Nanoparticle (NP) high pressure behavior has been extensively studied over the years. In this review, we summarize recent progress on the studies of pressure induced NP phase behavior, property, and applications. This review starts with a brief overview of high pressure characterization techniques, coupled with synchrotron X-ray scattering, Raman, fluorescence, and absorption. Then, we survey the pressure induced phase transition of NP atomic crystal structure including size dependent phase transition, amorphization, and threshold pressures using several typical NP material systems as examples. Next, we discuss the pressure induced phase transition of NP mesoscale structures including topics on pressure induced interparticle separation distance, NP coupling, and NP coalescence. Pressure induced new properties and applications in different NP systems are highlighted. Finally, outlooks with future directions are discussed.

Pressure Induced Nanoparticle Phase Behavior, Property, and Applications

Here, a new three-dimensional (3D) multi-shell Fe3O4/SiO2/ZnO/ZnSe (FSZ-ZnSe) photocatalyst with a type II heterostructure was successfully produced by a convenient synthetic route. The amount of ZnSe particles can be regulated by varying the reactant concentration, and five kinds of FSZ-ZnSe samples (FSZ-ZnSe0, FSZ-ZnSe1, FSZ-ZnSe2, FSZ-ZnSe3 and FSZ-ZnSe4) were obtained. The photocatalytic performances of all as-prepared samples under UV and visible light irradiation were evaluated by the photocatalytic elimination of rhodamine B (RhB) aqueous solution. No matter which light source was used, the FSZ-ZnSe3 sample exhibited enhanced photocatalytic activity in comparison with other samples, benefiting from the sensitization of a proper amount of ZnSe particles, which not only facilitated the separation of photo-induced carriers but also extended the light absorption. Moreover, compared to visible light radiation, the FSZ-ZnSe3 sample under UV light showed remarkably enhanced degradation efficiency toward RhB base on the Z-scheme type transfer of photo-generated electron-hole pairs. The Z-scheme mechanism was confirmed using radical trapping experiments and hydroxyl radical ( OH) formation determination study. Meanwhile, the FSZ-ZnSe3 sample exhibited excellent magnetic response and high stability during the recycling photocatalytic experiments.

Optimized design of three-dimensional multi-shell Fe3O4/SiO2/ZnO/ZnSe microspheres with type II heterostructure for photocatalytic applications

Structure and order in cobalt/platinum-type nanoalloys: from thin films to supported clusters

Photocatalytic degradations of three dyes with different chemical structures using ball-milled TiO2

Unsupported bimetallic Co/Pt nanoparticles (NPs) of 4.4 ± 1.9 nm can be easily obtained by a simple reaction of [bis(cylopentadienyl)cobalt(II)] and [tris(dibenzylideneacetone) bisplatinum(0)] complexes in 1-n-butyl-3-methylimidazolium hexafluorophosphate IL at 150 °C under hydrogen (10 bar) for 24 h. These bimetallic NPs display core–shell like structures in which mainly Pt composes the external shell and its concentration decreases in the inner-shells (CoPt3@Pt-like structure). XPS and EXAFS analyses show the restructuration of the metal composition at the NP surface when they are subjected to hydrogen and posterior H2S sulfidation, thus inducing the migration of Co atoms to the external shells of the bimetallic NPs. Furthermore, the isolated bimetallic NPs are active catalysts for the Fischer–Tropsch synthesis, with selectivity for naphtha products.

Straightforward synthesis of bimetallic Co/Pt nanoparticles in ionic liquid: atomic rearrangement driven by reduction–sulfidation processes and Fischer–Tropsch catalysis

Preparation of morphology-controlled TiO2 nanocrystals for the excellent photocatalytic activity under simulated solar irradiation

A set of CoxPt100−x nanoparticles (NPs) was synthesized by the sol–gel method. The structure and magnetic properties of the produced samples were investigated by x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and a vibrating sample magnetometer. When the Co content ranged from 25 to 75 at%, the results of XRD, HRTEM and SAED revealed the formation of L12 CoPt3, L10 CoPt and face-centred cubic Co3Pt NPs. Magnetic measurements indicated that CoPt3 and Co3Pt had soft magnetic properties. When the Co composition was 50 at%, the sample coercivity reached a giant value of ∼470 kA m−1.

http://iopscience.iop.org/article/10.1088/0022-3727/45/48/485001/pdf

Fabrication, structure and magnetic properties of CoPt3, CoPt and Co3Pt nanoparticles

Tuning red emission and photocatalytic properties of highly active ZnO nanosheets by Eu addition

Calcium fluoride (CaF2) nanoparticles with various terbium (Tb) doping concentrations were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and alternating current (AC) impedance measurement. The original shape and structure of CaF2 nanoparticles were retained after doping. In all the samples, the dominant charge carriers were electrons, and the F− ion transference number increased with increasing Tb concentration. The defects in the grain region considerably contributed to the electron transportation process. When the Tb concentration was less than 3%, the effect of the ionic radius variation dominated and led to the diffusion of the F− ions and facilitated electron transportation. When the Tb concentration was greater than 3%, the increasing deformation potential scattering dominated, impeding F− ion diffusion and electron transportation. The substitution of Ca2+ by Tb3+ enables the electron and ion hopping in CaF2 nanocrystals, resulting in increased permittivity.

https://www.mdpi.com/2079-4991/8/7/532/pdf

Effect of Tb-doped Concentration Variation on the Electrical and Dielectric Properties of CaF₂ Nanoparticles.

The charge transport behavior of barium fluoride nanocrystals has been investigated by in situ impedance measurement up to 23 GPa. It was found that the parameters changed discontinuously at each phase transition. The charge carriers in BaF2 nanocrystals include both F− ions and electrons. Pressure makes both the F− ions diffusion and electronic transport more difficult. The defects at grains dominate the electronic transport process. Pressure could make the charge–discharge processes in the Fm3m and Pnma phases more difficult. The electron conduction plays a dominant role in the transport process. In the Fm3m and Pnma phases, the electron transference number increases with increasing pressure.

/pdf/mixed-conduction-in-baf2-nanocrystals-under-high-pressure-kruxa5ekev.pdf

Jingshu Wang

Papers

Preparation of morphology-controlled TiO2 nanocrystals for the excellent photocatalytic activity under simulated solar irradiation

Fabrication, structure and magnetic properties of CoPt3, CoPt and Co3Pt nanoparticles

Tuning red emission and photocatalytic properties of highly active ZnO nanosheets by Eu addition

Effect of Tb-doped Concentration Variation on the Electrical and Dielectric Properties of CaF₂ Nanoparticles.

Mixed conduction in BaF2 nanocrystals under high pressure