Core-shell Nanoparticle Films Research Articles

CsPbBr3@SiO2 Core–Shell Nanoparticle Films for Superhydrophobic Coatings

CsPbBr₃@SiO₂ Core–Shell Nanoparticle Films for Superhydrophobic Coatings

Au–Pd core–shell nanoparticle film for optical detection of hydrogen gas

Hydrogen use, as a clean and almost infinite energy source, has an economic impact in many industries. The problem is that this gas cannot be used like any gas because of its explosiveness at 4% in the air, hence the need to know its concentration any time for security reasons. The permanent detection of hydrogen leaks is essential to monitor and to control the hydrogen concentration to prevent any possible risk. In our current research, we have developed hydrogen ultrasensitive sensors by depositing a thin film of Au–Pd core–shell nanoparticles (NPs) on a transparent glass substrate in order to detect hydrogen in its gaseous form. The colloidal Au–Pd core–shell NPs were synthesized according to a multi-reduction step method. The structural characterizations, the nature, and the density of Au–Pd core–shell NPs have been characterized by scanning electron microscopy and transmission electron microscopy. The morphology, size, and structure of Au–Pd core–shell NPs can be controlled under synthesis conditions. The size of the core–shell studied in this work is 13 nm for gold NP diameter and 0 nm–2.3 nm for palladium thicknesses. The physical properties of NPs, such as the optical absorbance response under hydrogen, strongly depend on the nature of the shell and the ratio between the core and the shell. At different hydrogen concentrations ranging from 1% to 4%, the optical response changes in the position of the surface plasmon resonance peak on the absorbance spectrum after the first loading/unloading hydrogen cycle.

TiO2@TiO2−xHx core-shell nanoparticle film/Si heterojunction for ultrahigh detectivity and sensitivity broadband photodetector

A simple hydrogenation treatment is used to synthesize unique oxygen-deficient TiO2 with a core/shell structure (TiO2@TiO2−xHx), superior to the high H2-pressure process (under 20 bar for five days). It is demonstrated that oxygen-deficient TiO2 nanoparticle film/Si heterojunction possesses improved photoresponse performance compared to the untreated TiO2 nanoparticle film/Si heterojunction. Particularly, under 900 nm of 0.5 μW cm−2, the oxygen-deficient TiO2 nanoparticle film (TiO2@TiO2−xHx core–shell nanoparticle film)/Si heterojunction shows high responsivity (R) of 336 A W−1, prominent sensitivity (S) of 1.3 × 107 cm2 W−1, accompanied with a fast rise and decay time of 6 and 5 ms, respectively. Significantly, the detectivity (D*) of the photodetector is up to 1.17 × 1014 cm Hz1/2 W−1, which is better than that reported in metal oxide nanomaterials/Si heterojunction photodetectors, and is 4–5 orders of magnitude higher than some 2D nanosheets/Si heterojunctions of 109–1010 cm Hz1/2 W−1, indicating the excellent ability to detect weak signals. The oxygen vacancies generated in amorphous shell TiO2−xHx make the Fermi level of TiO2−x shift near the conduction band minimum and can lead to reduced dark current. The high absorption and reduced dark current of the heterojunction ensure excellent photoresponse properties of oxygen-deficient TiO2 nanoparticle film/Si heterojunction. The H-reduced oxygen-deficient amorphous shell may be an excellent candidate to enhance the photoresponse performance of metal oxide/Si heterojunction.

多层Au-Pd核壳纳米颗粒膜增敏的光纤氢气传感器

多层Au-Pd核壳纳米颗粒膜增敏的光纤氢气传感器

Steering the magnetic properties of Ni/NiO/CoO core-shell nanoparticle films: The role of core-shell interface versus interparticle interactions

Supported core-shell Ni/NiO/CoO nanoparticle (NP) films were obtained by deposition of preformed and mass-selected Ni NPs on a buffer layer of CoO, followed by a top CoO layer. The resulting NPs have core/shell morphology, with a McKay icosahedral Ni core and a partially crystalline CoO shell. X-ray photoelectron spectroscopy evidenced the presence of a thin NiO layer, which was shown to be between the Ni core and the CoO shell by elemental TEM mapping. CoO and NiO shells with different thickness values were obtained, allowing us to investigate the evolution of the magnetic properties of the NP assemblies as a function of the oxide shell thickness. Both exchange-coupling and magnetostatic interactions significantly contribute to the magnetic behavior of Ni/NiO/CoO NP films. After the Ni/NiO/CoO NPs are cooled in a weak magnetic field, they have blocking temperature higher than room temperature because of strong magnetostatic interactions, which support the formation of a spin-glass-like state below $\ensuremath{\sim}250\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Exchange coupling dominates the magnetic behavior after the NPs are cooled in a strong magnetic field. The exchange bias (EB) is in the 0.17--2.35 kOe range and strongly depends on the CoO thickness (0.4--2.7 nm), showing the onset of the EB at the few-nanometer scale. The switching field distribution showed that the EB opposes the magnetization reversal from the direction along the cooling field but it does not significantly ease the opposite process. The EB depends on ${t}_{\mathrm{CoO}}$ only for ${t}_{\mathrm{NiO}}\ensuremath{\le}0.5\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$, but when NiO is 0.7 nm thick it strongly interacts with CoO and a large increase of the EB and coercivity is observed.

Solar evaporation enhancement by a compound film based on Au@TiO2 core–shell nanoparticles

Abstract Solar water evaporation attracts much attention owing to its widespread applications, including in power generation, seawater desalination, wastewater treatment, and clean water production. A multilayer thin film with a physically combined structure has been designed to achieve multi-functionality. However, this film leads to a decline in the evaporation capacity because of the mutual influences of different layers. In this work, a compound film based on Au@TiO 2 core–shell nanoparticles was designed and fabricated for achieving highly efficient solar water evaporation. The effects on solar evaporation enhancement of different evaporation styles, nanoparticle films, and light intensities were determined by solar evaporation experiments. It was found that the core–shell nanoparticle film showed better solar evaporation enhancement than the suspension of Au@TiO 2 core–shell nanoparticles, films based on solely Au or TiO 2 nanoparticles, and multilayer thin films of Au and TiO 2 nanoparticles because of the formation of a core–shell nanostructure. The solar evaporation enhancement achieved by the Au@TiO 2 core–shell nanoparticle film could simplify the film structures, reduce costs, and expand their applicability.

Bifunctional Au@TiO2 core–shell nanoparticle films for clean water generation by photocatalysis and solar evaporation

With water scarcity becoming an increasingly critical issue for modern society, solar seawater desalination represents a promising approach to mitigating water shortage. In addition, solar seawater desalination shows great potential for mitigating the energy crisis due to its high photo-thermal conversion efficiency. However, the increasing contamination of seawater makes it difficult to generate clean water through simple desalination processes. In this work, clean water is generated by a newly designed bifunctional Au@TiO2 core-shell nanoparticle film with a high photo-thermal conversion efficiency that is capable of photocatalysis and solar evaporation for seawater desalination. Bifunctional films of Au@TiO2 core-shell nanoparticles with good stability were prepared. It was found that the formation of the core-shell structures played a key role in promoting the photo-thermal conversion efficiency and the evaporation of seawater, while the photocatalytic function demonstrated herein could contribute to the purification of polluted seawater. Furthermore, the film structure can serve to concentrate the NPs for the photo-reaction, as well as heat for water evaporation, improving both the photo-reaction efficiency and photo-thermal conversion efficiency. This efficient approach to solar seawater desalination, which combines evaporation with the photodegradation of pollutants, could help to address the dual issues of water scarcity and water pollution.

Investigation of Ni@CoO core-shell nanoparticle films synthesized by sequential layer deposition

Films of Ni@CoO core-shell nanoparticles (NP Ni core size d≈11nm) have been grown on Si/SiOx and lacey carbon supports, by a sequential layer deposition method: a first layer of CoO was evaporated on the substrate, followed by the deposition of a layer of pre-formed, mass-selected Ni NPs, and finally an overlayer of CoO was added. The Ni NPs were formed by a magnetron gas aggregation source, and mass selected with a quadrupole mass filter. The morphology of the films was investigated with Scanning Electron Microscopy and Scanning Transmission Electron Microscopy. The Ni NP cores have a shape compatible with McKay icosahedron, caused by multitwinning occurring during their growth in the source, and the Ni NP layer shows the typical random paving growth mode. After the deposition of the CoO overlayer, CoO islands are observed, gradually extending and tending to merge with each other, with the formation of shells that enclose the Ni NP cores. In situ X-ray Photoelectron Spectroscopy showed that a few Ni atomic layers localized at the core-shell interface are oxidized, hinting at the possibility of creating an intermediate NiO shell between Ni and CoO, depending on the deposition conditions. Finally, X-ray Magnetic Circular Dichroism at the Ni L2,3 absorption edge showed the presence of magnetization at room temperature even at remanence, revealing the possibility of magnetic stabilization of the NP film.

Investigation on the Photocatalytic Efficiency of Ag@TiO2 Core–Shell Nanoparticle Films

Investigation on the Photocatalytic Efficiency of Ag@TiO<SUB>2</SUB> Core–Shell Nanoparticle Films

Synthesis of oxidation-resistant core–shell copper nanoparticles

We present a simple method to synthesize non-oxidizable copper nanoparticles surrounded by copper formate. The formation of the core–shell nanoparticles was achieved via surface reaction induced by the injection of formic acid on the preformed core particles. High resolution transmission electron microscopy revealed that copper particles with a diameter of 77 nm are conformally surrounded by a 5 nm thick layer of copper formate, which prevents oxidation of the copper. This non-metallic shell was readily reduced to Cu during low temperature annealing without leaving behind organic residues, resulting in highly conductive films with a resistivity of 13.5 μΩ cm after annealing at 250 °C for 1 h in nitrogen. Time- and temperature-dependent sheet resistance measurements demonstrated that the resistivity of the core–shell nanoparticle films will double after exposure to an ambient atmosphere at room temperature for 27 years. Our core–shell Cu nanoparticles are a promising and cost-effective alternative to silver nanoparticles for the efficient production of printed conductors with enhanced chemical stability.

Fabrication and optical study of Ag@SnO2 core-shell structure nanoparticle thin films

Ag@SnO2 core-shell nanoparticles dispersed in poly-(vinyl) alcohol films were fabricated on glass substrate by employing a dip-coating technique. Synthesis of Ag@SnO2 nanoparticles with core-shell morphology is carried out by a soft-chemical technique in aqueous phase at 60°C. Formation of core-shell structure is monitored by the red-shift of the surface plasmon band of Ag nanoparticles (from 390 to 410 nm) in the UV-visible spectrum. These nanoparticles are deposited on the glass substrate. The structure and morphology of these films were investigated by X-ray diffraction technique and field-emission transmission electron microscopy, respectively. Optical properties of these pseudo-solids were studied by UV-visible spectroscopy. Surface plasmon spectrum of the core-shell nanoparticles film remained unaltered with increase in the number of layers. However, silver nanoparticles films have shown peak broadening and development of additional peaks with increase in the number of layers. Our investigations showed that the surface plasmon band of the silver nanoparticles could be preserved by controlled deposition of the tin dioxide shell.

Hole transport in sensitized CdS–NiO nanoparticle photocathodes

A general chemical approach was used to synthesise NiO-CdS core-shell nanoparticle films as photocathodes for p-type semiconductor-sensitized solar cells. Compared to dye-sensitized NiO photocathodes, the CdS-sensitized NiO cathodes exhibited two orders of magnitude faster hole transport (attributable to the passivation of surface traps by the CdS) and almost 100% charge-collection efficiencies.

Formation of Metal-Semiconductor Core-shell Nanoparticles Using Electrochemical Atomic Layer Deposition

We report the synthesis of CuI coated and CdS coated Au core-shell nanoparticle films using electrochemical atomic layer deposition (EC-ALD). Au nanoparticle thin films were prepared on glassy carbon supports by depositing alternating layers of poly-(diallyl dimethylammonium)-stabilized Au nanoparticles and CoP2W17061 8- polyoxometallate interlayers. CuI was deposited onto the surface of Au nanoparticles using electrochemical atomic layer epitaxy, while CdS films were grown by an atom-by-atom co-deposition technique. The semiconductor coated nanoparticles were characterized by electrochemistry, photoluminescence spectroscopy, and Raman spectroscopy. Our results indicate that the semiconductors are deposited onto the Au nanoparticles surface by surface limited electrochemical reactions.

Electrochemical properties of core-shell TiC–TiO2nanoparticle films immobilized at ITO electrode surfaces

Titanium carbide (TiC) nanoparticles are readily deposited onto tin-doped indium oxide (ITO) electrodes in the form of thin porous films. The nanoparticle deposits are electrically highly conducting and electrochemically active. In aqueous media (at pH 7) and at applied potentials positive of 0.3 V vs. SCE partial anodic surface oxidation and formation (at least in part) of novel core-shell TiC-TiO2 nanoparticles is observed. Significant thermal oxidation of TiC nanoparticles by heating in air occurs at a temperature of 250 degrees C and leads first to core-shell TiC-TiO2 nanoparticles, next at ca. 350 degrees C to TiO2 (anatase), and finally at temperatures higher than 750 degrees C to TiO2 (rutile). Electrochemically and thermally partially oxidized TiC nanoparticles still remain very active and for some redox systems electrocatalytically active. Scanning and transmission electron microscopy (SEM and TEM), temperature dependent XRD, quartz crystal microbalance, and voltammetric measurements are reported. The electrocatalytic properties of the core-shell TiC-TiO2 nanoparticulate films are surveyed for the oxidation of hydroquinone, ascorbic acid, and dopamine in aqueous buffer media. In TiC-TiO2 core-shell nanoparticle films TiO2 surface reactivity can be combined with TiC conductivity.

Transport of Charge Carriers in HgTe/CdTe Core-Shell Nanoparticle Film

HgTe and HgTe/CdTe core-shell structured nanoparticles were synthesized by the colloidal method. The photoluminescence (PL) spectrum of a HgTe/CdTe nanoparticle film exhibited an exciton peak at 700 nm, which was blue-shifted by about 400 nm for the HgTe nanoparticle film. The current–voltage curves and photoresponse of the HgTe/CdTe nanoparticle film were compared with those of the HgTe nanoparticle film. When the film is exposed to light, the current of the HgTe/CdTe nanoparticle film decreases in the ambient air while increasing in vacuum. Finally, the temperature dependence of the photocurrent is discussed in this paper.