Surface-engineered vertically-aligned ZnO nanorod for sensitive non-enzymatic electrochemical monitoring of cholesterol.

Developing highly sensitive and selective non-enzymatic electrochemical biosensors for disease biomarker detection has become challenging in healthcare applications. However, advances in material science are opening new avenues for creating more dependable biosensing technologies. In this context, the present work introduces a novel approach by engineering a hybrid structure of zinc oxide nanorod (ZnO NR) modified with iron oxide nanoparticle (Fe2O3 NP) on an FTO electrode. This Fe2O3 NP-ZnO NR hybrid material functions as a nanozyme, facilitating the catalysis of cholesterol and enabling the direct transfer of electrons to the fluorine-doped tin oxide (FTO) electrode, limiting the need for costly and traditional enzymes in the detection process. This innovative non-enzymatic cholesterol biosensor showcases remarkable sensitivity, registering at 642.8 µA/mMcm2 within a linear response range of up to 9.0 mM. It also exhibits a low detection limit (LOD) of ∼12.4 µM, ensuring its capability to detect minimal concentrations of cholesterol accurately. Moreover, the developed biosensor displays exceptional selectivity by effectively distinguishing cholesterol molecules from other interfering biological species, while exhibiting outstanding stability and reproducibility. Our findings indicate that the Fe2O3 NP-ZnO NR hybrid nanostructure on the FTO electrode holds promise for enhancing biosensor stability. Furthermore, the present device fabrication platform offers versatility, as it can be adapted with various enzymes or modified with different metal oxides, potentially broadening its applicability in a wide range of biomarkers detection.

Hybrid nanostructures for neurodegenerative disease theranostics: the art in the combination of biomembrane and non-biomembrane nanostructures.

The diagnosis of neurodegenerative diseases (NDDs) remains challenging, and existing therapeutic approaches demonstrate little efficacy. NDD drug delivery can be achieved through the utilization of nanostructures, hence enabling multimodal NDD theranostics. Nevertheless, both biomembrane and non-biomembrane nanostructures possess intrinsic shortcomings that must be addressed by hybridization to create novel nanostructures with versatile applications in NDD theranostics. Hybrid nanostructures display improved biocompatibility, inherent targeting capabilities, intelligent responsiveness, and controlled drug release. This paper provides a concise overview of the latest developments in hybrid nanostructures for NDD theranostics and emphasizes various engineering methodologies for the integration of diverse nanostructures, including liposomes, exosomes, cell membranes, and non-biomembrane nanostructures such as polymers, metals, and hydrogels. The use of a combination technique can significantly augment the precision, intelligence, and efficacy of hybrid nanostructures, therefore functioning as a more robust theranostic approach for NDDs. This paper also addresses the issues that arise in the therapeutic translation of hybrid nanostructures and explores potential future prospects in this field.

An Electroanalytical Enzymeless α-Fe2O3-ZnO Hybrid Nanostructure-Based Sensor for Sensitive Quantification of Nitrite Ions.

Nitrite monitoring serves as a fundamental practice for protecting public health, preserving environmental quality, ensuring food safety, maintaining industrial safety standards, and optimizing agricultural practices. Although many nitrite sensing methods have been recently developed, the quantification of nitrite remains challenging due to sensitivity and selectivity limitations. In this context, we present the fabrication of enzymeless iron oxide nanoparticle-modified zinc oxide nanorod (α-Fe2O3-ZnO NR) hybrid nanostructure-based nitrite sensor fabrication. The α-Fe2O3-ZnO NR hybrid nanostructure was synthesized using a two-step hydrothermal method and characterized in detail utilizing x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). These analyses confirm the successful synthesis of an α-Fe2O3-ZnO NR hybrid nanostructure, highlighting its morphology, purity, crystallinity, and elemental constituents. The α-Fe2O3-ZnO NR hybrid nanostructure was used to modify the SPCE (screen-printed carbon electrode) for enzymeless nitrite sensor fabrication. The voltammetric methods (i.e., cyclic voltammetry (CV) and differential pulse voltammetry (DPV)) were employed to explore the electrochemical characteristics of α-Fe2O3-ZnO NR/SPCE sensors for nitrite. Upon examination of the sensor's electrochemical behavior across a range of nitrite concentrations (0 to 500 µM), it is evident that the α-Fe2O3-ZnO NR hybrid nanostructure shows an increased response with increasing nitrite concentration. The sensor demonstrates a linear response to nitrite concentrations up to 400 µM, a remarkable sensitivity of 18.10 µA µM-1 cm-2, and a notably low detection threshold of 0.16 µM. Furthermore, its exceptional selectivity, stability, and reproducibility make it an ideal tool for accurately measuring nitrite levels in serum, yielding reliable outcomes. This advancement heralds a significant step forward in the field of environmental monitoring, offering a potent solution for the precise assessment of nitrite pollution.

Construction of Nickel Molybdenum Sulfide/Black Phosphorous 3D Hierarchical Structure Toward High Performance Supercapacitor Electrodes.

Supercapacitors (SCs) with outstanding versatility have a lot of potential applications in next-generation electronics. However, their practical uses are limited by their short working potential window and ultralow-specific capacity. Herein, the facile one-step in-situ hydrothermal synthesis is employed for the construction of a NiMo3S4/BP (black phosphorous) hybrid with a 3D hierarchical structure. After optimization, the NiMo3S4/BP hybrid displays a high specific capacitance of 830 F/g at 1 A/g compared to the pristine NiMo3S4 electrode. The fabricated NiMo3S4/BP//NiCo2S4/Ti3C2Tx asymmetric supercapacitor exhibits a better specific capacitance of 120 F/g at 0.5 A/g, which also demonstrates a high energy density of 54 Wh/kg at 1148.53 W/kg and good cycle stability with capacity retention of 86% and 97% of Coulombic efficiency after 6000 cycles. Further from the DFT simulations, the hybrid NiMo3S4/BP structure shows higher conductivity and quantum capacitance, which demonstrate greater charge storage capability, due to enhanced electronic states near the Fermi level. The lower diffusion energy barrier for the electrolyte K+ ions in the hybrid structure is facilitated by improved charge transfer performance for the hybrid NiMo3S4/BP. This work highlights the potential significance of hybrid nanoarchitectonics and compositional tunability as an emerging method for improving the charge storage capabilities of active electrodes.

Nanostructure Control of GaN by Electrochemical Etching for Enhanced Perovskite Quantum Dot LED Backlighting.

Upgraded technology has realized miniaturization and promoted transformation in each field. Miniaturized light-emitting diode (LED) chips enable higher resolution and create a full sense of immersion in displays. Porous GaN is a structure that can reduce excitation light leakage and enhance the light conversion efficiency. Perovskite quantum dots with the highest optical density as candidate materials for loading in pores can significantly decrease the aggregation phenomenon and increase the path of light absorption. Here, the porous tunability is explored by electrochemical etching under a range of voltages, concentrations, and etching times with acid and base electrolytes, such as oxalic acid and potassium hydroxide. Based on scanning electron microscopy images, the distribution of the pores and the morphology of pore channels can be distinguished under acid and base etching. Larger pore sizes and distorted channels (∼680 nm) are presented on the oxalic acid-etched GaN chip. In contrast, smaller pore sizes and straight-deeper channels (∼5650 nm) are demonstrated on the GaN by potassium hydroxide etching. Therefore, the hybrid nanostructure is etched by oxalic acid and potassium hydroxide, separately. The green and red light conversion efficiencies of perovskite quantum dots pumped by a blue LED can be improved by 3 and 10 times, respectively, resulting in a color gamut of approximately 124%.

Site-specific growth of gold nanoparticles on Bismuth Selenide hexagonal nanoplates.

Highly site-specific growth of gold nanoparticles (AuNPs) on Bismuth Selenide (Bi2Se3) hexagonal nanoplates was achieved by fine-tuning the growth kinetics of Au through controlling the coordination number of the Au ion in MBIA-Au3+ complex. With increasing concentration of MBIA, the increased amount and the coordination number of the MBIA-Au3+ complex results in the decrease of the reduction rate of Au. The slowed growth kinetics of Au allowed the recognition of the sites with different surface energy on the anisotropic Bi2Se3 hexagonal nanoplates. As a result, the site-specific growth of AuNPs at the corner, the edge, and the surface of the Bi2Se3 nanoplates were successfully achieved. This way of growth kinetic control was proven to be effective in constructing well-defined heterostructures with precise site-specificity and high purity of the product. This is helpful for the rational design and controlled synthesis of sophisticated hybrid nanostructures and would eventually promote their applications in various fields.

Development, Characterization, and Evaluation as Food Active Packaging of Low-Density-Polyethylene-Based Films Incorporated with Rich in Thymol Halloysite Nanohybrid for Fresh "Scaloppini" Type Pork Meat Fillets Preservation.

A new era is rising in food packaging and preservation, with a consequent focus on transition to "greener" and environmentally friendly techniques. The environmental problems that are emerging nowadays impose use of natural materials for food packaging applications, replacement of chemical preservatives with natural organic extractions, such as essential oils, and targeting of new achievements, such as further extension of food shelf-life. According to this new philosophy, most of the used materials for food packaging should be recyclable, natural or bio-based, and/or edible. The aim of this work was to investigate use and efficiency of a novel food packaging developed based on commercial LDPE polymer incorporated with natural material halloysite impregnated with natural extract of thyme oil. Moreover, a direct correlation between the stiff TBARS method and the easiest heme iron measurements method was scanned to test food lesions easier and faster. The result of this study was development of the LDPE/10TO@HNT film, which contains the optimum amount of a hybrid nanostructure and is capable to be used as an efficient active food packaging film. Furthermore, a linear correlation seems to connect the TBARS and heme iron measurements.

Dual-mode visual detection strategies of viable pathogens for point-of-care testing.

Here, we introduce a power-free foldable poly(methyl methacrylate) (PMMA) microdevice fully integrating DNA extraction, amplification, and visual detection, realized in novel dual modes - colorimetric and aggregate formation - using 4-Aminoantipyrine (4-AP) for monitoring pathogens. The microdevice contains two parts: reaction and detection zones. A sealing film was utilized to connect the two zones and make the device foldable. The FTA card was deposited in the reaction zone for DNA extraction, followed by loop-mediated isothermal amplification (LAMP) at 65 °C for 45 min. When the detection zone is folded toward the reaction zone, paper discs modified with 4-AP placed in the detection zone are delivered to the reaction zone. Specifically, in the presence of LAMP amplicons, 4-AP is oxidized into antipyrine red or generates aggregates by interacting with copper sulfate, forming copper hybrid nanostructure (Cu-hNs). In the absence of LAMP amplicons, 4-AP is not oxidized and maintains yellow color or fails to form aggregates. Furthermore, we introduced the ethidium homodimer-1 (EthD-1) to identify viable bacteria. EthD-1 penetrated the compromised membranes of nonviable cells and prevented further DNA amplification by intercalating with the DNA. In this way, only samples containing viable cells displayed color change or formed aggregates upon reaction with 4-AP. Using this method, SARS-CoV-2 RNA and Enterococcus faecium were identified by naked eye, with the limit of detection of 103 copies/µL and 102 CFU/mL, respectively, within 60 min. The introduced microdevice can be used for rapidly monitoring viable pathogens and controlling outbreaks of infectious disease in resource-limited settings.

Chiral Third-Harmonic Metasurface for Multiplexed Holograms.

Chiral nonlinear metasurfaces could natively synergize nonlinear wavefront manipulation and circular dichroism, offering enhanced capacity for multifunctional and multiplexed nonlinear metasurfaces. However, it is still quite challenging to simultaneously enable strong chiral response, precise wavefront control, high nonlinear conversion efficiency, and independent functions on spins and chirality. Here, we propose and experimentally demonstrate multiplexed third-harmonic (TH) holograms with four channels based on a chiral Au-ZnO hybrid metasurface. Specifically, the left- and right-handed circularly polarized (LCP and RCP) components of the TH holographic images can be designed independently under the excitation of an LCP (or RCP) fundamental beam. In addition, the TH conversion efficiency is measured to be as large as 10-5, which is 8.6 times stronger than that of a bare ZnO film with the same thickness. Thus, our work provides a promising platform for realizing efficient and multifunctional nonlinear nanodevices.

An intelligent DNA nanorobot for detection of MiRNAs cancer biomarkers using molecular programming to fabricate a logic-responsive hybrid nanostructure.

Herein, we designed a DNA framework-based intelligent nanorobot using toehold-mediated strand displacement reaction-based molecular programming and logic gate operation for the selective and synchronous detection of miR21 and miR125b, which are known as significant cancer biomarkers. Moreover, to investigate the applicability of our design, DNA nanorobots were implemented as capping agents onto the pores of MSNs. These agents can develop a logic-responsive hybrid nanostructure capable of specific drug release in the presence of both targets. The prosperous synthesis steps were verified by FTIR, XRD, BET, UV-visible, FESEM-EDX mapping, and HRTEM analyses. Finally, the proper release of the drug in the presence of both target microRNAs was studied. This Hybrid DNA Nanostructure was designed with the possibility to respond to any target oligonucleotides with 22 nucleotides length.

Graphdiyne reinforced multifunctional Cu/Ni bimetallic Phosphides-Graphdiyne hybrid nanostructure as high performance electrocatalyst for water splitting.

Obtaining of non-noble metal catalyst with bifunctional effect for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water splitting is highly desired to get high purity hydrogen. Here in, we design and fabricate Cu/Ni bimetallic phosphides with Graphdiyne (GDY) to form hybrid nanomaterial CuNiPx-GDY on Ni foam for the first time. The synergistical effect between GDY and transition metal phosphides, and the atomic scale heterojunctions between Cu3P and Ni2P, effectively accelerate the catalytical process both in HER and OER, resulting in extraordinarily small overpotentials of 178 mV and 110 mV at 10 mA cm-2 for OER and HER in CuNiPx-GDY(1:1) in 1 M KOH, respectively. Density functional theory results show that, compared with pure CuNiPx, the introduced GDY can considerably improve the activity of OER and generate different active sites for OER and HER in CuNiPx-GDY(1:1). Thus CuNiPx-GDY(1:1) exhibits good catalytical performance and stability as catalyst for overall water splitting. This study provides a new sight into the structure and catalytic properties of GDY and transition metal phosphides hybrid nanomaterial, and also offers a new way to obtain advanced materials with remarkable catalytic properties.

Improving Nonenzymatic Biosensing Performance of Electrospun Carbon Nanofibers decorated with Ni/Co Particles via Oxidation.

Nonenzymatic biosensors do not require enzyme immobilization nor face degradation problem. Hence, nonenzymatic biosensors have recently attracted growing attention due to the stability and reproducibility. Here, a comparative study was conducted to quantitatively evaluate the glucose sensing of pure/oxidized Ni, Co, and their bimetal nanostructures grown on electrospun carbon nanofibers (ECNFs) to provide a low-cost free-standing electrode. The prepared nanostructures exhibited sensitivity (from 66.28 to 610.6 µA mM-1 cm-2), linear range of 2-10 mM, limit of detection in the range of 1 mM, and the response time (< 5 s), besides outstanding selectivity and applicability for glucose detection in the human serum. Moreover, the oxidizable interfering species, such as ascorbic acid (AA), uric acid (UA), and dopamine (DA), did not cause interference. Co-C and Ni-C phase diagrams, solid-state diffusion phenomena, and rearrangement of dissolved C atoms after migration from metal particles were discussed. This study undoubtedly provides new prospects on the nonenzymatic biosensing performance of mono-metal, bimetal, and oxide compounds of Ni and Co elements, which could be quite helpful for the fabrication of biomolecules detecting devices.

Metal-Organic Framework-Derived Core-Shell Nanospheres Anchored on Fe-Filled Carbon Nanotube Sponge for Strong Wideband Microwave Absorption.

Metal-organic frameworks (MOFs) are booming as a promising precursor for constructing lightweight, high-efficiency microwave absorbing (MA) material. However, it is still a challenge to rationally design three-dimensional (3D), porous MOF-derived MA materials with a stable structure and strong and wideband MA performance. Herein, a 3D hybrid nanostructure (CNT/FeCoNi@C) comprising MOF-derived magnetic nanospheres and Fe-filled carbon nanotube (CNT) sponge has been controllably fabricated to enhance the absorption ability and broaden the effective absorption bandwidth (EAB). The magnetic nanospheres are uniformly anchored on the CNT skeleton, forming hybrid network structures, which enhance interface polarization, electron transportation, and impedance matching. The minimum reflection loss (RL) and EAB of the as-prepared CNT/FeCoNi@C sponges reach -51.7 dB and 6.0 GHz, respectively, outperforming most reported MOF-based wave absorbers. This work provides not only a novel design of MOF-derived 3D nanostructures but also an effective guide for the optimization of electromagnetic properties and absorbing performance in MA material.

1T-Phase molybdenum sulfide/cobalt oxide nanopillars hybrid nanostructure coupled with nitrogen-doped carbon thin-film as high efficiency electrocatalyst for oxygen evolution.

High efficient and durable catalysts are always needed to lower the kinetic barriers as well as prolong the service life associated with oxygen evolution reaction (OER). Herein, a sequential synthetic strategy is considered to prepare a hierarchical nanostructure, in which each component can be configured to achieve their full potential so that endows the resulting nanocatalyst a good overall performance. In order to realize this, well-organized cobalt oxide (Co3O4) nanopillars are firstly grown onto ultrathin 1T-molybdenum sulfide (1T-MoS2) to obtain high surface area electrocatalyst, providing electron transfer pathways and structural stability. After that, zeolitic imidazolate framework-67 (ZIF-67) derived carbonization film is further in situ deposited on the surface of nanopillars to generate plentiful active sites, thereby accelerating OER kinetics. Based on the combination of different components, the electron transfer capability, catalytic activity and durability are optimized and fully implemented. The obtained nanocatalyst (defined as 1T-MoS2/Co3O4/CN) exhibits the superior OER catalytic ability with the overpotential of 202 mV and Tafel slope of 57 mV·dec-1 at 10 mA·cm-2 in 0.1 M KOH, and good durability with a minor chronoamperometric decay of 9.15 % after 60,000 s of polarization.

Near Infrared Fluorescent Nanostructure Design for Organic/Inorganic Hybrid System.

Near infrared (NIR) light offers high transparency in biological tissue. Recent advances in NIR fluorophores including organic dyes and lanthanide-doped inorganic nanoparticles have realized the effective use of the NIR optical window for in vivo bioimaging and photodynamic therapy. The narrow energy level intervals used for electronic transition that involves NIR light, however, give rise to a need for guidelines for reducing heat emission in luminescence systems, especially in the development of organic/inorganic hybrid structures. This review presents an approach for employing the polarity and vibrational energy of ions and molecules that surround the luminescence centers for the development of such hybrid nanostructures. Multiphonon relaxation theory, formulated for dealing with heat release in ionic solids, is applied to describe the vibrational energy in organic or molecular systems, referred to as phonon in this review, and we conclude that surrounding the luminescence centers either with ions with low vibrational energy or molecules with small chemical polarity is the key to bright luminescence. NIR photoexcited phosphors and nanostructures in organic/inorganic mixed systems, designed based on the guidelines, for photodynamic therapy are reviewed.

Carbon Quantum Dots Conjugated Rhodium Nanoparticles as Hybrid Multimodal Contrast Agents.

Nanoparticle (NP)-based contrast agents enabling different imaging modalities are sought for non-invasive bio-diagnostics. A hybrid material, combining optical and X-ray fluorescence is presented as a bioimaging contrast agent. Core NPs based on metallic rhodium (Rh) have been demonstrated to be potential X-ray Fluorescence Computed Tomography (XFCT) contrast agents. Microwave-assisted hydrothermal method is used for NP synthesis, yielding large-scale NPs within a significantly short reaction time. Rh NP synthesis is performed by using a custom designed sugar ligand (LODAN), constituting a strong reducing agent in aqueous solution, which yields NPs with primary amines as surface functional groups. The amino groups on Rh NPs are used to directly conjugate excitation-independent nitrogen-doped carbon quantum dots (CQDs), which are synthesized through citrate pyrolysis in ammonia solution. CQDs provided the Rh NPs with optical fluorescence properties and improved their biocompatibility, as demonstrated in vitro by Real-Time Cell Analysis (RTCA) on a macrophage cell line (RAW 264.7). The multimodal characteristics of the hybrid NPs are confirmed with confocal microscopy, and X-ray Fluorescence (XRF) phantom experiments.

Nanostructured ZnO and ZnO: Pd with MXene overlayer SPR biosensors.

The development of biosensors based on various novel techniques has become highly significant in the context of the outburst of a pandemic like COVID 19. The present work reports the theoretical modeling of two surface plasmon resonance (SPR) based biosensing probe configurations on optical fiber employing Metal/ZnO/MXene and Metal/ZnO: Pd/MXene. Maximum sensitivities of 19,400 nm/RIU and 8350 nm/RIU are calculated with Metal/ZnO/MXene and Metal/ZnO: Pd/MXene, respectively. The sensors are suitable for analytes with refractive index values ranging from 1.354 to 1.422. The refractive index of mucus and serum being in this range, the proposed biosensor, can be a potential tool for COVID-19 detection.

Low-Temperature Hydrothermal Synthesis of Novel 3D Hybrid Nanostructures on Titanium Surface with Mechano-bactericidal Performance.

Titanium is extensively employed in modern medicines as orthopedic and dental implants, but implant failures frequently occur because of bacterial infections. Herein, three types of 3D nanostructured titanium surfaces with nanowire clusters (NWC), nanowire/sheet clusters (NW/SC) and nanosheet clusters (NSC), were fabricated using the low-temperature hydrothermal synthesis under normal pressure, and assessed for the sterilization against two common human pathogens. The results show that the NWC and NSC surfaces merely display good bactericidal activity against Escherichia coli, whereas the NW/SC surface represents optimal bactericidal efficiency against both Escherichia coli (98.6 ± 1.23%) and Staphylococcus aureus (69.82 ± 2.79%). That is attributed to the hybrid geometric nanostructure of NW/SC, i.e., the pyramidal structures of ∼23 nm in tip diameter formed with tall clustered wires, and the sharper sheets of ∼8 nm in thickness in-between these nanopyramids. This nanostructure displays a unique mechano-bactericidal performance via the synergistic effect of capturing the bacteria cells and penetrating the cell membrane. This study proves that the low-temperature hydrothermal synthesized hybrid mechano-bactericidal titanium surfaces provide a promising solution for the construction of bactericidal biomedical implants.

Self-Assembled BaTiO3-AuxAg1-x Low-Loss Hybrid Plasmonic Metamaterials with an Ordered "Nano-Domino-like" Microstructure.

Metallic plasmonic hybrid nanostructures have attracted enormous research interest due to the combined physical properties coming from different material components and the broad range of applications in nanophotonic and electronic devices. However, the high loss and narrow range of property tunability of the metallic hybrid materials have limited their practical applications. Here, a metallic alloy-based self-assembled plasmonic hybrid nanostructure, i.e., a BaTiO3-AuxAg1-x (BTO) vertically aligned nanocomposite, has been integrated by a templated growth method for low-loss plasmonic systems. Comprehensive microstructural characterizations including high-resolution scanning transmission electron microscopy (HRSTEM), energy-dispersive X-ray spectroscopy (EDS), and three-dimensional (3D) electron tomography demonstrate the formation of an ordered "nano-domino-like" morphology with Au0.4Ag0.6 nanopillars as cylindrical cores and BTO as square shells. By comparing with the BTO-Au hybrid thin film, the BTO-Au0.4Ag0.6 alloyed film exhibits much broader plasmon resonance, hyperbolic dispersion, low-loss, and thermally robust features in the UV-vis-NIR wavelength region. This study provides a feasible platform for a complex alloyed plasmonic hybrid material design with low-loss and highly tunable optical properties toward all-optical integrated devices.

Promotion effects of halloysite nanotubes on catalytic activity of Co3O4 nanoparticles toward reduction of 4-nitrophenol and organic dyes.

Nanosized clay minerals have been widely used as efficient supports to immobilize catalyst nanoparticles. However, clay support-induced interactions and their influences on the catalyst structure and performance currently have not been fully understood. Here, Co3O4 nanoparticles supported on halloysite nanotubes (HNTs) were synthesized by a facile deposition-precipitation approach followed by thermal treatment. A series of characterization methods were employed for the Co3O4/HNTs hybrid nanostructure to identify its crystal phase, chemical composition, morphology, specific surface area, surface chemical states, and redox property. Characterization results showed that HNTs not only impacted the particle size of Co3O4 nanoparticles, but also modified surface chemical surface states of the later, which ultimately promoted the effective catalytic reduction of 4-nitrophenol (4-NP) and azo dyes with sodium borohydride. The interaction between HNTs and Co3O4 nanoparticles was found to shorten the induction period of the 4-NP reduction. Meanwhile, the Co3O4/HNTs catalyst for the 4-NP reduction achieved an apparent rate constant of 0.265 min-1 and an activity parameter of 1.63 × 104 min-1 g-1 as well as a turnover frequency of 4.37 min-1. In addition, Co3O4/HNTs showed an improvement in reduction efficiency of the azo dyes when compared to bare Co3O4 nanoparticles.