Immobilization Of Au Nanoparticles Research Articles

Exciting Surface Plasmon Resonances on Gold Thin Film‐Coated Optical Fibers Through Nanoparticle Light Scattering

AbstractSurface plasmon resonance (SPR) conventionally occurs at the interface of a thin metallic film and an external dielectric medium in fiber optics through core‐guided light. However, this work introduces theoretical and experimental evidence suggesting that the SPR in optical fibers can also be induced through light scattering from Au nanoparticles (NPs) on the thin metallic film, defined as nanoparticle‐induced SPR (NPI‐SPR). This method adheres to phase‐matching conditions between SPR dispersion curves and the wave vectors of scattered light from Au NPs. Experimentally, these conditions are met on an etched optical fiber, enabling direct interaction between light and immobilized Au NPs. Compared to SPR, NPI‐SPR exhibits stronger field intensity in the external region and wavelength tuning capabilities (750 to 1250 nm) by varying Au NP diameters (20 to 90 nm). NPI‐SPR demonstrates refractive index sensitivities of 4000 to 4416 nm per refractive index unit, nearly double those of typical SPR using the same optical fiber configuration sans Au NPs. Additionally, NPI‐SPR fiber configuration has demonstrated its applicability for developing biosensors, achieving a remarkable limit of detection of 0.004 nm for thrombin protein evaluation, a twenty‐fold enhancement compared to typical SPR. These findings underscore the intrinsic advantages of NPI‐SPR for sensing.

Immobilization of Au nanoparticles on black phosphorus modified spherical covalent organic frameworks for the flow-through reduction of 4-nitrophenol

Covalent organic frameworks (COFs), due to their unique structure and morphology, manifest great potential as active substrates to support noble metals for sustainable catalytic applications. However, it is still a challenge for efficient and effective catalysis using these kinds of COFs-based catalysts. Here, black phosphorus (BP) nanosheets modified spherical COFs (SCOFs) were synthesized, followed by the immobilization of Au nanoparticles (Au NPs) to fabricate Au NPs/BP/SCOFs microspheres. The as-prepared Au NPs/BP/SCOFs microspheres were then filled in a column for the continuous catalytic reduction of 4-nitrophenol. A fast and highly efficient flow-through catalysis of 4-nitrophenol with a reduction efficiency of 99 % under the flux of 2500 L m−2 h−1 was obtained. Furthermore, a stable catalytic performance under flow-through process was exhibited with only 0.13 wt% of total Au NPs releasing after testing for 24 h. The strategy for designing COFs-based substrates with enhanced electron transfer and controllable morphology would develop a new route to promote the application of these kinds of COFs-based catalysts.

2,5-Thiophenedicarboxylic Acid Bridging Hexameric CeIII-Substituted Selenotungstate and Its Application for Detecting Mucin 1.

The development of polyoxometalate chemistry not only is derived from the continuous discovery of novel polyoxometalates (POMs) but also stems from the exploitation of their new functionalities. In this work, we obtained a rigid sulfur-containing heterocyclic ligand-linking aggregate [N(CH3)4]10Na6H6[Ce8(H2O)26W8(HTDA)2(TDA)2O20][SeW4O18]2[SeW9O33]4·112H2O (1) (H2TDA = 2,5-thiophenedicarboxylic acid). Its polyanionic unit consists of one [Ce4(H2O)13W4O10(HTDA)(TDA)O10]18+ cluster and two kinds of Keggin-type [SeW4O18] and [SeW9O33] segments. It is noteworthy that H2TDA ligands not only work as connectors to link two symmetrical {[Ce4(H2O)13W4(HTDA)(TDA)O10][SeW4O18][SeW9O33]2}11- units but also function as ornaments to graft to the polyanionic backbone. Furthermore, 1 and 3,4-ethylenedioxythiophene (EDOT) were deposited on the glassy carbon electrode (GCE) by the electropolymerization (EPM) method, resulting in a 1-poly(3,4-ethylenedioxythiophene) (1-PEDOT) composite film, which can provide sufficient binding sites to immobilize Au nanoparticles (Au NPs). Hereafter, the Au NPs-immobilized 1-PEDOT modified electrode (Au/1-PEDOT/GCE) was used to construct an electrochemical aptasensor to detect mucin 1, showing a low detection limit of 29.5 fM in the Tris solution. This work not only demonstrates that rigid heterocyclic ligands are beneficial for the creation of novel rare-earth-substituted selenotungstate hybrids but also provides more enlightenment for POM-based materials used for electrochemical detection of cancer markers.

Core–shell magnetic mesoporous 3-aminophenol–formaldehyde resin microspheres with rich functional groups via interface co-assembly and polymerization

Core–shell magnetic mesoporous 3-aminophenol–formaldehyde resin microspheres were designed to immobilize Au nanoparticles for use as magnetically separable heterogeneous catalysts for the efficient hydrogenation of 4-nitrophenol at room temperature.

Efficient cascade conversion of starch to gluconic acid by a chemoenzymatic system with co-immobilized Au nanoparticles and enzymes

A chemoenzymatic cascade system (GA&GOx@Au–SiO2) was fabricated by immobilizing Au nanoparticles onto silica (SiO2) followed by the co-immobilization of glucoamylase (GA) and glucose oxidase (GOx) for the production of gluconic acid from starch.

Mussel-Inspired Surface Modification of α-Zirconium Phosphate Nanosheets for Anchoring Efficient and Reusable Ultrasmall Au Nanocatalysts

The shortage of powerful functionalities on scalable α-zirconium phosphate (ZrP) materials blocks the facile preparation of highly dispersed and immobilized metal nanocatalysts. We herein present a mild and facile mussel-inspired strategy based on polydopamine (PDA) for the surface modification of ZrP, and hence, the generation of powerful functionalities at a high density for the straightforward reduction of chloroauric acid to Au nanoparticles (AuNPs) and the immobilization of AuNPs. The resulting ternary ZrP@PDA/Au exhibited ultra-small AuNPs with a particle size of around 6.5 nm, as estimated based on TEM images. Consequently, the ZrP@PDA/Au catalyst showed significant activity in the catalytic conversion of 4-nitrophenol (4NP) to 4-aminophenol (4AP), a critical transformation reaction in turning the hazard into valuable intermediates for drug synthesis. The PDA was demonstrated to play a critical role in the fabrication of the highly efficient ZrP@PDA/Au catalyst, far outperforming the ZrP/Au counterpart. The turnover frequency (TOF) achieved by the ZrP@PDA/Au reached as high as 38.10 min−1, much higher than some reported noble metal-based catalysts. In addition, the ZrP@PDA/Au showed high stability and reusability, of which the catalytic efficiency was not significantly degraded after prolonged storage in solution.

The Impact of Secondary Building Units in Metal–Organic Frameworks on Plasmonic Gold‐Sensitized Photocatalysis

AbstractEmbedding plasmonic metals in metal–organic frameworks (MOFs) can build an advanced visible‐light photocatalyst architecture utilizing the localized surface plasmon resonance (LSPR) effect, while the practical performances have been restricted by the sluggish charge transfer at metal–MOF interface and through the secondary building units (SBUs) of the adopted carboxylate MOFs currently. Herein, a pyrazolate Ni‐MOF (PFC‐9) featured with an 1D SBU chain is selected to be the host catalyst to immobilize Au nanoparticles as a novel and optimized construction for LSPR photocatalysis. Compared with the common 3D‐connected SBUs of carboxyl‐ZrOx and pyrazole‐NiOx configurations in the reference MOFs, the 1D (−Ni−NPz−NPz−)∞ chain in PFC‐9 creates abundant Au/MOF contacts, a short and low‐resistant pathway for Au‐to‐Ni2+ transport of hot electrons, and enables fluent electron utilization at the continuous active Ni sites. Consequently, the Au/PFC‐9 photocatalyst achieves the optimum activity for visible‐light‐driven H2 production. This work shows an example to promote the LSPR‐sensitized photocatalysis taking the advantage of MOFs’ structural tunability, providing significant guidance for the rational design of highly efficient photocatalysts.

Dopamine‐loaded Liposomes‐amplified Electrochemical Immunoassay Based on MXene (Ti3C2)−AuNPs

AbstractA simple and novel electrochemical immunoassay based on MXene (Ti3C2)−Au nanoparticles (AuNPs) was designed for sensitive screening of a disease‐related biomarker, prostate‐specific antigen (PSA), by using dopamine‐loaded liposomes (DLL) for signal amplification. The system involves two parts, namely, sandwich‐type immunoreaction to capture DLL and electrochemical measurement of dopamine. The target PSA can cause a specific antigen‐antibody reaction and DLL are enriched in the enzyme‐labeled pores. After Triton X‐100 is injected into the detection cell, the carried DLL was quickly cracked to release dopamine wrapped in the cavity. A nanocomposite consisting of MXene (Ti3C2) support to immobilize Au nanoparticles (Ti3C2−Au) was utilized to modify a glassy carbon electrode, which gives a strongly enhanced differential pulse voltammetric (DPV) signals for dopamine. In this case, the change of DPV signal depends on the amount of dopamine released by liposomes, which is further positively correlated with the concentration of the analyte PSA. Combining the of MXene (Ti3C2)−AuNPs nanomaterials (large specific surface area, excellent electrical conductivity, and good electrocatalytic properties) with the liposome signal amplification strategy, the electrochemical immunoassay exhibited excellent performance toward PSA determination with a broad linear range of 1 pg/mL to 50 ng/mL and limit of detection down to 0.31 pg/mL (S/N=3) under the optimized testing conditions. High specificity for PSA over other disease‐related biomarkers and acceptable nanocomposite/electrode stability were acquired. The excellent analytical performance shows that the current strategy provides an effective detection platform for clinical sample analysis.

Ultrasensitive Glucose Biosensor Using Micro-Nano Interface of Tilted Fiber Grating Coupled With Biofunctionalized Au Nanoparticles

Monitoring glucose levels is one of the main diagnostic methods for preventing and treating diabetes. Conventionally monitoring of blood glucose through a finger-stick procedure brings pain. It is essential to develop biosensors for low concentration glucose detection in non-invasive samples. In this paper, a tilted fiber grating based localized surface plasmon resonance (LSPR) biosensor for ultrasensitive glucose detection has been demonstrated. The glucose biosensor was fabricated by immobilization of Au nanoparticles (AuNPs) onto an excessively tilted fiber grating (Ex-TFG) and subsequent biofunctionalization by coating polydopamine and concanavalin A onto the AuNPs/Ex-TFG surface. The biosensor has the response regions covering low, middle and high glucose concentrations. The resonance peak indicates a redshift of 0.24 nm, 0.06 nm and 0.48 nm in the concentration ranges of 1.0 nM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 1.0\,\, \boldsymbol {\mu }\text{M}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.0\,\, \boldsymbol {\mu }\text{M}- 50.0\,\, \boldsymbol {\mu }\text{M}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50.0\,\, \boldsymbol {\mu }\text{M}-5.0$ </tex-math></inline-formula> mM, respectively. The limit of detection (LOD) of the biosensor in pure phosphate buffered saline is 2.5 nM. The high sensitivity and specific selectivity for D-glucose detection are attributed to strong coupling between the evanescent fields from transverse magnetic (TM) cladding modes of the Ex-TFG and the localized electric fields from LSPR of the AuNPs and their biofunctionalization, and resulting in remarkable enhancement of localized effective refractive index with slightly increased D-glucose concentration. Especially, the glucose biosensor based on the Ex-TFG coupled with the biofunctionalized AuNPs, has been demonstrated to be of practical utility to detect the glucose in artificial urine, which has potential applications in non-invasive glucose monitoring for early diagnosis and better management of diabetes.

Self-assembled monolayer-immobilized gold nanoparticles for WO3/TiO2 nanocomposite films to yield remarkably enhanced ultraviolet and visible-light photocatalytic activity

This study proposes a self-assembled monolayer nickel-seeding process to immobilize Au nanoparticles (NPs) onto WO3-containing mesoporous TiO2 films as superhydrophilic coatings for self-cleaning applications. Through the redox reactions between nickel seeds and HAuCl4, the loading of Au NPs is confirmed by X-ray photoelectron spectroscopy and transmission electron microscopy. The WO3/TiO2 film is visible-light inactive and displays sound superhydrophilic surface only under ultraviolet light irradiation. By contrast, the Au loaded WO3/TiO2 film under ultraviolet light irradiation has a much longer lifetime of superhydrophilic surface than the WO3/TiO2 film (>300 vs. 90 days); it also responds sharply to visible light, yielding a long, lasting superhydrophilic surface of up to 180 days. Surface plasmon resonance created by the loaded Au NPs is confirmed by light absorbance and Raman measurements, which allows for the proposal of a mechanism for the remarkable enhancement of ultraviolet and visible-light photocatalytic activity.

Multi-Pathway Microenvironment Regulation for Atherosclerosis Therapy Based on Beta-Cyclodextrin/L-Arginine/Au Nanomotors with Dual-Mode Propulsion.

Most of the current non-pharmacological treatment strategies for atherosclerosis (AS) suffer from poor penetration into the plaque and only aim at a certain factor in its formation process, resulting in limited therapeutic effect. Herein, a kind of nanomotor with dual-mode propulsion is constructed, which is sensitive to higher reactive oxygen species (ROS) at the AS site and near-infrared (NIR) laser by the covalent binding and self-assembly of β-cyclodextrin (β-CD) and L-arginine (LA) with immobilization of Au nanoparticles. NIR laser irradiation can be used as a driving force and to ablate inflammatory macrophages through the photothermal effect. The nitric oxide (NO) released by the nanomotors can be used as another driving force and a therapeutic agent to promote endothelial repair in the plaque site. LA can eliminate ROS in the inflammatory site, and β-CD can promote the removal of cholesterol from foam cells. In particular, the two driving modes of nanomotors synergistically promote their aggregation and penetration in the plaque. This kind of nanomotor can regulate the microenvironment of AS in multiple ways, including combination therapy for endothelial repair, lipid clearance, and reducing ROS, which is expected to become a potential non-pharmacological strategy in the treatment of AS.

Immobilized Au nanoparticles on chitosan-biguanidine modified Fe3O4 nanoparticles and investigation of its anti-human lung cancer activity

In current nanoscience bioengineered magnetic nanoparticles (NPs) have come into prominence with considerable impact. These advanced functional materials find outstanding applications in chemical science in catalysis, environmental issues, sensing etc, as well as in biology as drug delivery agent, chemical therapeutics and others. We have been prompted to architect and synthesize a novel Au NP adorned over chitosan-biguanidine polyplex modified core–shell type magnetic nanocomposite (Fe3O4/CS-biguanidine/Au NPs). The bioshells facilitate to protect the core ferrite NPs as well as provides stability to the synthesized Au NPs by capping. The material was characterized using different analytical techniques like Fourier Transformed Infra-Red spectroscopy (FT-IR), Inductively Coupled Plasma-Optical Emission Microscopy (ICP-OES), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray spectroscopy (EDX), Transmission Electron Microscopy (TEM), Vibrating Sample Magnetometer (VSM) and X-ray Diffraction (XRD) studies. We explored the biological application of the nanocomposite in determining cytotoxicity of three adenocarcinoma cell lines (PC-14, LC-2/ad, HLC-1) through the MTT assay. The material showed very good activity by exhibiting very low % cell viability over the cell lines dose-dependently. The IC50 of Fe3O4/CS-biguanidine/Au NPs were observed 503, 398 and 475 µg/mL respectively against the three cell lines. The best output was observed at a concentration of 1000 µg/mL of catalyst in terms of cytotoxicity and inhibition of lung cancer growth. The anti-cancer potential was found in close relation to their antioxidant potential.

Zeolitic imidazolate framework derived porous ZnO/Co3O4 incorporated with gold nanoparticles as ternary nanohybrid for determination of hydrazine

A sensing platform based on porous ZnO/Co3O4 is introduced for determination of hydrazine in alkaline media. The bimetallic oxides were prepared by calcination of bimetallic zeolitic imidazolate framework (Zn/CoZIF) as a sacrificial template. Zn/CoZIF and ZnO/Co3O4 were characterized via several techniques. The porous ZnO/Co3O4 was utilized to modify glassy carbon electrode (ZnO/Co3O4/GCE), followed by immobilization of Au nanoparticles (NPs) on its surface to prepare Au/ZnO/Co3O4/GCE. The electrode exhibited two linear ranges of 2–1900 μM and 1900–8500 μM with sensitivity of 0.058 and 0.048 μA μM−1 for determination of hydrazine in aqueous solution. The sensor showed remarkable lower oxidation potential and limit of detection rather than ZnO/Co3O4/GCE. Furthermore, the sensor displayed acceptable selectivity toward oxidation of hydrazine in the presence of some interfering species. The results confirm that Au/ZnO/Co3O4/GCE can be considered as sensitive and reliable sensor toward the oxidation of hydrazine due to the porous structure of ZnO/Co3O4, high conductivity of Au NPs, and the synergic effect among the constituents.

Nitroarene and dye reduction with 2:1 Co/Al layered double hydroxide catalysts – Is gold still necessary?

A 2:1 Co/Al layered double hydroxide (LDH) material was synthesized with Cl– anions intercalated and then anion exchanged with deprotonated methionine. This allowed further immobilization of Au nanoparticles. The catalytic performance of the set of three LDH materials for comparative benchmarking was assessed in the aqueous reduction of nitroaromatic compounds and of rhodamine dyes in the presence of NaBH4. All catalysts were found to be very active for the nitro-to-amine reduction. The same was observed for the dyes, where reduction rhodamine 6G was faster than that of rhodamine B, for all catalysts.While the Au-containing catalyst was apparently the one showing the best catalytic activity the LDH with Cl– was found to follow it closely in terms of catalytic performance. In addition, while the LDH catalyst with Au was prone to deactivation by amine products in recycling experiments, the LDH catalyst with Cl– was almost insensitive to that, which is a large advantage. These results showed that using a catalyst based on first-row metals for efficient processes is possible and addresses current sustainable and environmental concerns.

Synthesis of Densely Immobilized Gold-Assembled Silica Nanostructures.

In this study, dense gold-assembled SiO2 nanostructure (SiO2@Au) was successfully developed using the Au seed-mediated growth. First, SiO2 (150 nm) was prepared, modified by amino groups, and incubated by gold nanoparticles (ca. 3 nm Au metal nanoparticles (NPs)) to immobilize Au NPs to SiO2 surface. Then, Au NPs were grown on the prepared SiO2@Au seed by reducing chloroauric acid (HAuCl4) by ascorbic acid (AA) in the presence of polyvinylpyrrolidone (PVP). The presence of bigger (ca. 20 nm) Au NPs on the SiO2 surface was confirmed by transmittance electronic microscopy (TEM) images, color changes to dark blue, and UV-vis spectra broadening in the range of 450 to 750 nm. The SiO2@Au nanostructure showed several advantages compared to the hydrofluoric acid (HF)-treated SiO2@Au, such as easy separation, surface modification stability by 11-mercaptopundecanoic acid (R-COOH), 11-mercapto-1-undecanol (R-OH), and 1-undecanethiol (R-CH3), and a better peroxidase-like catalysis activity for 5,5′-Tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2) reaction. The catalytic activity of SiO2@Au was two times better than that of HF-treated SiO2@Au. When SiO2@Au nanostructure was used as a surface enhanced Raman scattering (SERS) substrate, the signal of 4-aminophenol (4-ATP) on the surface of SiO2@Au was also stronger than that of HF-treated SiO2@Au. This study provides a potential method for nanoparticle preparation which can be replaced for Au NPs in further research and development.

An electrochemical biosensor based on AuNPs/Ti3C2 MXene three-dimensional nanocomposite for microRNA-155 detection by exonuclease III-aided cascade target recycling

A novel electrochemical biosensor based on AuNPs/Ti3C2 MXene three-dimensional nanocomposite for sensitive miRNA-155 detection by exonuclease III (Exo III)-aided cascade target recycling is reported. Ti3C2 MXene is synthesized and used as a support to immobilize Au nanoparticles (AuNPs) due to its special layered structure and metallic properties. The three-dimensional (3D) structure of the AuNPs/Ti3C2 MXene nanocomposite for the biosensor platform leverages the integrated advantages of a large specific surface area, excellent electrical conductivity and electrocatalytic properties. AuNPs are used to immobilize capture DNA (C-DNA) by AuS chemical bonds. The C-DNA was modified with methylene blue (MB) at the 3′ end, resulting in an initial DPV electrochemical signal (Id). In the presence of target, miRNA-155 and C-DNA formed a double-stranded structure by complementary base pairing. Subsequently, Exo III digested the 3′ end of the C-DNA in the double-stranded structure and caused the electrochemical signal to “turn off” (the final signal denoted as Ih). By Exo III-aided cascade cleavage of the target, one miRNA-155 chain causes the release of several C-DNAs under certain conditions, which significantly amplifies the peak current difference on the fabricated biosensor (ΔI = Id﹣Ih). The electrochemical sensor achieved a detection limit of 0.35 fM (S/N = 3) with a linear range from 1.0 fM to 10 nM. This sensor also shows desirable stability, reproducibility and specificity.

Immobilization of Au nanoparticles on poly(glycidyl methacrylate)‐functionalized magnetic nanoparticles for enhanced catalytic application in the reduction of nitroarenes and Suzuki reaction

We report a novel strategy for the synthesis of magnetic nanocomposite for highly efficient catalysis. Poly(glycidyl methacrylate) (PGMA) chains were grafted to the surface of magnetic nanoparticles (MNPs) through surface‐initiated reversible addition‐fragmentation chain transfer polymerization. Then, the oxirane rings in the PGMA chains were opened with 2,6‐diamino pyridine (DAP) molecules as ligands to prepare the solid support. Finally, this magnetic nanocomposite was used for the immobilization of gold nanoparticles. Fourier‐transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, transmission electron microscopy, scanning electron microscopy, gel permeation chromatography, vibrating sample magnetometry, and atomic absorption spectroscopy were used for characterization of the catalyst. The loading of gold nanoparticles on the solid support was 0.52 mmol/g. The catalytic activity of the prepared catalyst (MNP@PGMA@DAP@Au) was evaluated for the reduction of nitro compounds and C–C coupling reaction in water. The catalyst can be easily recovered and reused seven times without significant loss of catalytic activity.

Uncalcined TS‐2 immobilized Au nanoparticles as a bifunctional catalyst to boost direct propylene epoxidation with H2 and O2

AbstractDeveloping stable yet efficient Au–Ti bifunctional catalysts is important but challenging for direct propylene epoxidation with H2 and O2. This work describes a novel strategy of employing uncalcined titanium silicalite‐2 (TS‐2‐B) to immobilize Au nanoparticles as a bifunctional catalyst for the reaction. Under no promoter effects, the Au/TS‐2‐B catalyst compared to the referenced Au/TS‐1‐B catalyst delivers outstanding catalytic performance, that is, exceptionally high stability over 100 hr, propylene oxide (PO) formation rate of 118 gPO·hr−1·kgcat−1, PO selectivity of 90% and hydrogen efficiency of 35%. The plausible relationship of catalyst structure and performance is established by using multiple techniques, such as UV–vis, high‐angle annular dark‐field scanning transmission electron microscopy, thermogravimetric analysis, and X‐ray photoelectron spectroscopy. A unique synergy of Au–Ti4+–Ti3+ triple sites is proposed for our developed Au/TS‐2‐B catalyst with the higher stable PO formation rate and hydrogen efficiency. The insights reported here could shed new light on the rational design of highly stable and efficient Au–Ti bifunctional catalysts for the reaction.

Porous POM/PLLA membranes decorated with gold nanoparticles as flexible and efficient plasmonic substrates for surface-enhanced Raman scattering

In this work, we have developed a flexible and efficient Surface-enhanced Raman scattering (SERS) substrate by a facile way of fabricating gold nanoparticles (NPs) decorated Poly(oxymethylene)/poly(L-lactic acid) (POM/PLLA) membranes. Firstly, POM/PLLA membranes were aminolyzed by1,6-hexanediamine to render the membranes with amino groups and porous structure simultaneously. The membranes were then immersed in tetrachloroauric acid (H4AuCl4) solution, where the AuCl4− anions were able to complex with the free amine groups of POM/PLLA, followed by in situ reduction by sodium borohydride to immobilize Au NPs on POM/PLLA membranes. The POM/PLLA/Au membranes exhibited high SERS sensitivity as well as good Raman signal reproductivity for rhodamine 6G (R6G). The minimum detection concentration was 10−14 M and the enhancement factor was calculated to be 1.54 × 109.

Nonsacrificial Self-Template Synthesis of Colloidal Magnetic Yolk-Shell Mesoporous Organosilicas for Efficient Oil/Water Interface Catalysis.

Using interfacial reaction systems for biphasic catalytic reactions is attracting more and more attention due to their simple reaction process and low environmental pollution. Yolk-shell structured materials have broad applications in biomedicine, catalysis, and environmental remediation owing to their open channels and large space for guest molecules. Conventional methods to obtain yolk-shell mesoporous materials rely on costly and complex hard-template strategies. In this study, a mild and convenient nonsacrificial self-template strategy is developed to construct yolk-shell magnetic periodic mesoporous organosilica (YS-mPMO) particles by using the unique swelling-deswelling property of low-crosslinking density resorcinol formaldehyde (RF). The obtained YS-mPMO microspheres possess an amphiphilic outer shell, high surface area (393 m2 g-1 ), uniform mesopores (2.58 nm), a tunable middle hollow space (50-156 nm), and high superparamagnetism (34.4-37.1 emu g-1 ). By tuning the synthesis conditions, heterojunction structured yolk-shell Fe3 O4 @RF@void@PMO particles with different morphologies can be produced. Owing to the amphipathy of PMO framworks, the YS-mPMO particles show great emulsion stabilization ability and recyclability under a magnetic field. YS-mPMO microspheres with immobilized Au nanoparticles (≈3 nm) act as both solid emulsifier for dispersing styrene (St) in water and interface catalysts for selective conversion of St into styrene oxide with a high selectivity of 86%, and yields of over 97%.