Nanoplates Research Articles

ZnO/SnO2 based composite heterostructure for NO2 gas sensing properties

In recent years, interest in heterostructures and research on them has been increasing day by day. While semiconductors mainly exhibit different characteristics, they can exhibit different characteristics when they come together to form a heterostructure, and investigating the reasons for these is of great interest. For this purpose, in this study, such a hetero structure (ZnO/SnO2) was obtained by the Sol-Gel Dip Coating (SGDC) combined method and its effects on its characteristics against NO2 gas were tried to be examined.In this study, SnO2/ZnO composite heterostructures were grown by SGDC method. In this sense, this study is a first in the literature in terms of enlarging this structure with the SGDC technique. The number of SnO2 cycles was kept constant at 1 cycles and the ZnO layers were at different cycles as 1, 2, 3 and 5. The effect of ZnO cycles number on structural, morphological and most importantly NO2 gas detection properties was investigated in the formed heterostructures. In the XRD results, both ZnO and SnO2 peaks were observed and it was determined that these peaks belonged to the hexagonal wurtzite phase for ZnO and to the tetragonal rutile phase for SnO2. The lattice strain and crystallite size were calculated using Williamson-Hall and Scherrer method. The SEM images of ZnO-SnO2 manifest the change in the microstructure with increasing ZnO layer. The microstructure consisted of thin crystalline plates and small round-shape particles. The nano plates and walls shape and size changed with increasing ZnO layers. The operating temperature was defined as 165 °C for all sensors from NO2 gas sensing measurements. The responses of 1 ppm NO2 gas concentrations were calculated as 20 %, 201 %, 1078 % and 676 % for Z1S1, Z2S1, Z3S1 and Z5S1 heterosturucture respectively.

Two-photon upconversion photoluminescence in CsPbBr3 nanoplates

The utilization of solar energy by light conversion processes in both natural and artificial photosynthesis systems has become a pivotal means of sustaining a consistent power supply for our daily lives and production. In general, these reactions rely on the visible spectra region where the sun produces abundant energy according to the black body's emission. Further expanding the adoption of the near-infrared (NIR) spectral region through upconversion has become an intelligent strategy to improve the entire utilization rate of solar energy. In this work, the two-photon upconversion (TPUC) properties were discovered in CsPbBr3 nanoplates (NPs) emitted at 450 nm, and a sub-gap energy level was observed to serve as the center to facilitate the upconversion process. The excitation threshold for TPUC is drastically lower than that for the two-photon absorption, another nonlinear upconversion path that requires strengthened excitation power. Moreover, a significant negative correlation between the excitation threshold for TPUC in the CsPbBr3 NPs and the exciton binding energy was unveiled, which could be attributed to the enhanced quantum confinement effects. Our work paved the way for a feasible way to expand the utilization of the NIR spectral region in light conversion applications.

Hydrothermally derived Cr-doped SnS2 layered nanoplates: investigation of their controlled structural, morphological, optical, magnetic, photo response and photocatalytic activities

A facile method has been employed to synthesize pristine and Cr-doped SnS2 (Cr: SnS2) nanoplates (Sn1-xCrxS2, here x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) and Cr: SnS2 nanoplates (NPs) were successfully synthesized via hydrothermal method. The nanoplates' structure was hexagonal, with a preference for orientation along the (001) plane; there was no evidence of additional undesirable phases. FTIR and EDX were used to observe the existence of functional groups in the samples where Sn-S bonds were present in each of the produced pristine and Cr: SnS2 nanoplates. XPS measurements demonstrated the existence of Sn, S, and Cr. FESEM revealed that the morphological properties of the nanoplates included several hexagonal grains. Magnetic characterizations showed that with increasing doping concentration of Cr, SnS2 nanoplates become superparamagnetic from ferromagnetic. The band gap values for the pristine and Cr: SnS2 nanoplates calculated from the absorbance spectra decreased from 2.53 to 2.08 eV with an increase in doping concentration. The photoluminescence spectra of the pristine SnS2 and Cr: SnS2 nanoplates exhibit two strong emission peaks at around 562 and 666 nm for an excitation wavelength of 420 nm. The Cr: SnS2 nanoplates have demonstrated the resistive behavior of the sample. The Cr: SnS2 nanoplates have shown good photocatalytic activity towards the decolorization of rhodamine B under visible irradiation.

Facet-Controlled Synthesis of Unconventional-Phase Metal Alloys for Highly Efficient Hydrogen Oxidation.

Facet control and phase engineering of metal nanomaterials are both important strategies to regulate their physicochemical properties and improve their applications. However, it is still a challenge to tune the exposed facets of metal nanomaterials with unconventional crystal phases, hindering the exploration of the facet effects on their properties and functions. In this work, by using Pd nanoparticles with unconventional hexagonal close-packed (hcp, 2H type) phase, referred to as 2H-Pd, as seeds, a selective epitaxial growth method is developed to tune the predominant growth directions of secondary materials on 2H-Pd, forming Pd@NiRh nanoplates (NPLs) and nanorods (NRs) with 2H phase, referred to as 2H-Pd@2H-NiRh NPLs and NRs, respectively. The 2H-Pd@2H-NiRh NRs expose more (100)h and (101)h facets on the 2H-NiRh shells compared to the 2H-Pd@2H-NiRh NPLs. Impressively, when used as electrocatalysts toward hydrogen oxidation reaction (HOR), the 2H-Pd@2H-NiRh NRs show superior activity compared to the NiRh alloy with conventional face-centered cubic (fcc) phase (fcc-NiRh) and the 2H-Pd@2H-NiRh NPLs, revealing the crucial role of facet control in enhancing the catalytic performance of unconventional-phase metal nanomaterials. Density functional theory (DFT) calculations further unravel that the excellent HOR activity of 2H-Pd@2H-NiRh NRs can be attributed to the more exposed (100)h and (101)h facets on the 2H-NiRh shells, which possess high electron transfer efficiency, optimized H* binding energy, enhanced OH* binding energy, and a low energy barrier for the rate-determining step during the HOR process.

Surface reconstruction of hierarchical CoNiP@Ni2P nanoarray to promote overall water splitting

Efficient water splitting remains a challenge to produce clean and pure H2 in an industrial scale for the lack of high-performance cost-effective stable electrocatalysts of hydrogen and oxygen evolution (HER and OER). Surface engineering is a novel proposal to upgrade the electrocatalytic performances of HER and OER catalysts. Herein, a hierarchical architecture composed of carbon-supported CoNiP nanoplates (NPs) on Ni2P nanowire was constructed. The nanoarray of CoNiP@Ni2P heterostructure shows a high bifunctional activity of HER and OER. The overpotential is 46 mV required for HER at 10 mA·cm−2 and 292 mV for OER at 100 mA·cm−2 in 1 mol·L−1 KOH. In addition, the nanoarray of CoNiP@Ni2P heterostructure also shows a high stability for HER. The HER activity can be maintained at 11 mA·cm−2 without loss after 50 h cathode polarization at the overpotential of 100 mV, while the OER activity continuously increases from 26 to 64 mA·cm−2 at an overpotential of 400 mV after 50 h anode polarization. The enhancement of the oxygen evolution performance can be ascribed to the surface reconstruction of CoNiP/Ni2P heterostructure nanoarray, which can offer more active sites to OER. Density functional theory (DFT) reveals surface reconstruction can create an oxygen-rich surface in favor of intermediate adsorption, thus enabling a fast OER kinetics at the interface of NiCoOOH/Ni2P heterostructure. This work highlights surface reconstruction adaptability to design advanced catalysts of efficient water splitting for commercial H2 production.

Catalytic and photocatalytic remediation of toxic dye on hexagonal CuS/Cu2S nanoplates derived from a single source precursor

Bis(4-(2-hydroxyethyl)piperazine-1-carbodithioato)copper(II) was synthesized and decomposed to hexagonal copper sulfide (CuS/Cu2S) nanoplates (NPs) under ambient conditions using ethylenediamine as a decomposing agent and solvent. The optical property (UV–Vis) and structural analysis (XRD, HRTEM, TEM, SAED, and EDS) revealed the formation of visible light active (2.24 eV) hexagonal nanoplates of mixed composition (CuS/Cu2S) with size varying from 310 to 890 nm. CuS/Cu2S nanoplates possess both catalytic and photocatalytic properties and degrade Congo red entirely (100%) both in dark and light. However, in the presence of light (80 min) the degradation is faster than in the dark (120 min). The degradation follows pseudo-first-order kinetics in the presence and absence of light. The kinetics also explain that the dye first adsorb on the surface of CuS/Cu2S and then is mineralized. Furthermore, CuS/Cu2S nanoplates were photostable with good reusability. Additionally, the environmentally benign nature, catalyst photocatalytic properties, complete dye degradation, and no generation of secondary pollutants make CuS/Cu2S nanoplates an excellent material for environmental cleansing.

The influence of rGO and GO nano plates on structural, optical and magnetic properties of SnFe2O4 nanocomposites synthesised by sol–gel, microwave and co-precipitation methods

The influence of rGO and GO nano plates on structural, optical and magnetic properties of SnFe2O4 nanocomposites synthesised by sol–gel, microwave and co-precipitation methods

Waning-and-waxing shape changes in ionic nanoplates upon cation exchange

Flexible control of the composition and morphology of nanocrystals (NCs) over a wide range is an essential technology for the creation of functional nanomaterials. Cation exchange (CE) is a facile method by which to finely tune the compositions of ionic NCs, providing an opportunity to obtain complex nanostructures that are difficult to form using conventional chemical synthesis procedures. However, due to their robust anion frameworks, CE cannot typically be used to modify the original morphology of the host NCs. In this study, we report an anisotropic morphological transformation of Cu1.8S NCs during CE. Upon partial CE of Cu1.8S nanoplates (NPLs) with Mn2+, the hexagonal NPLs are transformed into crescent-shaped Cu1.8S–MnS NPLs. Upon further CE, these crescent-shaped NPLs evolve back into completely hexagonal MnS NPLs. Comprehensive characterization of the intermediates reveals that this waxing-and-waning shape-evolution process is due to dissolution, redeposition, and intraparticle migration of Cu+ and S2−. Furthermore, in addition to Mn2+, this CE-induced transformation process occurs with Zn2+, Cd2+ and Fe3+. This finding presents a strategy by which to create heterostructured NCs with various morphologies and compositions under mild conditions.

Liquid Phase Exfoliation of Few-Layer Non-Van der Waals Chromium Sulfide.

Exfoliation of 2D non-Van der Waals (non-vdW) semiconductor nanoplates (NPs) from inorganic analogs presents many challenges ahead for further exploring of their advanced applications on account of the strong bonding energies. In this study, the exfoliation of ultrathin 2D non-vdW chromium sulfide (2D Cr2S3) by means of a combined facile liquid-phase exfoliation (LPE) method is successfully demonstrated. The morphology and structure of the 2D Cr2S3 material are systematically examined. Magnetic studies show an obvious temperature-dependent uncompensated antiferromagnetic behavior of 2D Cr2S3. The material is further loaded on TiO2 nanorod arrays to form an S-scheme heterojunction. Experimental measurements and density functional theory (DFT) calculations confirm that the formed TiO2@Cr2S3 S-scheme heterojunction facilitates the separation and transmission of photo-induced electron/hole pairs, resulting in a significantly enhanced photocatalytic activity in the visible region.

Tunable Localized Charge Transfer Excitons in Nanoplatelet-2D Chalcogenide van der Waals Heterostructures.

Observation of interlayer, charge transfer (CT) excitons in van der Waals heterostructures (vdWHs) based on 2D-2D systems has been well investigated. While conceptually interesting, these charge transfer excitons are highly delocalized and spatially localizing them requires twisting layers at very specific angles. This issue of localizing the CT excitons can be overcome via making nanoplate-2D material heterostructures (N2DHs) where one of the components is a spatially quantum confined medium. Here, we demonstrate the formation of CT excitons in a mixed dimensional system comprising MoSe2 and WSe2 monolayers and CdSe/CdS-based core/shell nanoplates (NPLs). Spectral signatures of CT excitons in our N2DHs were resolved locally at the 2D/single-NPL heterointerface using tip-enhanced photoluminescence (TEPL) at room temperature. By varying both the 2D material and the shell thickness of the NPLs and applying an out-of-plane electric field, the exciton resonance energy was tuned by up to 100 meV. Our finding is a significant step toward the realization of highly tunable N2DH-based next-generation photonic devices.

Water‐Assisted Synthesis of Layer‐Controlled CsPbBr3 Nanoplates Spontaneously Encapsulated in PbBr(OH)

AbstractCsPbBr3 nanoplates (NPs) have shown great potential in diverse optoelectronic applications. Despite the wonderful luminescence properties, the inherent instability of these NPs hinders their use in practical situations. Herein, a facile water‐assisted strategy is reported to synthesize highly stable blue emission CsPbBr3 NPs encapsulated in PbBr(OH). The introduction of water directly into the reaction mixture is pivotal, as it triggers the transformation of bulk CsPbBr3 nanocubes into 2‐D CsPbBr3 NPs within the PbBr(OH) matrix, resulting in the formation of CsPbBr3@PbBr(OH) microbricks. Remarkably, the water content in the reaction mixture allows the control of the number of perovskite layers in the NPs, thus enabling the emission color to be tuned from deep blue to green. The unconventional approach presented herein not only offers a cost‐effective pathway to synthesize blue‐emitting perovskites which are highly stable in a wide variety of polar and non‐polar solvents, but also holds immense potential for propelling the advancement of high‐performance LEDs and other optoelectronic devices. The findings underscore the significance of water in dictating the growth dynamics and emission characteristics of perovskite NPs, paving the way for their practical application.

DNA tetrahedral nanostructure-corbelled DNA walker for intramolecular electrochemiluminescence resonance energy transfer sensing of tumor exosomes

Exosomes as new noninvasive biomarkers play a prominent role in early cancer diagnosis, but tumor-derived exosomes are difficult to detect upon tumor initiation because of their low levels. Herein, we proposed a novel and stable strategy for exosomes detection based on intramolecular electrochemiluminescence resonance energy transfer (ECL-RET) and DNA tetrahedral nanostructures (DTNs)-corbelled DNA walker. To enhance the ECL efficiency of luminophores, abundant Ru(bpy)32+ molecules were coordinatively immobilized on Zr12-adb nanoplates (NPs) to form Ru-Zr12-adb NPs. So, high ECL-RET efficiency based on the combination of Zr12-adb NPs (donor) and Ru(bpy)32+ (acceptor) into one nanostructure resulted in considerably enhanced ECL response. Impressively, DNA walker with six track strands supported by DTNs demonstrated enhanced walking speed and high reaction efficiency because of the improved local concentration and space confinement effect of DTNs. In consequence, this as-designed ingenious ECL biosensor exhibited excellent sensing performance for exosomes.

Van der Waals epitaxy of CsPbBr3/WSe2 heterostructure and dynamics study of exciton recombination

Van der Waals heterostructures formed by inorganic perovskites and transition metal dichalcogenides (TMDCs) have promising applications in photonics and optoelectronics. However, there are few studies on the properties of CsPbBr3/TMDC at low temperatures. Here, we demonstrate van der Waals epitaxy of CsPbBr3 nanowires (NWs), nanoplates (NPs) and nanocones (NCs) on monolayer (ML) WSe2, and investigate the lattice dynamics of the heterostructure at low temperatures using temperature-dependent Raman spectroscopy. In addition, temperature-dependent photoluminescence (PL) spectroscopy shows that the type II band alignment between CsPbBr3 and ML WSe2 leads to a broad emission peak at the low-energy side of the ML WSe2 emission at low temperatures. Meanwhile, a high-energy peak appears near the CsPbBr3 emission below 133 K, which may be related to the phase transition of CsPbBr3 from the cubic to the orthorhombic phase. These findings are important for the development of van der Waals heterostructure based self-powered photodetector with high performance.

Unveiling the Growth Mechanism of Ordered-Phase within Multimetallic Nanoplates.

Tuning the crystal phase of alloy nanocrystals (NCs) offers an alternative way to improve their electrocatalytic performance, but, how heterometals diffuse and form ordered-phase remains unclear. Herein, for the first time, the mechanism for forming tetrametallic ordered-phase nanoplates (NPLs) is unraveled. The observations reveal that the intermetallic ordered-phase nucleates through crystallinity alteration of the seeds and then propagates by reentrant grooves. Notably, the reentrant grooves act as intermediate NCs for ordered-phase, eventually forming intermetallic PdCuIrCo NPLs. These NPLs substantially outperform for oxygen evolution reaction (221mV at 10mA cm-2) and hydrogen evolution reaction (19mV at 10mA cm-2) compared to commercial Ir/C and Pd/C catalysts in acidic media. For OER at 1.53V versus RHE, the PdCuIrCo/C exhibits an enhanced mass activity of 9.8 A mg-1 Pd+Ir (about ten times higher) than Ir/C. For HER at -0. 2V versus RHE, PdCuIrCo/C shows a remarkable mass activity of 1.06 A mg-1 Pd+Ir, which is three-fold relative to Pd/C. These improvements can be ascribed to the intermetallic ordered-structure with high-valence Ir sites and tensile-strain. This approach enabled the realization of a previously unobserved mechanism for ordered-phase NCs. Therefore, this strategy of making ordered-phase NPLs can be used in diverse heterogeneous catalysis.

Surface-Enriched Single-Bi-Atoms Tailoring of Pt Nanorings for Direct Methanol Fuel Cells with Ultralow-Pt-Loading.

Single-atom decorating of Pt emerges as a highly effective strategy to boost catalytic properties, which can trigger the most Pt active sites while blocking the smallest number of Pt atoms. However, the rational design and creation of high-density single-atoms on Pt surface remain as a huge challenge. Herein, a customized synthesis of surface-enriched single-Bi-atoms tailored Pt nanorings (SE-Bi1/Pt NRs) toward methanol oxidation is reported, which is guided by the density functional theory (DFT) calculations suggesting that a relatively higher density of Bi species on Pt surface can ensure a CO-free pathway and accelerate the kinetics of *HCOOH formation. Decorating Pt NRs with dense single-Bi-atoms is achieved by starting from PtBi intermetallic nanoplates (NPs) with intrinsically isolated Bi atoms and subsequent etching and annealing treatments. The SE-Bi1/Pt NRs exhibit a mass activity of 23.77 A mg-1 Pt toward methanol oxidation in alkaline electrolyte, which is 2.2 and 12.8 times higher than those of Pt-Bi NRs and Pt/C, respectively. This excellent activity endows the SE-Bi1/Pt NRs with a high likelihood to be used as a practical anodic electrocatalyst for direct methanol fuel cells （DMFCs） with high power density of 85.3mW cm-2 and ultralow Pt loading of 0.39 mg cm-2.

Two-dimensional Cs3Sb2Br9 inducing transformation of three-dimensional CsPbBr3 to nanoplates.

This communication describes an effective morphological control strategy involving introducing two-dimensional (2D) Cs3Sb2Br9 to induce a transformation of three-dimensional (3D) CsPbBr3 to 2D nanoplates (NPLs). By tuning the Sb/Pb ratio, 2D CsPbBr3 NPLs exhibiting a deep-blue emission centered at a wavelength of 464 nm with an FWHM of 24 nm have been produced. The absence of organic ligands in these high-quality 2D NPLs mitigate the instability issue induced by organic ligand migration and penetration, and these NPLs exhibit 80% of the initial PL intensity after 55 days.

Enhancing photocathodic protection of Q235 carbon steel by co-sensitizing TiO2 nanotubes with CdIn2S4 nanogranules and WO3 nanoplates

In order to improve the photocathodic protection (PCP) performance of TiO2 and its continuous protection ability in the dark, we designed and prepared CdIn2S4/WO3/TiO2 (C/W/T) photoanodes through sequentially depositing WO3 nanoplates (NPs) and CdIn2S4 nanogranules (NGs) on TiO2 nanotubes (NTs) by simple hydrothermal method. The effect of hydrothermal time on the PCP performances of C/W/T for Q235 carbon steel (CS) was studied. The PCP performance of C/W/T was compared with that of pure TiO2, CdIn2S4/TiO2 (C/T) and WO3/TiO2 (W/T). When the hydrothermal time for preparing WO3 NPS and CdIn2S4 NGs was both 6 h, the prepared C/W/T possessed the optimal PCP performance. The photogenerated potential drop of C/W/T could reach 490 mV vs. SCE. The C/W/T exhibited higher photocurrent density (633 μA·cm−2) and lower charge transfer resistance (11.34 Ω·cm2) than bare TiO2, C/T and W/T. The electron storage capacity of C/W/T was 2.88 times that of C/T, which may be attributed to the electronic storage properties of WO3 NPs. In addition, C/W/T can provide continuous protection for Q235 CS for up to 10 h in the dark. This work provides a new idea for designing energy storage photoanode materials with good PCP properties.

Corrosion-induced growth control of lead halide perovskite nanoparticles

Ultrasmall CsPbBr3 perovskite nanoparticles (NPs) have gained great attention as a potential blue-cyan emissive material due to their strong quantum confinement effects. However, the preparation of these ultrasmall perovskite NPs remains a challenging task due to their high ionicity and low formation energy. In this study, we propose and demonstrate a corrosion-growth synthesis strategy to achieve size-adjustable, highly-confined CsPbBr3 NPs. Initially, we obtain seed nanoplates (NPLs) through a controlled nucleation process. Subsequently, ethylenediamine (EDA), serving as a polar solvent, controls the corrosion process of unstable NPLs. Interestingly, these corroded NPLs then act as monomers, supplying for the growth of the remaining, stable NPLs. Concurrently, these robust NPLs undergo passivation via the chelation of EDA. By increasing the dosage of EDA, the three dimensions of CsPbBr3 exhibit distinct growth patterns, leading to shape transformation. During the entire process, the absorption and photoluminescence (PL) of the NPLs are predominantly influenced by their thickness, which continues to grow through a modified Ostwald ripening process. Consequently, we achieve thickness-controlled NPs whose PL wavelength can be adjusted from 435 nm to 510 nm, with steps as fine as 1 nm. These NPs exhibit remarkable stability and high PL quantum yield (QYs) due to the passivation by EDA and the strong Mn-ligand interaction.

Blue Emitting CsPbBr3: High Quantum Confinement Effect and Well‐Adjusted Shapes (Nanorods, Nanoplates, and Cubes) toward White Light Emitting Diodes

AbstractControlled nucleation and slow growth endow blue emitting CsPbX3 nanocrystals (NCs) with bright photoluminescence (PL), which is crucial needed in luminescent devices. In this paper, a low‐temperature injection synthesis method is developed to control nucleation and the growth process by decreasing the reaction rate of ions, thereby controlling the morphologies of CsPbX3 NCs in clusters, nanorods (NRs), nanoplates (NPLs), and nanocubes by adjusting precursors, ligands, and injection parameters. CsPbX3 NCs exhibit excellent PL properties such as high quantum confinement effect. The PL peak wavelengths of CsPbBr3 NPLs and NRs are at 451 and 467 nm, respectively, in which their full width at half maximum (FWHM) of PL spectra is 22 and 12 nm, while their PL efficiencies are 65 and 74%, respectively. The method is further used to create CsPbI3 and CsPbCl3. CsPbI3 NPLs and NRs reveal PL peaks at 590 and 600 nm and PL efficiencies of 56% and 60%, respectively. These NCs exhibit excellent stability against ultraviolet light irradiation. A color conversion layer for white light‐emitting diodes is fabricated using these highly bright NCs. A Commission Internationale d'Eclairage color coordinate of (0.31,0.33) is located at the white light region specified by Rec.2020 standard, and the color temperature reaches 6189 K.

Influence of the Morphological and Chemical Properties of Nanosized Metal Oxides on Catalytic Efficiency for the Cycloaddition Reaction of CO<sub>2</sub> to Epoxides

Metal oxides represent “workhorse catalysts” for the chemical industry with multifarious applications in dehydrogenation, metathesis, transesterification, and combustion reactions. It is therefore crucial, for each given catalytic process, to investigate the impact of morphological and physicochemical properties on catalytic performance. Metal oxide materials are being increasingly applied as inexpensive catalytic materials for the cycloaddition of CO2 to epoxides but the correlation between the chemical properties of the metal oxides and their catalytic activity has not been systematically investigated. In this work, we prepared nanostructured tin (IV) oxide (SnO2) and zinc oxide (ZnO) materials with different morphologies such as quantum dots (QDs), nanowires (NWs), microdisks (µDs) and nanoplates (NPLs). Following characterization, these materials were investigated, in combination with low amounts of tetrabutylammonium iodide (TBAI) as a nucleophile, for the CO2 cycloaddition to styrene oxide (SO) yielding cyclic styrene carbonate (SC) under atmospheric pressure. The correlation between catalytic performance, surface area, acidity and basicity was investigated and discussed.