Fabrication, Characterization, and Photoelectrochemical Properties of Cu-Doped PbTiO3and Its Hydrogen Production Activity

Investigations on the EPR g factors and local structures for the orthorhombic and tetragonal Cu2+ centers in Pb[Zr0.54Ti0.46]O3

The defect models of the orthorhombical and tetragonal Cu2+ centers in Pb[Zr0.54Ti0.46]O3 are attributed to Cu2+ ions occupying the sixfold coordinated octahedral Ti4+ site with and without charge compensation, respectively. The electron paramagnetic resonance (EPR) g factors gi (i = x, y, z) of the Cu2+ centers in Pb[Zr0.54Ti0.46]O3 are theoretically studied by using the perturbation formulas of a 3d9 ion under orthorhombically and tetragonally elongated octahedra. Based on the calculation, the impurity off-center displacements are about 0.253 and 0.162 Å for the orthorhombical and tetragonal Cu2+ centers, respectively. Meanwhile, the planar Cu2+-O2- bonds are found to experience the relative variation ΔR (≈0.102 Å) along the a- and b-axes for the orthorhombical Cu2+ center due to the Jahn-Teller (JT) effect. The theoretical EPR g factors based on the above local structures agree well with the observed values.

Recent Advances in Ferroelectric Materials-Based Photoelectrochemical Reaction

Inorganic perovskite ferroelectric-based nanomaterials as sustainable new energy materials, due to their intrinsic ferroelectricity and environmental compatibility, are intended to play a crucial role in photoelectrochemical field as major functional materials. Because of versatile physical properties and excellent optoelectronic properties, ferroelectric-based nanomaterials attract much attention in the field of photocatalysis, photoelectrochemical water splitting and photovoltaic. The aim of this review is to cover the recent advances by stating the different kinds of ferroelectrics separately in the photoelectrochemical field as well as discussing how ferroelectric polarization will impact functioning of photo-induced carrier separation and transportation in the interface of the compounded semiconductors. In addition, the future prospects of ferroelectric-based nanomaterials are also discussed.

Ag nanoparticles/PbTiO3 with in-situ photocatalytic process and its application in an ultra-sensitive molecularly imprinted hemoglobin detection

An electrochemical sensor based on loading molecularly imprinted polymers (MIP) on the material surface can improve the specificity towards the object. In this work, a T-shaped PbTiO₃ with a high active-exposed (110) facet was prepared by a hydrothermal process. Then, Ag nanoparticles (Ag NPs) modified T-shaped PbTiO₃ was obtained by in-situ photocatalytic reduced method under UV irradiation, where a hetero-junction was formed with a well lattice matching between the (111) facet of Ag⁰ and the (110) facet of PbTiO₃. A MIPs modified by Ag nanoparticles (NPs)/PbTiO₃ (MAP) electrodes was prepared via electro polymerization process by o-Phenylenediamine (o-PD) in the presence of the template molecule, bovine hemoglobin (BHb), i.e., the detected molecule. The response peak current and concentration of BHb is demonstrated with a good linear relationship in the range of 0.00294-0.41 nM (R² =0.98), and the detection limit at 0.23 pM (S/N = 3). A heterojunction between Ag NPs and high- active facet of PbTiO₃ is beneficial to oxidizing electroactive material ([Fe (CN)₆]^3-/4-), generating more BHb-imprinting cavities on the modified electrode and improving the sensitivity of sensor. The electrochemical sensor is with a simple, stable structure and high sensitivity to BHb detection. Furthermore, the sensor was successfully applied to detect BHb in the bovine serum samples.

Harnessing Plasmon-Induced Hot Carriers at the Interfaces With Ferroelectrics

This article reviews the scientific understanding and progress of interfacing plasmonic particles with ferroelectrics in order to facilitate the absorption of low-energy photons and their conversion to chemical fuels. The fundamental principles of hot carrier generation and charge injection are described for semiconductors interfaced with metallic nanoparticles and immersed in aqueous solutions, forming a synergistic juncture between the growing fields of plasmonically-driven photochemistry and semiconductor photocatalysis. The underlying mechanistic advantages of a metal-ferroelectric vs. metal-nonferroelectric interface are presented with respect to achieving a more optimal and efficient control over the Schottky barrier height and charge separation. Notable recent examples of using ferroelectric-interfaced plasmonic particles have demonstrated their roles in yielding significantly enhanced photocurrents as well as in the photon-driven production of molecular hydrogen. Notably, plasmonically-driven photocatalysis has been shown to occur for photon wavelengths in the infrared range, which is at lower energies than typically possible for conventional semiconductor photocatalysts. Recent results thus demonstrate that integrated ferroelectric-plasmonic systems represent a potentially transformative concept for use in the field of solar energy conversion.

Erratic charge transfer dynamics of Au/ZnTiO3 nanocomposites under UV and visible light irradiation and their related photocatalytic activities

The present article presents an in-depth discussion on the state-of-the-art multifarious roles of Au nanoparticles and their associated charge anti-recombination process in burgeoning photocatalysis research. Hexagonal-phase ZnTiO₃ was fabricated through a sol-gel auto-combustion method by optimizing the calcination temperatures. To further improve the charge separation efficiency and visible light induced photocatalytic activity of pristine ZnTiO₃, we designed a new type of Au/ZnTiO₃ nanocomposite by a precipitation-deposition method. The photocatalytic activities of the Au/ZnTiO₃ nanocomposites were substantiated by evaluating the rate of hydrogen evolution under both UV and visible light illumination. The photocatalytic activity of the Au/ZnTiO₃ nanocomposites rises proportionally with an increase in Au content up to 1.5 wt% under UV light illumination and it produce around 285 μmol h^-1 of H₂ which is approximately 2.6 times higher than that produced by pristine ZnTiO₃. Therefore, the Au nanoparticles present on the surface of ZnTiO₃ act as electron acceptors, leading to an increase in the rate of generation and separation of charge carriers. This process helps to enhance the congregation of electrons on Au nanoparticles through the Schottky junction. The obtained results are very consistent with steady-state PL and UV light induced photocurrent measurements. Conversely, such a trend was not detected under visible light illumination. The visible light induced photocatalytic activity of Au/ZnTiO₃ nanocomposites increases with a rise in Au content up to 1 wt% and thereafter decreases with further Au loading. Therefore, the initial increment in photocatalytic activity is due to the generation, separation and participation of a large number of SPR-induced charge carriers and thereafter decreases due to the recombination of SPR-generated charge carriers because of the formation of defect sites at the Au and ZnTiO₃ interface. That the excess Au loading causes the recombination of SPR charge carriers was well explained by undertaking SPR-induced TRPL analysis and this result is directly followed up with the results of visible light induced photocurrent and EIS measurements. The Au/ZnTiO₃ nanocomposites with optimal Au loading (1 wt%) delivered an amazingly high rate of hydrogen evolution i.e. 108 μmol h^-1 with an energy conversion efficiency of 7.14%, whereas pristine ZnTiO₃ shows negligible activity under visible light illumination.

Ferroelectric Materials: A Novel Pathway for Efficient Solar Water Splitting

Over the past few decades, solar water splitting has evolved into one of the most promising techniques for harvesting hydrogen using solar energy. Despite the high potential of this process for hydrogen production, many research groups have encountered significant challenges in the quest to achieve a high solar-to-hydrogen conversion efficiency. Recently, ferroelectric materials have attracted much attention as promising candidate materials for water splitting. These materials are among the best candidates for achieving water oxidation using solar energy. Moreover, their characteristics are changeable by atom substitute doping or the fabrication of a new complex structure. In this review, we describe solar water splitting technology via the solar-to-hydrogen conversion process. We will examine the challenges associated with this technology whereby ferroelectric materials are exploited to achieve a high solar-to-hydrogen conversion efficiency.

Effect of Au nanorods on potential barrier modulation in morphologically controlled Au@Cu2O core-shell nanoreactors for gas sensor applications

In this work, Au@Cu2O core-shell nanoparticles (NPs) were synthesized by simple solution route and applied for CO sensing applications. Au@Cu2O core-shell NPs were formed by the deposition of 30-60 nm Cu2O shell layer on Au nanorods (NRs) having 10-15 nm width and 40-60 nm length. The morphology of Au@Cu2O core-shell NPs was tuned from brick to spherical shape by tuning the pH of the solution. In the absence of Au NRs, cubelike Cu2O NPs having ∼200 nm diameters were formed. The sensor having Au@Cu2O core-shell layer exhibited higher CO sensitivity compared to bare Cu2O NPs layer. Tuning of morphology of Au@Cu2O core-shell NPs from brick to spherical shape significantly lowered the air resistance. Transition from p- to n-type response was observed for all devices below 150 °C. It was demonstrated that performance of sensor depends not only on the electronic sensitization of Au NRs but also on the morphology of the Au@Cu2O core-shell NPs.