Nanosilica Surface Research Articles

Mechanical properties and hydration mechanism of nano-silica modified alkali-activated thermally activated recycled cement

The recycling and reuse of waste concrete are crucial for reducing environmental pollution, minimizing resource waste, and lowering carbon emissions. However, current efforts to improve the performance of recycled cement (RC) using the synergistic effects of alkali activation and thermal activation have been suboptimal. Therefore, this study explores the influence of nano-silica (NS) incorporation on the mechanical properties and hydration mechanism of alkali-activated and thermally activated RC. The research focuses on cement mortar with a thermal activation temperature of 750°C, an RC replacement rate of 30%, and an alkali content of 6%. Various analytical techniques, including thermogravimetric analysis (TG-DTG), X-ray diffraction (XRD), and scanning electron microscopy (SEM), were used to evaluate the impact of different NS dosages (1%, 2%, 3%, and 5%) on the mechanical properties and hydration characteristics of nano-modified alkali-activated and thermally activated RC mortar. The study reveals the mechanism by which NS enhances the microstructure of alkali-activated and thermally activated RC. The experimental results show that as the NS content increases, the compressive and flexural strengths of RC initially increase and then decrease. The optimal strength was achieved with a 2% NS content, with a 31.5% increase in compressive strength compared to RC without NS. At this dosage, RC exhibited a higher hydration rate during the acceleration period of hydration. Additionally, the initial hydration heat release rate of RC increased with rising NS content. While NS incorporation did not alter the phase composition of RC, it activated the pozzolanic effect of RC, causing free active substances such as CaO and gypsum in the components to dissolve and react to form Aft at the start of the hydration reaction. The unsaturated bonds (≡Si-O- and ≡Si-) on the surface of NS absorbed Ca2⁺ and OH⁻ from the RC, promoting the hydration of C2S and C3S. However, excessive NS content (greater than 3%) led to a decline in RC strength and the formation of more cracks. This is primarily due to the excess NS particles not contributing to an increase in effective nucleation sites, causing agglomeration, an increase in large pores, and a reduction in transition and gel pores, which negatively affected the microstructure and thus reduced the mechanical properties of the RC. Our findings enhance the understanding of the role of nanomaterials in alkali-activated RC and provide valuable insights for further research into high-performance recycled cement materials.

Achieving the hydrophobic alteration by functionalized nano-silica for improving shale hydration inhibition

Shale hydration is the primary cause of wellbore instability during drilling processes. In this study, two non-fluorinated silane-coupling agents, octyltriethoxysilane (OTES) and (3-Aminopropyl) triethoxysilane (APTES), were grafted onto the nano-silica surface to develop a hydrophobic material (SHM). Various performance characterizations, including infrared spectroscopy, thermogravimetric analysis, surface tension, wetting alteration, capillary self-suction height, bentonite expansion, and shale dispersion, were employed to investigate the shale inhibition properties of SHM comprehensively. Experimental results revealed that SHM could significantly improve shale hydration inhibition. For instance, in a 2 % SHM liquids, the shale hot rolling recovery rate increased from 25.39 % to 83.78 %, and the bentonite expansion height decreased from 7.65 mm to 2.80 mm. The inhibition performance was notably superior to potassium chloride (KCl) and polyether amine (PEA). Inhibition mechanisms analysis unveiled that the outstanding inhibitory effect of SHM was achieved through electrostatic adsorption, wettability alteration, and surface tension reduction. Firstly, SHM contained numerous amine groups that could demonstrate strong adsorption on the clay surface through electrostatic and hydrogen bonding interactions. Secondly, with long hydrophobic alkyl chains, it formed a highly hydrophobic film enveloping the shale surface, effectively preventing water from invading. Thirdly, it reduced liquid surface tension, further minimizing the water infiltration. As a result, the use of SHM significantly enhanced shale hydration inhibition during the shale drilling process.

Effect of nano-silica@ chitosan phosphate ester on the mechanical properties and water resistance of magnesium oxychloride cement

Nano-silica is used in various composite materials as a kind of filler with good performance. In this study, hydrogen peroxide was used to repair and activate the hydroxyl group on the surface of nano-silica, and chitosan phosphate ester was loaded onto the surface of nano-silica through intermolecular dehydration to prepare nano-silica@ chitosan phosphate ester, and nano-silica@ chitosan phosphate ester was added to the magnesium oxychloride cement for water resistance modification. The results showed that the addition of nano-silica@ chitosan phosphate ester increased the compressive strength of magnesium oxychloride cement at different ages, and the compressive strength of the modified magnesium oxychloride cement at 7 days and 28 days were 116 MPa and 127 MPa, respectively, which increased by 11.5% and 5.8% compared with the unmodified samples. The compressive strength of the modified magnesium oxychloride cement reached 102 MPa after 28 days of water immersion, which was 8.3% higher than that of the phosphoric acid modified sample under the same water immersion duration. At the same time, it was found that nano-silica@ chitosan phosphate ester can increase the fluidity of magnesium oxychloride cement slurry, accelerate the hydration reaction rate and refine the pores.

Evaluation of Aminated Nano-Silica as a Novel Shale Stabilizer to Improve Wellbore Stability.

The issue of wellbore instability poses a significant challenge in the current exploration of shale gas reservoirs. Exploring more efficient shale stabilizers has always been a common goal pursued by researchers. In this paper, a novel shale stabilizer, denoted as ANS, was prepared by employing a silane-coupling modification method to graft (3-Aminopropyl) triethoxysilane (APTES) onto the surface of nano-silica. The structure of ANS was characterized through Fourier transforms infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA), and particle size tests (PST). The shale stabilizing properties of ANS were evaluated through tests such as pressure penetration, BET analysis, hydration expansion and dispersion. Furthermore, the interaction between ANS as a shale stabilizer and clay was explored through clay zeta potential and particle size analysis. The results indicated that ANS exhibited a stronger plugging capability compared to nano-silica, as evidenced by its ability to increase the shale pressure penetration time from 19 to 131 min. Moreover, ANS demonstrated superior hydration inhibition compared to commonly used KCl. Specifically, it reduced the expansion height of bentonite from 8.04 to 3.13 mm and increased the shale recovery rate from 32.84% to 87.22%. Consequently, ANS played a dual role in providing dense plugging and effective hydration inhibition, contributing significantly to the enhancement of wellbore stability in drilling operations. Overall, ANS proved to be a promising shale stabilizer and could be effective for drilling troublesome shales.

In situ synthesis of AgI on the nanosilica surface for potential application as a cloud seeding material.

A series of nanosilica/AgI composites was synthesized by in situ reactions between silver nitrate and ammonium iodide deposited on the nanosilica surface using the gas-phase solvate-stimulated mechanosorption modification (GSSMSM) under both dry and wet conditions. The characterization of the synthesized materials was performed by X-ray diffraction (XRD), SEM/EDX (Scanning Electron Microscopy-Energy Dispersive X-ray), thermogravimetric (TGA) and gas sorption methods. As a result of the mechanosorption modification of nanosilica, the bulk density of the samples synthesized in the dry and wet medium increases from 45 g/l for initial nanosilica to 249 g/l and 296 g/l for the modified samples, respectively. The specific surface area of the composites decreased in compared to the nanosilica precursor. The SEM data showed a denser aggregate structure of the nanocomposites compared to the initial nanosilica. The XRD, SEM/EDX and TEM/EDX data indicated the formation of AgI clusters. The AgI particle size was in the range of 6-45 nm. The ice-forming activity of the AgI-containing samples was examined as well. The sample with a smaller size of silver iodide on the surface exhibited superior ice-forming properties, and considering the quantity of utilized AgI, the prepared samples hold promise for application in this field.

A high temperature resistance and hyper‐dispersed nanoparticle grafted by multi‐monomer via in‐situ polymerization: Preparation, characterization, and its imbibition performance

AbstractIn recent years, the excellent cleaning‐oil capacity of nanofluid has attracted extensive attention and it has been widely used in oilfields as an imbibition agent. To solve the poor dispersion stability of nanoparticles in high‐temperature and high‐salt reservoir, this paper has prepared a hyper‐dispersed nanoparticle, polymer grafted nanosilica (PNS) that is anti‐salt monomer and anti‐temperature monomer simultaneously grafting on the surface of nanosilica via in‐situ polymerization reaction. Its imbibition performance has been discussed. Results show that (1) The two monomers are all successfully grafted on the surface of nanosilica via optimization of in‐situ polymerization reaction conditions. This hyper‐dispersed nanoparticle has 14.5% final grafting rate, approximately 18 nm in particle size, and −41.2 mV of zeta potential; (2) PNS fluid has excellent dispersion stability and its grain size has no obvious change in 20 wt.% of NaCl or 4 wt.% of CaCl2 fluids at room temperature (25°C), as well as in 18 wt.% of NaCl or 4 wt.% of CaCl2 fluids at 130°C after 1 week; (3) Crude oil–water interface tension can be decreased and the hydrophilicity is significantly boosted by this PNS fluid. Meanwhile, the 10−3 mN/m of interface tension can be obtained and the contact angle of water phase is decreased to 12.8° by surfactant erucamide propyl hydroxysulfobetaine (EHSB) synergizing with PNS fluid; (4) Oil recovery efficiency replaced by PNS in surfactant fluid has reached 39.3%. That is mainly because the hyper‐dispersed nanoparticle provides a stronger spreading force to enhance the efficiency of cleaning oil.

The relationship between cellular microstructure and the mechanical properties of styrene/methyl methacrylate copolymer‐silica nanocomposite foams prepared by a supercritical CO2 blowing agent

AbstractStyrene/methyl methacrylate (St/MMA) copolymer‐silica nanocomposite foams were prepared using supercritical CO2 as blowing agent, and the relationships between their cellular microstructure and mechanical properties were investigated. The effects of nanosilica content, size, and surface chemistry on the foam's microstructure and properties were examined. Dispersion and distribution of silica nanoparticles with different surface chemistry in St/MMA copolymer nanocomposites were discussed. To determine the most suitable copolymer composition for incorporating silica nanoparticles, some operating conditions such as temperature and pressure were primarily examined to study their effects on the microstructure of resulting foams. In compressive mechanical properties of final foams, a considerably high value was obtained for the compressive strength of the foams of up to 9.5 MPa. The prepared low‐density (below 0.2 g/cm3) St/MMA copolymer microcellular foams can be used in green lost foam iron casting processes.Highlights Styrene/methyl methacrylate copolymer‐silica nanocomposite foams were prepared via supercritical CO2. Foams' cell size was changed by changing silica nanoparticle surface chemistry and size. The uniform cellular microstructure was achieved by nanosilica size increment. Increasing nanoparticle size improved the foam's mechanical properties. Low‐density foams were achieved for potential application in lost foam casting.

Nano-lithium ferrite/nanosilica-filled butadiene-acrylonitrile rubber for microwave absorption

Recently, the development of flexible and lightweight microwave-absorbing materials has become a trendy topic. Hence, the principal aim of this work is to enhance the microwave-absorbing performance of butadiene-acrylonitrile rubber (NBR) by incorporating novel reinforcing nanofillers. Cost-effective nano-lithium ferrite/nanosilica is synthesized via the precipitation of two thin layers of lithium ferrite with thicknesses of 10 and 20 % on the surface of cheap nanosilica extracted from rice husk agro-waste. To achieve optimal microwave-absorbing performance, both LiFe 10 %/Si and LiFe 20 %/Si NPs were incorporated into the NBR matrix at various loadings (2, 4, 8, and 16 parts per hundred rubber (phr)). Several investigations were performed on the NBR nanocomposites to explore their morphology, curing behavior, mechanical, equilibrium swelling, magnetic properties, and microwave-absorbing behavior. The mechanical characteristics of NBR nanocomposites reveal that the inclusion of LiFe/Si NPs enhanced their modulus, tensile strength, and elongation at break while reducing their hardness. Moreover, the obtained findings clarify that the 16 phr (LiFe 20 %/Si) filled-NBR nanocomposite has superior microwave-absorbing performance with a maximum absorption bandwidth of 2.2 GHz. Overall results reveal that the novel lithium ferrite/silica nanoparticles could be an effective filler for enhancing the microwave absorption efficiency of NBR nanocomposites. Thus, this research suggests a novel viewpoint on the fabrication of flexible microwave-absorbing materials.

Application of a Core-Shell Structure Nano Filtration Control Additive in Salt-Resistant Clay-Free Water-Based Drilling Fluid

When drilling into a reservoir, the drilling fluid containing bentonite is prone to solid phase invasion, causing serious damage to the reservoir, and the conventional API barite suspension stability is poor, which makes it easy to cause sedimentation and blockage. Therefore, in order to avoid accidents, we use ultrafine barite to obtain a good suspension stability. More importantly, the method of modifying zwitterionic polymers on the surface of nano-silica is used to develop a temperature-resistant and salt-resistant fluid loss reducer FATG with a core-shell structure, and it is applied to ultra-fine clay-free water-based drilling fluid (WBDF). The results show that the filtration loss of clay-free drilling fluid containing FATG can be reduced to 8.2 mL, and AV can be reduced to 22 mPa·s. Although the viscosity is reduced, FATG can reduce the filter loss by forming a dense mud cake. The clay-free drilling fluid system obtained by further adding sepiolite can reduce the filtration loss to 3.8 mL. After aging at 220 °C for 15 d, it still has significant salt tolerance, the filtration loss is only 9 mL, the viscosity does not change much, a thinner and denser mud cake is formed, and the viscosity coefficient of the mud cake is smaller. The linear expansion test and permeability recovery evaluation were carried out. The hydration expansion inhibition rate of bentonite can reach 72.5%, and the permeability recovery rate can reach 77.9%, which can meet the long-term drilling fluid circulation work in the actual drilling process. This study can provide guidance for technical research in related fields such as reservoir protection.

Enhancing of anticancer efficiency of curcumin by functionalization of phosphonate functional group on surface of mesoporous nanosilica

The functionalization of the surface of silica-based nanoparticles with targeting ligands has demonstrated remarkable efficacy in enhancing their activity. In this study, the surface of mesoporous silica nanoparticles (MSN) was functionalized with the phosphonate group (-PO3) to facilitate the adsorption and targeted delivery of curcumin to cancer cells, concurrently significantly enhancing the stability of the nanomaterial. Methodologies including scanning electron microscopy, Fourier transform infrared spectroscopy, N2 adsorption isotherms, and thermal gravimetric analysis were systematically employed to characterize the features of the nanomaterials. The assessment of curcumin loading efficiency within both MSN and phosphonate-functionalized MSN (MSN-PO3) was conducted, predicated upon interactions with the loading solvent and the material's stability. Notably, stability assays revealed that unmodified particles exhibited agglomeration within a 96-h period, while their modified counterparts maintained their structural integrity. Moreover, discerning outcomes from in vitro cytotoxicity assays unveiled the potent efficacy of curcumin-loaded materials against colorectal cancer cells (C-26), with minimal impact on fibroblast cells (L929). These collective results substantiate the role of these materials as efficacious nanocarriers for delivering anticancer drugs.

Electrochemiluminescence biosensing of spatially conjugated ester groups triggered by smart bridging between nano-silica and poly (ethylene maleate)

Organic luminescent materials with unique photoelectric properties are as a kind of emerging luminophore at the forefront of research in biological detection on account of their facilely varied functional groups. However, most organic luminophores are aromatic compounds with certain biological toxicity to limit their application. Herein, we envisioned a green organic electrochemiluminescencence (ECL) luminophore without aromatic ring structure but electron-rich functional groups via in-situ growth of poly (ethylene maleate) (PEM) on nano-silica (NS). The experimental and theoretical modelling results indicate that ECL signal of PEM-NSs was enhanced by the spatial conjugation of ester groups (ester clusters), due to the contribution of smart bridging of NS with different sizes. The smaller the NS size is, the more growth of ester groups on the NS surface is, and the closer individual ester groups are linked via “through-space interaction” to form stable ester clusters with smaller energy gaps, thus achieving high ECL performance. For further application, PEM-NS-1 was selected as meaningful ECL luminophore, and integrated with exonuclease III-assisted catalytic hairpin assembly amplification strategy, an efficient platform for biomarkers (microRNA-21) detection was constructed with the detection limit of 2.73 fM (S/N = 3). This work sets the stage for strengthening ECL of electron-rich functional groups, and provides a way of thinking for low-toxicity organic luminophores.

The surface structure of nanosilica produced from sodium silicate by the carbonation process

CO2 was used to prepare nanosilica particles through a carbonization reaction in a Na2SiO3 solution, aiming to convert CO2 into value-added products. The relationship between the specific structure of the as-prepared nanosilica and the sodium silicate concentration, reaction temperature, reaction time, and aging time was explored by TEM, BET, and XRD analysis. The growth process of nanosilica particles was relatively slow with the increase in the Na2SiO3 concentration, which resulted in the formation of large primary particles, reducing the specific surface area. The decreasing temperature reduced the polymerization of Si(OH)4 and SiOSi(OH)3, reducing the specific surface area. Meanwhile, the effects of reaction time and aging time on the surface structure of silica nanoparticles were studied. Different surface structure of nanosilica particles were synthesized by controlling the carbonization process conditions, which expand the application of nanosilica products. At present, the research on the carbonization preparation of nanosilica mainly focused on the carbonization process conditions and modification technology, but the research of control mechanism of nanosilica surface structure and properties was insufficient. This study focused on the relationship between surface structure evolution and properties, and provided a theoretical basis for the mechanism of the influence factors of preparation process on the structure evolution of prepared nanosilica. And the process reduced CO2 emission, which had important environmental protection value.

Effect of Aging and Nano silica Surface Treatment of Zirconia Ceramics Crowns on Microleakage

Effect of Aging and Nano silica Surface Treatment of Zirconia Ceramics Crowns on Microleakage

Effect of Modified Nano Silica on the Protective Effect of Cement-Based Penetrating Crystallization Coating

In this article, the protective properties of modified nano silica and cement-based osmotic crystallization composite coating were studied. The results showed that there was a chemical bond between nano silica and silane coupling agent, and hydrophobic alkyl groups were grafted onto the surface of nano silica. It not only improves the hydrophobicity of nanoparticles, but also improves their dispersibility in the organic film-forming coatings. The permeability of the composite coating is significantly improved, effectively resisting the intrusion of chloride ions.

The critical role of interfacial Coulomb force in the orientation alignment behavior of lubricant molecules

The non-bonding interactions of four interfaces with typical polar interfacial characteristics are simulated using molecular dynamics methods. The Coulomb and Van der Waals terms in the optimized potentials for liquid simulations all-atom (OPLS_AA) force field are distinguished and their effects on the arrangement behavior of the lubricant molecules are investigated. A mathematical model is proposed to quantitatively characterize the influence on the tilt degree of lubricant molecules (PAO4 and PEG200) near the nano-silica surfaces. The tilt degree of the lubricant molecules at the interface is determined by the molecular chain tilt factor γ, which is calculated by combining the "polar characteristics of the solid surface", the characteristics of the "polar units" within the liquid molecules, and the linking modes between them.

Superhydrophobic Surface on Insulators by Using Perfluoropolyether-Functionalized Silica Nanostructures for Preventing Stress Corrosion Cracking at the Pin–Cement Junction

Stress corrosion accounts for 52% of the recorded breakdown of insulators utilized in transmission lines which may interfere with the reliability of power utilities. The suggested etching-free treatment is a workable environmentally benign method to prevent stress corrosion, even in old insulators with more excellent surface imperfections or cracks. The resilient slippery coating is developed on an insulator surface to address the challenges by infusing perfluoropolyether, lubricating oil into a porous nano-silica surface. The proposed coating layer, thickness 35.4 μm, exhibits superhydrophobicity with contact angle─160°, contact angle hysteresis─4°, self-healing, corrosion resistance with a corrosion rate of 2 × 10–3 mm/Y, Icorr 2.01 × 10–7 A/cm2, and 98% anti-bacterial adhesion performance against sulfate reducing bacterial stains. The outcome of this research is expected to pave the way for an approach to the future creation of incredibly robust etching-free coatings for insulators.

Investigating the performance of non-damaging hybrid gel to mitigate lost circulation in fractured formations: A comprehensive study using Box–Behnken design

Gels that have a low viscosity at the time of mixing and form a three-dimensional gel structure after some time delay can be applied successfully in controlling lost circulation. Cross-linked gels play an important role in sealing high permeable and fractured formations. This research aims to evaluate a novel gel that can mitigate lost circulation during drilling in fractured formations. The hybrid gel consists of a cross-linked polymer gel as the continuous phase and an oil as the internal phase. The purpose of designing hybrid gels is to reduce the possibility of formation damage caused by the presence of gel in the fractures. In addition, the use of an internal phase in the gel can increase the durability of the gel and reduce the final cost of the operation.This article consists of two parts, experimental investigation and empirical modeling using response surface methodology. A number of parameters such as initial gelation time, final gelation time, and cross-linking rate were defined to evaluate the gel behavior under different conditions. First, the effect of polymer type, internal phase viscosity, pH, temperature, salinity, and shear rate on the behavior of the hybrid gel was investigated. Furthermore, in order to increase cross-linking efficiency, the cross-linker was added onto the reactive nano-silica surface to achieve a nano-crosslinker, and then the performance evaluation was accomplished. Thereafter, the sealing pressure test was examined to measure the amount of pressure that the hybrid gels could withstand in the fractures to prevent further fluid loss. Finally, the amount of gel rupture in 15% and 28% hydrochloric (HCl) was studied over time at 25 and 60 °C so as to evaluate the formation damage of hybrid gels.Response surface methodology (RSM) was employed based on Box-Behnken design to determine a correlation for predicting the final viscosity of hybrid gel as a function of temperature, pH, and CaCl2 concentration. The predicted model was obtained by solving the quadratic regression model. The value of the correlation coefficient (R2 = 0.90) for the present mathematical model indicated good relation between experimental data and predicted values. Therefore, the proposed model is able to predict the final viscosity of hybrid gel adequately within the limits of input parameters being used.The experimental results show that hybrid gels, due to their flexible viscosity response, long-term stability, and non-damaging properties, can have proper performance and application in industry to combat lost circulation. Nano-crosslinker can effectively increase the cross-linking rate and final viscosity of the gel and also improve the gel performance at high temperatures. Based on dynamic sealing pressure experiments, the value of maximum sealing pressure for the guar-based hybrid gel is higher than that of xanthan. In addition, the nano-crosslinker enhances the maximum tolerable pressure of the gels to seal the fractures.

Synergistic behavior between the plasmonic Ag metal and the mesoporous β-Bi2O3/SiO2 heterostructure for the photocatalytic destruction of bacterial cells under simulated sunlight illumination: Schottky junction electron-transfer pathway

Undoubtedly, one of the most attractive alternative wastewater disinfection techniques is visible-light-driven photocatalysis. Unfortunately, the fast recombination of charge carriers still limits its practical application. This limitation can be addressed by developing a plasmon-induced nanocomposite photocatalyst by hybridizing the semiconductor with co-catalyst metallic nanoparticles (NPs). Herein, a Schottky junction Ag/β-Bi2O3/SiO2 (A/BO/SO) nanocomposite was constructed via a multistep method involving the immobilization of β-Bi2O3 and Ag NPs on the nanosilica surface. The characterization techniques demonstrated the ability of Ag/β-Bi2O3/SiO2 to extend the visible light absorption and boost the charge separation efficiency through the plasmonic actions of silver metal. It was revealed that the Ag/β-Bi2O3/SiO2 nanocomposite exhibited improved antimicrobial performance against the Staphylococcus aureus pathogen, in which 7-log of bacterial cells were inactivated within 120 min under simulated solar light illumination. These outcomes were ascribed to the synergistic impact of silica support, β-Bi2O3 semiconductor, and plasmonic Ag metal (electron acceptor) in one system. Besides, the Ag/β-Bi2O3/SiO2 nanocomposite displayed remarkable structural stability after five inactivation cycles, which is attributed to the mesoporous structure of the silica support. The mechanism studies revealed that •OH and •O2− are the main reactive species that drive the disinfection reaction, and the electrons' separation behavior is well matched with Schottky junction pathways. In conclusion, this work provided an efficient and stable photocatalyst with minimum energy consumption that can be applied in water disinfection for the removal of pathogenic microorganisms.

The Effect of Nano-Silica Surface Infiltration on Bond Strength of a Phosphate-Monomer-containing Composite Cement to Zirconia.

To evaluate the bonding receptiveness of zirconia treated with nano-silica surface infiltration and the bond strength of composite cement after aging. Zirconia ceramic green bodies (Ceramill zolid, Amann Girbach) with dimensions of 10 x 10 x 4 mm were divided into three groups (n = 4): group C (control: no treatment after sintering), group S (sandblasted: 50-μm alumina airborne particle abrasion after sintering) and group N (nanosintered: infiltrated with nano-silica colloid, sintered, and then etched with hydrofluoric acid). Phase transformations were examined through X-ray diffraction (XRD). Composite resin (Filtek Z250, 3M Oral Care) was bonded to zirconia using the 10-MDP-containing composite cement Panavia F (Kuraray Noritake). The composite-cement/zirconia bond strength was immediately measured using the microtensile bond strength test (µTBS) as well as after three months of artificial aging in water (n = 20 microstick specimens/group). Failure mode patterns were examined using SEM. The specimens of groups C and S, as tested by XRD, exhibited almost full tetragonal phases, while a small extent of tetragonal-monoclinic phase transformation (t→m) was observed for group N. Group N achieved the highest bond strengths (41.5 ± 8.6 MPa), which was significantly higher than that measured for groups C and S (p < 0.05). There was a significant drop in µTBS after 90 days of water storage for groups C and S. SEM revealed a decrease in the percentage of cohesive failure in groups N and S after water storage. Infiltrating zirconia with nano-silica is a reliable method to establish a strong and stable bond to zirconia. The combination of surface infiltration with nano-silica and application of a phosphate monomer-containing composite cement can significantly improve the composite-cement/zirconia bond strength.

Polyamidoamine dendrite-tailored mesoporous nanosilica surfaces for high drug loading and controlled release

Mesoporous silica nanoparticles (MSNs) have been demonstrated as a promising candidate in drug delivery applications. With the ambition of enhancing their drug loading capacity and controlled release, in this innovative study, MSNs were tailored with polyamidoamine (PAMAM) dendrimers thereby exerting advantageous properties onto the surface of the nanoplatforms. MSNs were prepared by Stöber’s method, sequentially functionalised by amine groups, and respectively grafted with PAMAMs layer-by-layer. Morphology and characterisation of the nanoparticles were carried out through transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, and Fourier-transform infrared spectroscopy. Ninhydrin assay and zeta potential analysis were further employed to investigate the amine-modified nanomaterials. The drug loading and release profiles of particles were also studied. As a result, PAMAM-grafted MSNs, with the highest hydrodynamic size of 185.3 nm, exhibited high encapsulation efficiency (85.8%) and controlled release ability compared to conventional MSNs, suggesting that PAMAM-grafted MSNs would be a promising drug delivery system.