Multifunctional Hyperbolic Nanogroove Metasurface for Submolecular Detection

Metasurface serves as a promising plasmonic sensing platform for engineering the enhanced light–matter interactions. Here, a hyperbolic metasurface with the nanogroove structure in the subwavelength scale is designed. This metasurface is able to modify the wavefront and wavelength of surface plasmon wave with the variation of the nanogroove width or periodicity. At the specific optical frequency, surface plasmon polaritons are tightly confined and propagated with a diffraction‐free feature due to the epsilon‐near‐zero effect. Most importantly, the groove hyperbolic metasurface can enhance the plasmonic sensing with an ultrahigh phase sensitivity of 30 373 deg RIU^?1 and Goos–Hänchen shift sensitivity of 10.134 mm RIU^?1. The detection resolution for refractive index change of glycerol solution is achieved as 10^?8 RIU based on the phase measurement. The detection limit of bovine serum albumin (BSA) molecule is measured as low as 0.1 × 10^?18m (1 × 10^?19 mol L^?1), which corresponds to a submolecular detection level (0.13 BSA mm^?2). As for low‐weight biotin molecule, the detection limit is estimated below 1 × 10^?15m (1 × 10^?15 mol L^?1, 1300 biotin mm^?2). This enhanced plasmonic sensing performance is two orders of magnitude higher than those with current state‐of‐art plasmonic metamaterials and metasurfaces.     

Dielectrophoresis‐Based Protein Enrichment for a Highly Sensitive Immunoassay Using Ag/SiO2 Nanorod Arrays

A nanoscale insulator‐based dielectrophoresis (iDEP) technique is developed for rapid enrichment of proteins and highly sensitive immunoassays. Dense arrays of nanorods (NDs) by oblique angle deposition create a super high electric field gradient of 2.6 × 10²⁴ V² m^?3 and the concomitant strong dielectrophoresis force successfully traps small proteins at a bias as low as 5 V. 1800‐fold enrichment of bovine serum albumin protein at a remarkable rate of up to 180‐fold s^?1 is achieved using oxide coated Ag nanorod arrays with pre‐patterned sawtooth electrodes. Based on this system, an ultrasensitive immunoassay of mouse immunoglobulin G is demonstrated with a reduction in the limit of detection from 5.8 ng mL^?1 (37.6 pM) down to 275.3 fg mL^?1 (1.8 f M), compared with identical assays performed on glass plates. This methodology is also applied to detect a cancer biomarker prostate‐specific antigen spiked in human serum with a detection limit of 2.6 ng mL^?1. This high sensitivity results from rapid biomarker enrichment and metal enhanced fluorescence through the integration of nanostructures. The concentrated proteins also accelerate binding kinetics and enable signal saturation within 1 min. Given the easy fabrication process, this nanoscale iDEP system provides a highly sensitive detection platform for point‐of‐care diagnostics.     

Carbon Nanotubes Multifunctionalized by Rolling Circle Amplification and Their Application for Highly Sensitive Detection of Cancer Markers

There are still challenges for the development of multifunctional carbon nanotubes (CNTs). Here, a multiwalled carbon nanotube (MWCNT)‐based rolling circle amplification system (CRCAS) is reported which allows in situ rolling circle replication of DNA primer on the surface of MWCNTs to create a long single‐strand DNA (ssDNA) where a large number of nanoparticles or proteins could be loaded, forming a nano‐biohybridized 3D structure with a powerful signal amplification ability. In this strategy, the binding ability of proteins, hybridization, replication ability of DNA, and the catalytical ability of enzymes are integrated on a single carbon nanotube. The CRCAS is then used to develop colorimetric and chemiluminescent assays for the highly sensitive and specific detection of cancer protein markers, alpha‐fetoprotein (AFP) and prostate specific antigen (PSA). The colorimetric CRCAS assay is 4000 times more sensitive than a conventional enzyme‐linked immunosorbent assay (ELISA), and its concentration range is 10 000 times wider. Control experiments show that as low as 10 pg mL^?1 AFP or PSA could be detected even in the presence of interfering protein markers with a more than 10⁵‐fold greater concentration in the sample, demonstrating the high specificity of the CRCAS assay. The limit of detection of the chemiluminescent CRCAS assays for AFP and PSA are 5 fg mL^?1 (70 aM) and 10 fg mL^?1 (0.29 fM), respectively, indicating that the sensitivity is much higher than that of the colorimetric CRCAS assay. Importantly, CRCAS works well with real biological samples.     

Design Details of Multi-Functional Color Analyzer for Reflective, Transmittive and Emittive Surfaces

A multi-functional color analyzer instrument (MFCA) capable to measure reflective, transmittive and emittive surfaces is designed at TUBITAK UME Optics Group Laboratories. MFCA is composed of a novel designed optical light source based on mixture of spectral power distributions (SPDs) of two light emitting diodes (LEDs), a custom-made integrating sphere capable of meeting standard measurement conditions of 0°:d, 8°:d, and 0°:45°, two color detectors with different field-of-views which are designed to measure reflective or transmittive and emittive surfaces separately, self-designed three-channel transimpedance amplifiers having gain selection switches from 1?×?10⁶ to 5?×?10⁹ and a color evaluation software written on LabView 8.0. The linearity and color measurement performance at each measurement geometry of the designed instrument are characterized by using neutral density filters and a standard telespectroradiometer. Design details of MFCA and characterization results are presented herein.     

Fused Hexacyclic Nonfullerene Acceptor with Strong Near‐Infrared Absorption for Semitransparent Organic Solar Cells with 9.77% Efficiency

A fused hexacyclic electron acceptor, IHIC, based on strong electron‐donating group dithienocyclopentathieno[3,2‐b ]thiophene flanked by strong electron‐withdrawing group 1,1‐dicyanomethylene‐3‐indanone, is designed, synthesized, and applied in semitransparent organic solar cells (ST‐OSCs). IHIC exhibits strong near‐infrared absorption with extinction coefficients of up to 1.6 × 10⁵m ^?1 cm^?1, a narrow optical bandgap of 1.38 eV, and a high electron mobility of 2.4 × 10^?3 cm² V^?1 s^?1. The ST‐OSCs based on blends of a narrow‐bandgap polymer donor PTB7‐Th and narrow‐bandgap IHIC acceptor exhibit a champion power conversion efficiency of 9.77% with an average visible transmittance of 36% and excellent device stability; this efficiency is much higher than any single‐junction and tandem ST‐OSCs reported in the literature.     

Bioinspired Hydrogel Interferometer for Adaptive Coloration and Chemical Sensing

Living organisms ubiquitously display colors that adapt to environmental changes, relying on the soft layer of cells or proteins. Adoption of soft materials into an artificial adaptive color system has promoted the development of material systems for environmental and health monitoring, anti‐counterfeiting, and stealth technologies. Here, a hydrogel interferometer based on a single hydrogel thin film covalently bonded to a reflective substrate is reported as a simple and universal adaptive color platform. Similar to the cell or protein soft layer of color‐changing animals, the soft hydrogel layer rapidly changes its thickness in response to external stimuli, resulting in instant color change. Such interference colors provide a visual and quantifiable means of revealing rich environmental metrics. Computational model is established and captures the key features of hydrogel stimuli‐responsive swelling, which elucidates the mechanism and design principle for the broad‐based platform. The single material–based platform has advantages of remarkable color uniformity, fast response, high robustness, and facile fabrication. Its versatility is demonstrated by diverse applications: a volatile‐vapor sensor with highly accurate quantitative detection, a colorimetric sensor array for multianalyte recognition, breath‐controlled information encryption, and a colorimetric humidity indicator. Portable and easy‐to‐use sensing systems are demonstrated with smartphone‐based colorimetric analysis.     

Sensitive Detection of Carcinoembryonic Antigen Using Stability‐Limited Few‐Layer Black Phosphorus as an Electron Donor and a Reservoir

The instability of few‐layer black phosphorus (FL‐BP) hampers its further applications. Here, it can be demonstrated that the instability of FL‐BP can also be the advantage for application in biosensor. First, gold nanoparticle/FL‐BP (BP‐Au) hybrid is facilely synthesized by mixing Au precursor with FL‐BP. BP‐Au shows outstanding catalytic activity (K = 1120 s^?1 g^?1) and low activation energy (17.53 kJ mol^?1) for reducing 4‐nitrophenol, which is attributed to the electron‐reservoir and electron‐donor properties of FL‐BP, and synergistic interaction of Au nanoparticles and FL‐BP. Oxidation of FL‐BP after catalytic reaction is further confirmed by transmission electron microscope, X‐ray photoelectron spectroscopy, and zeta potentials. Second, the catalytic activity of BP‐Au can be reversibly switched from “inactive” to “active” upon treatment with antibody and antigen in solution, thus providing a versatile platform for label‐free colorimetric detection of biomarkers. The sensor shows a wide detection range (1 pg mL^?1 to –10 µg mL^?1), high sensitivity (0.20 pg mL^?1), and selectivity for detecting carcinoembryonic antigen (CEA). Finally, the biosensor has been used to detect CEA in colon and breast cancer clinical samples with satisfactory results. Therefore, the instability of BP can also be the advantage for application in detecting cancer biomarker in clinic.     

Sensitive Label-Free Immunoassay by Colorimetric Plasmonic Biosensors Using Silver Nanodome Arrays

The sensitive direct detection of biomolecules is demonstrated by a colorimetric plasmonic biosensor utilizing the surface colors of plasmonic metasurfaces named Ag nanodome arrays. The Ag nanodome arrays consist of polystyrene bead monolayers coated with Ag thin films whose surface colors are optimized by changing the size of the polystyrene beads. The bulk refractive index sensitivity of colorimetric detection evaluated using the hue angle is 590° RIU⁻¹ (RIU: refractive index unit). For selected geometry, the refractive index resolution (5.0 × 10⁻⁵ RIU) obtained by colorimetric detection surpasses that of spectroscopic detection evaluated via the dip wavelength in the reflection spectrum. The numerical simulations predict an enhanced sensing performance when the hue angle of the surface colors of the Ag nanodome arrays changes from 300° to 200°, corresponding to changes in the dip wavelength from 570 to 600 nm in the reflection spectra. Furthermore, the detection sensitivity of the biomolecules is characterized using a direct IgG immunoassay format. The detection limit of the IgG concentration is as low as 134 pM using simple colorimetric detection. The feasibility of sensitive label-free immunoassays using a colorimetric plasmonic biosensor is expected to accelerate the development of highly sensitive and reliable smartphone-based plasmonic biosensors.     

Gold Nanoparticle‐Based Paper Sensor for Simultaneous Detection of 11 Benzimidazoles by One Monoclonal Antibody

A colloidal gold immunochromatographic assay based on a generic monoclonal antibody is developed for the simultaneous detection of benzimidazoles and metabolite residues in milk samples. The monoclonal antibody is prepared using 2‐(methoxycarbonylamino)‐3H‐benzimidazole‐5‐carboxylic acid as the hapten, and it can recognize 11 types of benzimidazoles simultaneously. The immunochromatographic strip is assembled and labeled using gold nanoparticles. This strip can detect 11 benzimidazoles including albendazole, albendazole s‐oxide, albendazole sulfone, fenbendazole, fenbendazole sulfone, flubendazole, mebendazole, parbendazole, oxfendazole, oxibendazole, and carbendazim within 15 min in milk samples. Results are obtained visually with the naked eye, and the cutoff values and the visual limit of detection values for these benzimidazoles are 25, 6.25, 12.5, 12.5, 50, 25, 50, 50, 50, 6.25, and 25 ng mL^?1, and 6.25, 3.125, 3.125, 1.56, 12.5, 6.25, 12.5, 12.5, 6.25, 0.78, and 12.5 ng mL^?1, respectively. Results are also obtained using a hand‐held strip scan reader, with calculated limit of detection values for these benzimidazoles of 0.83, 0.77, 1.83, 0.98, 7.67, 3.50, 3.96, 5.71, 0.92, 0.59, and 1.69 ng mL^?1, respectively. In short, the developed paper sensor is a useful tool for rapid and simple screening of residues of benzimidazoles in milk samples.     

Highly Fluorescent Magnetic Nanobeads with a Remarkable Stokes Shift as Labels for Enhanced Detection in Immunoassays

Fluorescence immunoassays are popular for achieving high sensitivity, but they display limitations in biological samples due to strong absorption of light, background fluorescence from matrix components, or light scattering by the biomacromolecules. A powerful strategy to overcome these problems is introduced here by using fluorescent magnetic nanobeads doped with two boron‐dipyrromethane dyes displaying intense emission in the visible and near‐infrared regions, respectively. Careful matching of the emission and absorption features of the dopants leads to a virtual Stokes shift larger than 150 nm achieved by an intraparticle Förster resonance energy transfer (FRET) process between the donor and the acceptor dyes. Additionally, the magnetic properties of the fluorescent beads allow preconcentration of the sample. To illustrate the usefulness of this approach to increase the sensitivity of fluorescence immunoassays, the novel nanoparticles are employed as labels for quantification of the widely used Tacrolimus (FK506) immunosuppressive drug. The FRET‐based competitive inhibition immunoassay yields a limit of detection (LOD) of 0.08 ng mL^?1, with a dynamic range (DR) of 0.15–2.0 ng mL^?1, compared to a LOD of 2.7 ng mL^?1 and a DR between 4.1 and 130 ng mL^?1 for the immunoassay carried out with direct excitation of the acceptor dye.     

Therapeutic Window of Ligand‐Free Silver Nanoparticles in Agar‐Embedded and Colloidal State: In Vitro Bactericidal Effects and Cytotoxicity

The inhibition of bacterial growth through effective non‐toxic antimicrobial substances is of great importance for the prevention and therapy of implant infections in various medical disciplines. For the evaluation of a therapeutic window of silver nanoparticles (AgNPs), their bactericidal properties were tested in agar composites and colloids on four medical relevant bacteria. Therefore, we produced AgNPs using high‐power nanosecond laser ablation in water showing a log‐normal particle diameter distribution centered at 17 nm. Bacteria were incubated with AgNP concentrations ranging from 5 to 70 µg · mL^?1 and the growth rate was recorded. Additionally, cytotoxic effects of AgNPs on human gingival fibroblasts were examined. The experiments demonstrated that laser‐synthesized AgNPs resulted in a significant bacterial growth inhibition of more than 80% at the indicated concentrations in a solid agar model (Pseudomonas aeruginosa 10 µg · mL^?1, Streptococcus salivarius 10 µg · mL^?1, Escherichia coli 20 µg · mL^?1, Staphylococcus aureus 70 µg · mL^?1). In a planktonic bacteria model, the growth of the tested bacteria was significantly delayed by the addition of AgNPs at a concentration of 35 µg · mL^?1. The cytotoxic assays showed limited adverse effects on human fibroblasts at concentrations of less than 20 µg · mL^?1. The present study illustrates the strong antibacterial effects of ligand‐free, laser‐generated AgNPs that exhibit moderate cytotoxic effects, resulting in a therapeutically applicable concentration of AgNPs for medical purposes between 10 and 20 µg · mL^?1.     

High‐Throughput,Protein‐Targeted Biomolecular Detection Using Frequency‐Domain Faraday Rotation Spectroscopy

A clinically relevant magneto‐optical technique (fd‐FRS, frequency‐domain Faraday rotation spectroscopy) for characterizing proteins using antibody‐functionalized magnetic nanoparticles (MNPs) is demonstrated. This technique distinguishes between the Faraday rotation of the solvent, iron oxide core, and functionalization layers of polyethylene glycol polymers (spacer) and model antibody–antigen complexes (anti‐BSA/BSA, bovine serum albumin). A detection sensitivity of ≈10 pg mL^?1 and broad detection range of 10 pg mL^?1 ? c_BSA ? 100 µ g mL^?1 are observed. Combining this technique with predictive analyte binding models quantifies (within an order of magnitude) the number of active binding sites on functionalized MNPs. Comparative enzyme‐linked immunosorbent assay (ELISA) studies are conducted, reproducing the manufacturer advertised BSA ELISA detection limits from 1 ng mL^?1 ? c_BSA ? 500 ng mL^?1. In addition to the increased sensitivity, broader detection range, and similar specificity, fd‐FRS can be conducted in less than ≈30 min, compared to ≈4 h with ELISA. Thus, fd‐FRS is shown to be a sensitive optical technique with potential to become an efficient diagnostic in the chemical and biomolecular sciences.     

Colorimetric Detection of Hg2+ Based on the Growth of Aptamer‐Coated AuNPs: The Effect of Prolonging Aptamer Strands

Herein, a versatile and sensitive colorimetric sensor for Hg²⁺ based on aptamer–target specific binding and target‐mediated growth of AuNPs is reported. The 15 T bases are first designed to detect Hg²⁺ through T–Hg²⁺–T coordination. Aptamer–target binding results in the desorption of the aptamer from AuNP surface, the remaining aptamers adsorbed on AuNP surface trigger the growth of AuNPs with morphologically varied nanostructures, and then different colored solutions are formed. On this occasion, the limit of detection (LOD) of 9.6 × 10^?9m is obtained. The other two aptamer strands (25‐ and 59‐mer) are designed by increasing A bases on either side and both sides of 15 T, respectively. The interaction of the binding domain and Hg²⁺ makes desorption of 15 T from AuNP surface, whereas excess bases not committed to the binding domain still adsorbed on AuNP surface. These excess bases control the growth of AuNPs, and enhance the sensitivity. The LODs are 4.05 and 3 × 10^?9m for 25‐ and 59‐mer aptamers, respectively. In addition, the 59‐mer aptamer system is applied to identify Hg²⁺ in real river samples, the LOD of 6.2 × 10^?9m is obtained.     

A Novel Fullerene Hydroxamic Acid for the Liquid–Liquid Extraction,Separation, Preconcentration,and Spectrophotometric and ICP‐AES Determination of Vanadium

Abstract

A new reagent N‐phenyl‐(1,2 methanofullerene C₆₀)61‐formohydroxamic acid (PMFFA) is reported for extraction and trace determination of vanadium(V) in nutritional and biological substrates. The extraction mechanism of vanadium from 6 M HCl media is investigated. The influence of PMFFA, diverse ions, and temperature on the distribution constant of vanadium examined. The over all stability constant (log β₂ K _e ) and extraction constant (K _ex) are 20.89 ± 0.02 and 8.0 ± 0.02 × 10^?15, respectively in chloroform. The thermodynamics parameters are calculated and kinetics of vanadium transport is discussed. The system obeys Beer's law in the range of 3.2–64.0 ng mL^?1 of vanadium(V). The molar absorptivity is 7.96 × 10⁵ L mol^?1 cm^?1, at 510 nm. The PMFFA–vanadium(V) complex chloroform extract in chloroform was directly inserted into plasma for ICP‐AES measurement, which increases the sensitivity by 50 folds and obey Beer's law in the range of 50–1200 pg mL^?1 of vanadium(V). The method is applied for determination vanadium in real standard samples, sea water, and environmental samples.     

A Nanoparticle‐Decorated Biomolecule‐Responsive Polymer Enables Robust Signaling Cascade for Biosensing

To meet the increasing demands for ultrasensitivity in monitoring trace amounts of low‐abundance early biomarkers or environmental toxins, the development of a robust sensing system is urgently needed. Here, a novel signal cascade strategy is reported via an ultrasensitive polymeric sensing system (UPSS) composed of gold nanoparticle (gNP)‐decorated polymer, which enables gNP aggregation in polymeric network and electrical conductance change upon specific aptamer‐based biomolecular recognition. Ultralow concentrations of thrombin (10^?18m ) as well as a low molecular weight anatoxin (165 Da, 10^?14m ) are detected selectively and reproducibly. The biomolecular recognition induced polymeric network shrinkage responses as well as dose‐dependent responses of the UPSS are validated using in situ real‐time atomic‐force microscopy, representing the first instance of real‐time detection of biomolecular binding‐induced polymer shrinkage in soft matter. Furthermore, in situ real‐time confocal laser scanning microscopy imaging reveals the dynamic process of gNP aggregation responses upon biomolecular binding.     

Changing the Blood Test: Accurate Determination of Mercury(II) in One Microliter of Blood Using Oriented ZnO Nanobelt Array Film Solution‐Gated Transistor Chips

The measurement of ultralow concentrations of heavy metal ions (HMIs) in blood is challenging. A new strategy for the determination of mercury ions (Hg²⁺) based on an oriented ZnO nanobelt (ZnO‐NB) film solution‐gated field‐effect transistor (FET) chip is adopted. The FET chips are fabricated with ZnO‐NB film channels with different orientations utilizing the Langmuir–Blodgett (L–B) assembly technique. The combined simulation and I–V behavior results show that the nanodevice with ZnO‐NBs parallel to the channel has exceptional performance. The sensing capability of the oriented ZnO‐NB film FET chips corresponds to an ultralow minimum detectable level (MDL) of 100 × 10^?12 m in deionized water due to the change in the electrical double layer (EDL) arising from the synergism of the field‐induced effect and the specific binding of Hg²⁺ to the thiol groups (‐SH) on the film surface. Moreover, the prepared FET chips present excellent selectivity toward Hg²⁺, excellent repeatability, and a rapid response time (less than 1 s) for various Hg²⁺ concentrations. The sensing performance corresponds to a low MDL of 10 × 10^?9 m in real samples of a drop of blood.     

Aminolated and Thiolated PEG‐Covered Gold Nanoparticles with High Stability and Antiaggregation for Lateral Flow Detection of Bisphenol A

The few lateral flow assays (LFAs) established for detecting the endocrine disrupting chemical bisphenol A (BPA) have employed citrate‐stabilized gold nanoparticles (GNPs), which have inevitable limitations and instability issues. To address these limitations, a more stable and more sensitive biosensor is developed by designing strategies for modifying the surfaces of GNPs with polyethylene glycol and then testing their effectiveness and sensitivity toward BPA in an LFA. Without the application of any enhancement strategy, this modified BPA LFA can achieve a naked‐eye limit of detection (LOD) of 0.8 ng mL^?1, which is 12.5 times better than the LOD of regular BPA LFAs, and a quantitative LOD of 0.472 ng mL^?1. This modified LFA has the potential to be applied to the detection of various antigens.     

Improved Biomolecule microarrays by Printing on Nanoporous Aluminum Oxide Using a Continuous‐Flow Microspotter

Biomolecules, including protein A, albumin, and immunoglobulin G, are spotted on top of a nanoporous substrate by using a continuous‐flow microspotter (CFM) system, which normally produces spots 3 to 4 orders of magnitude more sensitive than conventional biomolecule printing methods. The spots are observed with a fluorescence scanner. By using the CFM to print spots on nanoporous substrates, an additional order of magnitude increase in signal is observed, which leads to high signal‐to‐background ratios, highly saturated spots, and a measurable signal at printing concentrations as low as 1.6 ng mL^?1. This technique produces highly concentrated biomolecular spots from dilute samples and significantly increases the sensitivity of sensing platforms.     

A Sensitive Aptasensor Based on a Hemin/G‐Quadruplex‐Assisted Signal Amplification Strategy for Electrochemical Detection of Gastric Cancer Exosomes

Emerging evidence indicates that exosomes derived from gastric cancer cells enhance tumor migration and invasion through the modulation of the tumor microenvironment. However, it remains a major problem to detect cancer‐specific exosomes due to technical and biological challenges. Most of the methods reported could not achieve efficient detection of tumor‐derived exosomes in the background of normal exosomes. Herein, a label‐free electrochemical aptasensor is presented for specific detection of gastric cancer exosomes. This platform contains an anti‐CD63 antibody modified gold electrode and a gastric cancer exosome specific aptamer. The aptamer is linked to a primer sequence that is complementary to a G‐quadruplex circular template. The presence of target exosomes could trigger rolling circle amplification and produce multiple G‐quadruplex units. This horseradish peroxidase mimicking DNAzyme could catalyze the reduction of H₂O₂ and generate electrochemical signals. This aptasensor exhibits high selectivity and sensitivity toward gastric cancer exosomes with a detection limit of 9.54 × 10² mL^?1 and a linear response range from 4.8 × 10³ to 4.8 × 10⁶ exosomes per milliliter. Therefore, this electrochemical aptasensor is expected to become a useful tool for the early diagnosis of gastric cancer.     

Amorphous Intermediate Derivative from ZIF‐67 and Its Outstanding Electrocatalytic Activity

Increasing active sites is an effective method to enhance the catalytic activity of catalysts. Amorphous materials have attracted considerable attention in catalysis because of their abundant catalytic active sites. Herein, a series of derivatives is prepared via the low‐temperature heat treatment of ZIF‐67 hollow sphere at different temperatures. An intermediate product with an amorphous structure is formed during transformation from ZIF‐67 to Co₃O₄ nanocrystallines when ZIF‐67 hollow sphere is heat treated at 260 °C for 3 h. The chemical composition of the amorphous derivative is similar to that of ZIF‐67, and the carbon and nitrogen contents of the amorphous derivative are obviously higher than those of crystalline samples obtained at 270 °C or higher. As electrocatalysts for the oxygen evolution reaction (OER) and nonenzymatic glucose sensing, the amorphous derivative exhibits significantly better catalytic activity than crystalline Co₃O₄ samples. The amorphous sample as an OER catalyst has a low overpotential of 352 mV at 10 mA cm^?2. The amorphous sample as an enzyme‐free glucose sensing catalyst can provide a low detection limit of 3.9 × 10^?6 m and a high sensitivity of 1074.22 µA mM^?1 cm^?2.