•Ordered mesoporous cobalt oxide (meso-Co3O4) is obtained via KIT-6-templating route.•xAu/meso-Co3O4 nanocatalysts are prepared using the colloidal deposition method.•Au nanoparticles are highly ...dispersed inside the mesoporous channels of meso-Co3O4.•xAu/meso-Co3O4 perform well in the oxidation of CO, benzene, toluene, and o-xylene.•There is a strong interaction between Au nanoparticles and meso-Co3O4.
Three-dimensionally ordered mesoporous Co3O4 (meso-Co3O4) and its supported gold (xAu/meso-Co3O4, x=3.7–9.0wt%) nanocatalysts were prepared using the KIT-6-templating and polyvinyl alcohol-protected colloidal deposition methods, respectively. The meso-Co3O4 and xAu/meso-Co3O4 samples exhibited a high surface area of 91–94m2/g. The Au nanoparticles with a size of 1–5nm were uniformly deposited inside the mesoporous channels of meso-Co3O4. There were good correlations of oxygen adspecies concentration and low-temperature reducibility with catalytic activity of the sample for CO or BTX (benzene, toluene, and o-xylene) oxidation. Among meso-Co3O4 and xAu/meso-Co3O4, the 6.5Au/meso-Co3O4 sample performed the best, giving the T90% (the temperature required for achieving a CO or BTX conversion of 90%) of −45, 189, 138, and 162°C for the oxidation of CO, benzene, toluene, and o-xylene, respectively. The apparent activation energies (23 and 45–55kJ/mol) over 6.5Au/meso-Co3O4 were much lower than those (48 and 72–92kJ/mol) over bulk Co3O4 for CO and BTX oxidation, respectively. The effects of water vapor, carbon dioxide, and sulfur dioxide on the catalytic activity of the 6.5Au/meso-Co3O4 sample were also examined. It is concluded that the higher surface area and oxygen adspecies concentration, better low-temperature reducibility, and strong interaction between Au and meso-Co3O4 were responsible for the excellent catalytic performance of 6.5Au/meso-Co3O4.
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•AuyPd/meso-Co3O4 is prepared by polyvinyl alcohol-protected reduction.•AuyPd alloy nanoparticles are well dispersed on the surface of mesoporous Co3O4.•There is a strong interaction ...between AuyPd alloy and meso-Co3O4.•2.94Au0.50Pd/meso-Co3O4 shows excellent catalytic activity for methane combustion.•2.94Au0.50Pd/meso-Co3O4 exhibits good tolerance of CO2 and SO2.
Three-dimensionally ordered mesoporous Co3O4 (meso-Co3O4) and its supported Au, Pd, and Au–Pd alloy (xAuyPd/meso-Co3O4; x=0.43–2.94wt%; Au/Pd molar ratio (y)=0.43–0.50) nanocatalysts were prepared using the KIT-6-templating and polyvinyl alcohol-protected reduction methods, respectively. It is found that the meso-Co3O4 with a high surface area of 106m2/g was cubic in crystal structure and the noble metal nanoparticles (NPs) with a size of 2.7–4.5nm were uniformly dispersed on the surface of meso-Co3O4. The 2.94Au0.50Pd/meso-Co3O4 sample performed the best for methane combustion, showing the T10%, T50%, and T90% (temperatures required for achieving methane conversions of 10%, 50%, and 90%) of 230, 280, and 324°C at a space velocity of 20,000mL/(gh) and the lowest apparent activation energy of 44.4kJ/mol. Furthermore, the effects of CO2, SO2, and H2O addition on the catalytic stability of 2.94Au0.50Pd/meso-Co3O4 were also examined. It is concluded that the excellent catalytic performance of 2.94Au0.50Pd/meso-Co3O4 was associated with its porous structure, high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between Au–Pd alloy NPs and meso-Co3O4.
Developing new synthetic methods for carbon supported catalysts with improved performance is of fundamental importance in advancing proton exchange membrane fuel cell (PEMFC) technology. ...Continuous‐flow, microfluidic reactions in capillary tube reactors are described, which are capable of synthesizing surfactant‐free, ultrafine PtSn alloyed nanoparticles (NPs) on various carbon supports (for example, commercial carbon black particles, carbon nanotubes, and graphene sheets). The PtSn NPs are highly crystalline with sizes smaller than 2 nm, and they are highly dispersed on the carbon supports with high loadings up to 33 wt %. These characteristics make the as‐synthesized carbon‐supported PtSn NPs more efficient than state of the art commercial Pt/C catalysts applied to the ethanol oxidation reaction (EOR). Significantly enhanced mass catalytic activity (two‐times that of Pt/C) and improved stability are obtained.
Fluid to the influence: Formation of ultrafine PtSn nanoparticles on a carbon sphere with uniform loading using a microfluidic reactor with a confined lateral dimension is described.
3DOM-structured La0.6Sr0.4MnO3 (LSMO) and xAu/LSMO (x=3.4–7.9wt%) are prepared using the polymethyl methacrylate-templating and polyvinyl alcohol-protected reduction methods, respectively. The high ...Oads concentration, good low-temperature reducibility, and strong Au–LSMO interaction are responsible for excellent catalytic performance of 6.4Au/LSMO for CO and toluene oxidation. Display omitted
•3DOM La0.6Sr0.4MnO3 (LSMO) is prepared by polymethyl methacrylate-templating method.•xAu/LSMO catalysts are prepared by the polyvinyl alcohol-protected reduction method.•xAu/LSMO perform excellently in the oxidation of CO and toluene.•Activity is governed by Oads content, reducibility, and strong Au–LSMO interaction.
Three-dimensionally ordered macroporous (3DOM) La0.6Sr0.4MnO3 (LSMO) and its supported gold (xAu/LSMO, x=3.4–7.9wt%) catalysts were prepared using the polymethyl methacrylate-templating and gas-bubble-assisted polyvinyl alcohol-protected reduction methods, respectively. There were good correlations of surface-adsorbed oxygen species concentration and low-temperature reducibility with the catalytic activity of the sample for CO and toluene oxidation. Among the LSMO and xAu/LSMO samples, 6.4Au/LSMO performed the best, giving T50% and T90% values of −19 and 3°C for CO oxidation and 150 and 170°C for toluene oxidation, respectively. The apparent activation energies (31–32 and 44–48kJ/mol) obtained over xAu/LSMO were much lower than those (45 and 59kJ/mol) obtained over LSMO for the oxidation of CO and toluene, respectively. It is concluded that higher oxygen adspecies concentration, better low-temperature reducibility, and strong interaction between Au and LSMO are responsible for the excellent catalytic performance of 6.4Au/LSMO.
xAu/3DOM Mn2O3 (x=1.9−7.5wt%) nanocatalysts are prepared via the PMMA-templating and PVA-protected reduction routes. The high oxygen adspecies concentration, good low-temperature reducibility, and ...strong interaction between Au and Mn2O3 are responsible for the high catalytic performance of 5.8Au/3DOM Mn2O3.
Three-dimensionally ordered macroporous (3DOM) Mn2O3 and its supported gold (xAu/3DOM Mn2O3, x=1.9−7.5wt%) nanocatalysts were prepared using the polymethyl methacrylate-templating and polyvinyl alcohol-protected reduction methods, respectively. The 3DOM Mn2O3 and xAu/3DOM Mn2O3 samples exhibited a surface area of 34−38m2/g. The Au nanoparticles (NPs) with a size of 3.0−3.5nm were uniformly dispersed on the skeletons of 3DOM Mn2O3. The 5.8Au/3DOM Mn2O3 sample performed the best, giving the T90% (the temperature required for a conversion of 90%) of −15°C at space velocity (SV)=20,000mL/(gh) for CO oxidation and 244°C at SV=40,000mL/(gh) for toluene oxidation. The apparent activation energies (30 and 54kJ/mol) over 5.8Au/3DOM Mn2O3 were much lower than those (80 and 95kJ/mol) over 3DOM Mn2O3 for CO and toluene oxidation, respectively. The effects of SV, water vapor, CO2, and SO2 on catalytic activity were also examined. It is concluded that the excellent catalytic performance of 5.8Au/3DOM Mn2O3 was associated with its high oxygen adspecies concentration, good low-temperature reducibility, and strong interaction between Au NPs and 3DOM Mn2O3 as well as high-quality porous architecture.
Herein we fabricated the supported single-atom silver catalysts using an in situ molten salt method. The Mn2O3 nanowires supported single-atom silver catalyst (i.e., 0.06 wt% Ag/Mn2O3) exhibited ...excellent catalytic activity for toluene combustion, with the temperatures required for 50 and 90% of toluene conversions being 170 and 205 °C, respectively, at a space velocity of 40,000 mL/(g h). However, the toluene conversion at 205 °C quickly decreased from 90 to 30% within 2.5 h of on-stream reaction. Based on the various characterization results, we found that there were no aggregation of Ag particles, no change in crystal structure of the Mn2O3 nanowire support, and no carbon deposition on the catalyst surface, and the quick deactivation of 0.06 wt% Ag/Mn2O3 was mainly associated with the low oxygen activation ability. The proper CeO2 addition to the 0.06 wt% Ag/Mn2O3 catalyst was found to not only improve the catalytic activity but also significantly enhance the stability of the catalyst. Toluene conversion at 195 °C over 0.63 wt% CeO2-0.06 wt% Ag/Mn2O3 decreased by only 10% in 50 h of on-stream reaction. Because Ag and CeO2 particles were highly dispersed on the Mn2O3 nanowire support, the oxygen species formed at the surface oxygen vacancies of CeO2 could efficiently migrate to the active sites (i.e., the interface of Ag-Mn2O3) and replenish the surface reactive lattice oxygen species. Thus, the present single-atom silver catalyst is an alternative for commercial noble metal catalysts for the removal of VOCs.
An in situ molten salt strategy is developed for the convenient preparation of Mn2O3 nanowires-supported single-atom silver catalysts with high activity for toluene oxidation. The significant enhancement in catalytic stability of the ceria-modified single-atom silver catalyst is due to the timely replenishment of the surface reactive lattice oxygen species. Display omitted
•Single-atom Ag catalyst is prepared using an in situ molten salt method.•Single-atom Ag catalyst exhibits high catalytic activity for toluene removal.•Ce-doping greatly enhances catalytic stability of single-atom Ag catalyst.•Timely replenishment of surface reactive lattice oxygen species is important.•Single-atom Ag catalyst is an alternative for commercial noble metal catalysts.
A novel composite monolithic column based on graphene oxide–trimethyl-2-methacroyloxyethylammonium chloride-titania (GO-META-TiO2) was developed for the enrichment of phosphopeptides. META was ...proposed as a “bridge” to connect GO and TiO2 species to prepare GO-META-TiO2 composite. This high surface area composite (surface area = 196.93 m2 g−1) was fixed in the monolithic column via an in situ UV polymerization process. In-tube solid phase microextraction (IT-SPME) using this composite was coupled with matrix-assisted laser desorption ionization time-of-flight–mass spectrometry (MALDI-TOF-MS) for the enrichment and detection of phosphorylated peptides from a digestion mixture of α-casein, β-casein, and bovine serum albumin (BSA) in molar ratios of 1:1:1, 1:1:10, and 1:1:100. The key factors affecting the IT-SPME of the phosphopeptides, such as the elution solution concentrations, the extraction flow rate, and the elution flow rate were comprehensively investigated. For further demonstration, this method was employed for the enrichment and detection of phosphorylated peptides from digested chicken egg white. The obtained results indicated that the GO-META-TiO2 composite monolithic column rapidly and efficiently captured the phosphopeptides present in these complex biological samples, even in the 10 fmol β-casein tryptic digest. We therefore propose that the reported GO-META-TiO2 composite monolithic column possesses a suitable affinity for the selective extraction of phosphopeptides from biological samples. This method paves a way in extending the application of nanomaterials.
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•GO-META-TiO2 composite monolithic columns were developed for the IT-SPME of phosphopeptides.•GO-META-TiO2 composites were prepared using META as a “bridge” for in situ growth of TiO2 in the monolithic column.•This method paves a way in extending the application of nanomaterials.
An anomalous enhancement of fluorescence of carbon dots （CDs） was observed via lanthanum （La） doping. La-doped CDs （La-CDs） were prepared through microwave pyrolysis within 4 min. With La^3＋ doping, ...the emission band shifted from blue to green although LaB＋ is non-fluorescent. The quantum yield and fluorescence lifetime improved by about 20% and 35%, respectively. All experiment results indicate that La^3＋ doping is an effective way to tune fluorescence and improve the performance of CDs. Another unique attribute of La-CDs is high sensitivity to Fe^3＋. The La-CD-based fluorescence probe was established and used for sensitive and selective detection of Fe^3＋ with a limit of detection of 91 nmol/L. The proposed fluorescence probe also was successfully employed to visualize intracellular Fe^3＋ in live HeLa cells through cell imaging. It was also shown that yttrium exhibited the same fluorescence enhancement effect as La. The results may provide a new route for preparing CDs with special properties.
In the present work, a strongly chemiluminescence (CL) from the mixing of hydrogen peroxide (H
2O
2), hydrogen carbonate (HCO
3
−) and CdSe/CdS quantum dots (QDs) was observed. The addition of trace ...amount of
l-ascorbic acid into the CL system caused significant quenching luminescence intensity. Based on this phenomenon, a flow injection CL analysis system for the determination of
l-ascorbic acid was developed. The CL reaction conditions, such as mixing orders and concentrations of CL reagents, flow rates, pH, and particle size of quantum dots have been optimized. The CL intensity and the concentration of
l-ascorbic acid have a good linear relationship in the ranges of 1.0
×
10
−7–1.0
×
10
−4
mol
L
−1 (
R
2
=
0.9916). The limit of detection for
l-ascorbic acid is 6.7
×
10
−9
mol
L
−1 (S/N
=
3). This method has been successfully applied to determine
l-ascorbic acid in human serum. The recoveries for the real samples were from 83% to 111% and the variance coefficient was <5.3% for intra- and inter-assay precision. A possible mechanism of the CL system was proposed according to results of the kinetic curves of CdSe/CdS QDs in NaHCO
3–H
2O
2 CL system, the spectra of CL, fluorescent, UV–visible and ESR. Superoxide ion radical (
O
2
−) and hydroxide radical (
OH) were generated between the reaction of NaHCO
3 and H
2O
2, which were the key intermediates for the production of hole, electron-injected CdSe/CdS QDs and the CL emission.
Nitric oxide (NO), as a vital signaling molecule related to different physiological and pathological processes in living systems, is closely associated with cancer and cardiovascular disease. ...However, the detection of NO in real-time remains a difficulty. Here, PtBi alloy nanoparticles (NPs) were synthesized, dealloyed, and then fabricated to NP-based electrodes for the electrochemical detection of NO. Transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and nitrogen physical adsorption/desorption show that dealloyed PtBi alloy nanoparticles (dPtBi NPs) have a porous nanostructure. Electrochemical impedance spectroscopy and cyclic voltammetry results exhibit that the dPtBi NP electrode possesses unique electrocatalytic features such as low charge transfer resistance and large electrochemically active surface area, which lead to its excellent NO electrochemical sensing performance. Owing to the higher density of catalytical active sites formed PtBi bimetallic interface, the dPtBi NP electrode displays superior electrocatalytic activity toward the oxidation of NO with a peak potential at 0.74 V vs. SCE. The dPtBi NP electrode shows a wide dynamic range (0.09–31.5 μM) and a low detection limit of 1 nM (3σ/k) as well as high sensitivity (130 and 36.5 μA μM
−1
cm
−2
). Moreover, the developed dPtBi NP-based electrochemical sensor also exhibited good reproducibility (RSD 5.7%) and repeatability (RSD 3.4%). The electrochemical sensor was successfully used for the sensitive detection of NO produced by live cells. This study indicates a highly effective approach for regulating the composition and nanostructures of metal alloy nanomaterials, which might provide new technical insights for developing high-performance NO-sensitive systems, and have important implications in enabling real-time detection of NO produced by live cells.
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