Surfactant-assisted Method Research Articles

Fabrication of epoxy composite coating with superior anticorrosive properties using a pH-responsive system based on 2D Zn-MOF nanosheets

Herein, two-dimensional Zn(Bim)(OAc) nanosheets (ZNS) were prepared using ultrasonication and surfactant-assisted methods. Subsequently, it was used as nanocontainer loaded with benzotriazole (BTA) corrosion inhibitor to fabricate BTA@ZNS nanocomposites with pH-controlled release characteristics. The morphology analysis exhibits that BTA@ZNS has a distinct lamellar structure. UV spectrophotometer measurements indicated the release rate of BTA reached 94.38% in 24h at pH=1. Adding BTA@ZNS as fillers into epoxy resin (EP) coating can form BTA@ZNS/EP composite coating with active anti-corrosion properties. Electrochemical impedance spectroscopy (EIS) demonstrates that BTA@ZNS/EP coating has superior corrosion resistance than other EP-based coatings. The enhanced anti-corrosion performance is ascribed to the barrier effect and acid-responsive controlled release of BTA@ZNS.

In-situ synthesis of sunlight-driven CuO-ZnO heterostructure photocatalyst for enhanced elimination of organic pollutants and CO2 reduction.

Removing hazardous organic pollutants, such as 4-nitrophenol (4-NP) and Congo red (CR) dyes from aqueous media and CO2 from the atmospheric medium remains a significant challenge. Herein, we report a facile in-situ synthetic approach for fabricating CuO-ZnO heterostructure photocatalysts through the surfactant-assisted co-precipitation method. The catalytic results demonstrate that the Cu1O-ZnO photocatalyst exhibits excellent activity under direct sunlight irradiation, owing to the heterostructure formation between the CuO and ZnO. The Cu1O-ZnO photocatalyst showed higher reaction rate constant (k) values of 0.20 min-1 for 4-NP and 0.09 min-1 for CR compared to previous reports. Additionally, efficient CO2 reduction was also achieved over Cu1O-ZnO photocatalyst. The optical and structural characterization results indicate that the improved photocatalytic reduction and degradation observed for the Cu1O-ZnO photocatalyst can be attributed to the strong synergistic interaction between p-type CuO and n-type ZnO and the construction of the p-n heterojunction. As a result, the absorption of visible light distinctly increased and inhibited the recombination rate of the photo-created electron-hole (e-/h+). Furthermore, the Cu1O-ZnO photocatalyst exhibited remarkable durability and recyclability, retaining high photoactivity (≥ 93%) after five cycles, demonstrating its potential for real-world applications in the photocatalytic reduction and degradation reactions under direct sunlight irradiation.

Facile synthesis and electrochemical properties of FeO/Fe(OH)3 nanosheets

Iron oxides and hydroxides, including Fe(OH)3 and Fe(OH)2, exhibit diverse morphologies and compositions. Nanostructures of Fe(OH)3 such as nanosheets are non-toxic and offer multiple active sites that are advantageous for catalysis. We synthesized iron oxide/iron hydroxide (FeO/Fe(OH)3) nanosheets using a surfactant-assisted method and analyzed their structure and composition. Their phase transition to iron oxyhydroxides/oxides via heat treatment were also analyzed. The formation of FeOOH, which catalyzes the oxygen evolution reaction, significantly affected the electrochemical properties. We report the morphological and crystallographic characteristics of the as-synthesized and annealed FeO/Fe(OH)3 nanosheets, highlighting the influence of specific species on their electrochemical behavior. The proposed approach is simple and efficient for the synthesis of highly crystalline transition metal oxide nanosheets using different cation precursors.

Printed flexible supercapacitors utilizing composites of MWCNT/MOF ultrathin nanosheets: Exploring 1D/2D structural adjustment

The self-stacking propensity of metal–organic frameworks (MOFs) during synthesis, combined with their intrinsic limitations in electrical conductivity and mechanical stability, constrains their utility as high-capacity energy sources in wearable electronics. Here, we employ a surfactant-assisted method to mitigate the Z-axis stacking of zinc metalloporphyrin organic frameworks (NMOFs), yielding ultrathin two-dimensional (2D) material sheets. By integrating carboxyl multiwalled carbon nanotubes into these nanosheets (denoted as C-NMOF-x), the lamellar structure of MOF is preserved while promoting the formation of rich multistage micropores and continuous conductive channels. This structural refinement remarkably enhances electrochemical properties, including capacitance, electronic conductivity, and cycling stability. Leveraging synergistic interactions, the resulting C-NMOF-4 composite achieves a specific capacitance of 0.152 mAh/g in a three-electrode system at a current density of 1 A/g. Furthermore, the modulated C-NMOF-4 composites are successfully formulated into homogeneous e-inks suitable for dispensing printing, enabling the mass production of flexible micro-supercapacitors (MSCs). Notably, these MSCs maintain 95 % of their capacitance even after 180° bending under wearable conditions. This surface and interface microstructure modulation strategy holds promise for enhancing the synergistic coupling effects of 2D materials and offers new avenues for the application of innovative 2D materials in wearable electronics.

Influence of the La/Ce ratio on La-Ce oxides promoted by Sr in the methane oxidative coupling reaction

The high methane availability and its significant role as a greenhouse gas have led the scientific community to pursue methods for its use. This paper proposes the usage of the oxidative coupling of methane (OCM) as a promising path to transform methane directly into value-added hydrocarbons, mostly ethylene, which serves as a crucial compound in the petrochemical sector. An efficient OCM catalyst should contain substantial basicity and oxygen vacancies for providing surface electrophilic oxygen species, such as superoxides and peroxides, instrumental for boosting selectivity towards C2 products. Mixed lanthanum-cerium oxide (La-Ce) catalysts have emerged as strong candidates in OCM due to their high thermal stability, oxygen mobility, and high alkalinity. In this study, they were prepared through a surfactant-assisted hydrothermal method with different La/Ce ratios for fine-tuning their basic properties and promoting oxygen mobility on the surface of the catalysts. Samples followed a volcano-shaped relationship between C2 yield and La content, with optimal performance at a La/Ce molar ratio of 2.1, attributed to the interplay between the high amount of basic sites and oxygen vacancies, increasing the presence of superoxide species over lattice oxygen. Moreover, the Sr-promoted catalyst showed high density of strong basic sites while preserving the reactive oxygen species, achieving 20 % CH4 conversion, with 57 % C2 compounds selectivity at 750 °C and GHSV of 18.000 mL.gcat−1.h−1.

Surfactant-Mediated Assembly of Precision-Size Liposomes.

Liposomes can greatly improve the pharmacokinetics of therapeutic agents due to their ability to encapsulate drugs and accumulate in target tissues. Considerable effort has been focused on methods to synthesize these nanocarriers in the past decades. However, most methods fail to controllably generate lipid vesicles at specific sizes and with low polydispersity, especially via scalable approaches suitable for clinical product manufacturing. Here, we report a surfactant-assisted liposome assembly method enabling the precise production of monodisperse liposomes with diameters ranging from 50 nm to 1 μm. To overcome scalability limitations, we used tangential flow filtration, a scalable size-based separation technique, to readily concentrate and purify the liposomal samples from more than 99.9% of detergent. Further, we propose two modes of liposome self-assembly following detergent dilution to explain the wide range of liposome size control, one in which phase separation into lipid-rich and detergent-rich phases drives the formation of large bilayer liposomes and a second where the rate of detergent monomer partitioning into solution controls bilayer leaflet imbalances that promote fusion into larger vesicles. We demonstrate the utility of controlled size assembly of liposomes by evaluating nanoparticle uptake in macrophages, where we observe a clear linear relationship between vesicle size and total nanoparticle uptake.

Influence of Post Plasma Treatment on the Photocatalytic Activity of BiVO₄ Synthesized by Surfactant-Assisted Hydrothermal Method

Influence of Post Plasma Treatment on the Photocatalytic Activity of BiVO₄ Synthesized by Surfactant-Assisted Hydrothermal Method

Hollow fiber gas-diffusion electrodes with tailored crystal facets for tuning syngas production in electrochemical CO2 reduction

Electrochemical reduction of CO2 (CO2RR) in aqueous electrolytes not only relies on advanced gas diffusion electrodes (GDEs) to improve CO2 mass transportation but also efficient electrocatalysts to produce specific products. Herein, to produce syngas (CO and H2 mixture), a facet-orientated zinc nanosheet catalyst was electrodeposited on the Cu hollow fiber GDE via a controllable facile surfactant-assisted method. The introduction of cationic surfactant cetyl trimethyl ammonium bromide (CTAB) could manipulate the nucleation and crystal growth of zinc ions around the GDE during the electrodeposition process, leading to controlled changes in the surface free energy and tuned zinc crystal growth orientation. Consequently, the ZncNS-HF with the largest ratio of Zn (101)/Zn (002), resulted in a high current density of 73.3 mA/cm2 and a high syngas production rate of 1328.6 µmol/h∙cm2 at applied potential −1.3 V (vs. RHE). This comes from the hierarchical structure of HFGDE, which provides sufficient CO2 reaching the catalyst/electrolyte interface, and the well-connected zinc nanosheets contribute to a significant number of active sites for CO2RR. This is the first time to configure flow-through or gas-penetrated HFGDEs with zinc crystal facets controlled nanosheet catalysts for syngas production. This research demonstrates the high potential of nanoengineering catalysts for HFGDEs to achieve high production rates of syngas.

High-performance photocatalytic reduction of Cr(VI) using a retrievable Fe-doped WO3/SiO2 heterostructure

The enhancement of the photocatalytic performance of pristine WO3 was systematically adjusted due to its fast recombination rate and low reduction potential. A designed heterostructure photocatalyst was necessarily synthesised by Fe3+ metal ions doping into WO3 structure with and composition modification. In this study, we synthesised a retrievable Fe-doped WO3/SiO2 heterostructure using a surfactant-assisted hydrothermal method. This heterostructure was then employed as an effective photocatalyst for the removal of Cr(VI) under visible light irradiation. Enlarged photocatalytic reduction was observed over a synergetic 7.5 mol% Fe-doped WO3/SiO2-20 nanocomposite, resulting in dramatically increased activity compared with undoped WO3 and SiO2 nanomaterials under visible light illumination within 90 min. The presence of 7.5 mol% Fe3+ ion dopant in WO3 optimised electron–hole recombination, consequently reducing WO3 photocorrosion. After adding SiO2 nanoparticles, the binary WO3-SiO2 nanocomposite played roles as both adsorbent and photocatalyst to increase specific surface area. Thus, the 7.5 mol% Fe-doped WO3/SiO2-20 nanocomposite catalyst had more active sites on the surface of catalyst, and enhanced photocatalytic reduction was significantly achieved. The results showed 91.1% photocatalytic reduction over the optimum photocatalyst, with a photoreduction kinetic rate of 21.1 × 10–3 min−1, which was approximately four times faster than pristine WO3. Therefore, the superior optimal photocatalyst demonstrated reusability, with activities decreasing by only 9.8% after five cycles. The high photocatalytic performance and excellent stability of our photocatalyst indicate great potential for water pollution treatments.

Porphyrin-Based Nanomaterials for the Photocatalytic Remediation of Wastewater: Recent Advances and Perspectives

Self-organized, well-defined porphyrin-based nanostructures with controllable sizes and morphologies are in high demand for the photodegradation of hazardous contaminants under sunlight. From this perspective, this review summarizes the development progress in the fabrication of porphyrin-based nanostructures by changing their synthetic strategies and designs. Porphyrin-based nanostructures can be fabricated using several methods, including ionic self-assembly, metal–ligand coordination, reprecipitation, and surfactant-assisted methods. The synthetic utility of porphyrins permits the organization of porphyrin building blocks into nanostructures, which can remarkably improve their light-harvesting properties and photostability. The tunable functionalization and distinctive structures of porphyrin nanomaterials trigger the junction of the charge-transfer mechanism and facilitate the photodegradation of pollutant dyes. Finally, porphyrin nanomaterials or porphyrin/metal nanohybrids are explored to amplify their photocatalytic efficiency.

Dimension dependent photocatalysis over Znln2S4: Controllable synthesis and catalytic mechanism insight

Dimensional control of nano-photocatalysts enables the enhancement of catalytic activity through optimization of electronic structures. In this study, we take Znln2S4 as an example to demonstrate the influence of dimensional structure on photocatalytic reactions. Firstly, we successfully prepared three different dimensional structures of Znln2S4 (including 1D, 2D, and 3D Znln2S4) using a surfactant-assisted synthesis method. In photocatalytic experiments, we found that Znln2S4 exhibits dimension-dependent catalytic performance in both photocatalytic hydrogen production and photodegradation of dye solutions. Among them, 2D ZnIn2S4 demonstrates highest photocatalytic performance. The hydrogen evolution rate of 2D ZnIn2S4 reached 0.69 mmol g−1 h−1, which was 3.29 and 1.17 times higher than 1D ZnIn2S4 and 3D ZnIn2S4, respectively. In addition, the degradation rate of Rodamine B (RhB) by 2D ZnIn2S4 reached 92.3 % within 30 min, significantly higher than that of 1D ZnIn2S4 (70.3 %) and 3D ZnIn2S4 (86.3 %). The origin for high activity of 2D ZnIn2S4 was investigated by multiple perspectives including light absorption range, charge separation efficiency, band structure, and specific surface area. The results revealed that the high activity of 2D ZnIn2S4 may mainly originate from its dimension-controlled high charge separation efficiency.

Synthesis and electrochemical evaluation of nickel hydroxide nanosheets with phase transition to nickel oxide.

Transition metal hydroxides are commonly used to develop nanostructures with desired functionalities by controlling their size, morphology, and structure. In this study, nickel hydroxide nanosheets with a hexagonal island shape are synthesized via a surfactant-assisted method. Using this method, nickel hydroxide nanosheets can be easily achieved in a quick manner. The synthesized nanosheets are 3-6 nm thick and exhibit a curly and wrinkled morphology with increasing surfactant concentration. These nanosheets demonstrate superior catalytic properties for the oxygen evolution reaction activity compared to nickel oxide sheets obtained via a simple heat treatment. Furthermore, we conduct surface enhanced Raman scattering analysis to confirm that the nickel hydroxide nanosheets serve as active species for NiOOH during the oxygen evolution reaction, and we propose an electrochemical mechanism for this system. This study not only presents the detailed synthesis process but also proposes a straightforward approach, offering valuable insights into the structural and electrochemical properties of the resulting nanosheets.

Exploring moisture adsorption on cobalt-doped ZnFe2O4 for applications in atmospheric water harvesting.

Sorption-based atmospheric water harvesting (SBAWH) is a highly promising approach for extracting water from the atmosphere thanks to its sustainability, exceptional energy efficiency, and affordability. In this work, ZnFe2O4 and Zn0.4Co0.6Fe2O4 were evaluated for moisture adsorption. The desired materials were synthesized by a surfactant-assisted sol-gel method. Synthesized samples were characterized using X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM), and point of zero charge (PZC). Crystallinity and phase composition were evaluated by XRD analysis. Several parameters were determined using XRD analysis: lattice parameter, unit cell volume, crystallite size, and bulk density. The morphology of synthesized materials was assessed via SEM, and unveiled the acquisition of consistent, homogeneous, and uniform crystals. Elemental composition was determined through EDX spectroscopy. Water adsorption on the surface was evaluated by FTIR spectroscopy. The magnetic properties of synthesized ZnFe2O4 and cobalt-doped ZnFe2O4 ferrites were investigated using VSM. The negative charge on the Zn0.4Co0.6Fe2O4 surface was explored using PZC. Adsorption studies on synthesized materials were conducted with the help of an atmospheric water harvesting (AWH) plant created by our team. Moisture adsorption isotherms of synthesized materials were determined using a gravimetric method under varying temperature and relative humidity (45-95%) conditions. The moisture content (Mc) of Zn0.4Co0.6Fe2O4 and ZnFe2O4 was 597 mg g-1 and 104 mg g-1, respectively. Key thermodynamic properties, including isosteric heat of adsorption (Qst), change in Gibbs free energy (ΔG), and change in sorption entropy (ΔS), were evaluated. Qst was negative, which confirmed the sorption of water vapors on the material surface. ΔG and ΔS indicated that water-vapor adsorption was spontaneous and exothermic. A second-order kinetics study was carried out on synthesized materials, demonstrating their chemisorption behavior. The latter was due to the oxygen defects created by replacement of Co2+ and Fe3+ at tetrahedral and octahedral sites. Water vapors in the atmosphere became attached to the surface and deprotonation occurred, and the hydroxyl ions were formed. Water vapor attached to these hydroxyl ions. A second-order kinetics study was carried out to confirm the chemisorption behavior of synthesized materials.

Water Dispersible Colloidal Metal and Metal Oxide Nanoparticles Synthesis for Agarwood Inoculation: A Review

Agarwood is one of the most expensive natural products, produced from Aquilaria Spp. These plants produce agar resin through mechanical, biological, or chemical stress. Besides these, the particles having size in the range of 1-100 nm, are known as nanoparticles, have ultra-high surface area and surface plasmon resonance, can create stress on living plants when incorporated into the plant body. Adopting this concept, we intend to produce agarwood by inoculating water-dispersible metal/metal oxide nanoparticles. Therefore, we aim to synthesize water-dispersible four noble metals (Au, Ag, Pt, Pd) and five metal oxides (Fe3O4, TiO2, SnO2, MnO2, CuO) nanoparticles in aqueous colloidal states for application in biotechnology, considering the facile synthetic routes, readily available and inexpensive precursors, and stability of the products under normal laboratory conditions for an extended period, utilizing the synthesis methods of precipitation of metal/metal oxide nanoparticles from an aqueous solution, microwave and ultrasound-assisted rapid heating methods, sol-gel methods, and surfactant-assisted microemulsion methods. We believe that by applying any of these methods, water-dispersible, long-lasting colloidal metal/metal oxide nanoparticles can be synthesized using a simple laboratory setup, without the need for sophisticated tools or instruments. IUBAT Review, 6(2): 41-76

NIR-II Excitable Water-Dispersible Two-Dimensional Conjugated Polymer Nanoplates for In Vivo Two-Photon Luminescence Bioimaging.

While two-dimensional conjugated polymers (2DCPs) have shown great promise in two-photon luminescence (TPL) bioimaging, 2DCP-based TPL imaging agents that can be excited in the second near-infrared window (NIR-II) have rarely been reported so far. Herein, we report two 2DCPs including 2DCP1 and 2DCP2, with octupolar olefin-linked structures for NIR-II-excited bioimaging. The 2DCPs are customized with the fully conjugated donor-acceptor (D-A) linkage and aggregation-induced emission (AIE) active building blocks, leading to good two-photon absorption into the NIR-II window with a 2PACS of ∼64.0 GM per choromophore for both 2DCPs. Moreover, 2DCP1 powders can be exfoliated into water-dispersible nanoplates with a Pluronic F-127 surfactant-assisted temperature-swing method, accompanied by both a drastic reduction of 2PACS throughout the range of 780-1080 nm and a sharp increase of photoluminescence quantum yield to 33.3%. The 2DCP1 nanoplates are subsequently proven to be capable of assisting in visualizing mouse brain vasculatures with a penetration depth of 421 μm and good contrast in vivo, albeit that only 19% of previous 2PACS at 1040 nm is preserved. This work not only provides important insights on how to construct NIR-II excitable 2DCPs for TPL bioimaging but also how to investigate the exfoliation-photophysical property correlation of 2DCPs, which should aid in future research on developing highly efficient TPL bioimaging agents.

Catalytic Dry-reforming of Methane Process with Co,Ni,Pd/Ca-La-O Mixed Oxides

A surfactant-assisted co-precipitation method was used to prepare the catalysts Co,Ni,Pd/CaO, Co,Ni,Pd/Ca0.97La3+0.03O, Co,Ni,Pd/Ca0.93La3+0.07O, and Co,Ni,Pd/Ca0.85La3+0.15O (1% each of Co, Ni, and Pd). La2O3 doping effect on the activity and stability of Co,Ni,Pd/CaO catalysts was investigated in dry reforming of methane. Catalysts were characterized by several techniques (X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray Fluorescence (XRF), Fourier Transform Infra Red (FTIR), Temperature Programmed Desorption H2 (H2-TPR), Transmission electron microscopes (TEM), and Temperature Gravimetric Analysis (TGA)) and were tested in a fixed-bed reactor at 900 °C and (Gas Hourly Specific Velocity (GHSV) = 15000 mL.gcat−1.h−1, atmospheric pressure). Adding La2O3 had little effect on the morphology of the Co,Ni,Pd/CaO catalyst. However, it played a crucial role in enhancing the catalyst’s reducibility and CO2 adsorption at high temperatures, as indicated by the activity and stability of the Co,Ni,Pd/CaO catalyst. The carbon deposition on utilized catalysts after 5 hours at 900 °C was examined using TEM and thermal gravimetric analysis (TGA) techniques. Compared to Co,Ni,Pd/CaO catalysts across the entire temperature range, the tri-metallic Co,Ni,Pd/Ca0.85La3+0.15O catalyst with a lanthanum promoter demonstrated a greater conversion of CH4 (84%) and CO2 (92 %) at a 1:1 CH4:CO2 ratio. The selectivity of H2/CO reduced in the following order: Co,Ni,Pd/Ca0.85La3+0.15O > Co,Ni,Pd/Ca0.93La3+0.07O > Co,Ni,Pd/Ca0.97La3+0.03O > Co,Ni,Pd/CaO. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Electrodeposition of gold-platinum nanoparticles on 2D M-TCPP (M = Co, Cu, Zn) for electrochemical monitoring of H2O2 from living cells

Two-dimensional (2D) metal–organic frameworks (MOFs) as supporting nanomaterials to encapsulate or load metal nanoparticles have been widely applied in electrochemical sensing. Therefore, the influences of tetrakis(4-carboxyphenyl) porphyrin-based MOFs (M-TCPP (M = Co, Cu, Zn)) as supporting materials on the electrocatalytic activity were studied. A surfactant-assisted method was employed to facilely synthesize three types of 2D M-TCPP nanosheet MOFs. Polyvinylpyrrolidone was selected as a surfactant for preparing M-TCPP and played a key role in the controlled anisotropic growth of MOF crystals, resulting in the formation of 2D MOF nanosheets. Then, one-step electrodeposition of gold-platinum nanoparticles (AuPt NPs) on the M-TCPP-modified glassy carbon electrode (AuPt/M-TCPP/GCE) was explored for reducing hydrogen peroxide (H2O2). Cyclic voltammetry was applied to investigate the electrocatalytic performance of AuPt/M-TCPP/GCE, and AuPt/Cu-TCPP/GCE exhibited better electrocatalytic characteristics than AuPt/Co-TCPP/GCE and AuPt/Zn-TCPP/GCE. The electrochemical H2O2 sensor displayed a low detection limit of 3.1 nM in the wide concentration range of 0.01 μM to 80 mM. In addition, the proposed sensor showed high stability, good reproducibility, and selectivity. Moreover, HepG2 human liver cancer cells were selected for real-time detection of H2O2 to verify the feasibility of this technology for the evaluation of anticancer drugs. The results showed that Cu-TCPP can be used as an efficient supporting material for enhancing the detection property of electrochemical sensors.

An Eco-Friendly, Interference, and Solvent Free Surfactant-Assisted Dual-Wavelength β-CorrectionSpectrometric Method for Total Determination and Speciation of Cu2+ Ions in Water

Spectral interference through the presence of uninformative variables, excess reagents, and complications in the refinement of the analyte signal is common in the quest to identify complex species in real samples. Therefore, an economical green, facile, and sensitive strategy has been developed for Cu2+ detection using the anionic surfactant sodium dodecylsulphate- (SDS-) assisted dual-wavelength β-correction spectrophotometric strategy combined with the chromogenic reagent zincon (ZI). The low limits of detection (LOD) and quantification (LOQ) of Cu2+ using ordinary (single wavelength) spectrophotometry were 0.19 (3.02) and 0.63 (10.0) μgmL−1, and these values were improved to 0.08 (1.27) and 0.26 μgmL−1 (4.12 μM)) using β-correction (dual wavelength) spectrophotometry, respectively. The LOD and LOQ were improved from 0.08 (1.27) and 0.26 (4.12) μgmL−1 to 0.02 (0.32) and 0.08 μgmL−1 (1.27 μM) using SDS-assisted dual-β-correction spectrometry, respectively. Ringbom, s, and the corrected absorbance (Ac) versus Cu2+ concentration plots were linear over the concentration range 1.10–2.4 (17.4–38.1) and 0.50–2.40 μgmL−1 (7.94–38.1 μM), respectively. Sandell’s sensitivity index of 3.0 × 10−3 μg/cm2 was achieved. The selectivity was further confirmed via monitoring the impact of common diverse ions and surfactants on the corrected absorbance. Total determination and Cu2+ speciation in water were favorably implemented and validated by ICP-OES at 95% ( P = 0.05 ). Satisfactory Cu2+ recoveries in tap (92.2–98.0%) and mineral (105–111.0%) water samples were achieved. The sensing system is simple, reliable, sensitive, and selective for Cu2+ detection.

A general and facile approach to flower-like ZnO fabrication

ZnO nanosheets with nanograin distributions, high mesoporosity, and ultrathin thickness have garnered considerable attention owing to their intriguing properties, such as high surface-to-volume ratio and chemical reactivity. Although various methods for fabricating two-dimensional structures have been reported, the surfactant-assisted method is advantageous as it produces nanosheet structures at the water–air interface without affecting the crystal structure of the material. This study developed an innovative surfactant-assisted synthesis method to fabricate flower-like Zinc Oxide (f-ZnO) nanostructures. The synthesis, performed at a mild temperature of 70 °C, yields f-ZnO with high surface area-to-volume ratios and porous morphology. The f-ZnO demonstrates photoelectrochemical (PEC) performance due to increased interfacial contact with electrolytes and the formation of a wurtzite ZnO crystal structure. Additionally, f-ZnO exhibits sensitivity and selectivity as a hydrogen sulfide (H2S) gas sensor. This facile synthesis method opens new avenues for developing functional oxide nanostructures for sensors, catalysts, and energy storage systems.

Synthesis of CoO/Co(OH)2 Nanosheets Depending on Reaction Temperatures

Transition metal oxides formed by a single or heterogeneous combination of transition metal ions and oxygen ions have various types of crystal structures, which can be classified as layered structures and non-layered structures. With non-layered structures, it is difficult to realize a two-dimensional structure using conventional synthesis methods. In this study, we report the synthesis of cobalt oxide into wafer-scale nanosheets using a surfactant-assisted method. A monolayer of ionized surfactant at the water-air interface acts as a flexible template for direct cobalt oxide crystallization below. The nanosheets synthesized on the water surface can be easily transferred to an arbitrary substrate. In addition, the synthesizing morphological and crystal structures of the nanosheets were analyzed according to the reaction temperatures. The electrochemical properties of the synthesized nanosheets were also measured at each temperature. The nanosheets synthesized at 70 °C exhibited higher catalytic properties for the oxygen evolution reaction than those synthesized at other temperatures. This work suggests the possibility of changing material performance by adjusting synthesis temperature when synthesizing 2D nanomaterials using a wide range of functional oxides, resulting in improved physical properties.