Recent progress in single-molecule fluorescence technology in nanocatalysis

Nanoparticles(NPs)play a vital role in the energy catalysis process,so understanding the heterogeneous catalytic properties of nanocatalysts is of great significance for rationally guiding the design of catalysts.However,the traditional method obtains the average information based on the whole and cannot study the catalytic activity of a single nanoparticle.It is critical to investigate the catalytic activity of individual nanoparticles using in situ techniques.This review summarizes some of Prof.Xu's recent accomplishments in studying the catalytic behavior of nanoparticles at the single-particle level using single-molecule fluorescence microscopy(SMFM).These achievements include revealing the effect of size,shape,and surface atoms of Pd nanoparticles on catalytic kinetics and dynamics as well as obtaining the activation energy of single Au nanoparticles for catalytic reactions by single-molecule methods.It is the first time to study the kinetics and dynamics of single-atom Pt catalysts.Furthermore,the method was extended to study the Pt deactivation process for hydrogen oxidation reactions as well as the catalytic kinetics of two-electron oxygen reduction reactions of individual Fe3O4 nanoparticles in electrocatalysis.Finally,single-molecule super-resolution techniques were used to observe the evolution of the activity of single Sb doped TiO2 nanorod domains.These studies are of guiding significance for in-depth understanding and realization of rational design of optimal catalysts.

Active catalytic species generated in situ in zirconia incorporated hydrogen storage material magnesium hydride

This study explores how zirconia additive interacts with MgH_(2)to improve its hydrogen storage performance.Initially it is confirmed that the zirconia added MgH_(2)powder releases hydrogen at a temperature of about 50℃below that of the additive free MgH_(2).Subsequent tests by X ray diffraction(XRD)and infrared(IR)spectroscopy techniques reveal that the ZrO_(2) mixed MgH_(2)powder contains ZrHx(2<x>1.5)and MgO secondary phases.This observation is supported by the negative Gibbs free energy values obtained for the formation of ZrH_(2)/MgO from ZrO_(2)/MgH_(2)powder samples.An X ray photoelectron spectroscopy(XPS)study reveals that apart from Zr^(4+)cations,Zr^(2+) and zero valent Zr exist in the powder.Atomic force microscopy(AFM)study reveals that the average grain size is 20 nm and the elemental line scan profiles further proves the existence of oxygen deficient Zr bearing phase(s).This study strengthens the belief that functional metal oxide additives in fact chemically interact with MgH_(2)to make active in-situ catalysts in the MgH_(2)system.

Pd-Ni nanoparticles supported on titanium oxide as effective catalysts for Suzuki-Miyaura coupling reactions

We have successfully prepared a series of Pd- Ni/TiO2 catalysts by a one-step impregnation-reduction method. Among these catalysts with different compositions of Ni and Pd, the one with the Ni：Pd ratio of 2.95 showed the best activity. Small monodispersed Pd-Ni bimetallic nanoparticles were loaded on the surface of titanium oxide nanopowder as confirmed with TEM and EDS mapping. The XPS analysis demonstrated that Pd exists as 31% Pd（II） species and 69% Pd（0） species and all nickel is Ni（II）. The prepared Pd-Ni/TiO2 exhibited enhanced catalytic activity compared to an equal amount of Pd/TiO2 for Suzuki-Miyaura reactions together with excellent applicability and reusability.

Resonance scattering spectral detection of ultratrace IgG using immunonanogold-HAuCl_4-NH_2OH catalytic reaction

Nanogold particles of 10 nm were used to label goat anti-human IgG (GIgG) to obtain nanogold-labeled GIgG (AuGIgG). In a citrate-HCl buffer solution of pH 2.27,AuGIgG showed a strong catalytic effect on the reaction between HAuCl4 and NH2OH to form big gold particles that exhibited a resonance scatter-ing (RS) peak at 796 nm. Under the chosen conditions,AuGIgG combined with IgG to form immuno-complex AuGIgG-IgG that can be removed by centrifuging at 16000 r/min. AuGIgG in the centrifuging solution also showed catalytic effect on the reaction. On those grounds,an immunonanogold catalytic RS assay for IgG was designed. With addition of IgG,the amount of AuGIgG in the centrifuging solution decreased; the RS intensity at 796 nm (I796 nm) decreased linearly. The decreased intensity ΔI796 nm was linear with respect to the IgG concentration in the range of 0.08-16.0 ng·mL-1 with a detection limit of 0.02 ng·mL-1. This assay was applied to analysis of IgG in sera with satisfactory sensitivity,selectivity and rapidity.

Electrocatalytic acidic oxygen evolution reaction:From nanocrystals to single atoms

Hydrogen is the most preferred choice as an energy source to replace the nonrenewable energy resources such as fossil fuels due to its beneficial features of abundance,ecofriendly,and outstanding gravimetric energy density.Splitting water through a proton exchange membrane(PEM)electrolyzer is a well-known method of hydrogen production.But the major impediment is the sluggish kinetics of oxygen evolution reaction(OER).Currently,scientists are struggling to build out an acid-stable electrocatalyst for OER with low overpotential and excellent stability.In this review,the reaction mechanism and characterization parameters of OER are introduced,and then the improvement method of metal nanocatalysts(noble metal catalysts and noble metal-free catalysts)in acidic media is discussed.Particularly,the application of single-atom catalysts in acidic OER is summarized,which is current researching focus.At the same time,we also briefly introduced the cluster phenomenon,which is easy to occur in the preparation of single-atom catalysts.More importantly,we summarized the in situ characterization methods such as in situ X-ray absorption spectroscopy,in situ X-ray photoelectron spectroscopy,and so forth,which are conducive to further understanding of OER reaction intermediates and active sites.Finally,we put forward some opinions on the development of acidic OER.

Nanocatalytic resonance scattering spectral analysis

The resonance scattering spectral technique has been established using the synchronous scanning technique on spectrofluorometry.Because of its advantages of simplicity,rapidity and sensitivity,it has been widely applied to analyses of proteins,nucleic acids and inorganic ions.This paper summarizes the application of immunonanogold and aptamer modified nanogold(AptAu) catalytic resonance scattering spectral technique in combination with the work of our group,citing 53 references.

Catalyst-free multicomponent polymerization of sulfonyl azide,aldehyde and cyclic amino acids toward zwitterionic and amphiphilic poly(N-sulfonyl amidine)as nanocatalyst precursor

Polymers with metal coordination ability are outstanding precursors of nanocatalysts,attracting numerous attention in nanocatalysis area.It has been rarely reported for the poly(N-sulfonyl amidines)as macromolecular ligands for nanocatalysis.Herein,a catalyst-free multicomponent polymerization(MCP)strategy is developed to facilely prepare a library of amphiphilic poly(Nsulfonyl amidines)with zwitterionic properties starting from disulfonyl azide,hydrophilic dialdehyde and cyclic amino acids including proline and pipecolinic acid.Metals or additives can be thorougly avoided through this method.All the obtained polymers have well-defined structures,high yields and weight-average molecular weights(M_(w)s,up to 99,300 g/mol).The unique zwitterionic property,amphiphilicity and Cu(Ⅰ)coordination ability of the obtained poly(N-sulfonyl amidines)endow them to form the polymer-Cu(Ⅰ)complexes as nanocatalysts.Such nanocatalysts exhibit high catalytic efficiency in aqueous Cucatalyzed azide-alkyne cycloaddition(CuAAC)reaction at a low Cu(Ⅰ)loading of 50 ppm.Nanocatalysts with a high ratio of polymers to Cu(Ⅰ)have also been demonstrated with Cu(Ⅰ)stabilization ability.This work provides a“green”MCP method toward zwitterionic and amphiphilic poly(N-sulfonyl amidines),and highlights their unique potentials for nanocatalysis.