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Interest in multifunctional nanoparticles is currently rising due to the increasing demand in green energy and environmental applications. The aerosol-based synthetic route emerges as a promising method for enabling the fabrication of multifunctional nanoparticles in a continuous and scalable manner. Meanwhile, interfacial catalysis is receiving great attention to enhance the performance of chemical reactions. In this regard, the utilization of aerosol nanoparticles is highly beneficial to the catalysis field by the creation of strong metal-support-promoter interactions for promoting interfacial catalysis. In this Perspective, aerosol-based synthesis of hybrid nanoparticles is briefly discussed. In addition, the interfacial catalysis of CO oxidation, methane combustion, CO

Background Nanostructured mixed-valence vanadium oxides (VOx) are attractive as electrode materials for supercapacitor applications. Development of suitable synthetic and characterization methods for the fabrication of VOx nanostructures with controlled properties is of crucial importance. Methods A continuous aerosol-based synthetic route with in-situ mobility size characterization is developed to fabricate VOx nanoparticles (NPs) in this study. Differential mobility analysis, X-ray diffractometry, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy are employed complementarily for material characterization. Cyclic voltammetry and galvanostatic charge-discharge tests are used to evaluate the specific capacitance and charge-discharge stability of the synthesized VOx NPs. Significant Findings Particle size and mean valence of VOx NPs are controllable by adjusting the gas-phase synthetic conditions (atmosphere, temperature, gas flow rate). The specific capacitance of VOx NPs is shown to be proportional to the average valence of V, and the maximum specific capacitance (147.8 F/g) is achievable at an average oxidation state of 4.79 for vanadium. This work demonstrates a prototype study of fast and continuous production of VOx NPs with controlled material properties, showing promise in the tuning of cluster size and valence for the optimization of the corresponding supercapacitive performance.

We demonstrate a facile aerosol-based approach to fabricate hybrid nanostrcutures, NiPdOx-CeO2 nanoparticles deposited on the SiO2 nanoparticle clusters, for the catalysis of steam-promoted CO2 reforming with methane. Ultrafine crystallites of active metal and promoter (≈5 nm) are created with tunable cluster sizes and chemical compositions. A superior catalytic performance achieves at low temperature (550 °C): remarkable turnover frequency (≈2 s−1), tunable H2/CO ratio (1.1–1.9) and high 100-h operation stability. Incorporation of SiO2 nanoparticle cluster as support material increases dispersion of active metals and suppresses metal sintering during material synthesis and catalysis. Hybridization with Pd significantly improves the activity of Ni-based catalyst especially ≤600 °C. Addition of steam suppresses the coke formation by > 10 times. The work demonstrates a prototype study of developing bimetallic hybrid nanocatalysts homogeneously dispersed with promoter on the NPC mesoporous support by design, showing promise for the syngas production via synergistic catalysis of methane-CO2 reforming.

A facile approach is demonstrated for the fabrication of Cu-ZnO-based hybrid nanostructures for the catalytic CO2 conversion to methanol. The method combines colloid stabilization of Al2O3 nanoparticles (as support material) and controlled co-precipitation of Cu (active metal) and ZnO (promoter) onto the Al2O3 nanoparticles. Complementary approaches, including X-ray diffractometry, Brunauer-Emmett-Teller surface area analysis, N2O pulse chemisorption, CO2-based temperature-programmed desorption, transmission electron microscopy coupled with energy dispersive spectroscopy, inductively coupled plasma optical emission spectrometry and thermal gravimetric analysis are employed for the characterization of catalyst materials. The results show a successful synthesis of ultrafine Cu-ZnO nanocrystallites deposited on the Al2O3 nanoparticle clusters (Cu-ZnO@Al2O3). Hybridization with Al2O3 nanoparticles enhanced metal dispersion and number of basic sites of the Cu-ZnO-based nanocatalyst. Aminosilane-based surface functionalization on the Al2O3 nanoparticle increased metal surface area in the hybrid nanostructure. The CO2 conversion catalyzed by the synthesized Cu-ZnO@Al2O3 was shown to be proportional to active surface area of the hybrid nanostructure. An optimum selectivity of the synthesized catalyst was identified (≈47–49%) when the mass fraction of Al2O3 was (35–36) %, in correspondence to the highest moderate basicity of the synthesized hybrid nanostructures. The highest yield of methanol achieved 12989 ± 2007 µmolg−1 h−1 by the developed Cu-ZnO@Al2O3. Our work demonstrates a prototype study of fabricating high-performance hybrid nanocatalyst with the support of mechanistic understanding in material synthesis for the synergistic catalysis of CO2 hydrogenation to methanol.

The assembly-disassembly of hyaluronic acid (HA) with a bovine serum albumin-conjugated gold nanoparticle (BSA-AuNP) was demonstrated using a gas-phase electrophoresis approach, electrospray-differential mobility analysis (ES-DMA). Physical sizes, number and mass concentrations, and degrees of aggregation of HA, BSA, and AuNP were successfully quantified using ES-DMA hyphenated with inductively coupled plasma mass spectrometry. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed complementarily for an orthogonal characterization of the assembly of HA with BSA-AuNP and the subsequent HA detachment. The results show that the surface packing density of HA on BSA-AuNP was proportional to the concentration of HA (CHA) when CHA ≤ 5 × 10-3 μmol/L, and the equilibrium binding constant of HA on BSA-AuNP was identified as ≈ 4 × 105 L/mol at pH 3. The pH-sensitive and enzyme-induced detachments of HA from BSA-AuNP were both successfully characterized using ES-DMA and ATR-FTIR. In the absence of enzymatic catalysis, the rate constant of HA detachment (k) was shown to increase by at least 3.7 times on adjusting the environmental acidity from pH 3 to pH 7. A significant enzyme-induced HA detachment was identified at pH 7, showing a remarkable increase of k by at least two times in the presence of an enzyme. This work provides a proof of concept for assembly of HA-based hybrid colloidal nanomaterials through the tuning of surface chemistry in the aqueous phase with the ability of in situ quantitative characterization, which has shown promise for the development of a variety of HA-derivative biomedical applications (e.g., drug delivery).

Spherical porous nanoclusters composed of NiO and CeO2 nanoparticles were successfully developed by a refined gas-phase controlled synthesis method, which were shown to be useful for syngas product...

A real-time quantitative analytical approach, differential mobility analysis coupled to gas-phase Fourier-transform infrared spectroscopy (DMA/FTIR), is demonstrated for an aerosol spray-based synt...

In this review, we introduce advanced synthetic methods for functional nanostructured materials (in powder form) bridging to the development in emerging energy and environmental applications. Three types of synthetic methods (aerosol-based, aerogel-based, and de novo methods) are introduced, all of which have shown to be extensively investigated as novel routes to create nanostructured materials with designed material properties (i.e., controlled size, shape, porosity, and chemical composition are to be achievable). The typical experimental setup and the general experimental procedure for material preparation via the above three synthesis routes are discussed. Complementary characterization approaches are employed to study material properties of the synthesized nanostructured materials via the three synthesis routes. Here we investigate: (1) CuxO-CeO2, Ni-CeO2, and CuxO nanoparticle-encapsulating metal–organic framework (MOF) hybrid nanoparticles synthesized via the aerosol-based method; (2) Cr-encapsulating MOF (Cr-MOF-199), Au-encapsulating MOF (Au@ZIF-8), and MOF-derived nanocomposites (CuO/CuCr2O4) produced via the de novo route; (3) a variety of aerogels (carbon, metal oxide, polymer) with high porosity created by the aerogel-based approach. Finally, several examples of emerging energy and environmental applications are introduced using these functional nanostructured materials, including (1) catalytic transformation to chemicals by using precious metal nanoparticles-embedded MOFs and the MOF-derived nanocomposites as the catalysts; (2) methane combustion using CuxO-CeO2 hybrid nanoparticles as catalyst, (3) methane dry reforming with CO2 using Ni-CeO2 hybrid nanoparticles as catalyst; (4) CO2 capture by fluoroalkyl silane-modified mesoporous silica and polymethylsilsesquioxane (PMSQ) aerogel membranes; (5) adsorption of organic solvent, dye, and oil by cetyltrimethylammonium bromide-modified PMSQ aerogel.

The hybrid nanostructures, Ni-only and Ni–CeO2 nanoparticles decorated on Al2O3 nanoparticle clusters (Ni–Al2O3 NPC and Ni–CeO2–Al2O3 NPC, respectively), were successfully synthesized as catalysts ...

We demonstrated an aerosol-based approach to synthesize Ni-CeO2-Al2O3 hybrid nanostructure as a potent nanopowder catalyst for the production of polyetheramine via reductive amination of polypropylene glycol. The method combines a gas-phase evaporation-induced self-assembly with two-stage thermal treatments of the aerosol particles. The hybrid Ni-CeO2 nanoparticles (NPs) composed of ultrafine, homogeneously-distributed nanocrystallites of metallic Ni and ceria were shown to uniformly decorate on the surface of Al2O3 nanoparticle cluster (NPC). The composition, physical size and surface state of the hybrid nanostructure were tunable by design. It was found that hybridization with Al2O3 or CeO2 enhanced catalytic activity of the Ni catalyst. A high yield of ≈77% of the desired PEA and a high selectivity to primary amine (≈100%) achieved simultaneously. The surface nitridation of Ni catalyst was effectively suppressed via the incorporation with CeO2 NPs. An enhanced operation stability was observed by using the Ni-CeO2-Al2O3 hybrid nanostructure as catalyst in comparison to the Ni-only NP. The work demonstrated a facile route for controlled gas-phase synthesis of hybrid nanopowder catalysts using Al2O3 NPC as the support matrix and CeO2 NP as the promoter to further enhance the performance of Ni catalyst toward reductive amination.

Ni-only and Ni-CeO2 particles decorated on Al2O3 support material were prepared for an effective catalytic reductive amination of polypropylene glycol (PPG) to polyetheramines (PEA). Incipient wetness impregnation was employed for the preparation of catalysts followed by complementary material characterization (powder XRD, SEM, HRTEM, XPS, H2-TPR and NH3-TPD). High selectivity to PEA (~ 100%) was achieved. The catalytic activity obtained was proportional to Ni and Ce loadings (CCe), when CCe ≤ 15%. Hybridization with CeO2 inhibited formation of nickel nitride and enhanced activity (by 15.3%) and operation stability of Ni catalyst (by 20×). The present work has demonstrated a facile route to fabricate Ni-CeO2 hybrid catalysts on alumina support material and provided mechanistic understanding of the synergistic effect occurred for the heterogeneous catalytic reductive amination.

Electrospray-differential mobility analysis coupled with aerosol particle mass analysis (ES-DMA/APM) was demonstrated for the development of a metal–organic framework (MOF) nanocarrier system. A successful quantification of ibuprofen loading in UiO-66-NH2 (i.e., the representative drug molecule and MOF, respectively) achieved based on the aerosol particle mass of MOF measured by ES-DMA/APM (≈55 mg of ibuprofen/g of UiO-66-NH2). The structural stability of UiO-66-NH2 versus ibuprofen release was successfully quantified over a 7-day period in an acidic phosphate buffer solution. The methodology provides a proof-of-concept scheme for controlled release studies of different types of active pharmaceutical ingredients from a variety of MOF-based nanocarrier systems.

In this study, a facile synthetic approach was demonstrated for the preparation of graphene oxide (GO)-modified soluble polyimide (SPI) nanocomposites with enhanced mechanical properties. Firstly, a two-step method was employed to form SPI via polymerization of cycloaliphatic dianhydride (bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride) and aromatic diamine (2,2′-Bis[4-(4-aminophenoxy)phenyl]propane). Amino-substituted silsesquioxane (SQ) was used to conjugate with GO to form SQ-grafted graphene oxide (SQ@GO) and thermally-treated SQ@GO (TSQ@GO). Fourier-transformed infrared spectroscopy, 29Si nuclear magnetic resonance spectroscopy, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectrometry were used complementarily for the study of the chemical structures of the prepared SQ@GO, TSQ@GO and SPI/TSQ@GO nanocomposite film (i.e., TSQ@GO in SPI matrix). Results show successful synthesis of SQ@GO, TSQ@GO and SPI/TSQ@GO nanocomposite film. With support of excellent dispersibility of TSQ@GO in SPI matrix, the tensile properties of SPI improved significantly via hybridization with TSQ@GO: tensile strength enhanced to 1.3X and elongation at break increased to 3 folds. This study demonstrated a prototype method for fabrication of pre-imidized SPI/TSQ@GO nanocomposite, which has shown the promise for moderate-temperature manufacture (below 200 °C) of emerging electronic applications.

A facile aerosol-based synthetic approach is demonstrated for the fabrication of silsesquioxane-graphene oxide (rGO-SQ) and reduced graphene oxide-manganese oxide (MnOx-rGO) nanocomposites, as the materials for negative and positive electrodes in an asymmetric supercapacitor (ASC), respectively. Microwave-assisted hydrothermal treatment is employed to form reduced graphene oxide (AS-rGO). Fourier-transformed infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and x-ray photoelectron spectrometry are used to provide complementary material characterizations for the synthesized nanocomposites. The results show that the composition and the morphology of the synthesized materials are tunable by the adjustment of precursor concentration and annealing temperature. From the shapes of cyclic voltammetric and galvanostatic charge-discharge curves, the conductivity and the subsequent capacitive performance of MnOx are enhanced effectively by the hybridization with rGO. The highest double-layer capacitance of AS-rGO is 118 F g−1, and the highest specific capacitance of MnOx-rGO reaches 183 F g−1 under a scan rate of 5 mV s−1. The ASC assembled with AS-rGO and MnOx-rGO possessed high charge-discharge reversibility at a cell voltage of 2.0 V. A high operation stability of ASC can be achieved, as evidenced by the high retention (98% of the retention) in the 10,000-cycle charge-discharge test at a current density of 2 A g−1. The maximum specific energy and specific power of the ASC respectively reach 16.6 Wh kg−1 and 1.052 kW kg−1 at a current density of 1 A g−1. This study demonstrates a prototype approach for the fabrication of nanocomposite electrode materials by design with the ability of scalable mass production.

We report a facile, high-resolution approach to quantitatively characterize hyaluronic acid (HA) and study its crosslinking reaction using electrospray-differential mobility analysis (ES-DMA). Mobility size distributions, number concentrations, molecular mass distributions, and polydispersity index of HAs were obtained successfully via a rapid analysis by ES-DMA ( 30 min). The limit of detection, the limit of quantification, and the precision of the mobility size measurement achieve 2.5 nm, 4.0 nm, and 0.3 nm, respectively. Size exclusion chromatography (SEC) was employed as an orthogonal approach, showing that the averaged molecular mass and polydispersity index of HA measured by ES-DMA were close to the results of SEC on a semi-quantitative basis. The 1,4-butanediol diglycidyl ether (BDDE)-induced crosslinking of HA was also able to be successfully characterized through a time-dependent study using ES-DMA, which has shown the promise of direct analysis of solution-based reactions. Both the extent and the rate of HA crosslinking (induced by BDDE) were proportional to reaction temperature and concentration ratio of HA to BDDE. The activation energy of the reaction-limited BDDE-induced crosslinking of HA was found to be ≈ 21 kJ/mol. The prototype study demonstrates ES-DMA as a new method for a rapid quantitative characterization of HA and its derivative product and providing a capability of real-time monitoring of the HA crosslinking during formulation process. Graphical abstract.

A monoethanolamine (MEA) aerosol growth model was developed to quantify the aerosol growth factor in an amine-based CO2 capture absorber that considers the gas-liquid interactions, and it is empirically validated by measuring the aerosol particle size and concentration. The aerosol growth model, using sucrose as the aerosol nuclei instead of sulfuric acid to prevent the corrosion of the test equipment, accurately predicted that the outlet aerosol size increased to the same level regardless of the sucrose concentration. It also found that particle concentration was the primary factor affecting aerosol growth and amine emissions. We found an inverse relationship between aerosol particle concentration and the aerosol size, while the MEA emissions were proportional to particle concentration.

In this study, a monoethanolamine aerosol growth model was developed to investigate the aerosol growth factor. Interactions among the internal conditions in an absorber were considered in this aerosol model. Additionally, an experiment was conducted to measure aerosol particle size, for collecting in-house validation data. Sucrose was used as the aerosol nuclei instead of sulfuric acid to prevent the corrosion of equipment used in the experiment. Experimental results showed that the outlet aerosol sizes increased to the same size regardless of the sucrose concentrations. The aerosol growth model was validated using the in-house experimental data. The aerosol growth model efficiently predicted the aerosol size. For investigating aerosol growth effects, particle number concentration was determined to be the primary factor affecting aerosol growth and amine emissions. When the particle number concentration increased, the aerosol size decreased, whereas the MEA emission increased.

Syngas, consisting of equimolar CO and H2, is an important feedstock for large-scale production of a wide range of commodity chemicals including aldehyde, methanol, ammonia, and other oxygenated chemicals. Dry reforming of methane (DRM), proceeding by reacting greenhouse gases, CO2 and CH4, at high temperatures in the presence of a metal catalyst, is considered one of the most environmentally friendly routes for syngas production. Nevertheless, nonprecious metal-based catalysts, which can operate at relatively low temperatures for high product yields and selectivities, are required to drive the DRM process for industrial applications effectively. Here, we developed NiCo@C nanocomposites from a corresponding NiCo-based bimetallic metal-organic framework (MOF) to serve as high-performance catalysts for the DRM process, achieving high turnover frequencies (TOF) at low temperatures (>5.7 s-1 at 600 °C) and high product selectivities (H2/CO = 0.9 at 700 °C). The incorporation of Co in Ni catalysts improves the operation stability and light-off stability. The present development for MOF-derived nanocomposites opens a new horizon for design of DRM catalysts.

Controlled synthesis of metal–organic framework (MOF)-derived Mg-Zn hybrid nanostructure was demonstrated for the development of basic catalysts applied in biodiesel production from soybean oil. Two types of Mg-Zn hybrid nanostructures were successfully fabricated under different atmospheres (Ar, air), (1) MgO nanoparticles encapsulated in Zn-based MOF (MgO@Zn-MOF) and (2) MgO nanoparticles uniformly decorated on ZnO nanoparticles derived from Zn-MOF (MgO@ZnO), respectively. Ultrafine MgO nanoparticles (

The synergistic effect of Cu Ce O hybrid nanostructure has shown the promise for catalytic methane combustion. In this study, we develop an aerosol-based two-stage thermal treatment method to (1) synthesize the Cu Ce O hybrid nanoparticle (NP) with a tunable oxidation state directly in gas phase, and (2) provide a mechanistic understanding of surface reduction of the Cu Ce O hybrid NP for catalysis of methane combustion. After evaporation-induced self-assembly followed by a thermal decomposition to form metal oxide NP at the 1st stage thermal treatment, a temperature-programmed, aerosol-based hydrogen reduction process was employed for direct tuning the oxidation state of the NP in the gas phase (the 2nd stage thermal treatment). Differential mobility analysis, x-ray diffractomery, x-ray photoelectron spectroscopy, and scanning electron microscopy were employed complementarily for characterization of particle size, morphology, crystallinity, elemental composition, and oxidation state of the NPs. The results show a successful surface reduction of Cu for both Cu-only NP and Cu Ce O hybrid NP by the aerosol-based two-stage thermal treatment method. Using the Cu Ce O hybrid nanoparticle as catalyst, our results show a successfully catalysis on methane combustion over various initial oxidation states of Cu. The results show a high activity with a low light-off temperature, a high light-off stability and operation stability toward catalytic methane combustion. The prototype method proposed in this study provides the mechanistic understanding of the synergistic catalysis of the surface-reduced Cu Ce O hybrid nanoparticle with different oxidation states. The method can be especially useful to fabricate a variety of nanocatalysts with different oxidation states of active metals by design for the study of methane-based energy and environmental applications (e.g., CO2 dry reforming by methane).

We develop a new Ni–CeOx hybrid nanoparticle as a high-performance catalyst for dry reforming of methane with carbon dioxide (DRM) using a facile gas-phase synthetic approach. The crystallites of Ni and CeO2 were homogeneously self-assembled as a hybrid nanostructure, creating a large amount of Ni–Ce–O interface for a strong metal–support interfacial interaction. Chemical composition and oxidation state of the hybrid nanostructure were tunable directly in the aerosol state. The results show that the starting temperature of catalysis by Ni-based catalysts reduced by ∼150 °C through the hybridization with CeO2 followed by a direct H2 reduction in the aerosol state. In comparison to Ni-only nanoparticle, the Ni–CeOx hybrid nanoparticle showed stable and high conversion for CH4 and CO2 with a remarkably turnover frequency at low temperature (0.1 s–1 at 450 °C). The amount of coke formation greatly reduced by 18×, whereas the H2/CO ratio was constant at ∼0.8 by a 1.5× of the increase of CO2/CH4 ratio. The work...

Here we aim to develop a facile emulsion-based method to prepare tripod gold nanoparticles (AuNPs) with high suspension stability in an aqueous environment. A gyroid-structured polymer template formed by the hydrolysis of a degradable block copolymer, polystyrene (PS)-b-poly(l-lactide), is used for the fabrication of AuNPs. Also, a successful emulsification of dichloromethane (DCM) in the aqueous phase is developed by using thiolated polyethylene glycol (PEG-SH) as the stabilizer. Subsequently, the nanohybrids of PS/Au can be fabricated by templated electroless plating, and then selectively dissolving in the DCM dispersive phase. Most interestingly, a dedicated process for the simultaneous release of the tripod AuNPs from the dissolution of PS associated with PEG-SH at the interface of the emulsion is achieved, giving PEG-SH-functionalized tripod AuNPs dispersed in the aqueous phase, which significantly improves the suspension stabilization of tripod AuNPs. The in situ temperature-programmed electrospray-differential mobility analysis provides a quantitative, statistical analysis of mobility diameter, dynamic shape factor, polydispersity, and colloidal stability.

An aerosol-based synthetic approach, in combination with a real-time characterization method using differential ion-mobility analyses coupled to temperature-programmed Fourier-transform infrared spectroscopy (DMA/TP-FTIR), was demonstrated for the development of raspberry-structured Ag‑carbon hybrid nanoparticle clusters (Ag-C-NPC). Physical size, number concentration, and compositions of the Ag-C-NPC were shown to be successfully characterized directly in the aerosol state on a quantitative basis. Remarkable high salt adsorption capacity (15.6 mg/g), good charging/discharging stability, and low requirement of cell voltage were attainable by using the Ag nanoparticle-decorated carbon nanoparticle clusters as the positive electrode material. This work provides a proof of concept of using the aerosol-based synthesis, with the support of in-situ characterization, for the development of Ag C nanocomposite clusters to achieve high CDI performance. The method also shows promise for the tuning of the material properties of Ag-C-NPC for the optimization of the CDI capacity and cyclic stability useful for a variety of the water desalination applications (e.g., brackish water).

We demonstrate a new, facile gas-phase electrostatic approach to successfully quantify equivalent surface area of graphene oxide (GO) colloid on a number basis. Mobility diameter (dp,m)-based distribution and the corresponding equivalent surface area (SA) of GO colloids (i.e., with different lateral aspect ratios) were able to be identified by electrospray-differential mobility analysis (ES-DMA) coupled to a condensation particle counter (CPC) and an aerosol surface area analyzer (ASAA). A correlation of SA ∝ dp,m2.0 was established using the ES-DMA-CPC/ASAA, which is consistent with the observation by the 2-dimensional image analysis of size-selected GOs. An ultrafast surface area measurement of GO colloid was achieved via a direct coupling of ES with a combination of ASAA and CPC (i.e., measurement time was 2 min per sample; without size classification). The measured equivalent surface area of GO was ∼202 ± 7 m2 g–1, which is comparable to Brunauer–Emmett–Teller (BET) surface area, ∼240 ± 59 m2 g–1. The...

A facile aerosol-based synthetic approach is demonstrated for the fabrication of silver-manganese oxide (Ag-MnOx) and cetyltrimethylammonium bromide (CTAB)-templated silver-manganese oxide (c-Ag-MnOx) hybrid nanostructures as the positive electrode materials of supercapacitors. Through gas-phase evaporation-induced self-assembly, silver nanoparticles are homogeneously decorated in the hybrid nanostructure to create a conductive path at the interface of the cluster of MnOx crystallites. The utilization of the capacitance of MnOx increases by the addition of Ag nanoparticles (>2 times for Ag-MnOx and ∼1.7 times for c-Ag-MnOx). An optimal specific capacitance is achieved when the concentration of the silver precursor (CAg) is 0.5 wt %, 118 F g-1 for Ag-MnOx, and 154 F g-1 for c-Ag-MnOx at a specific current of 1 A g-1. The enhanced supercapacitive performance by the addition of CTAB at low CAg is attributed to the increased surface area (>19.4%) for electrochemical reactions. The prototype method with mechanistic understanding demonstrated in this study shows promise for the fabrication of a variety of MnOx-based hybrid nanostructures for supercapacitor applications.

A facile, aerosol-based controlled synthesis of porous Mg-Al-O composite nanoparticle is demonstrated for developing solid base catalysts with high performance for transesterification of soybean oil to biodiesel. Pore size, crystallite size and chemical composition of the Mg-Al-O composite nanoparticle are tunable by design. A significantly higher surface area (by 1.8 times) and a smaller pore size (i.e., decreased by 20%) of the Mg-Al-O composite particle achieved by using the aerosol-based synthesis than the conventional method. Hybridization with Al2O3 remarkably increased surface area of the MgO particle by decreasing pore size using homogenous Al precursor or increasing pore volume via choosing heterogeneous Al precursor. The fatty acid methyl esters (FAME) yield catalyzed by Mg-Al-O composite particle was significantly higher in comparison to the results without catalysts (i.e., a maximum of 3.4×). The FAME yield was proportional to methanol-to-oil molar ratio, and the highest yield was identified at Mg/Al = 4, in accordance to the highest number of strong basic site quantified via a CO2-based temperature-programmed desorption study. Operation stability (i.e., FAME yield declined by

In this work, ZnO nanoparticles were surface-modified by thermal shock method with HAuCl4 and KF as precursors at different temperatures. The impacts of our modification process on the crystal structure, morphology, surface functional groups and surface composition of catalysts were characterized by XRD, TEM, FTIR and XPS spectra, respectively. Their photocatalytic activity was investigated through the degradation of methylene blue under UVA light and visible light irradiation. According to the results, our modification method successfully improved the photocatalytic activity of ZnO. Among all catalysts, the sample co-modified with Au and F at thermal shock temperature of 400 °C showed the best performance which was three times greater than that of unmodified ZnO sample under both UVA light and visible light. The enhanced photocatalytic activity of our modified catalysts can be attributed to the synergic effect of HAuCl4 and KF precursors which are able to produce Au(0) nanoparticles, Au+ ions and zinc vacancies on the oxide surface.

A new CuO–CeO2 hybrid nanoparticle (CuCeOx-NP) with a tunable homogeneous chemical composition was successfully prepared for high-performance catalytic methane combustion. The substantial amounts of Cu–Ce–O interfaces were created for enhanced catalysis using gas-phase evaporation-induced self-assembly. The CuCeOx-NP exhibited an ultralow light-off temperature (320 °C), high activity, selectivity, and operation stability for catalytic methane combustion. The optimal reducibility and the corresponding catalytic activity of CuCeOx-NP were achieved when the molar fraction of Ce was 0.17. The operation stability increased as the concentration ratio of oxygen in the reactant gas and the corresponding oxidation rate of carbon species from the catalyst surface increased. This work demonstrates a facile route for controlled synthesis of CuCeOx-NP. The mechanistic understanding of synergistic catalysis developed in this study can be used to further enhance activity of methane combustion and reduce environmental po...

A quantitative study of the stability of silver nanoparticles (AgNPs) conjugated with thiolated polyethylene glycol (SH-PEG) was conducted using gas-phase ion-mobility and mass analyses. The extents of aggregation and surface dissolution of AgNPs, as well as the amount of SH-PEG adsorption and desorption, were able to be characterized simultaneously for the kinetic study. The results show that the SH-PEG with a molecular mass of 6 kg/mol (SH-PEG6K) was able to adsorb to the surface of AgNP to form PEG6K-HS-AgNP conjugates, with the maximum surface adsorbate density of ∼0.10 nm(-2). The equilibrium binding constant for SH-PEG6K on AgNPs was calculated as ∼(4.4 ± 0.9) × 10(5) L/mol, suggesting a strong affinity due to thiol bonding to the AgNP surface. The formation of SH-PEG6K corona prevented PEG6K-HS-AgNP conjugates from aggregation under the acidic environment (pH 1.5), but dissolution of core AgNPs occurred following a first-order reaction. The rate constant of Ag dissolution from PEG6K-HS-AgNP was independent of the starting surface packing density of SH-PEG6K on AgNP (σ0), indicating that the interactions of H(+) with core AgNP were not interfered by the presence of SH-PEG6K corona. The surface packing density of SH-PEG6K decreased simultaneously following a first-order reaction, and the desorption rate constant of SH-PEG6K from the conjugates was proportional to σ0. Our work presents the first quantitative study to illustrate the complex mechanism that involves simultaneous aggregation and dissolution of core AgNPs in combination with adsorption and desorption of SH-PEG. This work also provides a prototype method of coupled experimental scheme to quantify the change of particle mass versus the corresponding surface density of functional molecular species on nanoparticles.

We report a systematic study of gas-phase controlled synthesis of copper oxides-based hybrid nanoparticles for catalytic CO oxidation. The complementary physical, spectroscopic, and microscopic analyses were conducted to obtain a better understanding of the material properties, including particle size, crystallinity, elemental composition, and oxidation state. Results showed that the synthesized nanoparticles exhibited highly durable catalytic activity and stability, also the particle size, crystallite size, and chemical composition were tunable by choosing suitable chemical compositions of precursors and temperatures. The crystallite size of CuO influenced the reducibility of CuO by CO and the subsequent catalytic activity of CO oxidation. The hybridization process of CeO2 and CuO induces the formation of new active sites at the Cu–Ce–O interface, which enhances reproducibility of CuO and the catalytic activity. However, the reproducibility of CuO and catalytic activity were considerably decreased when C...

We demonstrate a controlled synthesis of silica microsphere with the surface-decorated functional gold nanoparticles. Surface of silica microsphere was modified by 3-aminopropypltriethoxysilane and 3-aminopropyldimethylethoxysilane to generate a positive electric field, by which the gold nanoparticles with the negative charges (unconjugated, thiolated polyethylene glycol functionalized with the traceable packing density and conformation) were able to be attracted to the silica microsphere. Results show that both the molecular conjugation on gold nanoparticle and the uniformity in the amino-silanization of silica microsphere influenced the loading and the homogeneity of gold nanoparticles on silica microsphere. The 3-aminopropyldimethylethoxysilane-functionalized silica microsphere provided an uniform field to attract gold nanoparticles. Increasing the ethanol content in aminosilane solution significantly improved the homogeneity and the loading of gold nanoparticles on the surface of silica microsphere. For the gold nanoparticle, increasing the molecular mass of polyethylene glycol yielded a greater homogeneity but a lower loading on silica microsphere. Bovine serum albumin induced the desorption of gold nanoparticles from silica microsphere, where the extent of desorption was suppressed by the presence of high-molecular mass polyethylene glycol on gold nanoparticles. This work provides the fundamental understanding for the synthesis of gold nanoparticle-silica microsphere constructs useful to the applications in chemo-radioactive therapeutics.

A gas-phase controlled synthesis method is demonstrated to prepare Ni-CeO2 nanocrystallites decorating on Al2O3 nanoparticle clusters (NPC) for synergistic catalysis of dry reforming of methane with CO2 (DRM). The method combines the principles of aerosol-phase evaporation-induced self-assembly with colloid-phase stabilization of Al2O3 nanoparticles in sprayed aqueous droplets. Hybrid NPC was successfully created with ultrafine Ni crystallites (