Structure Of Nanocrystals Research Articles

A nanostructured TiZrNbTaMo high-entropy alloy thin film with exceptional corrosion properties for biomedical application

High-entropy alloys (HEAs) have attracted extensive attention for biomedical application due to their excellent corrosion resistance. In this study, a simple body-center cubic TiZrNbTaMo nanostructured high-entropy alloy thin film (HEATF) was synthesized via magnetron sputtering. Its microstructure, phase structure and corrosion properties were identified by SEM, TEM, electrochemical tests and XPS, respectively. The corrosion properties of this nanostructured TiZrNbTaMo HEATF were studied in phosphate buffer solution at 37 ℃. It was found that the nanocrystals were randomly distributed in the HEATF, and the average grain size was statistically counted to be ∼ 70 nm. This nanostructured TiZrNbTaMo HEATF showed a higher open circuit potential value (−328 mVSCE), lower corrosion current density (0.017 μA/cm2) as compared with the traditional Ti6Al4V alloy. The cyclic polarization experiments implied that this nanostructured HEATF was not prone to local corrosion. The constant potential polarization demonstrated that the density of the passive film (k = -0.96) formed on the surface the nanostructured TiZrNbTaMo HEATF was better than that of the Ti6Al4V alloy (k = -0.87). Furthermore, the Mott-Schotty analysis showed that the passive film formed on the nanostructured TiZrNbTaMo HEATF exhibited n-type semiconductor. The donor density was smaller than that of the Ti6Al4V alloy at the same film forming potential, verifying that the HEATF’s passive film had higher stability and lower conductivity. The exceptional corrosion properties of this TiZrNbTaMo HEATF were ascribed to the synergistic effects of multiple elements, nanocrystal structure, and a stable surface passive film formation.

Surface Plasmon Modulation in Cu3-xP Nanocrystals.

We demonstrate modulation of the surface plasmon resonance in nonstoichiometric copper phosphide nanocrystals using spectroelectrochemical methods. Application of an anodic potential resulted in a blue-shift of the surface plasmon resonance and an incremental increase in its extinction coefficient. Conversely, upon application of a cathodic potential, the surface plasmon band red-shifted and reduced in intensity. These changes were found to be reversible over multiple cycles of anodic and cathodic potential steps. We also discuss how the postsynthetic ligand treatment impacts the surface plasmon peak and the structure of Cu3-xP nanocrystals. For example, the addition of alkylthiols resulted in the chemical decomposition of the nanocrystals. This work demonstrates how the surface plasmon peak in Cu3-xP can be used to probe changes in the structure and carrier density in these nanocrystals.

Novel Bulk Quantum Hall Effect in Nanostructured TaP Macroscopic Crystals.

Bulk quantum Hall effect (QHE), the natural extension of the two-dimensional (2D) QHE, is one of the representative phenomena of coherent electron transport. However, bulk QHE has rarely been reported in real materials with macroscopic sizes. Here, we report a novel bulk QHE in macroscopic millimeter-sized and nanostructured TaP crystals consisting of nanometer-scale lamellae. Specifically, the simultaneous quantum plateaus were observed in both transverse resistivity ρxy and vertical resistivity ρzz. The bulk QHE is attributable to synergetic action between Landau cyclotron movement under magnetic field B and periodically modulated potential due to the nanometer-scaled lamellae. This mechanism would form the fixed number of edge states along B-perpendicular and B-parallel directions respectively, equivalent to stacked 2D-QHE layers, leading to quantized ρxy and ρzz. Our work verifies that microstructure engineering could result in the coherent transport of electrons and generate new quantum phenomena in bulk materials.

Comparative Analysis of Structural, Optical, and Electronic Properties of Nickel Oxide and Potassium‐Doped Nickel Oxide Nanocrystals

ABSTRACTMetal oxide semiconductors, known for their exceptional optical transparency, high carrier mobility, and stability, have found extensive use in emerging technologies such as optoelectronics and energy storage devices. Among all metal oxide semiconductors, nickel oxide (NiO) stands out as a highly favorable candidate due to its p‐type conductivity along with its substantial band gap (3.5–4 eV) for the broad range of applications, including gas sensors, high‐rate Lithium‐ion batteries, high‐performance supercapacitors, and photovoltaic devices. In light of these versatile applications, our current study presents a comprehensive comparative analysis of the structural and optoelectronic properties of NiO and potassium (K)‐doped NiO nanocrystals. The nanocrystals were synthesized using the co‐precipitation route and subsequently annealed at 500°C under ambient conditions. The effect of K doping on the structural and optoelectronic characteristics was systematically examined using various techniques, including x‐ray diffraction, UV–visible spectroscopy, Raman spectroscopy, and Hall effect measurements. To explore the structural characteristics, XRD measurements were performed, which confirm the FCC structure of nanocrystals. The optical property analysis suggested that the formation of the energy level can contribute to reduction of the band gap. A sharp peak at 397 cm−1 is associated with NiO bond in FTIR spectra which verifies the formation of nanocrystals. Moreover, the incorporation of K increases the intensity of the Raman peaks, which provides evidence for the higher degree of crystallinity in doped samples. These results of Raman scattering are in good agreement with XRD outcomes. In addition, the resistivity of NiO nanocrystals decreases monotonically with the increasing K concentration. The results of temperature‐dependent resistivity further demonstrate that electrons required more energy to jump from one polaron state to another in the case of x = 0.01 M and 0.03 M doped Ni0.5‐xKxO samples. The combination of a diminished band gap and enhanced conductivity makes these materials exceptionally promising for applications in optoelectronics and energy storage.

Defect crystal structure of α-Na0.5-xR0.5+xF2+2x (R = Dy-Lu, Y) on X-Ray and electron diffraction data. I. MethoD of Defect structure modelling on the α-Na0.35Dy0.65F2.30 example

For the first time, the crystal α-Na0.35Dy0.65F2.30 was studied using X-ray diffraction at 293 K and 85 K and electron diffraction at 293 K. A unified cluster model of the defective structure of nanostructured crystals with a fluorite-type structure, based on the polymorphism of ordered phases KR3F10 (R = Er, Yb), was expanded with a matrix part model based on the structure of the KYF4 compound. The unified cluster model was applied to construct the defective structure of α-Na0.35Dy0.65F2.30. It was found that the matrix part of the crystal contains Na+ и Dy3+ cations in a 1:1 ratio. Some of the anions in the matrix are displaced to the 32f positions (space group Fm3m). The excess Dy3+ forms octahedral-cubic clusters with Na+ [Na14–nDynF64+n] with cores in the form of distorted and regular cuboctahedrons {F12}. These are composed of interstitial anions in two 32f positions and one 48i position. The cluster component of the α-Na0.35Dy0.65F2.30 crystal contains octahedral-cubic clusters of f-, f–i- and i-types. Electron diffraction showed that α-Na0.35Dy0.65F2.30 is a nanostructured crystal. Its cluster component is in the form of plate-like inclusions about 5 nm thick with superstructural ordering and individual octahedral-cubic clusters. A model of their structure was proposed. Lowering the temperature to 85 K increases the number of interstitial F(32f)1 anions in the matrix component of the crystal.

Multitwinned Ice Nanocrystals.

Multitwinned nanocrystals are commonly found in substances that preferentially adopt tetrahedral local arrangements, but not yet in water crystals. Ice nanocrystals are pivotal in cloud microphysics, and their surfaces become increasingly prominent in determining structure as crystal size decreases. Nevertheless, discussions on nanocrystal structures have predominantly centered on ice polymorphs observed in bulk: hexagonal (Ih), cubic (Ic), and stacking-disordered (Isd) ices. Here, we demonstrate, through molecular dynamics (MD) simulations, that decahedral and icosahedral nanocrystals form from liquid water droplets of a few nanometers in size without violating the ice rule. The brute force spontaneous crystallization is conducted using the mW model, and the thermodynamic stability is examined using the TIP4P/Ice model. During the crystallization process, the formation of twin boundaries precedes the emergence of centers exhibiting 5-fold and icosahedral symmetry. The free energy calculation suggests the icosahedron has comparable stability with ice Ih nanocrystal. The frequent occurrence of these unreported ice nanocrystals aligns with the fact that natural polycrystalline snow crystals predominantly display a 70.5-degree angle between the Ih c-axes of adjacent branches. Moreover, we show that the formation of multitwinned ice nanocrystals is enhanced within a fullerene, providing a potential avenue for experimental observations.

Atomistic simulations of polysaccharide materials for insights into their crystal structure, nanostructure, and dissolution mechanism

AbstractCrystalline polysaccharides are abundant in nature and can be transformed into highly functional materials. However, the molecular basis for the formation of higher-order structures remains unclear. Computer simulation is an advanced tool for modeling macromolecular structures, and the atomistic simulations provide valuable information on the crystalline polysaccharides. Fiber deformation, crystalline transition, and novel nanostructures of cellulose were characterized through molecular dynamics simulations and density functional theory calculations of models of molecular chain sheets extracted from the crystal structure of the cellulose polymorphs. Extended ensemble molecular dynamics simulations were applied to analyze the artificial crystal structure of non-natural amylose analog polysaccharides, revealing the hexagonal packing of double helices through the self-assembly of molecular chains dispersed in aqueous solution. Dissolution simulations of the cellulose and chitin crystalline fibers revealed that the anions of ionic liquids, with their solvation power, played a key role in the cleavage of intermolecular hydrogen bonds in the crystal structure, whereas the cations contributed to irreversible molecular chain dispersion. The good correlation between the actual solubility of polysaccharides and the predicted number of intermolecular hydrogen bonds prompted the development of a platform that combined simulations and machine learning for high-throughput screening of solvents for cellulose and chitin.

Organic-Inorganic Copolymerization Induced Oriented Crystallization for Robust Lightweight Porous Composite.

Porous composites are important in engineering fields for their lightweight, thermal insulation, and mechanical properties. However, increased porosity commonly decreases the robustness, making a trade-off between mechanics and weight. Optimizing the strength of solid structure is a promising way to co-enhance the robustness and lightweight properties. Here, acrylamide and calcium phosphate ionic oligomers are copolymerized, revealing a pre-interaction of these precursors induced oriented crystallization of inorganic nanostructures during the linear polymerization of acrylamide, leading to the spontaneous formation of a bone-like nanostructure. The resulting solid phase shows enhanced mechanics, surpassing most biological materials. The bone-like nanostructure remains intact despite the introduction of porous structures at higher levels, resulting in a porous composite (P-APC) with high strength (yield strength of 10.5MPa) and lightweight properties (density below 0.22 gcm-3). Notably, the density-strength property surpasses most reported porous materials. Additionally, P-APC shows ultralow thermal conductivity (45 mWm-1k-1) due to its porous structure, making its strength and thermal insulation superior to many reported materials. This work provides a robust, lightweight, and thermal insulating composite for practical application. It emphasizes the advantage of prefunctionalization of ionic oligomers for organic-inorganic copolymerization in creating oriented nanostructure with toughened mechanics, offering an alternative strategy to produce robust lightweight materials.

Construction of Pickering emulsions stabilized by small molecular bioactive nanocrystals: Crosstalk between bioactive molecular structure and initial aqueous phase

Pickering emulsions stabilized with bioactive nanocrystals (BNC-PEs) have attracted increasing attentions in recent years. However, the mechanisms for the construction of stable BNC-PEs remain obscure. This study aimed to investigate the effects of the bioactive molecular structure and the initial pH of the aqueous phase on the fabrication and stability of BNC-PEs and the crosstalk between the two factors. Puerarin, tanshinone IIA and ferulic acid with unique structural characteristics were employed as model components to prepare BNC-PEs. Results showed that the initial pH of the aqueous phase significantly affected the stability of BNC-PEs through influencing the particle sizes and charges of nanocrystals, while the molecular structure of bioactive substances affected the three-phase contact angles or interfacial tensions. The construction and stability of the three kinds of BNC-PEs were all improved with increasing initial pH of the aqueous phase. Moreover, it was first found that the bioactive molecular structure strongly interfered with the influences of the initial pH of the aqueous phase on the stability of BNC-PEs. This study demonstrated for the first time that there might be a crosstalk between the bioactive molecular structure and the initial pH of the aqueous phase, and that the optimal pH of the aqueous phase might be intricately linked to the molecular structure of bioactive nanocrystals for BNC-PEs.

In situ revealing the dehydration and atomic structure evolution of protonated titanate nanotubes via environmental transmission electron microscopy

The precise control of nanomaterial microstructure at the atomic level relies on the comprehensive understanding of atomic structural transition during the fabrication process at the atomic level. The phase transition from protonated titanate to TiO2 is a prevalent route to synthesize low dimensional TiO2-based nanomaterials, which exhibit excellent photocatalytic, lithium-ion battery performances, while the detailed phase transition mechanism remains to be clarified due to lack of atomic-level in situ information. Herein, the atomic structural transitions from one-dimensional H2Ti3O7 (HT) to TiO2(B) and anatase TiO2 (TB and TA) nanocrystals were revealed through in situ environmental transmission electron microscopy, which exhibited a two-step phase transition at 200–600 °C. (I) H2Ti3O7 to TiO2(B) transition began via an indirect pathway at ∼200 °C: The HT (200) interlayer dehydration occurred firstly with lattice shrinkage; Then TB discretely nucleated at the dehydrated H2Ti3O7 nanotube wall with a crystallographic relationship of (200)HT∥(200)TB {[001]HT∥[001]TB}; At higher temperature, the separated nuclei grew up with defects and distorted crystal lattice among them, which then connected and jointed to a single crystalline TB nanotube by atomic rearrangement. (II) The further transition of TiO2(B) to anatase TiO2 occurred via a direct pathway above 400 °C: Scarce nucleation event of TA phase was observed, which generated within TB nanocrystal with a crystallographic relationship of (200)TB∥(002)TA {[001]TB∥[010]TA}. Once a TA nucleus formed, it grew up to a large crystal by consuming the neighbor TB nanocrystals. These findings may contribute to comprehensively understanding phase transition and precisely manipulating the atomic structure of one-dimensional TiO2 nanocrystals.

Evolution of microstructure and mechanical properties of electroplated nanocrystalline Ni–Co coating during heating

Ni–Co alloy coating is applied to crystallizer surface to enhance its wear resistance for continuous steel casting. This study investigated the effects of heating temperature on the hardness, strength, and elongation of Ni–21wt.% Co coatings obtained by electroplating. The evolution of microstructure was analyzed by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results indicated that the as-deposited coating had a mixed structure of nanocrystals and microcrystals, containing numerous nanotwins and stacking faults. Its hardness, tensile strength, yield strength, and elongation were 371 HV0.1, 1170MPa, 1117MPa, and 13.8%, respectively. After low-temperature heating, the number of nanocrystals decreased, whereas the fraction of microcrystals increased. At heating temperatures of 100–200 °C, a reverse Hall–Petch phenomenon occurred owing to the formation of annealing twins and the transformation of dislocation-emission mechanisms, resulting in a stable hardness and tensile strength. As the heating temperature was further increased, the grains continuously grew, thereby decreasing the hardness and tensile strength. After annealed at 400 °C, the elongation reached 32.5%, whereas the hardness, tensile strength, and yield strength decreased to 200 HV0.1, 662MPa, and 577MPa, respectively.

Fabrication and Characterization of Ce3+-Doped Lithium Alumino-Silicate Scintillating Glass-Ceramic and Fiber.

Ce3+-doped lithium alumino-silicate (Li-Al-Si) scintillating glass was prepared using a melting method and crystallized via heat treatment. X-ray diffraction and transmission electron microscopy confirmed the presence of nanocrystals in the materials. Radioluminescence spectra, obtained by X-ray excitation, and luminescence spectra, obtained by 338 nm excitation, showed that the luminescence intensity increased after crystallization. The glass was combined with pure silica as the inner cladding to fabricate a hybrid fiber core using a melt-in-tube technique. The composition of the fiber core was examined using an electron probe microanalyzer. The glass fiber produced strong blue luminescence under UV excitation. After a micro-crystallizing heat treatment of the hybrid fiber at 850 °C in a reducing atmosphere, a Ce3+-doped lithium alumino-silicate glass-ceramic scintillating hybrid fiber was obtained. The nanocrystal structure of the fiber core was examined using micro-Raman spectroscopy. Excitation and luminescence spectra of the hybrid fiber before and after micro-crystallization were measured using microspectrofluorimetry. The results demonstrated that the fiber remained luminous after micro-crystallization. Hence, this work provides a new way to prepare scintillating glass-ceramic hybrid fibers for neutron detection.

Enhancement of Mechanical Properties of NiCo Alloy Induced by Inhomogeneous Gradient of Solute Element Segregation

Inhomogeneous gradient nanocrystals have better mechanical properties than uniform gradient nanocrystals. The segregation of solute elements in inhomogeneous gradient nanocrystals is expected to induce the re‐enhancement of mechanical properties of alloys. Herein, solute element segregation structures of inhomogeneous gradient structure nanocrystalline NiCo alloy are established, simulating tensile deformation via molecular dynamics. The results show that the segregation of solute elements in the inhomogeneous gradient structure of nanocrystals can improve the mechanical properties of the alloy, especially the structure of the intragranular segregation. The intragranular segregation of solute elements induces the decrease of grain boundary energy and greatly enhances the stability of grain boundaries. In addition, the segregation of solute elements within grains can hinder the dislocation movement to a certain extent, and the hindering effect on dislocation movement of stable grain boundaries induced by intragranular segregation of solute elements further enhances the mechanical properties of nanocrystalline alloys. This strategy of combining heterogeneous gradient structure and solute element segregation structure provides a positive and interesting perspective for the design of advanced alloys with excellent properties.

High-performance hydrogen sensor based on γ-Fe2O3/α-Fe2O3 heterostructures produced by a one-step hydrothermal method

The construction of heterostructures is an effective strategy for enhancing the properties of functional materials. However, the problem of the weak built-in field at the heterointerface usually degrades the interfacial charge transfer efficiency, severely limiting the improvement of the sensing properties of gas sensors. To overcome this limitation, γ-Fe2O3/α-Fe2O3 (p-p) heterojunction structures were constructed via a one-step hydrothermal method. Interestingly, the morphology and structure of the Fe2O3 nanocrystals could be easily controlled by the amount of urea (CH4N2O). Thus, the response of Fe2O3-M to H2 (200 ppm) at 280 °C was 2.2 and 1.2 times greater than that of Fe2O3–R and Fe2O3–N, respectively. In addition, density functional theory (DFT) calculations were used to explore the sensing mechanism in detail, further confirming the experimental conclusions. The strong and ultrafast response to hydrogen was attributed to the synergistic effects of the unique heterostructure and large specific surface area. The development of efficient and stable new hydrogen-sensing materials will help further expand their application scope in the sensing field.

Polarization-Controlled Exciton-Polaritons in WS2 Strongly Coupled with Low-Symmetry Photonic Crystal Nanostructures.

Atomically thin transition metal dichalcogenides (TMDs) with ambient stable exciton resonances have emerged as an ideal material platform for exciton-polaritons. In particular, the strong coupling between excitons in TMDs and optical resonances in anisotropic photonic nanostructures can form exciton-polaritons with polarization selectivity, which offers a new degree of freedom for the manipulation of the light-matter interaction. In this work, we present the experimental demonstration of polarization-controlled exciton-polaritons in tungsten disulfide (WS2) strongly coupled with polarization singularities in the momentum space of low-symmetry photonic crystal (PhC) nanostructures. The utilization of polarization singularities can not only effectively modulate the polarization states of exciton-polaritons in the momentum space but also facilitate or suppress their far field coupling capabilities by tuning the in-plane momentum. Our results provide new strategies for creating polarization-selective exciton-polaritons.

Tailoring of Circularly Polarized Beams Employing Bound States in the Continuum in a Designed Photonic Crystal Metasurface Nanostructure.

We propose a photonic crystal (PC) nanostructure that combines bound states In the continuum (BIC) with a high-quality factor up to 107 for emitting circularly polarized beams. We break the in-plane inversion symmetry of the unit cell by tilting the triangular hole of the hexagonal lattice, resulting in the conversion of a symmetrically protected BIC to a quasi-BIC. High-quality circularly polarized light is obtained efficiently by adjusting the tilt angles of the hole and the thickness of the PC layer. By changing the hole's geometry in the unit cell, the Q-factor of circularly polarized light is further improved. The quality factor can be adjusted from 6.0 × 103 to 1.7 × 107 by deliberately changing the shape of the holes. Notably, the proposed nanostructure exhibits a large bandgap, which significantly facilitates the generation of stable single-mode resonance. The proposed structure is anticipated to have practical applications in the field of laser technology, particularly in the advancement of low-threshold PC surface emitting lasers (PCSELs).

Unveiling complex magnetic behaviour and effective photo-Fenton catalytic activity in the mixed phases of spinel and wurtzite structures of Fe-incorporated ZnO nanocrystals

A comprehensive exploration was conducted on the structural features, optical bandgap, magnetic characteristics and photo-Fenton catalytic activity of chemically synthesized Fe-substituted ZnO nanocrystals. Previous studies have demonstrated that undoped ZnO adopts a hexagonal wurtzite structure. X-ray powder diffraction analysis disclosed the persistence of the wurtzite hexagonal structure in 1 % Fe-incorporated ZnO, while the presence of a secondary cubic phase of spinel type structures (ZnFe2O4) emerged in the ZnO lattice with Fe content ≥ 3 %. Remarkably, the proportion of the secondary phase is systematically increased from 2.75 % to 17.90 % as the Fe content was raised from 3 % to 10 %. Microscopy analysis unveiled hexagonal, spherical, and rod-like structures across all nanocrystals. Selected area electron diffraction patterns further confirmed the coexistence of cubic and hexagonal phases. Raman spectroscopy indicated a decline in crystalline quality and the introduction of defects and disorder in the host lattice due to Fe integration. The absorption spectra were taken to assess the impact of Fe substitution on the optical properties and revealed a decreasing trend in the optical bandgap from 3.23 to 3.21 eV and 2.21–2.05 eV with rising Fe content. The first band gap is related to the ZnO and the latter is the optical band gap of ZnFe2O4. The photoluminescence plots displayed near band edge emissions as well as visible emissions, which intensified with increased Fe-doped nanocrystal concentrations. X-ray photoelectron spectroscopy analysis affirmed the integration of Fe2+ and Fe3+ cations into the ZnO matrix. Thorough magnetic investigation uncovered complex magnetic behaviour attributed to the emergence of a secondary spin glass-like phase within the weak ferromagnetic ZnO host. The co-existence of two phases containing Fe2+ and Fe3+ ions enhanced the photo-Fenton catalytic activity, leading to the complete decomposition of various organic pollutants such as methylene blue and crystal violet. The photocatalytic test also showed the ZnO co-hosting ZnFe2O4 had a decolouration efficiency of 80.62 % and 77.88 % for methyl orange and thymol blue dyes. The coexistence of two phases in Fe-incorporated ZnO nanocrystals reveals complex magnetic behaviour and enhanced photo-Fenton catalytic activity. This finding holds potential for designing innovative materials applicable in futuristic spintronics devices and waste water treatment methodologies.

Preparation and surface photovoltage regulation of (Cs/MA)3Bi2I9 double A-site cation mixed-phase perovskite nanocrystal structure

This paper reports a novel (Cs/MA)3Bi2I9 double A-site cations perovskite nanostructured photoelectrode and its fabrication method, utilizing a stoichiometric dissolution of MAI, CsI, and BiI3 solutes in DMF solvent. The (Cs/MA)3Bi2I9 perovskite electrodes are then prepared on FTO glass substrates using the spin-coating technique. Furthermore, by adjusting the molar ratio x of Cs+ to the total moles of Cs+ and MA+ in precursor, the morphology and size of the (Cs/MA)3Bi2I9 perovskite nanostructures can be effectively modulated, thereby tuning their photoelectrical properties. (Cs/MA)3Bi2I9 consists of two phases: (CsMA)3Bi2I9 formed by substituting Cs+ with MA+, and (MACs)3Bi2I9 formed by substituting MA+ with Cs+. The surface photovoltage performance of the (Cs/MA)3Bi2I9 perovskites prepared at different x values surpasses that of pure MA3Bi2I9 and Cs3Bi2I9 bismuth-based perovskites. Particularly noteworthy is that at x = 0.6, the surface photovoltage performance of (Cs/MA)3Bi2I9 perovskite is nearly double that of the pure MA3Bi2I9 and Cs3Bi2I9 perovskites.

The Thermal Stability and Photoluminescence of ZnSeO3 Nanocrystals Chemically Synthesized into SiO2/Si Track Templates

We report the effect of high-temperature treatment on the structure and photoluminescence of zinc selenite nanocrystals (ZnSeO3) deposited into SiO2/Si track templates. The templates were formed via irradiation with Xe ions (200 MeV, 108 ions/cm2) followed by etching in HF solution. ZnSeO3 nanocrystals were obtained via chemical deposition from the aqueous solution of ZnCl2 and SeO2 as Zn-, Se- and O-precursors. To estimate the thermal stability of the deposited precipitates, heat treatment was carried out at 800 and 1000 °C for 60 min in a vacuum environment. Scanning electron microscopy (SEM), X-ray diffractometry (XRD), photoluminescence (PL) spectroscopy, and electrical measurements were used for the characterization of ZnSeO3/SiO2nanoporous/Si nanocomposites. Thermal treatment of the synthesized nanocomposites resulted in structural transformations with the formation of ZnSe and ZnO phases while the content of the ZnSeO3 phase decreased. For the as-deposited and annealed precipitates, an emission in the range of (400 to 600) nm was observed. PL spectra were approximated by four Gaussian curves with maxima at ~550 nm (2.2 eV), 488 nm (2.54 eV), ~440 nm (2.82 eV), and 410 nm (3.03 eV). Annealing resulted in a decrease in PL intensity that was possibly due to the weight loss of the deposited substance during high-temperature treatment. The redistribution of maxima intensities after annealing was also observed with an increase in blue and violet emissions. The origin of the observed PL is discussed. The I–V curve analysis revealed an electronic type of conductivity for the ZnSeO3(NCs)/SiO2nanoporous/Si structure. The values of the specific conductivity were calculated within the percolation model. The sample annealed at 800 °C showed the highest specific conductivity of 8.5 × 10−6 Ohm−1·cm−1.

Vacancy-Engineered 1D Nanorods with Spatially Segregated Dual Redox Sites for Visible-Light-Driven Cooperative CO2 Reduction.

Cooperative CO2 photoreduction with tailored organic synthesis offers a potent avenue for harnessing concurrently generated electrons and holes, facilitating the creation of both solar fuels and specialized chemical compounds. However, controlling the crystallization and morphologies of metal-free molecular nanostructures with exceptional photocatalytic activities toward CO2 reduction remains a significant challenge. These hurdles encompass insufficient CO2 activation potential, sluggish multielectron processes, delayed charge-separation kinetics, inadequate storage of long-lived photoexcitons, unfavorable thermodynamic conditions, and the precise control of product selectivity. Here, melem oligomer 2D nanosheets (MNSs) synthesized through pyrolysis are transformed into 1D nanorods (MNRs) at room temperature with the simultaneous engineering of vacancies and morphology. Transient absorption spectral analysis reveals that vacancies in MNRs trap charges, extending charge carrier lifetimes. Additionally, carbon vacancies enhance CO2 adsorption by increasing amine functional centers. The photocatalytic performance of MNRs for CO2 reduction coupled with benzyl alcohol oxidation is approximately ten times higher (CH3OH and aromatic aldehyde production rate 27 ± 0.5 and 93 ± 0.5 mmol g-1 h-1, respectively) than for the MNSs (CH3OH and aromatic aldehyde production rate 2.9 ± 0.5 and 9 ± 0.5 mmol g-1 h-1, respectively). The CO2 reduction pathway involved the carbon-coordinated formyl pathway through the formation of *COOH and *CHO intermediates, as mapped by in situ Fourier-transform infrared spectroscopy. The superior performance of MNRs is attributed to favorable energy-level alignment, enriched amine surfaces, and unique morphology, enhancing solar-to-chemical conversion.