Silica-based nanocomposites via reverse microemulsions: classifications, preparations, and applications

Tri-signal CdS@SiO2 nanoprobes for accurate and sensitive detection of human immunoglobulin G with enhanced flexibility and internal validation

Accurate and sensitive determination of human immunoglobulin G (HIgG) level is critical for diagnosis and treatment of various diseases, including rheumatoid arthritis, humoral immunodeficiencies, and infectious disease. In this study, versatile tri-signal probes were developed by preparing CdS@SiO2 nanorods that integrate photoluminescence (PL), multi-phonon resonant Raman scattering (MRRS) and infrared absorption (IRA) properties. Through the coating of multiple CdS nanoparticles as cores within SiO2 shells, the PL and MRRS properties of CdS were improved, resulting in a significantly lowered limit of detection (LOD), with the lowest LOD of 12.37 ag mL-1. Integration with the distinctive IRA property of SiO2 shells widened the detection range towards higher concentrations, establishing a final linear range of 50 ag mL-1 to 10 μg mL-1. The remarkable consistency among the three signals highlighted the robust internal verification capability for accurate detection. This approach enhances flexibility in selecting detection methodologies to suit diverse scenarios, facilitating HIgG detection. The tri-signal nanoprobes also exhibited excellent detection selectivity, specificity and repeatability. This study presents a fresh idea for developing high-performance detection strategies.

Silica-Based Materials Containing Inorganic Red/NIR Emitters and Their Application in Biomedicine

The low absorption of biological substances and living tissues in the red/near-infrared region (therapeutic window) makes luminophores emitting in the range of ~650-1350 nm favorable for in vitro and in vivo imaging. In contrast to commonly used organic dyes, inorganic red/NIR emitters, including ruthenium complexes, quantum dots, lanthanide compounds, and octahedral cluster complexes of molybdenum and tungsten, not only exhibit excellent emission in the desired region but also possess additional functional properties, such as photosensitization of the singlet oxygen generation process, upconversion luminescence, photoactivated effects, and so on. However, despite their outstanding functional applicability, they share the same drawback-instability in aqueous media under physiological conditions, especially without additional modifications. One of the most effective and thus widely used types of modification is incorporation into silica, which is (1) easy to obtain, (2) biocompatible, and (3) non-toxic. In addition, the variety of morphological characteristics, along with simple surface modification, provides room for creativity in the development of various multifunctional diagnostic/therapeutic platforms. In this review, we have highlighted biomedical applications of silica-based materials containing red/NIR-emitting compounds.

Fe3O4@C@MCM41-guanidine core-shell nanostructures as a powerful and recyclable nanocatalyst with high performance for synthesis of Knoevenagel reaction

In this study, preparation, characterization and catalytic application of a novel core-shell structured magnetic with carbon and mesoporous silica shells supported guanidine (Fe₃O₄@C@MCM41-guanidine) are developed. The Fe₃O₄@C@MCM41-guanidine was prepared via surfactant directed hydrolysis and condensation of tetraethyl orthosilicate around Fe₃O₄@C NPs followed by treatment with guanidinium chloride. This nanocomposite was characterized by using Fourier transform infrared spectroscopy, vibrating sample magnetometry, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, thermal gravimetric analysis, wide-angle X-ray diffraction and low-angle X-ray diffraction techniques. This nanocomposite have high thermal, chemical stability, and uniform size. Fe₃O₄@C@MCM41-guanidine catalyst demonstrated high yield (91-98%) to prepare of Knoevenagel derivatives under the solvent free conditions at room temperature in the shortest time. Also, this catalyst was recovered and reused 10 times without significant decrease in efficiency and stability. Fortunately, an excellent level of yield (98-82%) was observed in the 10 consecutive catalyst cycles.

Specific nanoarchitecture of silica nanoparticles codoped with the oppositely charged Mn2+ and Ru2+ complexes for dual paramagnetic-luminescent contrasting effects

The silica nanoparticles (SNs) co-doped with paramagnetic ([Mn(HL)]^n-,) and luminescent ([Ru(dipy)₃]²⁺) complexes are represented. The specific distribution of [Mn(HL)]^n- within the SNs allows to achieve about ten-fold enhancing in magnetic relaxivities in comparison with those of [Mn(HL)]^n- in solutions. The leaching of [Mn(HL)]^n- from the shell can be minimized through the co-doping of [Ru(dipy)₃]²⁺ into the core of the SNs. The co-doped SNs exhibit colloid stability in aqueous solutions, including those modeling a blood serum. The surface of the co-doped SNs was also decorated by amino- and carboxy-groups. The cytotoxicity, hemoagglutination and hemolytic activities of the co-doped SNs are on the levels convenient for "in vivo" studies, although the amino-decorated SNs cause more noticeable agglutination and suppression of cell viability. The co-doped SNs being intravenously injected into mice allows to reveal their biodistribution in both ex vivo and in vivo conditions through confocal microscopy and magnetic resonance imaging correspondingly.

Oxygen Vacancy-Rich Ni-CeO2 Heterojunction Catalyst for Hydrogenating Halogenated Nitroarenes with High Activity and Selectivity

Halogenated arylamines are important intermediates for the synthesis of dyes, pesticides, herbicides, and other chemicals. One important way to prepare halogenated arylamines is catalytic hydrogenation of halogenated nitroarenes. Ni-based catalysts have been used in the hydrogenation of halogenated nitroarenes but suffer from low activity and dehalogenation side reaction. In this paper, Ni-CeO₂/SiO₂ heterojunction catalyst with a "raisin-bun" structure was prepared by reverse microemulsion. A built-in electric field and more oxygen vacancies were formed due to electron transfer from Ni to CeO₂ as a result of their work function difference. The built-in electric field leads to the heterolytic cleavage of H₂, thereby improving the hydrogenation activity. Oxygen vacancies preferentially adsorb and activate nitro groups, inhibiting the dehalogenation side reaction. Through the cooperation of built-in electric field and oxygen vacancy, synchronous enhancement of the activity and selectivity is obtained successfully. This finding provides a new view for the design of non-noble metal-based catalysts with high activity and selectivity.

In-situ formation of MnO2 nanoparticles on Ru@SiO2 nanospheres as a fluorescent probe for sensitive and rapid detection of glutathione

Glutathione (GSH)-switched fluorescent assays have appealed much attention due to rapid signal changes of fluorescent probes. However, exposure to exterior environment of fluorescent probe causes photobleaching and premature leakage, leading to low sensitivity and poor photostability. Herein, luminescent SiO₂ nanoparticles encapsulated with Ru(bpy)₃²⁺ (Ru@SiO₂) were designed and synthesized as fluorescent probe to construct a GSH-switched fluorescent assay. The encapsulation of Ru(bpy)₃²⁺ in the SiO₂ nanoparticles could effectively prevent the leakage of Ru(bpy)₃²⁺ molecules, improving the photostability of probe. The fluorescence of Ru@SiO₂ nanoparticles was quenched by coating MnO₂ nanoparticles on Ru@SiO₂ surface (Ru@SiO₂@MnO₂ nanocomposites) through an in situ growth approach, which reduced background of the assay. The MnO₂ nanoparticles not only further inhibited the leakage of Ru(bpy)₃²⁺ molecules, but also could serve as a recognition unit of GSH. In the presence of GSH, the MnO₂ nanoparticles on the surface of Ru@SiO₂ nanoparticles were reduced to Mn²⁺, resulting the fluorescence recovery of Ru@SiO₂ nanoparticles. Thus, a signal-on fluorescent strategy was constructed for GSH detection. The assay displayed good analytical performance for GSH detection with a low detection limit of 16.2 nM due to excellent fluorescence quenching ability of MnO₂ nanoparticles and special role of Ru@SiO₂ nanoparticles to block probe leakage. The proposed assay was also applied to measure GSH levels in human serum samples. This work paves a new way to detect GSH with high sensitivity.

A review on functional nanoarchitectonics nanocomposites based on octahedral metal atom clusters (Nb6, Mo6, Ta6, W6, Re6): inorganic 0D and 2D powders and films

This review is dedicated to various functional nanoarchitectonic nanocomposites based on molecular octahedral metal atom clusters (Nb₆, Mo₆, Ta₆, W₆, Re₆). Powder and film nanocomposites with two-dimensional, one-dimensional and zero-dimensional morphologies are presented, as well as film matrices from organic polymers to inorganic layered oxides. The high potential and synergetic effects of these nanocomposites for biotechnology applications, photovoltaic, solar control, catalytic, photonic and sensor applications are demonstrated. This review also provides a basic level of understanding how nanocomposites are characterized and processed using different techniques and methods. The main objective of this review would be to provide guiding significance for the design of new high-performance nanocomposites based on transition metal atom clusters.

Solid-State Reaction Synthesis of Nanoscale Materials: Strategies and Applications

Nanomaterials (NMs) with unique structures and compositions can give rise to exotic physicochemical properties and applications. Despite the advancement in solution-based methods, scalable access to a wide range of crystal phases and intricate compositions is still challenging. Solid-state reaction (SSR) syntheses have high potential owing to their flexibility toward multielemental phases under feasibly high temperatures and solvent-free conditions as well as their scalability and simplicity. Controlling the nanoscale features through SSRs demands a strategic nanospace-confinement approach due to the risk of heat-induced reshaping and sintering. Here, we describe advanced SSR strategies for NM synthesis, focusing on mechanistic insights, novel nanoscale phenomena, and underlying principles using a series of examples under different categories. After introducing the history of classical SSRs, key theories, and definitions central to the topic, we categorize various modern SSR strategies based on the surrounding solid-state media used for nanostructure growth, conversion, and migration under nanospace or dimensional confinement. This comprehensive review will advance the quest for new materials design, synthesis, and applications.

Concurrent Oxidation-Reduction Reactions in a Single System Using a Low-Plasma Phenomenon: Excellent Catalytic Performance and Stability in the Hydrogenation Reaction

The catalytic activity and stability of metal nanocatalysts toward agglomeration and detachment during their preparation on a support surface are major challenges in practical applications. Herein, we report a novel, one-step, synchronized electro-oxidation-reduction "bottom-up" approach for the preparation of small and highly stable Cu nanoparticles (NPs) supported on a porous inorganic (TiO₂@SiO₂) coating with significant catalytic activity and stability. This unique embedded structure restrains the sintering of CuNPs on a porous TiO₂@SiO₂ surface at a high temperature and exhibits a high reduction ratio (100% in 60 s) and no decay in activity even after 30 cycles (>98% conversion in 3 min). This occurs in a model reaction of 4-nitrophenol (4-NP) hydrogenation, far exceeding the performance of most common catalysts observed to date. More importantly, nitroarene, ketone/aldehydes, and organic dyes were reduced to the corresponding compounds with 100% conversion. Density functional theory (DFT) calculations of experimental model systems with six Cu, two Fe, and four Ag clusters anchored on the TiO₂ surface were conducted to verify the experimental observations. The experimental results and DFT calculations revealed that CuNPs not only favor the adsorption on the TiO₂ surface over those of Fe and AgNPs but also boost the adsorption energy and activity of 4-NP. This strategy has also been extended to the preparation of other single-atom catalysts (e.g., FeNPs-TiO₂@SiO₂ and AgNPs-TiO₂@SiO₂), which exhibit excellent catalytic performance.

Ghost-Template-Faceted Synthesis of Tunable Amorphous Hollow Silica Nanostructures and Their Ordered Mesoscale Assembly

Despite the enormous applications of and fundamental scientific interest in amorphous hollow-silica nanostructures (h-SiNSs), their synthesis in crystal-like nonspherical polygonal architectures is challenging. Herein, we present a facile one-shot synthetic procedure for various unconventional h-SiNSs with controllable surface curvatures (concave, convex, or angular), symmetries (spherical, polygonal, or Janus), and interior architectures (open or closed walls) by the addition of a metal salt and implementing kinetic handles of silica precursor (silanes/ammonia) concentrations and reverse-micellar volume. During the silica growth, we identified the key role of transiently in situ crystallized metal coordination complexes as a nanopolyhedral "ghost template", which provides facet-selective interactions with amino-silica monomers and guides the differential silica growth that produces different h-SiNSs. Additionally, crystal-like well-defined polygonal h-SiNSs with flat surfaces, assembled as highly ordered close-packed octahedral mesoscale materials (ca. 3 μm) where h-SiNSs with different nanoarchitectures act as building units (ca. 150 nm) to construct customizable cavities and nanospaces, differ from conventionally assembled materials.

The precise modification of nanoscaled Keplerate-type polyoxometalate with NH2-groups: reactive sites, mechanisms and dye conjugation

The interaction of alkoxysilanes with nanoscaled giant polyoxoclusters is a challenging route for efficiently building blocks for supramolecular smart-tune design. 3-aminopropyltrimethoxysilane (APTMS) treatment grafts amino groups onto the surface of...

Emerging Applications of Silica Nanoparticles as Multifunctional Modifiers for High Performance Polyester Composites

Nano-modification of polyester has become a research hotspot due to the growing demand for high-performance polyester. As a functional carrier, silica nanoparticles show large potential in improving crystalline properties, enhancing strength of polyester, and fabricating fluorescent polyester. Herein, we briefly traced the latest literature on synthesis of silica modifiers and the resultant polyester nanocomposites and presented a review. Firstly, we investigated synthesis approaches of silica nanoparticles for modifying polyester including sol-gel and reverse microemulsion technology, and their surface modification methods such as grafting silane coupling agent or polymer. Then, we summarized processing technics of silica-polyester nanocomposites, like physical blending, sol-gel processes, and in situ polymerization. Finally, we explored the application of silica nanoparticles in improving crystalline, mechanical, and fluorescent properties of composite materials. We hope the work provides a guideline for the readers working in the fields of silica nanoparticles as well as modifying polyester.

Magnetic Nanoparticles Used in Oncology

Recently, magnetic nanoparticles (MNPs) have more and more often been used in experimental studies on cancer treatments, which have become one of the biggest challenges in medical research. The main goal of this research is to treat and to cure advanced or metastatic cancer with minimal side effects through nanotechnology. Drug delivery approaches take into account the fact that MNPs can be bonded to chemotherapeutical drugs, nucleic acids, synthetized antibodies or radionuclide substances. MNPs can be guided, and different treatment therapies can be applied, under the influence of an external magnetic field. This paper reviews the main MNPs’ synthesis methods, functionalization with different materials and highlight the applications in cancer therapy. In this review, we describe cancer cell monitorization based on different types of magnetic nanoparticles, chemotherapy, immunotherapy, magnetic hyperthermia, gene therapy and ferroptosis. Examples of applied treatments on murine models or humans are analyzed, and glioblastoma cancer therapy is detailed in the review. MNPs have an important contribution to diagnostics, investigation, and therapy in the so called theranostics domain. The main conclusion of this paper is that MNPs are very useful in different cancer therapies, with limited side effects, and they can increase the life expectancy of patients with cancer drug resistance.

Effect of Counterions on the Interaction among Concentrated Spherical Polyelectrolyte Brushes

The effect of counterions on interactions among spherical polyelectrolyte brushes (SPBs) was systematically investigated by rheology, small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The SPB particles consist of a solid polystyrene (PS) core with a diameter of ca.100 nm and a chemically grafted poly-(acrylic acid) (PAA) brush layer. Metal ions of different valences (Na+, Mg2+ and Al3+) were used as counterions to study the interactions among concentrated SPBs. The so-called "structure factor peak" in SAXS, the "local ordered structure peak" in WAXS and rheological properties indicated the interactions among concentrated SPBs. Combining SAXS, WAXS and rheology, the formation mechanism of the local ordered structure among PAA chains in the overlapped area of adjacent SPB, which was generated due to the bridge function of counterions, was confirmed. In contrast, excessive counterions shielded the electrostatic interaction among PAA chains and destroyed the local ordered structure. This work enriches our understanding of the polyelectrolyte assembly in concentrated SPBs under the effect of counterions and lays the foundations for SPB applications.

Nanoparticles: A New Approach to Upgrade Cancer Diagnosis and Treatment

Traditional cancer therapeutics have been criticized due to various adverse effects and insufficient damage to targeted tumors. The breakthrough of nanoparticles provides a novel approach for upgrading traditional treatments and diagnosis. Actually, nanoparticles can not only solve the shortcomings of traditional cancer diagnosis and treatment, but also create brand-new perspectives and cutting-edge devices for tumor diagnosis and treatment. However, most of the research about nanoparticles stays in vivo and in vitro stage, and only few clinical researches about nanoparticles have been reported. In this review, we first summarize the current applications of nanoparticles in cancer diagnosis and treatment. After that, we propose the challenges that hinder the clinical applications of NPs and provide feasible solutions in combination with the updated literature in the last two years. At the end, we will provide our opinions on the future developments of NPs in tumor diagnosis and treatment.

Gold Nanorods for LSPR Biosensing: Synthesis, Coating by Silica, and Bioanalytical Applications

Nanoparticles made of coinage metals are well known to display unique optical properties stemming from the localized surface plasmon resonance (LSPR) phenomenon, allowing their use as transducers in various biosensing configurations. While most of the reports initially dealt with spherical gold nanoparticles owing to their ease of synthesis, the interest in gold nanorods (AuNR) as plasmonic biosensors is rising steadily. These anisotropic nanoparticles exhibit, on top of the LSPR band in the blue range common with spherical nanoparticles, a longitudinal LSPR band, in all respects superior, and in particular in terms of sensitivity to the surrounding media and LSPR-biosensing. However, AuNRs synthesis and their further functionalization are less straightforward and require thorough processing. In this paper, we intend to give an up-to-date overview of gold nanorods in LSPR biosensing, starting from a critical review of the recent findings on AuNR synthesis and the main challenges related to it. We further highlight the various strategies set up to coat AuNR with a silica shell of controlled thickness and porosity compatible with LSPR-biosensing. Then, we provide a survey of the methods employed to attach various bioreceptors to AuNR. Finally, the most representative examples of AuNR-based LSPR biosensors are reviewed with a focus put on their analytical performances.

Ion-specific clustering of metal-amphiphile complexes in rare earth separations

The nanoscale structure of a complex fluid can play a major role in the selective adsorption of ions at the nanometric interfaces, which is crucial in industrial and technological applications. Here we study the effect of anions and lanthanide ions on the nanoscale structure of a complex fluid formed by metal-amphiphile complexes, using small angle X-ray scattering. The nano- and mesoscale structures we observed can be directly connected to the preferential transfer of light (La and Nd) or heavy (Er and Lu) lanthanides into the complex fluid from an aqueous solution. While toluene-based complex fluids containing trioctylmethylammonium-nitrate (TOMA-nitrate) always show the same mesoscale hierarchical structure regardless of lanthanide loading and prefer light lanthanides, those containing TOMA-thiocyanate show an evolution of the mesoscale structure as a function of the lanthanide loading and prefer heavy lanthanides. The hierarchical structure indicates the presence of attractive interactions between ion-amphiphile aggregates, causing them to form clusters. A clustering model that accounts for the hard sphere repulsions and short-range attractions between the aggregates has been adapted to model the X-ray scattering results. The new model successfully describes the nanoscale structure and helps in understanding the mechanisms responsible for amphiphile assisted ion transport between immiscible liquids. Accordingly, our results imply different mechanisms of lanthanide transport depending on the anion present in the complex fluid and correspond with anion-dependent trends in rare earth separations.

A Nano-Rattle SnO2@carbon Composite Anode Material for High-Energy Li-ion Batteries by Melt Diffusion Impregnation

The huge volume expansion in Sn-based alloy anode materials (up to 360%) leads to a dramatic mechanical stress and breaking of particles, resulting in the loss of conductivity and thereby capacity fading. To overcome this issue, SnO₂@C nano-rattle composites based on <10 nm SnO₂ nanoparticles in and on porous amorphous carbon spheres were synthesized using a silica template and tin melting diffusion method. Such SnO₂@C nano-rattle composite electrodes provided two electrochemical processes: a partially reversible process of the SnO₂ reduction to metallic Sn at 0.8 V vs. Li⁺/Li and a reversible process of alloying/dealloying of Li_xSn_y at 0.5 V vs. Li⁺/Li. Good performance could be achieved by controlling the particle sizes of SnO₂ and carbon, the pore size of carbon, and the distribution of SnO₂ nanoparticles on the carbon shells. Finally, the areal capacity of SnO₂@C prepared by the melt diffusion process was increased due to the higher loading of SnO₂ nanoparticles into the hollow carbon spheres, as compared with Sn impregnation by a reducing agent.

Interaction among Spherical Polyelectrolyte Brushes in Concentrated Aqueous Solution

Interaction among concentrated spherical polyelectrolyte brushes (SPB) dispersions in water was systematically investigated by means of small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and rheological methods. SPB consist of a core of polystyrene (PS) and a poly(acrylic acid) (PAA) brush shell. The "polyelectrolyte peak" appeared in SAXS spectra and was observed in WAXS curves for the first time. The size of the polyelectrolyte peak and the rheological properties of SPB were found to be strongly effected by SPB concentration, pH, and ionic strength. Combined with SAXS, WAXS, and rheological results, it is confirmed that the polyelectrolyte peak is originated from local ordered structures of polyelectrolyte chains bridged by counterions in the overlapping area among SPB driven by electrostatic interactions.

The synthesis of monodispersed M-CeO2/SiO2nanoparticles and formation of UV absorption coatings with them

CeO₂/polymer nanoparticles have drawn considerable attention for their excellent UV absorption properties. However, many challenges still exist in the successful incorporation of ceria into the polymer matrix for the easy agglomeration and photocatalytic activity of CeO₂ nanoparticles. Herein, we address these issues by constructing three-layer structured nanoparticles (M-CeO₂@SiO₂) and incorporating them into a polymer matrix through a mini-emulsion polymerization process. During this process, small-sized nano-ceria became uniformly anchored on the surfaces of monodisperse silica particles first, and then the particles were coated with an MPS/SiO₂ shield. The morphology and dispersion of the nanoparticles were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The performance of the hybrid films was characterized using UV-vis absorption spectroscopy (UV-vis) and water contact angle (WCA) measurements. Results showed that the M-CeO₂@SiO₂ nanoparticles exhibited a three-layer structure with a mean diameter of 360 nm, and they possess good compatibility with acrylic monomers. After the addition of M-CeO₂@SiO₂, hybrid films exhibited enhanced UV absorption capacity as expected, accompanied by an obvious improvement in hydrophobicity (the water contact angle increased from 84.2° to 98.2°). The results showed that the hybrid films containing M-CeO₂@SiO₂ particles possess better global performance as compared with those containing no particles.

Herein, we report the synthesis of monodispersed M-CeO₂/SiO₂ nanoparticles and their use in the construction of a UV absorption coating.

Coating of upconversion nanoparticles with silica nanoshells of 5-250 nm thickness

A concept for the growth of silica shells with a thickness of 5-250 nm onto oleate-coated NaYF₄:Yb³⁺/Er³⁺ upconversion nanoparticles (UCNP) is presented. The concept enables the precise adjustment of shell thicknesses for the preparation of thick-shelled nanoparticles for applications in plasmonics and sensing. First, an initial 5-11 nm thick shell is grown onto the UCNPs in a reverse microemulsion. This is followed by a stepwise growth of these particles without a purification step, where in each step equal volumes of tetraethyl orthosilicate and ammonia water are added, while the volumes of cyclohexane and the surfactant Igepal^® CO-520 are increased so that the ammonia water and surfactant concentrations remain constant. Hence, the number of micelles stays constant, and their size is increased to accommodate the growing core-shell particles. Consequently, the formation of core-free silica particles is suppressed. When the negative zeta potential of the particles, which continuously decreased during the stepwise growth, falls below -40 mV, the particles can be dispersed in an ammoniacal ethanol solution and grown further by the continuous addition of tetraethyl orthosilicate to a diameter larger than 500 nm. Due to the high colloidal stability, a coalescence of the particles can be suppressed, and single-core particles are obtained. This strategy can be easily transferred to other nanomaterials for the design of plasmonic nanoconstructs and sensor systems.

PEG-coated and Gd-loaded fluorescent silica nanoparticles for targeted prostate cancer magnetic resonance imaging and fluorescence imaging

Background: Multimodal imaging probes have become a powerful tool for improving detection sensitivity and accuracy, which are important in disease diagnosis and treatment.

Methods: In this study, novel bifunctional magnetic resonance imaging (MRI)/fluorescence probes were prepared by loading gadodiamide into fluorescent silica nanoparticles (NPs) (Gd@Cy5.5@SiO₂-PEG-Ab NPs) for targeting of prostate cancer (PCa). The physicochemical characteristics, biosafety and PCa cell targeting ability of the Gd@Cy5.5@SiO₂-PEG-Ab NPs were studied in vitro and in vivo.

Results: The Gd@Cy5.5@SiO₂-PEG-Ab NPs had a spherical morphology with a relatively uniform size distribution and demonstrated high efficiency for Gd loading. In vitro and in vivo cell-targeting experiments demonstrated a high potential for the synthesized NPs to target prostate-specific membrane antigen (PSMA) receptor-positive PCa cells, enabling MRI and fluorescence imaging. In vitro cytotoxicity assays and in vivo hematological and pathological assays showed that the prepared NPs exhibited good biological safety.

Conclusion: Our study demonstrates that the synthesized Gd@Cy5.5@SiO₂-PEG-Ab NPs have great potential as MRI/fluorescence contrast agents for specific identification of PSMA receptor-positive PCa cells.

Metal@SiO2 Core-Shells with Self-Arrested Migrating Core

Developing easy and customizable strategies for the directional structure modulation of multicomponent nanosystems to influence and optimize their properties are a paramount but challenging task in nanoscience. Here, we demonstrate highly controlled eccentric off-center positioning of metal-core in metal@silica core-shells by utilizing an in situ generated biphasic silica-based intraparticle solid-solid interface. In the synthetic strategy, by including Ca²⁺-ions in silica-shell and successive oxidative and reductive annealing at high temperature, a unique hairline-biphasic interface is evolved via the heat-induced concentric radial segregation of calcium silicate phase at the interior and normal silica phase at the exterior of core-shell, which can effectively arrest the outwardly migrating metal-core within rubbery calcium silicate phase, affording various eccentric core-shells, where core-positions are flexibly controlled by the annealing time and amounts of initially added Ca²⁺-ions. In the structure-property correlation study, the strategy allows fine-tuning of dipolar interaction-based blocking temperatures and magnetic anisotropies of different eccentric core-shells as the function of variable off-center distance of magnetic core without changing the overall size of nanoparticles. This work demonstrates the discovery and potential application of biphasic solid-solid media interface in controlling the heat-induced migration of metal nanocrystals and opens the avenues for exploiting the rarely studied high-temperature solid-state nanocrystal conversion chemistry and migratory behavior for directional nanostructure engineering.

Classification, Synthesis, and Application of Luminescent Silica Nanoparticles: a Review

Luminescent materials are of worldwide interest because of their unique optical properties. Silica, which is transparent to light, is an ideal matrix for luminescent materials. Luminescent silica nanoparticles (LSNs) have broad applications because of their enhanced chemical and thermal stability. Silica spheres of various sizes could be synthesized by different methods to satisfy specific requirements. Diverse luminescent dyes have potential for different applications. Subject to many factors such as quenchers, their performance was not quite satisfying. This review thus discusses the development of LSNs including their classification, synthesis, and application. It is the highlight that how silica improves the properties of luminescent dye and what role silica plays in the system. Further, their applications in biology, display, and sensors are also described.

Synthesis of silica-alginate nanoparticles and their potential application as pH-responsive drug carriers

Composite silica-alginate nanoparticles were prepared via silica sol-gel technique using a water-in-oil microemulsion system. In our system, cyclohexane served as the bulk oil phase into which aqueous solutions of sodium alginate were dispersed as droplets that confined nanoparticle formation after addition of tetraethylorthosilicate (TEOS). Our studies showed that much of the particle growth is completed within the first 24 hours and reaction times up to 120 hours only resulted in an additional 5% increase in particle diameter. Average particle size was found to decrease with increasing water-to-surfactant molar ratio (R) and with increasing cocentration of alginate in the aqueous phase. The potential for drug loading during particle formation was demonstrated using rhodamine B as a model drug. In vitro release studies showed that particles incubated in pH 2.5 phosphate buffer released only about 7% of the drug load in 27 days, while 42% was released in pH 7.5 phosphate buffer over the same period. Analysis of the release profile suggested that rhodamine B was homogeneously distributed throughout the particle and that the drug diffusivity was 40-fold greater in pH 7.5 buffer compared to that at pH 2.5. These results suggest that silica-alginate nanoparticles could be used as a pH-responsive drug carrier for controlled drug release.

Luminescent silica mesoparticles for protein transduction

Unlike silica nanoparticles, the potential of silica mesoparticles (SMPs) (i.e. particles of submicron size) for biological applications in particular the in vitro (let alone in vivo) cellular delivery of biological cargo has so far not been sufficiently studied. Here we examine the potential of luminescent (namely, octahedral molybdenum cluster doped) SMPs synthesised by a simple one-pot reaction for the labelling of cells and for protein transduction into larynx carcinoma (Hep-2) cells using GFP as a model protein. Our data demonstrates that the SMPs internalise into the cells within half an hour. This results in cells that detectably luminesce via conventional methods. In addition, the particles are non-toxic both in darkness and upon photo-irradiation. The SMPs were modified to allow their functionalisation by a protein, which then delivered the protein (GFP) efficiently into the cells. Thus, the luminescent SMPs offer a cheap and trackable alternative to existing materials for cellular internalisation of proteins, such as the HIV TAT protein and commercial protein delivery agents (e.g. Pierce™).

Embedding hexanuclear tantalum bromide cluster {Ta6Br12} into SiO2 nanoparticles by reverse microemulsion method

Hexanuclear tantalum bromide cluster units [{Ta₆Brⁱ₁₂}L^a₆] (i = inner, a = apical, L = ligand OH or H₂O) are embedded into SiO₂ nanoparticles by a reverse microemulsion (RM) based method. [{Ta₆Brⁱ₁₂}Br^a₂ (H₂O)^a₄]·nH₂O (noted TBH) and tetraethyl orthosilicate (TEOS) are used as the starting cluster compound and the precursor of SiO₂, respectively. The RM system in this study consists of the n-heptane (oil phase), Brij L4 (surfactants), ethanol, TEOS, ammonia solution and TBH aqueous sol. The size and morphology of the product namely {Ta₆Br₁₂}@SiO₂ nanoparticles are analyzed by HAADF-STEM and EDS mappings. The presence and integrity of {Ta₆Br₁₂} in the SiO₂ nanoparticles are evidenced by EDS mapping, ICP-OES/IC and XPS analysis. The optical properties of {Ta₆Br₁₂}@SiO₂ nanoparticles are analyzed by diffuse reflectance UV-vis spectroscopy, further evidencing the integrity of the embedded {Ta₆Br₁₂} and revealing their oxidation state. Both {Ta₆Br₁₂}²⁺ and {Ta₆Br₁₂}³⁺ are found in SiO₂ nanoparticles, but the latter is much more stable than the former. The by-products in this RM-based synthesis, as well as their related factors, are also discussed.

Interface formation during silica encapsulation of colloidal CdSe/CdS quantum dots observed by in situ Raman spectroscopy

We investigate the encapsulation of CdSe/CdS quantum dots (QDs) in a silica shell by in situ Raman spectroscopy and find a distinct shift of the CdS Raman signal during the first hours of the synthesis. This shift does not depend on the final silica shell thickness but on the properties of the initial core-shell QD. We find a correlation between the Raman shift rate and the speed of the silica formation and attribute this to the changing configuration of the outermost layers of the QD shell, where an interface to the newly formed silica is created. This dependence of Raman shift rate on the speed of silica formation process will give rise to many possible studies concerning the growth mechanism in the water-in-oil microemulsion, rendering in situ Raman a valuable instrument in monitoring this type of reaction.

Surface self-assembly of colloidal crystals for micro- and nano-patterning

The controlled patterning of polymeric surfaces at the micro- and nanoscale offers potential in the technological development of small-scale devices, particularly within the fields of photovoltaics, micro-optics and lab- and organ-on-chip, where the topological arrangement of the surface can influence a system's power generation, optical properties or biological function - such as, in the latter case, biomimicking surfaces or topological control of cellular differentiation. One of the most promising approaches in reducing manufacturing costs and complexity is by exploitation of the self-assembling properties of colloidal particles. Self-assembly techniques can be used to produce colloidal crystals onto surfaces, which can act as replicative masks, as has previously been demonstrated with colloidal lithography, or templates in mold-replication methods with resolutions dependent on particle size. Within this context, a particular emerging interest is focused on the use of self-assembled colloidal crystal surfaces in polymer replication methods such as soft lithography, hot and soft embossing and nano-imprint lithography, offering low-cost and high-resolution alternatives to conventional lithographic techniques. However, there are still challenges to overcome for this surface patterning approach to reach a manufacturing reliability and process robustness comparable to competitive technologies already available in the market, as self-assembly processes are not always 100% effective in organizing colloids within a structural pattern onto the surface. Defects often occur during template fabrication. Furthermore, issues often arise mainly at the interface between colloidal crystals and other surfaces and substrates. Particularly when utilized in high-temperature pattern replication processes, poor adhesion of colloidal particles onto the substrate results in degradation of the patterning template. These effects can render difficulties in creating stable structures with little defect that are well controlled such that a large variety of shapes can be reproduced reliably. This review presents an overview of available self-assembly methods for the creation of colloidal crystals, organized by the type of forces governing the self-assembly process: fluidic, physical, external fields, and chemical. The main focus lies on the use of spherical particles, which are favorable due to their high commercial availability and ease of synthesis. However, also shape-anisotropic particle self-assembly will be introduced, since it has recently been gaining research momentum, offering a greater flexibility in terms of patterning. Finally, an overview is provided of recent research on the fabrication of polymer nano- and microstructures by making use of colloidal self-assembled templates.

One-pot organometallic synthesis of alumina-embedded Pd nanoparticles

Herein we report a one pot organometallic strategy to access alumina-embedded Pd nanoparticles. Unexpectedly, the decomposition of the organometallic complex tris(dibenzylideneacetone)dipalladium(0), Pd₂(dba)₃, by dihydrogen in the presence of aluminum isopropoxide, Al(iPrO)₃, and without extra stabilizers, was found to be an efficient method to generate a Pd colloidal solution. Careful characterization studies revealed that the so-obtained Pd nanoparticles were stabilized by an aluminum isopropoxide tetramer and 1,5-diphenyl-pentan-3-one, which was produced after reduction of the dba ligand from the organometallic precursor. Moreover, calcination of the obtained nanomaterial in air at 773 K for 2 h resulted in a nanocomposite material containing Pd nanoparticles embedded in Al₂O₃. This stabilization strategy opens new possibilities for the preparation of transition metal nanoparticles embedded in oxides.

Core-Shell-Corona Silica Hybrid Nanoparticles Templated by Spherical Polyelectrolyte Brushes: A Study by Small Angle X-ray Scattering

Core-shell-corona silica/polymer hybrid nanoparticles with narrow size distribution were prepared in the template of spherical polyelectrolyte brushes (SPB) which consist of a solid polystyrene (PS) core densely grafted with linear poly(acrylic acid) (PAA) chains. The microstructure of obtained hybrid nanoparticles was studied by small-angle X-ray scattering (SAXS) and in combination with dynamic light scattering (DLS) and transmission electron microscopy (TEM). The generation of silica shell within the brush is confirmed by the significant increase of the electron density in the shell, and the silica shell showed a unique inner-loose-outer-dense structure, whose thickness is pH sensitive but is insensitive to ionic strength as revealed by fitting SAXS data. After dissolving the PS core, hollow silica nanoparticles were obtained and determined by SAXS, which should be ideal carriers for pH-triggered drug delivery. SAXS is confirmed to be a powerful method to characterize the core-shell-corona silica/polymer hybrid and hollow silica nanoparticles.

Mussel-Inspired Polydopamine-Coated Lanthanide Nanoparticles for NIR-II/CT Dual Imaging and Photothermal Therapy

Nanomedicine has attracted substantial attention for the accurate diagnosis or treatment of carcinoma in recent years. Nd³⁺-doped lanthanide nanophosphor-based near-infrared-II (NIR-II) optical imaging is widely used for deep penetration tissue imaging while X-ray computed tomography (CT) is well-suited for in vivo imaging. Polymer-coated lanthanide nanophosphors are increasingly used in both diagnostics and therapies for tumor in vivo. However, the biocompatibility of nanocomposites and the efficiency of tumor ablation should be taken into consideration when constructing a nanotheranostic probe. In this article, we have fabricated polydopamine (PDA)-coated NaYF₄:Nd³⁺@NaLuF₄ nanocomposites using the reverse microemulsion approach. The thickness of the PDA shell can be precisely modulated from ∼1.5 to ∼18 nm, endowing the obtained NaYF₄:Nd³⁺@NaLuF₄@PDA with an excellent colloidal stability and considerable biocompatibility. The photothermal conversion efficiency of the resultant nanocomposites was optimized and maximized by the increase of the PDA shell thickness. Because of the remarkable photothermal conversion efficiency, the mice xenograft tumors were completely eradicated after NIR irradiation. Given the considerable photoluminescence and X-ray attenuation efficiency, the performance of NaYF₄:Nd³⁺@NaLuF₄@PDA for NIR-II optical imaging and X-ray CT dual imaging of the tumor in vivo was evaluated. All of the results above highlight the great potential of PDA-based NaYF₄:Nd³⁺@NaLuF₄ nanocomposites as a novel multifunctional nanotheranostic agent.

One-Step Synthesis of Hydrophobic Multicompartment Organosilica Microspheres with Highly Interconnected Macro-mesopores for the Stabilization of Liquid Marbles with Excellent Catalysis

The combination of an emulsion template with polymerization is a very convenient approach to the one-step realization of both simple control porous structures via a change in emulsion formulation and easy functionalization via the concomitant choice of an on-demand monomer. A major challenge of this approach is the inherent instability of the oil/water interface in emulsions, especially the occurrence of chemical reactions in oil or aqueous phases. This study reports the pioneering preparation of highly interconnected macro-mesopores and multicompartment (HIMC) vinyl organosilica microspheres with hydrophobicity by the one-step formation of W/O/W emulsions acting as a template. The emulsion system consists of acidified deionized water, a stabilizer, and vinyltriethoxysilane (VTEO) in which VTEO can be used to produce an organosilica skeleton of the resultant microsphere by a sol-gel process. The study demonstrated that the marvelous stability of W/O/W emulsions aids the formation of multicompartment organosilica microspheres with highly interconnected macro-mesopores by emulsion droplets rather than single-compartment (SC) microspheres. Meanwhile, the internal porous structure and surface morphology of as-prepared organosilica microspheres could be largely tuned by a simple variation of the pH value, the volume fraction of the water phase, and the stabilizer concentration in the initiating multiemulsions. Benefiting from such a well-orchestrated structure and the existence of numerous vinyl groups on the surface, HIMC organosilica microspheres exhibit very high hydrophobicity (with a water contact angle larger than 160°), which allows them to stabilize liquid marbles with excellent stability and high mechanical robustness. Because of its strong catalyst, Ag nanoparticles within HIMC organosilica microspheres enable Ag/HIMC-vinyl organosilica microsphere-based liquid marbles to be an efficient catalytic microreactor, realizing the complete degradation of MB to leuco methylene blue by NaBH₄ in 10 min. The result of this work could provide some guidance for the easy, low-cost, benign preparation of HIMC microspheres having the potential to be excellent supporter of metal nanoparticles or other functionalized compounds for applications in sensing, optoelectronics, and catalysis.

Highly luminescent silica-coated CdS/CdSe/CdS nanoparticles with strong chemical robustness and excellent thermal stability

We present facile synthesis of bright CdS/CdSe/CdS@SiO₂ nanoparticles with 72% of quantum yields (QYs) retaining ca 80% of the original QYs. The main innovative point is the utilization of the highly luminescent CdS/CdSe/CdS seed/spherical quantum well/shell (SQW) as silica coating seeds. The significance of inorganic semiconductor shell passivation and structure design of quantum dots (QDs) for obtaining bright QD@SiO₂ is demonstrated by applying silica encapsulation via reverse microemulsion method to three kinds of QDs with different structure: CdSe core and 2 nm CdS shell (CdSe/CdS-thin); CdSe core and 6 nm CdS shell (CdSe/CdS-thick); and CdS core, CdSe intermediate shell and 5 nm CdS outer shell (CdS/CdSe/CdS-SQW). Silica encapsulation inevitably results in lower photoluminescence quantum yield (PL QY) than pristine QDs due to formation of surface defects. However, the retaining ratio of pristine QY is different in the three silica coated samples; for example, CdSe/CdS-thin/SiO₂ shows the lowest retaining ratio (36%) while the retaining ratio of pristine PL QY in CdSe/CdS-thick/SiO₂ and SQW/SiO₂ is over 80% and SQW/SiO₂ shows the highest resulting PL QY. Thick outermost CdS shell isolates the excitons from the defects at surface, making PL QY relatively insensitive to silica encapsulation. The bright SiO₂-coated SQW sample shows robustness against harsh conditions, such as acid etching and thermal annealing. The high luminescence and long-term stability highlights the potential of using the SQW/SiO₂ nanoparticles in bio-labeling or display applications.

MoO3 subnanoclusters on ultrasmall mesoporous silica nanoparticles: an efficient catalyst for oxidative desulfurization

MoO₃ subnanoclusters encapsulated in ultrasmall mesoporous silica nanoparticles (ca. 14 nm) exhibited enhanced catalytic activity for oxidative desulfurization.