Oxide Nanoflowers Research Articles

Dual-Doped Spinel Nickel-Iron Oxide Nanoflowers for Remarkably Enhanced Oxygen Evolution Reaction

Dual-Doped Spinel Nickel-Iron Oxide Nanoflowers for Remarkably Enhanced Oxygen Evolution Reaction

Chirality Engineering of Nanostructured Copper Oxide for Enhancing Oxygen Evolution from Water Electrolysis.

The exploration of a new conceptual strategy for improving the oxygen evolution reaction (OER) of earth-abundant electrocatalysts is critical. In this study, chiral copper oxide nanoflower is explored by a self-assembly method. The characterization suggests the chiral structure originates from the crystal plane-level helical stack of the secondary nanosheets. Of note, the assembly illustrates a record-high degree of spin polarization of 96%, indicating the ideal alignment of electron spin. Moreover, density function theory calculations show the chiral structure reducing the reaction energy barrier (REB) while switching the potential-determining step from *O→*OOH to *OH→*O. Together with the enhanced electrochemical active surface area and accelerated charge transfer, the production of ground-state triplet O2 is improved via a spin-forbidden route that involves the singlet H2O/OH•. Consequently, the chiral nanoflower shows a overpotential of 308mV at 10mA cm-2 and a Tafel slope of 93.5mV dec-1, which is even superior to the commercial RuO2 (310mV, 101mV dec-1). This study presents a new strategy for improving the OER activity by simultaneously enhancing electronic properties and lowering the REB of an non-noble electrocatalyst via chirality engineering.

Growth of high-density Zinc Oxide (ZnO) nanoflowers in all aqueous two-step method and their application in second harmonic generation of femtosecond laser

This study presents a novel two-step all aqueous solution method for the growth of high-density Zinc Oxide (ZnO) nanoflowers, utilizing ZnO powder as a precursor. For this, initially, a seed layer of ZnO nanostructures is prepared using a non-conventional sol-gel technique in an all-aqueous medium. Subsequently, high-density ZnO nanoflowers are synthesized on these seed layers through the chemical bath deposition method. Four samples, each with varying numbers of seed layers (ranging from one to four) are prepared and analyzed using field emission scanning electron microscopy (FESEM). FESEM results indicate that the sample with three seed layers exhibits optimized morphological characteristics. Consequently, further detailed investigation is conducted exclusively on this optimized sample. Furthermore, a preliminary study is done on second harmonic generation (SHG) of this optimized sample.

Synthesis of a bimetal-organic framework-cobalt oxide nanoflowers (Ni/Co-MOF@Co3O4 NFs) for sensitive tebuconazole extraction from fruit juice and water samples using micro-solid phase extraction-HPLC-DAD

Tebuconazole (TBZ) is a widely used triazole fungicide that poses potential risks to human health and the environment due to its persistence in food and water. Effective monitoring of TBZ residues is crucial for ensuring food safety and environmental protection. This study presents a novel method for synthesizing Ni/Co-MOF@Co3O4 nanoflowers (NFs) and their application in extracting TBZ from water and fruit juice samples via micro-solid phase extraction (µ-SPE). Ni/Co-MOF@Co3O4 NFs was synthesized using the hydrothermal technique followed by calcination. The synthesized nanoflowers were characterized through SEM, XRD, and FT-IR analyses. Optimal extraction conditions were established at pH 8, using 10 mg of adsorbent, with adsorption and desorption times of 3 and 2 min, respectively. TBZ analysis was conducted using HPLC with a Poroshell 120 EC-C18 column and a diode array detector (DAD). The method demonstrates excellent recovery rates (90–102 %) and RSD% of 3.7 % in spiked fruit juice and natural water samples. The analytical performance showed a wide linear range (1–2000 µg L−1) with a high correlation coefficient (R2 = 0.9998), a detection limit of 4.0 ng L−1, and a quantification limit of 13.0 ng L−1. This approach is fast, simple, and highly sensitive, offering a reliable technique for detecting trace levels of TBZ in food and water environments.

Advancements in CuO nanoparticle technology: synthesis, characterization of copper oxide nanoflowers

Abstract Nanostructured materials, including metal and metal oxide nanoparticles, play a crucial role in advancing diverse scientific and technological areas. Transition metal oxides such as CuO are integral to developments in fields like antibacterial treatments, solar energy conversion, sensing technologies, catalysis, magnetic storage, supercapacitors, and semiconductor devices. This research is centered on the hydrothermal synthesis of pure copper oxide nanoflowers, which are noted for their extensive surface areas. Zeta potential analysis, ultraviolet-visible spectrophotometry, field-emission scanning electron microscopy, and Fourier-transform infrared spectroscopy were some of the methods utilized to characterize these nanoparticles. The results showed that band gap energies, crystallite size, and lattice characteristics are all greatly affected by CuO. XRD results indicated a covellite monoclinic polycrystalline structure predominantly orientation with average crystallite sizes around 15.84 nm. FE-SEM imagery depicted the hierarchical, cauliflower-like structure of the CuO nanoparticles. Optical assessments revealed band gap values ranging from 2.58 eV. The findings underscore the broad potential of CuO nanoflowers across various technological applications.

Cerium Enhanced Supercapacitive Properties of Zinc Oxide Nanoflowers

Cerium Enhanced Supercapacitive Properties of Zinc Oxide Nanoflowers

Electron transfer mechanism mediated MOF-derived nanoflowers catalyst for promoting peroxymonosulfate activation and ciprofloxacin degradation

Three MOF-derived nanoparticles were synthesized by manganese doping and calcination of ZIF-67 precursor. The surface physicochemical properties of these materials were compared using SEM, TEM, XRD, FTIR and BET analyses. Among them, cobalt-manganese oxide nanoflowers (CoMn2O4-NFs) exhibited excellent catalytic performance in the degradation of ciprofloxacin (CIP) by activated peroxymonosulfate (PMS), achieving 100 % removal within 30 minutes with a rate constant (kobs) of 0.2960 min−1. The catalytic mechanism was elucidated by quenching experiments, EPR, electrochemical analysis and X-ray photoelectron spectroscopy (XPS). The results show that the non-radical oxidation process was initiated mainly by direct electron transfer and 1O2 (∼80 %), with a small contribution from the radical SO4·- (∼20 %). The nano-confined structure on the surface of CoMn2O4-NFs makes it easy to combine with PMS to form CoMn2O4-NFs/PMS* complexes, which directly capture electrons from CIP to complete the degradation process. The double redox cycle of cobalt-manganese ions and oxygen vacancies on CoMn2O4-NFs could accelerate the electron transfer process. CoMn2O4-NFs maintained high removal efficiency (>99 %) over a wide pH range (3−11), with minimal interference from most environmental anions, demonstrating strong stability and interference resistance. This study provides insights into using metal-based materials for oxidative degradation of organic pollutants via non-radical pathways.

Dual-Functional Tungsten-Doped NiO for Highly Sensitive Triethylamine Sensor with ppb Level Detection Limit.

In this study, the W-doped Nickel oxide (NiO) nanoflowers were synthesized using a straightforward hydrothermal method, significantly enhancing the sensing performance toward triethylamine through dual-functional tungsten doping. The optimal doping concentration not only increased the specific surface area of NiO from 25.54 to 189.19 m2 g-1 but also reduced the formation energy of oxygen vacancies. The sensor containing 4 at % W-doped NiO demonstrated exceptional sensitivity to triethylamine, achieving a detection level as high as 229.0 for concentrations of 100 ppm at 237.5 °C. This triethylamine sensor represents a 135-fold enhancement over sensors fabricated from undoped NiO, and offers a rapid response/recovery time of 8 and 30 s, respectively. Furthermore, at a lower triethylamine concentration of 50 ppb, indicating a lower detection limit.

Oriented growth of NiCo metal–organic framework nanosheets on electrode materials for ternary mixed metal oxide supercapacitors

Metal–organic frameworks (MOFs) are porous structures that possess high specific surface areas, making them promising cathode materials for energy storage devices. However, solving the problems of random growth and easy aggregation of MOF nanosheets remains a challenge. In this study, hydrothermal and calcination methods were used to successfully create nickel cobalt molybdenum metal oxide (NCMO) nanoflowers, followed by the directional growth of NiCo–MOF on its surface. The oriented growth of NiCo–MOF nanosheets on NCMO nanospheres effectively prevented agglomeration, forming NCMO@NiCo–MOF with enhanced electrochemical sensitivity and a large quantity of active sites. When used as an electrode, NCMO@NiCo–MOF forms a large contact area with the electrolyte, demonstrating a high specific capacitance of 1724 F g−1 at a current density of 1 A g−1. Furthermore, at a power density of 824.8 W kg−1, an asymmetric supercapacitor constructed from NCMO@NiCo–MOF and activated carbon exhibited a high energy density of 44.5 Wh kg−1. This study presents a facile method for the assembly of MOF nanosheets for three-dimensional supercapacitors.

(Invited) Novel Anodic Oxide Nanotube Array Architectures for Solar Photoelectrochemical Fuel Generation

Electrochemical anodization has progressed from its level as a low-cost commercial technique to fabricate corrosion and abrasion resistant compact oxide coatings to the status of an effective method for growing a variety of oxide nano-architectures, particularly nanorods, nanowires, nanotubes, nanoporous films, and nanoflowers. Among these structures, self-organized vertically aligned nanotubes of oxide semiconductors have been demonstrated to possess interesting electrical, optical and mechanical properties. As in the case of most low dimensional materials, these structures also possess high surface area. Nevertheless, their unique properties applicable to solar energy conversion processes such as photoelectrochemical (PEC) fuel generation arise primarily from their vertical orientation, their ability to keep the charge carriers always in the vicinity of the surface and the pathways they offer for facile charge transport. They can form heterostructures with other low dimensional materials and function synergistically to enhance the efficiency of the PEC processes. Anodic nanotube arrays of only a few oxide semiconductors have been discovered so far; however, expanding the list further has been proven difficult. Recently, we have developed a few novel nanotubular semiconductors promising for PEC fuel generation. This presentation provides the details of their fabrication process and performance as photocatalysts for solar fuel generation.

Impact of reduced-graphene-oxide functionalization of flower-like zinc-oxide nanostructures on sensing performance of resistive ethanol gas sensor

This research presents a sensitive resistive ethanol gas sensor based on reduced graphene oxide (rGO)-functionalized Zinc oxide nanoflowers (ZnO NFs). Upon completion of synthesis, the resulting nanostructures were cast onto the photolithographed silver interdigitated electrodes positioned on an Al2O3 substrate. The graphene oxide (GO) with a low oxidation degree was synthesized using a Hummer's method. In the pursuit of optimizing sensing performance, rGO-functionalized ZnO NFs were synthesized through a one-pot hydrothermal process, utilizing different initial quantities of GO (0 mg, 2 mg, 8 mg, and 12 mg). According to the gas sensing measurements, the fabricated sensor with 8 mg initial GO showed the highest response to ethanol at 250 °C. The results show that the GO addition reduced the optimal working temperature of the pure ZnO NFs from 350 °C to 250 °C. The sensor exhibited a good selectivity, repeatability, and high long-term stability. Enhanced ethanol sensing response of the optimized gas sensor was related to the formation of p-n heterojunction between p-type rGO (formed during hydrothermal process at 200 °C) and n-type ZnO and the presence of the optimal amount of rGO on the surface of NFs. The results obtained in this investigation stress the significance of pinpointing the optimal quantity of GO for producing rGO-ZnO nanoflowers with the highest possible sensitivity to ethanol gas.

Multiquenching-Based Aggregation-Induced Electrochemiluminescence Sensing for Highly Sensitive Detection of the SARS-CoV-2 N Protein.

The rapid epidemic around the world of coronavirus disease 2019 (COVID-19), caused by the SARS-CoV-2 virus, proves the need and stimulates efforts to explore efficient diagnostic tests for the sensitive detection of the SARS-CoV-2 virus. An aggregation-induced electrochemiluminescence (AIECL) sensor was developed for the ultrasensitive detection of the SARS-CoV-2 nucleocapsid (N) protein in this work. Tetraphenylethylene doped in zeolite imidazole backbone-90 (TPE-ZIF-90) showed highly efficient aggregation-induced emission (AIE) to endow TPE-ZIF-90 with high ECL intensity. Upon the capture of the SARS-CoV-2 N protein by immune recognition, an alkaline phosphatase (ALP)-modified gold nanoparticle (AuNP)-decorated zinc oxide (ZnO) nanoflower (ALP/Au-ZnO) composite was introduced on the sensing platform, which catalyzed L-ascorbate-2-phosphate trisodium salt (AA2P) to produce PO43- and ascorbic acid (AA). Based on a multiquenching of the ECL signal strategy, including resonance energy transfer (RET) between TPE-ZIF-90 and Au-ZnO, disassembly of TPE-ZIF-90 triggered by the strong coordination between PO43- and Zn2+, and RET between TPE-ZIF-90 and AuNPs produced in situ by the AA reductive reaction, the constructed AIECL sensor achieved highly sensitive detection of the SARS-CoV-2 N protein with a low limit of detection of 0.52 fg/mL. With the merits of high specificity, good stability, and proven application ability, the present RET- and enzyme-triggered multiquenching AIECL sensor may become a powerful tool in the field of SARS-CoV-2 virus diagnosis.

Structure-Function Relationship of Iron Oxide Nanoflowers: Optimal Sizes for Magnetic Hyperthermia Depending on Alternating Magnetic Field Conditions.

Iron oxide nanoflowers (IONFs) that display singular magnetic properties can be synthesized through a polyol route first introduced almost 2 decades ago by Caruntu et al, presenting a multi-core morphology in which several grains (around 10 nm) are attached together and sintered. These outstanding properties are of great interest for magnetic field hyperthermia, which is considered as a promising therapy against cancer. Although of significantly smaller diameter, the specific adsorption rate (SAR) of IONFs reach valuesas large as for "magnetosomes" that are natural magnetic nanoparticles typically ~40 nm found in certain bacteria, which can be grown artificially but with much lower yield compared to chemical synthesis such as the polyol route. This work aims at better understanding the structure-property relationships, linking the internal IONF nanostructure as observed by HR-TEMto their magnetic properties. A library of mono- and multicore IONFs is presented, with diameters ranging from 11 to 30 nm in a narrow size distribution. More particularly, by relating their structural features to their magnetic properties investigated by utilizing AC magnetometry over a wide range of alternating magnetic field conditions, we showed that the SAR values of all synthesized batches vary with overall diameter and number of constituting cores.

Facile one-step solvothermal synthesis of Co3O4/CuO nanoflowers as an excellent catalyst for CO oxidation in coal mines

In the present study, Cobalt oxide (Co3O4)/Copper oxide (CuO) nanoflower catalysts were synthesized through a one-step solvothermal method, and the impact of various factors, including reaction time, on the catalytic activity of the catalysts towards carbon monoxide (CO) was investigated. The results showed that the catalysts synthesized at 140 °C and a reaction time of 4 h provided the best catalytic performance for carbon monoxide, and the regular nanoflower-like morphology provided a larger specific surface area as well as a greater number of active sites, allowing the instantaneous 100 % elimination of CO at 200 °C. Additionally, a plausible reaction mechanism was elucidated, wherein CO initially adsorbed onto the sample's surface, subsequently reacting with lattice oxygen to form intermediate carbonate species. This process ultimately led to the production of carbon dioxide (CO2), followed by the desorption of CO2 molecules from the sample's surface. The results demonstrate that these composite catalysts effectively mitigate CO levels during CO over limit in coal mines, thereby enhancing the safety of production personnel.

Biodegradation by Cancer Cells of Magnetite Nanoflowers with and without Encapsulation in PS-b-PAA Block Copolymer Micelles.

Magnetomicelles were produced by the self-assembly of magnetite iron oxide nanoflowers and the amphiphilic poly(styrene)-b-poly(acrylic acid) block copolymer to deliver a multifunctional theranostic agent. Their bioprocessing by cancer cells was investigated in a three-dimensional spheroid model over a 13-day period and compared with nonencapsulated magnetic nanoflowers. A degradation process was identified and monitored at various scales, exploiting different physicochemical fingerprints. At a collective level, measurements were conducted using magnetic, photothermal, and magnetic resonance imaging techniques. At the nanoscale, transmission electron microscopy was employed to identify the morphological integrity of the structures, and X-ray absorption spectroscopy was used to analyze the degradation at the crystalline phase and chemical levels. All of these measurements converge to demonstrate that the encapsulation of magnetic nanoparticles in micelles effectively mitigates their degradation compared to individual nonencapsulated magnetic nanoflowers. This protective effect consequently resulted in better maintenance of their therapeutic photothermal potential. The structural degradation of magnetomicelles occurred through the formation of an oxidized iron phase in ferritin from the magnetic nanoparticles, leaving behind empty spherical polymeric ghost shells. These results underscore the significance of encapsulation of iron oxides in micelles in preserving nanomaterial integrity and regulating degradation, even under challenging physicochemical conditions within cancer cells.

Bimetallic MOF-derived three-dimensional nanoflowers PdCoOx as peroxidase mimic activity for determining total antioxidant capacity

Bimetallic MOF derivatives have shown excellent performance as nano-enzymes in the field of catalysis. Herein, PdCo oxide nanoflowers with three-dimensional flower were prepared by a simple pyrolysis method on a precursor of bimetallic PdCo-MOF. PdCoOx showed excellent peroxidase mimic activity, which could significantly promote the oxidation of TMB by H2O2. Compared with CoOx, the peroxidase mimic activity of the optimized PdCoOx-300 increased by 2.41-fold. PdCoOx-300 has high affinity for TMB and H2O2 with Km values of 0.16 mM and 2.11 mM, which are only 57.03% and 36.87% of HRP, respectively. The highly specific peroxidase mimic activity is conducive to the sensitive detection of H2O2, glucose and ascorbic acid with limit of detection of 10, 100 and 10 nM, respectively. Furthermore, the total antioxidant capacity in the actual beverage samples was conducted, which showed good anti-interference ability and recovery rate.

Antibacterial Activity, Cell Wall Damage, and Cytotoxicity of Zinc Oxide Nanospheres, Nanorods, and Nanoflowers

Antibacterial Activity, Cell Wall Damage, and Cytotoxicity of Zinc Oxide Nanospheres, Nanorods, and Nanoflowers

Exploring Mo-ZnO@NF for hydrogen generation and methylene blue remediation: sunlight-driven catalysis

In this study, we elucidate the synthesis and characterization of molybdenum (Mo) doped zinc oxide (ZnO) nanoflowers (Mo-ZnO@NF) fabricated via a hydrothermal approach, showcasing their potential application in hydrogen generation and dye degradation. The successful synthesis of these nanoflowers is achieved through the deliberate incorporation of Mo ions into the ZnO lattice, yielding a distinctive hierarchical flower-like morphology. Comprehensive structural, morphological, and optical analyses are conducted employing a suite of analytical techniques, encompassing XRD, Raman, FESEM, and UV-Visible spectroscopy. XRD analysis confirms the retention of the hexagonal wurtzite crystal structure, accompanied by discernible peak shifts indicative of Mo ion integration. FESEM imaging further elucidates the flower-like architecture of Mo-ZnO, underscoring the intricate morphological features. Photocatalytic assessment reveals the remarkable efficacy of Mo-ZnO@NF, as evidenced by an unprecedented hydrogen evolution rate of 2024 mmol/h/g and 97% Methylene Blue (MB) dye degradation within a mere 40-minute timeframe. Furthermore, a comparative investigation between pristine ZnO and varying Mo doping concentrations (ranging from 1% to 5%) underscores the optimal doping concentration of 1% Mo in ZnO. This concentration threshold is shown to engender superior photocatalytic performance, potentially attributed to enhanced charge carrier separation and increased surface area conducive to catalytic reactions. Overall, this study not only advances our understanding of Mo-ZnO@NF nanostructures but also elucidates key insights into optimizing their photocatalytic efficacy for diverse environmental remediation applications.

Combined Effect of Adsorption and Photocatalytic Degradation Using Magnesium Oxide Nano-flowers for Tetracycline Removal

AbstractThe extensive use of antibiotics, including tetracycline (TC), has several negative impacts on ecosystems that need attention. In the present study, magnesium oxide nano-flowers (MgO NFs) were examined as an adsorbent and as a degradation photocatalyst for TC elimination. MgO NFs were characterized by XRD, UV-Vis, PL, SEM, TEM, and FTIR. Optimization of the removal process included varying the treatment time, initial pH, MgO NFs dosage, and testing with different initial TC concentrations. The highest removal efficiency (77.3%) was achieved for 50 mg/L TC using 0.6 g/L of MgO NFs at pH 9. Adsorption removal contributed to 26.0% of this removal, while 51.3% was attributed to photocatalytic removal. A one-way analysis of variance (ANOVA) revealed significant impacts of time, initial pH, MgO NFs dose, and initial TC concentrations on TC removal. Although adding different ions showed strong effects on TC adsorption on MgO NFs, those ions inhibited TC removal by about 5% after photocatalytic degradation. Adsorption data fitted well with the Langmuir isotherm and pseudo-second-order kinetic models, the adsorption process was monolayer on a homogenous surface based on chemical interactions. Based on the Langmuir-Hinshelwood model, t1/2 values ranged from 60.79 to 76.15 min for TC concentrations varying from 10 to 60 mg/L. Bacterial growth inhibition of Escherichia coli (ATCC 25,922) and Bacillus cereus (ATCC 33,019) were reduced after TC treatment. The study evidenced that using MgO NFs in photodegradation is an effective approach for TC removal from water bodies.

Durable Antimicrobial Microstructure Surface (DAMS) Enabled by 3D-Printing and ZnO Nanoflowers.

A. Numerous studies have been trying to create nanomaterials based antimicrobial surfaces to combat the growing bacterial infection problems. Mechanical durability has become one of the major challenges to applying those surfaces in real life. In this study, we demonstrate the Durable Antimicrobial Microstructures Surface (DAMS) consisting of DLP 3D printed microstructures and zinc oxide (ZnO) nanoflowers. The microstructures serve as a protection armor for the nanoflowers during abrasion. The antimicrobial ability was tested by immersing in 2E8 CFU/mL Escherichia coli ( E. coli ) suspension and then evaluated using electron microscopy. Compared to the bare control, our results show that the DAMS reduces bacterial coverage by more than 90% after 12 hrs of incubation and approximately 50% after 48 hrs of incubation before abrasion. Importantly, bacterial coverage is reduced by approximately 50% after 2 min of abrasion with a tribometer, and DAMS remains effective even after 6 min of abrasion. These findings highlight the potential of DAMS as an affordable, scalable, and durable antimicrobial surface for various biomedical applications.