Monodisperse Silica Spheres Research Articles

Controllable synthesis of NiCoMo-LDH with nanofloral structure assisted by monodisperse spherical silica for asymmetric supercapacitor

Traditional layered double hydroxides (LDH) have disadvantages such as small layer spacing, insufficient active sites and poor electrical conductivity, which seriously restricts their future utilization in the realm of energy storage. In this paper, a controlled synthesis strategy of tercomponent metal NiCoMo-LDH is proposed by using the structural advantages of metal-organic skeleton (MOF) templates, combining structural regulation and atom doping. On the basis of the synthesis of Ni-MOF 74, Co and Mo atoms are introduced for a small amount of doping, and the monodisperse spherical SiO2 is inserted to adjust the pore structure of NiCoMo-MOF, expand the lamellar spacing, and effectively avoid the accumulation and agglomeration of lamella. Finally, NiCoMo-LDH cathode material with loose porous and coarsely curled nanosphere structure was synthesized through the chemical reaction of OH− with SiO2 and the destruction of the skeleton structure of MOF. The specific capacitance of the material is 1423.3 F·g−1 at 0.5 A·g−1, and after 5000 cycles of charging and discharging, 80.0% of the original specific capacitance is sustained. Moreover, NiCoMo-LDH//AC ASC possesses a high energy density of 39.1 Wh·kg−1 at the power density 400 W·kg−1. Combined with density functional theory (DFT) calculation, the fact that metal doping can not only effectively improve the conductivity of electrode materials has been further proved, but also accelerate the electron/ion migration rate, which successfully reveal the synergistic enhancement mechanism of electrochemical properties of materials.

Controlling cisplatin release by synergistic action of silver-cisplatin on monodispersed spherical silica for targeted anticancer and antibacterial activities

Recently, metal-based nanoformulations have been explored for targeted cancer therapeutics. In this study, synergistic therapeutic action of silver (Ag)-cisplatin nanoparticles loaded on monodispersed spherical silica (MSS) was investigated to evaluate anti-cancer (HCT-116 and HeLa cells) and antibacterial activity (P.aeruginosa, and S.aureus). Four different wt% of Ag (1, 2, 4 and 6 wt%) was loaded on MSS using a wet impregnation method. Characterization using XRD revealed the cubic phase of Ag nanoparticles with (111), (200) and (220) plane on MSS. The chemical state, dispersion of Ag and synergistic cohabitation with cisplatin (Cpt) was identified using diffuse reflectance UV–visible spectroscopy (DR-UV Vis), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM-EDS) and High-resolution transmission electron microscopy (HR-TEM). Zeta potential analysis indicated an increase in hydrodynamic diameter with high colloidal stability (–23.3 to −28.5 mV). The percentage cumulative Cpt release was studied using automated Franz cell and dialysis membrane technique. The effect of Cpt release on 4 wt%Ag impregnated on different shaped supports was investigated using cubic SBA-16 (Santa Barbara Amorphous), MFI type Ti-ZSM-5 (Zeolite Socony Mobil #5), hexagonal mesosilicalite, nanotube halloysite, and Ag-silicalite, respectively. Drug release study indicates that Ag loading controls the Cpt release. The kinetics of drug release for the different formulations was examined using Korsmeyers-Peppas model. Release constant (k) and release exponent (n) were utilized for the rate of drug release and diffusion mechanisms, respectively. The in vitro study revealed an efficient interaction of nanoformulations promoting both antibacterial and anticancer activities.

Hollow core mesoporous carbon spheres as catalyst support for improved platinum utilization in phosphoric acid fuel cells

Using a well-known sol-gel technique, monodispersed silica spheres measuring 380 nm in size are generated in situ. These silica spheres serve as a template for the synthesis of hollow core mesoporous shell (HCMS) carbon spheres. Inside the pores of the template, a polymer is synthesized using azoisobutyronitrile and divinylbenzene polymerization route. Polymer carbonization followed by template remotion yielded HCMS carbon spheres. This HCMS carbon is mesoporous and offers uniform Pt crystallite distribution for acid fuel cell applications. As-prepared HCMS carbon is examined by field emission gun SEM, TEM, nitrogen adsorption/desorption isotherm (BET surface area and BJH pore size distribution analysis), and apparent density using Helium pycnometry. The HCMS carbon obtained demonstrates a BET surface area of 623 m2g-1, showcasing a uniform pore size distribution centered at 3.8 nm. This specific characteristic renders it an ideal support material for fuel cell catalysts. The electrochemical studies reveal the key parameters like corrosion resistance, bulk electrical conductivity, the electrochemical surface area of Pt chemically deposited on HCMS carbon, and unit fuel cell performance under phosphoric acid environment. These parameters are compared with the standard carbon powder, Vulcan XC72R and a commercial catalyst to evaluate the HCMS carbons’ suitability for fuel cell applications.

Подготовка тетраэтоксисилана для получения сферических частиц кремнезема. Часть 2. Примеси и их влияние на размеры формирующихся глобул

Monodisperse spherical silica particles, as a basis for creating supramolecular 3D matrices, are currently of increasing interest due to the prospects for their wide application in the synthesis of new nanocomposite materials. At the same time, one of main problems of their large-scale synthesis is associated with the unstable behavior of tetraethoxysilane (TEOS) during hydrolysis, which leads both to the deviation of the particles from a given size and their shape from a spherical one. In this paper, on the basis of the study of tetraethoxysilane from various manufacturers, we continued to work on determining factors that can influence the process of hydrolysis of tetraethoxysilane and, as a result, the monodispersity and size of the formed particles, and also other factors. To solve this task, all TEOS samples were studied by various physicochemical methods of analysis, including Fourier IR and Raman spectroscopy, gas chromatography-mass spectrometry. As a result of the studies, we showed that the presence of di- and trisiloxanes in the system did not significantly affect the size of the formed silica particles, while significantly accelerating the rate of formation of silica spheres. Moreover, the presence of methoxyl groups in the initial silane, and an insignificant content of ethanol in the system did not affect the size stability of the formed particles. At the same time, the replacement of part of the ethoxy groups in the initial TEOS by methyl or ethyl groups, as they are not capable of participating in the hydrolysis reaction, largely contribute to the deviation of sizes of the formed silica particles from each other. The results obtained on the effect of impurities on the size of the formed silica globules are important, among other things, for understanding the processes of formation of natural supramolecular structures of silica.

Environment-friendly coating with good weather resistance prepared by amorphous photonic crystals and water-dispersible resin

Traditional coatings are fabricated from chemical colorants and oleoresinous resins. However, chemical colorants and organic solvents as diluents of oleoresinous resins are pollutant for environment. Herein, environment-friendly coatings with good weather resistance are proposed by using amorphous photonic crystals (APC) and water-dispersible resins. Monodispersed silica spheres are used for producing APC and structural color. And the water-dispersible epoxy resin has a good weather resistance property. After environment-friendly coatings are submerged in toluene, acidic solution (pH = 2) and alkaline solution (pH = 12) for 2040, 840 and 840 h, respectively, the coatings are still intact, and they do not fade. The environment-friendly coatings also are able to withstand the test of 336 h under ultraviolet light. The coatings have great potential applications in displays, decorations and automotive coatings.

Effect of a double-chain surfactant on the stabilization of suspensions of silica and titania particles against agglomeration and sedimentation

Dispersions of vesicles of didodecyldimethylammonium bromide (DDAB) were prepared with magnetic stirring of multilamellar liposomes followed by ultrasonication (SS) in order to generate dispersions that contained only unilamellar vesicles, unlike the stirring-only (S) method which also produces many large liposomes. With the SS method, the vesicles had average diameters ranging from 68 to 80 nm, which were much smaller than the diameters generated with the S method. The new vesicle dispersions had nearly infinite viscosities at very low shear stresses at DDAB weight fractions wD from 0.025 to 0.027, even though they were not close-packed, in contrast to the S dispersions. The new SS vesicle dispersions stabilized completely against sedimentation polydisperse nonspherical crystalline titania particles with sizes ranging from ca. 96–156 nm, as well as suspensions of monodisperse spherical amorphous silica particles with diameters of dsed = 454 nm, 691 nm, and 826 nm. These results establish that DDAB vesicle dispersions can stabilize against sedimentation a broad range of particle types and sizes. In addition, at the low values of wD = 0.009 and 0.018, the effective viscosities, ηeff, of the DDAB dispersions, determined from the sedimentation velocities, ranged from 1.35-1.87 cP and 4.34–5.57 cP, respectively. At higher shear stresses, however, these dispersions were highly shear-thinning and still flowable in a capillary under gravity. This behavior is critical for the practical applications of such dispersions for inkjet printing and possibly paints.

Size-preset Synthesis of Highly Monodisperse Silica Spheres for Self-Assembly of Photonic Crystals with Narrow Band Width

Size-preset Synthesis of Highly Monodisperse Silica Spheres for Self-Assembly of Photonic Crystals with Narrow Band Width

Гибридные сферические микрорезонаторы с люминесцентными органическими красителями FITC и DCM

Luminescent hybrid spherical microresonators of two types consisting of monodisperse spherical silica particles with a diameter of 3.5 mcm coated with either FITC dye molecules or a 200 nm thick mesoporous silica shell containing DCM dye are fabricated. The luminescence spectra of microresonators are studied and the experimental emission spectra are simulated using the method of spherical wave transfer matrices. The ratio of intensities of emission lines into whispering gallery modes with different polarizations and the same polar and radial indices is analyzed. It is shown that the ratio depends on the orientation of the dipole moment of the radiative transition of dye molecules relative to the surface of spherical silica particles.

Hybrid spherical microresonators with luminescent organic dyes FITC and DCM

Luminescent hybrid spherical microresonators of two types consisting of monodisperse spherical silica particles with a diameter of 3.5 μm coated with either FITC dye molecules or a 200 nm thick mesoporous silica shell containing DCM dye are fabricated. The luminescence spectra of microresonators are studied and the experimental emission spectra are simulated using the method of spherical wave transfer matrices. The ratio of intensities of emission lines into whispering gallery modes with different polarizations and the same polar and radial indices is analyzed. It is shown that the ratio depends on the orientation of the dipole moment of the radiative transition of dye molecules relative to the surface of spherical silica particles. Keywords: spherical microresonator, whispering gallery modes, organic dyes, photoluminescence.

Подготовка тетраэтоксисилана для получения сферических частиц кремнезема. Часть 1. Ультрафильтрация

The paper considers the problem of instability of tetraethoxysilane hydrolysis in an ethanol medium in the presence of ammonia as a catalyst to obtain monodisperse spherical silica particles of a given size. This problem is associated with the presence of various impurities affecting rate of particle formation and, as a consequence, their size, monodispersity and shape. To solve this problem, we present novel studies of possible application of ultrafiltration for hydrolysis of initial tetraethoxysilane and ethanol through hydrophobic filters with a pore size of 50 nm. In both cases, we noted a decreasing intensity of light scattering after filtration. The elemental analysis of filtered impurities showed a significant content of SiO2 solid phases in tetraethoxysilane, and a number of impurities in ethanol. The experiments on the synthesis of silica particles from pre-filtered components showed that the resulting silica particles had a greater degree of monodispersity, and their sizes were much more reproducible, regardless of the used tetraethoxysilane. Thus, according to the obtained data, ultrafiltration is one of the effective ways to solve the problem of instability in the synthesis of monodisperse spherical silica particles.

Unconscious factors affecting physical characteristics of sol–gel-derived monodispersed silica spheres

Unconscious factors affecting physical characteristics of sol–gel-derived monodispersed silica spheres

Continuous Synthesis of Monodisperse Spherical Silica Powder Using Tubular Reaction System

In the present study, monodisperse silica nanospheres were synthesized using a tubular reaction system in a continuous way. Screw-type blades were inserted inside a T-mixer for static mixing of the reactant streams which consisted of TEOS and NH4OH/H2O diluted with ethanol, for the continuous synthesis of the silica suspension. The diameter of the silica powder was monitored as a function of production time using dynamic light scattering to determine the optimum retention time and tube length, which were found to be 125 minutes and 7.5 m, respectively. The effects of reactant compositions on particle size were investigated by adjusting the amount of ammonia and water in the sol-gel reaction, which were then compared with the results from a batch reactor. Both the particle size and polydispersity index (PDI) of the silica suspension were measured to be comparable to nanospheres synthesized using a batch reactor. This implies that the tubular reaction system is more beneficial for potential industrial production applications in the size range from 115 to 310 nm, due to its continuous powder synthesis. The effect of the reaction medium was also studied, by replacing ethanol with methanol or propanol, indicating that the deviation in particle size with production time was not a serious issue in alcohols with lower molecular weight, such as methanol and ethanol.

Electrochemical detection of food preservative SO2 in red wine using SiO2 coated CdS nanomaterials

Cadmium sulfide is an important chalcogenide semiconductor nanoparticle prepared by reverse micelle method using cetyltrimethylammonium bromide (CTAB), surfactant. Toxic CdS is coated with silica using tetraethyl orthosilicate (TEOS) precursor and are well characterized. SiO2 provides a sufficient contrast to show the core homogeneously surrounded by the silica shell. The coating can be made thicker by the addition of TEOS resulting in monodispersed silica spheres with CdS core. SO2 is the most important chemical (as preservative and antioxidant) used to prevent wine oxidation. CdS@SiO2 is serving as adsorbent for the detection of SO2 in wine. The detection mechanism and the sensitivity of the method were validated using limit of detection and the limit of quantification values which are determined from differential pulse voltammetric technique. This electrochemical sensing is found to be simple and reliable to detect the free SO2 present in the wine sample.

Investigating the effect of nonionic surfactant on the silica nanoparticles formation and morphology in a microfluidic reactor

The conventional sol-gel method used to synthesize monodispersed spherical silica nanoparticles produces particles with irregular shapes and low monodispersity. Microreactors show a promising new platform to synthesize nanomaterials due to their unique flow and mixing characteristics. In most known shear-based droplet generation microreactors, the effect of the flowing liquid’s physical properties on the reactor performance and product characteristics are not well investigated. Scaling-down the flow system was proven to change the flow behavior which will be dominated by the liquid apparent physical properties that are highly controllable. A new method to synthesize silica nanoparticles adapting the sol-gel approach in a microfluidic chip is proposed and experimentally tested in the present work. This work also analyzes changing the flowing reactants’ physical properties using nonionic surfactants with different concentrations on the reaction performance and nanoparticle size and properties. A custom-made microreactor, made from polydimethylsiloxane, was designed and then fabricated using a direct writing technique. The investigated surfactant concentration was within the range of 1 to 5 vol/vol%, respective to tetraethyl orthosilicate. A traditional bench-scale sole-gel method was also performed with the same reaction properties for comparison purposes. The obtained nanoparticles were characterized using transmission electron microscopy and EDX. The silica nanoparticles synthesized from a bench-scale system showed poor monodispersity and an irregular shape compared to the perfect spherical particles produced from the microflow system. The addition of surfactant reduced the coalescence of the droplet besides reducing the size of the droplets. Increasing the surfactant concentration reduces the silica nanoparticle size. The results showed that highly monodispersed silica nanoparticles with an average size of 5.76 ± 1.27 nm were synthesized using the microflow system comparing to silica nanoparticles with a mean size of 95 ± 4 nm produced from the bench-scale.

Robust synthesis of mono-dispersed spherical silica nanoparticle from rice husk for high definition latent fingermark development

Silica is one of the most functional metalloid oxides with a widespread application as semiconductor, fillers, silicone and ceramic primarily due to its structural versatility. In this work, a robust step-wise thermochemical treatment was successfully formulated for the controlled fabrication of high-purity mono-dispersed spherical silica nanoparticle from rice husk. The silica nanoparticle with the desired morphology was formed in two stages; thermal-assisted seed particle formation followed by particle growth through acidification of the solvent modified sodium silicate solution. The obtained powder was characterised, and the effectiveness of the powder for latent fingermark development across varied donors and surfaces was tested at the introductory level. The formed spherical particles were in the range of 200 to 400 nm, as confirmed by FESEM and HRTEM analysis. Minimising the degree of silica nanoparticle agglomeration notably affected their selectivity to fingermark residue. There was a striking improvement in the selectivity of the silica nanoparticle to fingermark residue. The improvement was attributed to the strong interaction between the silica nanoparticle and the lipid components in the fingermark residue, as compared to the commercial white powder that works solely based on mechanical adherence. Additionally, the size and morphology of the fabricated silica nanoparticle were optimised to enhance the clarity of the developed fingermark. Findings of this study could improve quality of fingermarks obtained in a crime scene due to considerably lower background interference without compromising the effectiveness of fingermark development.

Luminescent Properties of Carbon Nanodots Bound to the Surface of Spherical Microresonator

Hybrid structures consisting of emitting carbon nanodots bound to the surface of monodisperse spherical silica particles, which function as microresonators, are synthesized. The carbon nanodots are deposited onto the particle surface through controllable coagulation in three different solvents: ammonia, hydrochloric acid, and glycerol. In photoluminescence spectra of hybrid structures, throughout the entire range of carbon nanodot emission, which extends from UV to near IR, we observe the presence of intensive narrow bands related to emission of the nanodots in the whispering gallery modes of a spherical microresonator. All the observed bands are identified by comparing the spectral positions of whispering gallery modes calculated using the transfer matrix method for spherical waves to the experimental data.

Formation of GaN Nanorods in Monodisperse Spherical Mesoporous Silica Particles

Gallium-nitride nanorods with a diameter of 15–40 nm and length of 50–150 nm are synthesized in monodisperse spherical mesoporous silica particles (MSMSPs) by high-temperature annealing of the Ga2O3 precursor in ammonia. The template material (a-SiO2) is selectively removed by etching the composite MSMSP/GaN particles with HF to give individual GaN nanorods. It is shown that the size of the GaN nanorods substantially exceeds the pore size of the MSMSPs (diameter ~3 nm, length ~10 nm). A possible mechanism by which GaN nanorods are formed is proposed. Redistribution of the material within the composite MSMSP/GaN particles possibly occurs via the surface diffusion of gaseous molecules within mesopores and via the diffusion of Ga and N atoms in a-SiO2.

Isotope effects on the high pressure viscosity of liquid water measured by differential dynamic microscopy

Differential dynamic microscopy is performed in diamond anvil cells to measure the viscosity of water along the 24 °C isotherm to high pressure by the determination of the tracer diffusion coefficient of monodisperse silica spheres of known diameter and the application of the Stokes–Einstein–Sutherland equation. This technique allows liquid samples to be compressed to greater pressure prior to freezing than with other viscometry methods. The highest-pressure measurement was made at 1.67 GPa, considerably deeper into the supercompressed regime than previously reported. The effect of the isotopic composition is investigated with samples of normal water, heavy water, and partially deuterated water. When data below 0.25 GPa are excluded, a free volume model fits the observed viscosities well, yielding a theoretical glass transition density close to that observed in very-high-density amorphous ice. The improved fit above 0.25 GPa coincides with the loss of other anomalous behaviors in liquid water caused by hydrogen bonding and represents a transition to properties closer to those of a simple liquid.

A green approach for tunable fluorescent and superhydrophobic monodisperse polysilsesquioxane spheres

Hypothesis:Typically, calcination at high temperature could bring fluorescence to hybrid silica spheres prepared with 3-aminopropyltriethoxysilane and tetraethylorthosilicate, but they tended to be hydrophilic. Further extra modification is required to gain superhydrophobicity, which might probably block the fluorescence. Short side organic chains are very thermostable at high temperature. Therefore, it might be possible to produce superhydrophobic and fluorescent hybrid silica spheres through the co-condensation of organosilanes with short side organic chains and calcination at high temperature.Experiments:Methyltrimethoxysilane (MTMS) and vinyltrimethoxysilane (VTMS) were co-condensed to prepare polysilsesquioxane (PSQ) spheres, which were subsequently calcinated at high temperature. The impact of MTMS/VTMS ratio on the chemical structures, fluorescence and wettability was investigated, and the applications of PSQ spheres were expanded.Findings:The PSQ spheres with the ratio of MTMS/VTMS as 3/1 and 2/2 exhibited strong fluorescence, and the calcination did not destroy the superhydrophobicity for the remaining of abundant methyl, vinyl, or ethyl groups. Our study provides an extremely green, simple and effective approach to prepare thermostable, fluorescent and superhydrophobic monodisperse silica spheres without using rare earth element, gold, conjugated polymer, phorsphore, fluoride chemical or organic solvent.

Люминесцентные плазмонные структуры из наночастиц золота и углеродных наноточек в мезопористых частицах кремнезема

The composite plasmonic structures consisting of gold nanoparticles and carbon nanodots within monodisperse spherical mesoporous silica particles were synthesized. A threefold increase of visible photoluminescence intensity of carbon nanodots in these structures was demonstrated compared to structures without gold nanoparticles