Porous Silica Spheres Research Articles

Contamination-Free Reference Electrode Using Prussian Blue for Small Oxygen Sensors.

In recent years, significant attention has been directed toward advancing compact, point-of-care testing (POCT) devices to better deliver patient care and alleviate the burden on the medical care system. Common POCTs, such as blood oxygen sensors, leverage electrochemical sensing in their design. However, conventional electrochemical devices typically use Ag/AgCl reference electrodes, which are likely to release trace amounts of silver ions that contaminate the working electrode, causing rapid deterioration of the devices. This study proposes an effective reference electrode using graphene-coated porous silica spheres (G/PSS) with embedded Prussian blue (PB), denoted PB/G/PSS, designed specifically for small oxygen sensors. PB is a redox species that is an improvement over Ag/AgCl since it is significantly less water-soluble than AgCl. Since PB is an insulator, we dispersed PB in G/PSS, well-conductive mesoporous matrices, to ensure contact between PB clusters and the electrolytes. Moreover, the monodispersed, spherically shaped PB/G/PSS is an advantageous medium for fabricating POCT devices by screen printing. In this study, the open-circuit potential of the PB/G/PSS electrode remained stable within 30 mV for 31 days. The small oxygen sensor assembled through screen printing using PB/G/PSS demonstrated stable operation for several days or more. In contrast, a similar sensor with Ag/AgCl reference electrode rapidly deteriorated within a day. This PB/G/PSS reference electrode with improved stability is expected to be an excellent alternative to the Ag/AgCl system for small electrochemical-based POCT devices.

Multifaceted Assessment of Porous Silica Nanocomposites: Unraveling Physical, Structural, and Biological Transformations Induced by Microwave Field Modification.

In response to the persistent challenge of heavy and noble metal environmental contamination, our research explores a new idea to capture silver through porous spherical silica nanostructures. The aim was realized using microwave radiation at varying power (P = 150 or 800 W) and exposure times (t = 60 or 150 s). It led to the development of a silica surface with enhanced metal-capture capacity. The microwave-assisted silica surface modification influences the notable changes within the carrier but also enforces the crystallization process of silver nanoparticles with different morphology, structure, and chemical composition. Microwave treatment can also stimulate the formation of core-shell bioactive Ag/Ag2CO3 heterojunctions. Due to the silver nanoparticles' sphericity and silver carbonate's presence, the modified nanocomposites exhibited heightened toxicity against common microorganisms, such as E. coli and S. epidermidis. Toxicological assessments, including minimum inhibitory concentration (MIC) and half-maximal inhibitory concentration (IC50) determinations, underscored the efficacy of the nanocomposites. This research represents a significant stride in addressing pollution challenges. It shows the potential of microwave-modified silicas in the fight against environmental contamination. Microwave engineering underscores a sophisticated approach to pollution remediation and emphasizes the pivotal role of nanotechnology in shaping sustainable solutions for environmental stewardship.

Thermochemical Properties of Synthesized Urea from Recovered Ammonia and Carbon Dioxide in Well-Ordered Nanospaces of Hollow Silica Spheres.

The present work investigated the thermochemical properties of urea synthesized in well-ordered nanospaces of porous hollow silica spheres' shells from recovered ammonia and carbon dioxide in aqueous solution. Thermochemical behaviors of the urea synthesized in well-ordered nanospaces of the hollow spheres' shells prepared with 1-dodeclyamine were analyzed from the results of thermogravimetric analysis (TGA) and differential thermal analysis (DTA), and endothermic peaks assigned as the phase transition and decomposition were observed at ca. 440 and 514 K, respectively, which were higher than those of pristine urea (405 and 408 K, respectively), probably because of the nanoconfinement effect. The decomposition behavior was also confirmed by the result of diffuse reflectance infrared Fourier transform (DRIFT) spectra of the samples treated at various temperatures up to 573 K, and the decomposition of urea synthesized in the well-ordered nanospaces of the hollow spheres' shells started at 468 K and completed up to 533 K.

Ionic liquid/covalent organic framework/silica composite material: Green synthesis and chromatographic evaluation

BackgroundDue to their large surface area and distinctive adsorption affinity, covalent organic frameworks (COFs) appear to be good candidates as liquid chromatographic separation materials with good application prospect. The development of COF materials in chromatographic science is currently in an exploratory stage. Especially, the practicability of COF@silica composite materials as liquid chromatographic stationary phases needs further exploration. Reasonably integrating a functional component such as ionic liquid (IL) into the COF@silica composite materials may provide customized functionality to achieve the purpose of synthesizing multi-functional COF based stationary phases. ResultsIn this study, an IL modified COF bonded silica composite material (IL-COF@SiO2) was successfully synthesized by using an environmentally friendly deep eutectic solvent as the reaction medium instead of the frequently-used organic solvent. The synthesized IL-COF@SiO2 composite material combines the excellent separation ability of COF and the excellent mass transfer function of spherical porous silica microsphere, and meanwhile, the introduction of IL endows COF@SiO2 with preferable separation performance. The slurry-packed IL-COF@SiO2 liquid chromatographic column could be applied to effectively separate hydrophobic and hydrophilic compounds with preferable separation selectivity and high column efficiency. By investigating the retention behavior and influencing factors, a mixed-mode retention mechanism was found. Multiple interaction forces endow the IL-COF@SiO2 with a hydrophilic-hydrophobic balance performance, demonstrating a good application prospect as a versatile liquid chromatographic separation material. SignificanceIn this study, a new strategy is proposed for greenly synthesizing a novel IL-COF@SiO2 composite material under mild conditions, which expands the potential application of COF materials in chromatographic science. One particular point to note is that the reaction medium in each step of the preparation process is low toxic and degradable deep eutectic solvent, which conforms to the concept of green chemistry.

Enzyme-immobilized Screen-printed Sensor for One Drop of Sample Using Porous Silica Spheres

Enzyme-immobilized Screen-printed Sensor for One Drop of Sample Using Porous Silica Spheres

Improved analysis ZIC-HILIC-HCD-Orbitrap method for mapping the glycopeptide by mass spectrometry

Glycosylation is one of the most common post-translational modifications (PTMs). Protein glycosylation analysis is the bottleneck to deeply understand their functions. At present, the LC-MS analysis of glycosylated post-translational modification is mainly focused on the analysis of glycopeptides. However, the factors affecting the identification of glycopeptides were not fully elucidated. In the paper, we have carefully studied the factors, e.g., HILIC materials, search engines, protein amount, gradient duration, extraction solution, etc. According to the results, HILIC materials were the most important factors affecting the glycopeptides identification, and the amphoteric sulfoalkyl betaine stationary phase enriched glycopeptides 6-fold more compared to the amphiphilic ion-bonded fully porous spherical silica stationary phase. We explored the influence of the extraction solutions on glycan identification. Comparing sodium dodecyl sulfate (SDS) and urea (UA), the results showed that N-glycolylneuraminic acid (NeuGc) type of glycan content was found to be increased 1.4-fold in the SDS compared to UA. Besides, we explored the influence of the search engine on glycopeptide identification. Comparing pGlyco3.0 and MSFragger-Glyco, it was observed that pGlyco3.0 outperformed MSFragger-Glyco in identifying glycopeptides. Then, using our optimized method we found that there was a significant difference in the distribution of monosaccharide types in plasma and brain tissue, e.g., the content of NeuAc in brain was 5-fold higher than that in plasma. To importantly, two glycoproteins (Neurexin-2 and SUN domain-containing protein 2) were also found for the first time by our method. In summary, we have comprehensively studied the factors influencing glycopeptide identification than any previous research, and the optimized method could be widely used for identifying the glycoproteins or glycolpeptides biomarkers for disease detection and therapeutic targets.

Development of Microdrip Enzyme Device Using Carbon-Coated Porous Silica Spheres

Carbon-coated porous silica spheres (C/PSSs) are particles with uniform particle and mesopore sizes, on which a thin layer of carbon is uniformly deposited on the surface by chemical vapor deposition. The continuous carbon deposit over the mesopore network allows the C/PSS to be electrically conductive and more chemically stable over its traditional counterparts, such as PSS, porous carbons, and carbon electrodes. As homogeneous particles, C/PSS can also be arranged uniformly on an electrode by screen printing to construct macroscopic networks that facilitate the diffusion of substances. Herein, C/PSS was synthesized and fabricated into a working electrode for a prototype glucose enzyme sensor to perform electrochemical measurements on a sample size of 20 μL. We selected the two enzymes, glucose dehydrogenase (GDH) and glucose oxidase (GOD), and water-soluble mediators, quinoline-5,8-dione (QD), to demonstrate the functionality of the sensor. The GDH sensor achieved a linear response up to 75 mM glucose concentration much higher than commercial sensor strips and the GOD sensor up to 25 mM. The results proved that the response current was mainly controlled by glucose diffusion. We succeeded in developing a sensor chip with C/PSS arranged on the surface with high efficiency by selecting a mediator that can smoothly transfer electrons to and from carbon, which enables various sensing applications. This work is the demonstration of the triple pore structure of the C/PSS electrode for enzyme electrode reactions.

Yeast cell templated porous hollow silica spheres for rapid hemostasis accompanied by antibacterial action.

Uncontrolled haemorrhage is the leading cause in nearly 91% of pre-hospital deaths, which were considered potentially survivable. In particular, severe trauma is susceptible to infection, which further affects the natural healing process and can even lead to life-threatening sepsis. Therefore, we established Ag@HMSN nanocomposites based on a yeast cell template that combines hemostasis with antibiosis and further studied the effects of different calcination temperatures on the hemostatic and antibacterial properties. From the experimental results, Ag@HMSNs/500 shows excellent bactericidal effect on a mouse skin infection model and outstanding hemostatic effect on a mouse liver injury model, which could be used as the next-generation hemostatic and antibacterial material.

Surface-Modified Wrinkled Mesoporous Nanosilica as an Effective Adsorbent for Benzene, Toluene, Ethylbenzene, and Xylene in Indoor Air

Surfactant-extracted spherical porous silica nanoparticles with wrinkled structures were synthesized, and their adsorption performance was altered by grafting three organosilanes: n-octyltriethoxysilane, hexadecyltrimethoxysilane, and triethoxyphenylsilane onto their surface. The surface-modified silica nanoparticles were used to capture frequently detected hazardous indoor air chemicals. The physical and chemical properties of the samples were characterized using thermogravimetric analysis, Fourier transform infrared spectroscopy, N2 adsorption–desorption experiments, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. Although the organosilane surface modification did not significantly change the surface areas and pore structures of porous silica nanoparticles, the capacities of the surface-modified porous silica nanoparticles for capturing benzene, toluene, ethylbenzene, and xylene (BTEX) molecules from air were considerably higher than those of pristine porous silica nanoparticles. The dispersion forces between adsorbates and adsorbents were the primary factor that affected the absorption capacity of the surface-modified porous silica nanoparticles. Consequently, the BTEX capturing potential of surface-modified mesoporous silica featuring a long alkyl chain was high because of the relatively high dispersion force between adsorbates and the adsorbent.

Preparation of Porous Silica Particles with a Controlled Mesopore Size by Ultrasonic Spray Drying for High-Performance Liquid Chromatography (HPLC)

Highly spherical porous silica particles (PSPs) with a controlled pore size were prepared by ultrasonic spray drying and were used as a packing material for high-performance liquid chromatography (HPLC). By using organic additives added to the silica sol as porogens instead of low-melting salts, choosing the size of the colloidal SiO2 particles, and varying the type and the ratio of additives, the pore size of the PSPs was finely tuned from 2.9 to 34.4 nm. Subsequently, PSPs having pore sizes of 7.4, 13.5, and 29.0 nm were modified by chlorodimethyloctadecylsilane (PSPs-C18), and HPLC columns packed with the different PSPs-C18 were evaluated systematically using aromatic compounds and alkylbenzene derivatives as probes. A plate number of 81,000/m and the relative standard deviation of less than 1% in the retention time were obtained for pentylbenzene over 100 injection and HPLC separation cycles for the 7.4-PSPs-C18 column. Five proteins were also separated within 25 min using the 29.0-PSPs-C18 column.

Fe2O3-decorated hollow porous silica spheres assisted by waste gelatin template for efficient purification of synthetic wastewater containing As(V)

Purification of As(V)-contaminated water through adsorption by Fe2O3-based materials is a promising technology due to its low-cost and high efficiency. Dispersing the Fe2O3 phase on silica supports can improve both the adsorption rate and capacity due to the reduction in Fe2O3 particle sizes and the prevention of clumping of the Fe2O3 particles. However, the clusters in conventional silica materials largely impede the diffusion of As(V) to reach the Fe2O3 sites dispersed inside the clusters. Here, by applying a gelatin template strategy, the structure of silica materials was tailored by changing the gelatin-to-silica ratio (0, 0.6, 1.2 and 1.8) and hydrothermal temperature (60 °C, 100 °C and 140 °C). The silica cluster size could be reduced using either a low gelatin-to-silica ratio (0.6) or a low hydrothermal temperature (60 °C). Increasing the gelatin-to-silica ratio to 1.2 created porous silica spheres with a hollow structure. The Fe2O3-loaded hollow porous silica spheres with a shell thickness of 280 nm had twice the maximum As(V) adsorption capacity (7.66 mg g−1) compared to the Fe2O3-loaded silica product prepared in the absence of gelatin (3.82 mg g−1). The maximum As(V) adsorption capacity could be further enhanced to 9.94 mg g−1 by reducing the shell thickness to 80 nm through increasing the gelatin-to-silica ratio to 1.8 and the hydrothermal temperature to 140 °C. In addition, the best Fe2O3-loaded hollow porous silica spheres had rapid As(V) adsorption and showed excellent durability as the As(V) removal efficiency slightly decreased to 98.9% subsequent to five adsorption-regeneration cycles.

Hierarchically porous Fe/N/S/C nanospheres with high-content of Fe-Nx for enhanced ORR and Zn-air battery performance

Heteroatom-doped carbon-based transition-metal single-atom catalysts (SACs) are promising electrocatalysts for oxygen reduction reaction (ORR). Herein, with the aid of hierarchically porous silica as hard template, a facile and general melting perfusion and mesopore-confined pyrolysis method was reported to prepare single-atomic Fe/N–S-doped carbon catalyst (FeNx/NC-S) with hierarchically porous structure and well-defined morphology. The FeNx/NC-S exhibited excellent ORR activity with a half-wave potential (E1/2) of 0.92 V, and a lower overpotential of 320 mV at a current density of 10 mA cm−2 for OER under alkaline condition. The remarkable electrocatalysis performance can be attributed to the hierarchically porous carbon nanospheres with S doping and high content of Fe-Nx sites (up to 3.7 wt% of Fe), resulting from the nano-confinement effect of the hierarchically porous silica spheres (NKM-5) during the pyrolysis process. The rechargeable Zn-air battery with FeNx/NC-S as a cathode catalyst demonstrated a superior power density of 194.5 mW cm−2 charge–discharge stability. This work highlights a new avenue to design advanced SACs for efficient sustainable energy storage and conversion.

Soft Magnetic Microrobot Doped with Porous Silica for Stability-Enhanced Multimodal Locomotion in a Nonideal Environment.

As an emerging field of robotics, magnetic-field-controlled soft microrobot has broad application prospects for its flexibility, locomotion diversity, and remote controllability. Magnetic soft microrobots can perform multimodal locomotion under the control of a magnetic field, which may have potential applications in precision medicine. However, previous research studies mainly focus on new locomotion in a relatively ideal environment, lacking exploration on the ability of magnetic microrobot locomotion to resist external disturbances and proceed in a nonideal environment. Here, a porous silica-doped soft magnetic microrobot is constructed for enhanced stability of multimodal locomotion in the nonideal biological environment. Porous silica spheres are doped into a NdFeB-silicone elastomer base, improving adhesion properties and refining the comprehensive mechanical properties of the microrobot. Multimodal locomotions are achieved, and the influence of porous silica doping on the stability of each locomotion in a nonideal environment is explored in depth. Motions in nonideal circumstances such as climbing, loading, current rushing, wind blowing, and obstacle hindering are conducted successfully with porous silica doping. Such a stability-enhanced multimodal locomotion system can be used in biocatalysis and thrombus removal, and its prospect for precision medicine is highlighted by in vivo demonstration of multimodal locomotion with nonideal disturbance.

Copper upcycling by hierarchical porous silica spheres functionalized with branched polyethylenimine: Antimicrobial and catalytic applications

The increment of environmental pollution from heavy metals released by industrial or urban sources drives the development of new smart adsorbents. In particular, copper pollution is a rising concern due to its presence in industrial streams and electronic wastes. Mesoporous silica is a useful adsorbent for copper uptake but it requires the incorporation of specific functionalities to enhance the uptake and selectivity. Branched polyethylenimine (PEI) is a specific copper chelate agent but its bulky structure hinders the loading on mesoporous supports. In this work, the incorporation of PEI on a hierarchical porous silica with wrinkled meso/macroporosity (w-SiO2) resulted in a smart adsorbent with higher copper adsorption capacity. After the uptake, the annealing of the adsorbed PEI-copper complex leads to a w-SiO2/CuO nanocomposite with outstanding antimicrobial properties and catalytic activity due to the enhanced copper bioavailability. The minimum inhibitory concentration of supported copper oxide on silica for E. coli in LB broth medium was 825.5 μg Cu/ml. Oxidation of the electron donor molecule ABTS in the presence of this nanocomposite and H2O2 is a first demonstrator of the potential application as a peroxidase-like nanozyme. The use of adsorbents with hierarchical porosity to support bulky functionalities with high selectivity is a novel strategy for heavy metals upcycling.

Antireflective laser coating with improved mechanical property and organic-contaminant resistance for high-power laser application

Mono-layer silica-based antireflective laser coating with modulated structure has been designed and fabricated, in which cross-linking network structure of polysiloxane was prepared as backbone and porous silica spheres (PSSs) were inserted to create interior porosity. Cured polysiloxane provided dense structure that could both prevent the invasion of volatile organic compounds (VOCs) and improve the mechanical property of this coating, while PSSs endowed this coating with proper porosity to adjust its refractive index and relax the high-power laser energy. With certain structure modulation, excellent transmission and laser-damage resistance of this coating at 355 nm (for the application in high-power laser system) and 1064 nm (for the application in laser-guided component) was both achieved. Meanwhile, the hardness of this coating increased significantly compared with that of the conventional porous silica coating. In addition, qualified VOCs endurance of this coating was also proved, which effectively extended the lifetime of such coating.

Constructing Hybrids Consisting of Porous Silica Particles and Carbon Nanotubes and their Polymer Composites

One type of 3D hybrid structure has been successfully fabricated by a chemical vapor deposition method, which consisted of carbon nanotubes (CNTs) shell and porous spherical silica core. A biphase reaction was employed to synthesize the porous silica spheres. The pores had an average size of 19.5 ± 9.4 nm, which offered an ideal place for the deposition of catalyst during the CVD process and enhanced the adhesion force between the particles and CNTs. The sonication test indicated that the porous silica-CNTs hybrids had stronger adhesion force than that of the pristine silica-CNTs hybrids. Then, an ultralow fraction (0.1 wt.%) of the hybrids was incorporated into epoxy matrix to prepare the composites. The storage modulus of composites has improved greatly comparing to the pure epoxy and pristine silica-CNTs hybrids/epoxy composite. A possible reinforcement mechanism has been described to explain the phenomenon.

Chiral salen - Ni (II) based spherical porous silica as platform for asymmetric transfer hydrogenation reaction and synthesis of potent drug intermediate montekulast

Heterogeneous catalyst has an edge over homogeneous systems in terms of recyclability, activity, stability and recovery. Silica has evolved as a good support material in heterogeneous systems due to its stability and ability to get modified as per the end application. Herein, we report a novel chiral Ni-Schiff base derived catalyst and its immobilization into mesoporous silica which was synthesized by post-grafting process. The chiral catalyst demonstrated remarkably high catalytic activity, enantioselectivity (up to 99 % enantiomers excess) for heterogeneous asymmetric transfer hydrogenation of various ketones. The developed catalyst was characterized by Ultraviolet-visible spectroscopy (UV–vis), Fourier-Transform Infrared spectroscopy (FT-IR), X-ray Powder Diffraction (XRD), Brunauer-Emmett-Teller (BET isotherm), Scanning Electron Microscopy – Energy Dispersive X-ray Spectroscopy (SEM-EDX), High Resolution – Transmission Electron Microscopy (HR-TEM), Vibrating Sample Magnetometer (VSM), X-ray Photoelectron Spectroscopy (XPS) and elemental analysis. The catalyst could be recovered and reused for multiple consecutive runs without losing the enantioselectivity. The chiral catalyst was used in asymmetric transfer hydrogenation reaction for synthesizing enantiomerically pure drug intermediate Montekulast.

Effective fenton catalyst from controllable framework doping of Fe in porous silica spheres

Controllable doping of iron (Fe) (3.9–17.8%) in hollow porous silica spheres with highly homogeneous distribution state was achieved successfully by a one-pot hydrothermal synthesis strategy. Based on the observation and analysis by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, nitrogen sorption, and X-ray photoelectron spectroscopy (XPS), it was found that molecular Fe species were intercalated into silica framework during the structural transformation of silica to hollow flake-shelled spheres, which leads to both stable fixation with open accessibility of Fe and high surface area of the Fe-doped silica hollow spheres (Fe-SHSs). When used as heterogeneous Fenton catalyst to degrade the dye of Acid orange 7 (AO7), enhanced catalysis performance was exhibited due to the sufficiently exposed active sites and fast mass transport in the system. The optimal catalysis condition was also studied by adjusting Fe-SHSs dosages, oxidant concentrations, and pH values). This work presents an effective strategy for chemical doping of metal components in the silica structures and may also be explored for other supported metal catalyst systems.

A phenylenediamine-based carbon dot-modified silica stationary phase for hydrophilic interaction chromatography.

Red emitting carbon dots derived from p-phenylenediamine (PPDCDs) were successfully prepared and grafted onto the surface of silica spheres, which served as a new stationary phase (Sil-PPDCDs) for liquid chromatography with excellent hydrophilic selectivity. Various hydrophilic analytes including nucleosides and bases, amino acids, saccharides and ginsenosides can be well separated on this stationary phase. Compared with the precursor-modified silica, i.e. p-phenylenediamine functionalized silica stationary phase (Sil-PPD), Sil-PPDCDs possessed enhanced selectivity for the separation of tested polar compounds. Moreover, compared with two commercially available hydrophilic columns, the selective behavior of the stationary phase was also considerable. The successful application of the Sil-PPDCDs stationary phase again indicated the great potential of carbon dots as a new modifier of the stationary phase in high performance liquid chromatography, and this kind of new stationary phase is very promising to be used for the separation of hydrophilic compounds in biochemical and pharmaceutical analysis.

Imidazolium ionic liquids-derived carbon dots-modified silica stationary phase for hydrophilic interaction chromatography

In this study, imidazolium ionic liquids-derived carbon dots (ImCDs) were successfully synthesized and bonded on the surface of spherical porous silica as a new stationary phase (Sil-ImCDs) for hydrophilic interaction chromatography (HILIC). First, the ImCDs were synthesized by the reaction of amino ionic liquids with citric acid, and then they were grafted onto the surface of aminopropyl-modified silica. A series of characterizations including infrared spectra, elemental analysis and laser confocal microscope proved that the preparation was successful. It was found that the Sil-ImCDs had good separation efficiency in the separation of bases, nucleosides, amino acids, saccharides and ginsenosides. It is interesting that we found that Sil-ImCDs has better hydrophilic chromatographic performance compared with methylimidazole-modified silica and aminopropyl-modified silica. It may be due to the rich functional group which is available after the formation of carbon dots from imidazolium ionic liquids and citric acid.