nonporous silica particles are seldom reported. This work aims to investigate the Hg(ii) adsorption properties of nonporous SiO₂-SH microspheres prepared by a simple one-step sol–gel method. The effects of pH, initial concentration of Hg(ii) and temperature on the adsorption properties of the SiO₂-SH microspheres were studied via batch adsorption experiments. The maximum adsorption capacity for Hg(ii) at 293 K calculated from the Langmuir equation was 377.36 mg g⁻¹. The adsorption kinetics and equilibrium data were well-fitted to the pseudo-second-order model and the Langmuir isotherm model, respectively.

The adsorption properties of nonporous SiO₂-SH microspheres prepared by a one-step sol–gel method for Hg(ii) in water were studied.     

Lanthanide-doped mesoporous MCM-41 nanoparticles as a novel optical–magnetic multifunctional nanobioprobe

To research and develop potential multifunctional nanoprobes for biological application, lanthanide-doped MCM-41 (Ln-MCM-41, Ln = Gd/Eu) silica nanoparticles with excellent pore structure and optical–magnetic properties were synthesized via a facile and economical sol–gel method. The microstructure and pore distribution of Ln-MCM-41 nanoparticles were obviously affected by the Ln-doping. As the Ln/Si mole ratio increased, the specific surface area and total pore volume of Ln-MCM-41 nanoparticles rapidly decreased. However, the Ln-MCM-41 nanoparticles still retained the typical well-ordered mesoporous structure, and exhibited excellent drug release behavior. Moreover, the drug release rate of Ln-MCM-41 was remarkably pH-dependent and increased gradually upon decreasing pH. Additionally, these nanoparticles also exhibit considerable photoluminescence properties, living cells photoluminescence imaging in vitro, and paramagnetism behavior at room temperature due to the Ln³⁺-ions doping. Our research shows the possibility of our Ln-MCM-41 nanoparticles as multifunctional nanoprobes for application in bioseparation, bioimaging, and drug delivery.

Mesoporous Ln-MCM-41 nanoparticles with optical–magnetic dual-modal properties can be used as a multifunctional nanoprobe for application in bioseparation, optical–magnetic bioimaging, and drug delivery.     

Ag decorated silica nanostructures for surface plasmon enhanced photocatalysis

In this article, we present a novel synthesis of mesoporous SiO₂/Ag nanostructures for dye (methylene blue) adsorption and surface plasmon mediated photocatalysis. Mesoporous SiO₂ nanoparticles with a pore size of 3.2 nm were synthesized using cetyltrimethylammonium bromide as a structure directing agent and functionalized with (3-aminopropyl)trimethoxysilane to introduce amine groups. The adsorption behavior of non-porous SiO₂ nanoparticles was compared with that of the mesoporous silica nanoparticles. The large surface area and higher porosity of mesoporous SiO₂ facilitated better adsorption of the dye as compared to the non-porous silica. Ag decorated SiO₂ nanoparticles were synthesized by attaching silver (Ag) nanoparticles of different morphologies, i.e. spherical and triangular, on amine functionalized silica. The photocatalytic activity of the mesoporous SiO₂/Ag was compared with that of non-porous SiO₂/Ag nanoparticles and pristine Ag nanoparticles. Mesoporous SiO₂ nanoparticles (k_d = 31.3 × 10⁻³ g mg⁻¹ min⁻¹) showed remarkable improvement in the rate of degradation of methylene blue as compared to non-porous SiO₂ (k_d = 25.1 × 10⁻³ g mg⁻¹ min⁻¹) and pristine Ag nanoparticles (k_d = 19.3 × 10⁻³ g mg⁻¹ min⁻¹). Blue Ag nanoparticles, owing to their better charge carrier generation and enhanced surface plasmon resonance, exhibited superior photocatalysis performance as compared to yellow Ag nanoparticles in all nanostructures.

In this article, we present a novel synthesis of mesoporous SiO₂/Ag nanostructures for dye (methylene blue) adsorption and surface plasmon mediated photocatalysis.     

Solvent-free hydrogenation of cyclohexene over Rh-TUD-1 at ambient conditions

Rhodium nanoparticles (≈3–5 nm) were incorporated into the 3D mesoporous TUD-1 material by using sol–gel technique. The prepared catalyst shows high activity in the liquid phase conversion of cyclohexene to cyclohexane at room temperature (298 K), 1 atm H₂ pressure, and under solvent-free conditions. Rhodium nanoparticles exhibited high stability, reusability and negligible leaching.

Total conversion of cyclohexene to cyclohexane was achieved in a liquid phase hydrogenation reaction at room temperature, 1 atm H₂ pressure and solvent-free system.     

The preparation,characterization and catalytic activity of Ni NPs supported on porous alginate-g-poly(p-styrene sulfonamide-co-acrylamide)

Herein, we report the synthesis of nickel nanoparticles under mild conditions using porous alginate-g-poly(p-styrene sulfonamide-co-acrylamide) as a protecting/stabilizing agent and sodium borohydride as a reducing agent. The porous cross-linked polymeric support was prepared via combining the use of sol–gel, nanocasting, and crosslinking techniques, in which the p-styrene sulfonamide monomer (PSSA) and N,N′-methylene-bis (acrylamide) (MBA) cross-linker underwent copolymerization on the surface of sodium alginate in the presence of a SiO₂ nanoparticle (NP) template (Alg–PSSA-co-ACA). The prepared catalyst (Alg–PSSA-co-ACA@Ni) showed high catalytic activity for the one-step synthesis of 1,3,4-oxadiazoles from the reaction of hydrazides and aryl iodides through isocyanide insertion/cyclization.

Ni NPs supported on novel porous alginate-g-poly(p-styrene sulfonamide-co-acrylamide) was investigated for the synthesis of 1,3,4-oxadiazoles.     

Organic–inorganic hybridization for the synthesis of robust in situ hydrophobic polypropylsilsesquioxane aerogels with fast oil absorption properties

In situ hydrophobic polypropylsilsesquioxane aerogels (PSAs) were successfully synthesized via an organic–inorganic hybridization method by a sol–gel process, in which propyltriethoxysilane (PTES) and tetraethylorthosilicate (TEOS) were used as co-precursors. ²⁹Si NMR and FTIR analyses indicated the high degree of condensation of the precursors and proved the attachment of propyl (–C₃H₇) groups in PSAs, respectively. By means of incorporating propyl groups, both mechanical robustness and in situ hydrophobicity were obtained. Meanwhile, the mechanical strength, contact angle and density obviously increased with the increase in propyl groups. Under optimized conditions, as-prepared PSA could endure up to a 70% maximum linear compression with few cracks. Benefiting from the robust structure and in situ hydrophobicity, PSAs showed high absorption capacities (8–10 times that of its own weight) and fast absorption properties (<20 s) for a wide range of organic solvents and could be reused at least 5 times.

In situ hydrophobic and mechanically robust polypropylsilsesquioxane aerogels (PSAs) were successfully synthesized via an organic–inorganic hybridization method by a sol–gel process.     

The facile synthesis and bioactivity of a 3D nanofibrous bioglass scaffold using an amino-modified bacterial cellulose template

Porous bioglass (BG) scaffolds are of great importance in tissue engineering because of their excellent osteogenic properties for bone regeneration. Herein, we reported for the first time the use of amino-modified bacterial cellulose (NBC) as a template to prepare a three-dimensional (3D) nanofibrous BG scaffold by a facile modified sol–gel approach under ultrasonic treatment. The results suggested that the amino groups on the BC template could effectively promote the absorption of the deposited CaO and SiO₂ precursors, and the as-obtained BG scaffold showed a 3D interconnected porous network structure consisting of nanofibers with a diameter of about 20 nm. Furthermore, the as-obtained BG scaffold showed very good bioactivity after being immersed in SBF for 7 days. This research provides a facile and efficient way to prepare a nanofibrous BG scaffold with 3D porous structure, which can be used as a promising candidate for biomedical applications.

A nanofibrous BG scaffold with a high quality 3D porous interconnected structure has been prepared via a facile modified sol–gel approach using amino-modified bacterial cellulose as the template.     

Carboxylation of sodium arylsulfinates with CO2 over mesoporous K-Cu-20TiO2

A mesoporous ternary metal oxide (K-Cu-20TiO₂) from a simple sol–gel method was prepared to catalyze heterogeneously the carboxylation reaction of various sodium arylsulfinates under atmospheric carbon dioxide. The catalyst showed excellent selectivity and good functional group tolerance to carboxylation recycle. The oxidation state of active copper(i) by characterization using FTIR, XRD, TG, XPS and TEM techniques proved to be efficacious to conduct atom economical reactions.

A mesoporous ternary metal oxide (K-Cu-20TiO₂) from a simple sol–gel method was prepared to catalyze heterogeneously the carboxylation reaction of various sodium arylsulfinates under atmospheric carbon dioxide.     

Mechanistic insight into the non-hydrolytic sol–gel process of tellurite glass films to attain a high transmission

The development of amorphous films with a wide transmission window and high refractive index is of growing significance due to the strong demand of integrating functional nanoparticles for the next-generation hybrid optoelectronic films. High-index TeO₂-based glass films made via the sol–gel process are particularly suitable as their low temperature preparation process promises high compatibility with a large variety of nanoparticles and substrates that suffer from low thermal stability. However, due to the lack of in-depth understanding of the mechanisms of the formation of undesired metallic-Te (highly absorbing species) in the films, the preparation of high-transmission TeO₂-based sol–gel films has been severely hampered. Here, by gaining insight into the mechanistic chemistry of metallic-Te formation at different stages during the non-hydrolytic sol–gel process, we identify the chemical route to prevent the generation of metallic-Te in a TeO₂-based film. The as-prepared TeO₂-based film exhibits a high transmission that is close to the theoretical limit. This opens up a new avenue for advancing the performance of hybrid optoelectronic films via incorporating a large variety of unique nanoparticles.

This work develops a high-transparency amorphous film with a wide transmission window and high refractive index, which can potentially meet the strong demand of integrating functional nanoparticles for the next-generation hybrid optoelectronic films.     

Preparation of a porous superhydrophobic foam from waste plastic and its application for oil spill cleanup

In order to cope with the increasing oil spill accidents and the intentional discharge of oily wastewater, a new oil-adsorbing material with superhydrophobicity and reusability is needed. In this paper, waste plastic was used to fabricate an alveolate polystyrene (PS) foam to reduce secondary pollution. The PS foam was synthesized from a high internal phase Pickering emulsion (HIPPE) technique in a one-step process. The emulsion was stabilized by a co-Pickering system of Span 80 surfactant and SiO₂ particles. To explain the super stability of the HIPPE, a novel model of the water-in-oil droplet was promoted. The obtained SiO₂@PS foam exhibited a multi-order-porous structure, and displayed superhydrophobicity and superoleophilicity. It can selectively remove various oily contaminants from water with a high adsorption capacity of 20.4–58.1 g g⁻¹ at a fast rate. The oil-adsorbed material can be reused by simple centrifugation, and no more than a 1% decline was obtained in the oil adsorption after 10 cycles. Therefore, the SiO₂@PS foam has a great potential application in oily water treatment.

In this paper, waste polystyrene (PS) plastic was used to fabricate alveolate PS foam via a high internal phase Pickering emulsion (HIPPE) which was stabilized by Span 80 and silica particle as a co-Pickering emulsifier in one-step progress.     

SiO2 thin film growth through a pure atomic layer deposition technique at room temperature

In this study, less contaminated and porous SiO₂ films were grown via ALD at room temperature. In addition to the well-known catalytic effect of ammonia, the self-limitation of the reaction was demonstrated by tuning the exposure of SiCl₄, NH₃ and H₂O. This pure ALD approach generated porous oxide layers with very low chloride contamination in films. This optimized RT-ALD process could be applied to a wide range of substrates that need to be 3D-coated, similar to mesoporous structured membranes.

In this study, less contaminated and porous SiO₂ films were grown via ALD at room temperature.     

Controlled synthesis of open-mouthed epitope-imprinted polymer nanocapsules with a PEGylated nanocore and their application for fluorescence detection of target protein

Epitope imprinting is an effective way to create artificial receptors for protein recognition. Surface imprinting with immobilized templates and sacrificial supports can generate high-quality imprinted cavities of homogeneous orientation and good accessibility, but it is still challenging to fabricate nanoscale imprinted materials by this approach. Herein, we propose a method for the controlled synthesis of open-mouthed epitope-imprinted polymer nanocapsules (OM-MIP NCs) by limiting the imprinting polymerization on the template-bearing side of the Janus nanoparticles (JNPs). Concurrent bromoacetyl (Ac–Br) and 2-bromoisobutyryl (iB–Br) functionalization of the major portion of SiO₂ nanoparticles is achieved via the molten-wax-in-water Pickering emulsion approach. The cysteinyl-derived epitope templates are immobilized through the Ac–Br groups, and then surface imprinting is fulfilled via ATRP initiated by the iB–Br groups. The SiO₂ supports are partially etched and then PEGlated, affording OM-MIP NCs with a PEGylated nanocore. The inside nanocore can facilitate collection of the NCs by centrifugation, and its PEGylation can inhibit non-specific binding. The surface imprinting can be optimized through the ATRP time, and the etching can be tailored via the concentration of NH₄HF₂ employed. For proof-of-concept, with a C-terminus nonapeptide of bovine serum albumin (BSA) chosen as a model epitope and polymerizable carbon dots added to the pre-polymerization solution, fluorescent OM-MIP NCs were fabricated for BSA sensing. The as-synthesized NCs exhibited satisfactory detection performance, with an imprinting factor of 6.1, a limit of detection of 38.1 nM, a linear range of 0.25–6 μM, and recoveries of 98.0 to 104.0% in bovine serum samples.

Surface epitope imprinting over the one side of Janus SiO₂ NPs via ATRP affords open-mouthed epitope-imprinted nanocapsules with imprinted cavities of homogeneous orientation and good accessibility for fluorescence detection of target protein.     

Dense,uniform, smooth SiO2/TiO2 hard coatings derived from a single precursor source of tetra-n-butyl titanate modified perhydropolysilazane

SiO₂/TiO₂ composite coatings are of great interest due to their optical, photocatalytic, electrical and mechanical properties. There are many methods for preparing SiO₂/TiO₂ composite coatings. Among these, the sol–gel process is eco-friendly and easily implementable for industrial applications. However, it is still a great challenge to prepare dense, uniform and smooth SiO₂/TiO₂ composite coatings with a sol–gel process. In this work, we show a modified sol–gel process for achieving dense, uniform and smooth SiO₂/TiO₂ coatings with tetra-n-butyl titanate modified perhydropolysilazane (PHPS) as a single precursor source, in which PHPS acts as the source for SiO₂ instead of a traditional alkoxylsilane compound. The micro-morphology and composition evolution during the preparation process have been investigated; a smooth surface with a roughness average (S_a) below 4.5 nm and a uniform distribution of Ti elements over the entire coating are shown. These dense, uniform SiO₂/TiO₂ coatings exhibit excellent mechanical robustness, with hardness values as high as 9.45 GPa, excellent optical transparency and hydrophilic properties.

Dense, uniform, smooth SiO₂/TiO₂ hard coatings derived from a single precursor source of tetra n-butyl titanate modified perhydropolysilazane.     

Lewis acid Ni/Al-MCM-41 catalysts for H2-free deoxygenation of Reutealis trisperma oil to biofuels

The activity of mesoporous Al-MCM-41 for deoxygenation of Reutealis trisperma oil (RTO) was enhanced via modification with NiO nanoparticles. Deoxygenation at atmospheric pressure and under H₂ free conditions required acid catalysts to ensure the removal of the oxygenated fragments in triglycerides to form liquid hydrocarbons. NiO at different weight loadings was impregnated onto Al-MCM-41 and the changes of Lewis/Brønsted acidity and mesoporosity of the catalysts were investigated. The activity of Al-MCM-41 was enhanced when impregnated with NiO due to the increase of Lewis acidity originating from NiO nanoparticles and the mesoporosity of Al-MCM-41. Increasing the NiO loading enhanced the Lewis acidity but not Brønsted acidity, leading to a higher conversion towards liquid hydrocarbon yield. Impregnation with 10% of NiO on Al-MCM-41 increased the conversion of RTO to hydrocarbons via the deoxygenation pathway and reduced the products from cracking reaction, consequently enhancing the green diesel (C11–C18) hydrocarbon products.

The activity of mesoporous Al-MCM-41 for deoxygenation of Reutealis trisperma oil (RTO) was enhanced via modification with NiO nanoparticles.     

A highly efficient nano-sized Cu2O/SiO2 egg-shell catalyst for C–C coupling reactions

Mesoporous SiO₂-supported Cu₂O nanoparticles as an egg-shell type catalyst were prepared by impregnation method. The obtained Cu₂O/SiO₂ egg-shell nanocatalyst had a large surface area and narrow pore size distribution. In addition, most of the Cu₂O nanoparticles, with sizes around 2.0 nm, were highly dispersed in the mesoporous silica. Accordingly, fast reactant diffusion to the active sites would occur, especially when the active metal sites are selectively located on the outer part of the support, i.e., the outer region of the egg shell. In solvent-free Sonogashira reactions for the synthesis of ynones from acyl chlorides and terminal alkynes, this catalyst exhibited a very high catalytic activity. The excellent catalytic performance can be attributed to the synergistic advantages of mesoporous structure and monodispersed Cu₂O nanoparticles.

Mesoporous SiO₂-supported Cu₂O nanoparticles as an egg-shell type catalyst were prepared by impregnation method.     

The pH-triggered drug release and simultaneous carrier decomposition of effervescent SiO2–drug–Na2CO3 composite nanoparticles: to improve the antitumor activity of hydrophobic drugs

To achieve a better release effect of hydrophobic drugs and spontaneous nanocarrier disintegration by dissolution as well as the CO₂ production of Na₂CO₃ further, improving the therapeutic effect of hydrophobic drugs, and thereby avoiding the accumulation of the nanocarrier in vivo to produce organ toxicity, effervescent SiO₂–drug–Na₂CO₃ composite nanoparticles (ESNs) were prepared in this study using a tetraethyl orthosilicate hydrolysis method. Sodium carbonate was used as the effervescent disintegrant to respond to the acidic microenvironment of the tumor. The properties of ESNs were assessed and TEM images were taken to verify the self-disintegration characteristics of nanocarrier materials. The in vitro anticancer efficacy of ESNs was evaluated in human breast cancer MCF-7 cells. ESNs loaded with hydrophobic drugs were successfully constructed, and showed high entrapment efficiency and drug loading. The nanocarrier successfully achieved self-disintegration in a PBS environment of pH value at 5.0, and showed excellent antitumor effect in vitro. ESNs can effectively load hydrophobic drugs and achieve self-disintegration, while avoiding toxicity from the accumulation of the nanocarrier. These results suggest that ESNs are a promising drug delivery system capable of maximizing the anticancer therapeutic efficacy and minimizing the systemic toxicity.

Effervescent SiO₂–drug–Na₂CO₃ composite nanoparticles were prepared in this study using a tetraethyl orthosilicate hydrolysis method to achieve a better release effect of hydrophobic drugs and spontaneous nanocarrier disintegration by dissolution.     

Polylactic acid based Janus membranes with asymmetric wettability for directional moisture transport with enhanced UV protective capabilities

Efficient directional moisture transport can remove excess sweat away from the human body and keep the body dry; fully utilizing this functionality to improve the wearing experience is urgently needed in the area of functional textiles. Herein, a facile strategy is used to design an eco-friendly and biodegradable PLA membrane with enhanced directional moisture transport and UV protection abilities. The PLA-based Janus membrane with asymmetric wettability is fabricated via sol–gel and electrospinning methods. Titanium dioxide nanoparticles (TiO₂) were anchored onto the surface of the PLA fabric during the TiO₂ sol–gel fabrication process using polydopamine, forming superhydrophilic TiO₂@PDA–PLA. Then a thin PLA fibrous membrane layer showing hydrophobicity was electrospun onto this (PLA-E). The Janus PLA-E/TiO₂@PDA–PLA membrane was successfully fabricated. Due to the asymmetric wettability and anchored TiO₂, the PLA-E/TiO₂@PDA–PLA Janus membrane exhibits efficient directional moisture transport and excellent UV protection abilities, and this work may provide a new pathway for fabricating multifunctional personal protective materials and have attractive potential applications in the future.

The PLA-E/TiO₂@PDA–PLA Janus membrane with asymmetric wettability exhibits efficient directional moisture transport and excellent UV protective capacity.     

Role of annealing temperature on the sol–gel synthesis of VO2 nanowires with in situ characterization of their metal–insulator transition

Among the techniques to create VO₂ nanostructures, the sol–gel method is the most facile and benefits from simple, manipulable synthetic parameters. Here, by utilizing various TEM techniques, we report the sequential morphological evolution of VO₂ nanostructures in a sol–gel film spin-coated on a customized TEM grid, which underwent oxygen reduction as the annealing temperature increased. In situ TEM dark-field imaging and Raman spectroscopy allowed us to confirm the sharp phase transition behavior of an individual nanowire by illustrating the effect of electrode-clamping-induced tensile stress on the nucleation of the R phase from the M1 phase. The electrical transport properties of a single-nanowire device fabricated on a customized TEM grid showed excellent control of the stoichiometry and crystallinity of the wire. These results offer critical information for preparing tailored VO₂ nanostructures with advanced transition properties by the sol–gel method to enable the fabrication of scalable flexible devices.

The single-VO₂ nanowire device synthesized via sequential morphological evolutions with oxygen reduction during annealing features a sharp metal-insulator transition.     

Photocatalytic degradation of rhodamine B catalyzed by TiO2 films on a capillary column

TiO₂ films on a capillary column were prepared using tetrabutoxytitanium as a source of TiO₂via the sol–gel method. The film thickness showed a linear increase with tetrabutoxytitanium concentration. The specific surface area of the film was improved by adding polyethylene glycol with different molecular weights. Under optimal conditions, the prepared film had a good mesoporous structure with specific surface area of 47.72 m² g⁻¹, and showed nearly spherical nanoparticles with a 10 nm diameter and anatase phase. Influences of the thickness, specific surface area, and initial solution concentration on photodegradation of rhodamine B using TiO₂ films as a catalyst were investigated. The results showed that the photodegradation efficiency increased with an increasing thickness and specific surface area of TiO₂ films. For a rhodamine B solution of 15 mg L⁻¹, the photodegradation efficiency was 98.33% in 30 min under the optimal conditions. The catalysts could be reused up to eight times with almost the same efficiency, indicating a firm immobilization of films on the inner wall of the capillary. Therefore, TiO₂ films are promising for the treatment of wastewater.

TiO₂ films on a capillary column were prepared using tetrabutoxytitanium as a source of TiO₂via the sol–gel method.     

A novel carboxylic-functional indole-based aerogel for highly effective removal of heavy metals from aqueous solution via synergistic effects of face–point and point–point interactions

A new type of carboxylic-functional indole-based aerogel (CHIFA) has been successfully prepared via a facile sol–gel technology, which possessed a highly effective removal of heavy metals from aqueous solution through the synergistic effects of face–point and point–point interactions.

A new type of carboxylic-functional indole-based aerogel (CHIFA) has been successfully prepared, which possessed highly effective removal of heavy metals from aqueous solution through the synergistic effects of face–point and point–point interactions.