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The major obstacle to developing nanozymes which are considered as promising alternatives to natural enzymes is their moderate performance, including poor affinity for substrates, low catalytic activity, and severe pH-dependence. To address these issues, herein, we synthesize ultrathin layered double hydroxide (LDH) nanosheets with a thickness of 1.4 nm and an average lateral size of 23 nm using a fast-precipitation method. Through the rational design of their compositions, it is found that NiMn LDHs exhibit the optimum peroxidase mimicking performance with excellent substrate affinity, high catalytic activity (a limit of detection (LOD) of 0.04 μM H2O2) and robustness in a wide pH range (from 2.6 to 9.0), which is superior to that of natural horseradish peroxidase (HRP). The main active centers are identified as Mn sites because of their strong Lewis acidity and low redox potential. Furthermore, a series of disposable paper bioassays based on NiMn LDH nanozymes are designed and used for the highly sensitive detection of H2O2 and ascorbic acid (AA).

Cobalt(ii) phthalocyanine (CoPc) was suspended in aqueous medium and the colloidal system was used as catalyst for the electrochemical determination of hydrogen peroxide on paper-based electrodes modified with carbon nanomaterials. H2O2 was oxidised at 0.275 V vs. Ag pseudoreference electrode. This system was adapted to develop a glucose sensor with glucose oxidase immobilized on the cellulose electrode. CoPc suspended nanoparticles acted as nanoenzyme mimicking peroxidase activity and were combined with different carbon nanomaterials to form hybrids with optimised catalytic performance. GO-CoPc paper-based electrodes yielded the best results with a linear range of ∼12 μM to 49 mM for H2O2 and 0.1 mM to 1 mM for glucose. Glucose was determined in physiological serum and juice samples with recoveries of 93.3 and 94.2% respectively. CoPc could replace HRP for the catalytic sensing of H2O2, without the need to be dissolved. This material can be used in situ in a simple protocol with other nanomaterials for electrode modification. The sensor described has the advantage of easy preparation, using the catalyst in colloidal form, long term stability, and versatility to be adapted to other low cost and disposable enzymatic systems.

A bio-inspired cellulose paper–poly(amidoxime) composite hydrogel is explored via UV-polymerization. This hydrogel has a highly efficient uranium capture capacity of up to 6.21 mg g−1 for WU/Wdry gel and 12.9 mg g−1 for WU/Wpoly(amidoxime) in seawater for 6 weeks, due to its enhanced hydrophilicity, good hydraulic/ionic conductivity and broad-spectrum antibacterial performance.

The first discrete bimetallic europium(iii)/copper(ii) complex for the fast, sensitive and selective luminescent detection of both aqueous and gaseous hydrogen sulfide has been developed. The chemosensor displayed an impressive response time of 30 seconds and a low theoretical limit of detection (100 ppb) for gaseous hydrogen sulfide.

An anthracene carboxyimide derivative was synthesized as a colorimetric and fluorogenic sensor to determine NO2- with a rapid response (

A green and facile method is presented for in situ synthesis of a novel photoluminescence-quenching nanopaper with a highly-efficient quenching ability, rapid reaction time and long-term storage. The as-prepared nanopaper is further used to construct an aptasensor platform with high performance, rapidness and robustness.

A modular, general method for trapping enzymes within the voids of paper, without chemical activation of cellulose, is reported. Glucose oxidase and peroxidase were crosslinked with poly(acrylic acid) via carbodiimide chemistry, producing 3-dimensional networks interlocked in cellulose fibers. Interlocking prevented enzyme activity loss and enhanced the washability and stability.

A strategy for aptamer-based biosensing termed linkage inversion assembled nano-aptasensors (LIANAs) is shown to be a generally applicable approach to the sensitive and specific detection of a target molecule in turn-on fluorescence solution-based and paper-based tests.

An ionophore-based ion-selective optode platform on paper is described for the first time with a sodium optode as the example. Cellulose paper is shown to be an excellent substrate for adsorption of the required chromoionophore, ionophore, and ion exchanger species. These adsorbed components form a hydrophobic phase that enables heterogeneous optical ion sensing in the absence of any plasticizer or organic polymer phase.

A novel 3D microfluidic paper-based turn-on electrochemiluminescence origami cyto-device with hollow channels is developed and applied for real-time visual determination of H2S released from multiple cancer cells for the first time.

This study reports a facile method for the synthesis of multi-enzyme co-embedded organic-inorganic hybrid nanoflowers, using glucose oxidase (GOx) and horseradish peroxidase (HRP) as the organic components, and Cu3(PO4)2 · 3H2O as the inorganic component. The synthesized nanoflowers enable the combination of a two-enzyme cascade reaction in one step, in which the GOx component of the nanoflowers oxidizes glucose to generate H2O2, which then reacts with the adjacent HRP component on the nanoflowers to oxidize the chromogenic substrates, resulting in an apparent color change. Given the close proximity of the two enzyme components in a single nanoflower, this novel sensor greatly reduces the diffusion and decomposition of H2O2, and greatly enhances the sensitivity of glucose detection. Thus, the obtained multi-enzyme co-embedded organic-inorganic hybrid nanoflowers can be unquestionably used as highly sensitive colorimetric sensors for the detection of glucose. Notably, this work presents a very facile route for the synthesis of multi-enzyme co-embedded nanomaterials for the simultaneous catalysis of multi-step cascade enzymatic reactions. Furthermore, it has great potential for application in biotechnology, and biomedical and environmental chemistry.

This Communication describes a prototype quantitative paper-based assay that simultaneously measures the levels of Pb(2+) and Hg(2+) in water. The assay requires only measurements of time to yield a quantitative readout, and the results are independent of sample volume, humidity, and sample viscosity.

ZnO nanorods inorganic-organic heterostructured light-emitting diodes have been demonstrated on a cheap/disposable paper substrate and applied in multiplexed photoelectrochemical immunoassay.

A simple, low-cost, and sensitive 3D microfluidic origami electrochemiluminescence aptamer-device was developed based on a novel gold nanoparticle modified porous paper working electrode for point-of-care diagnosis.

We used relief and planographic printing methods to print the catalytic effect of an enzyme, but not the enzyme molecules, onto paper. Printing enzymatic reactions have applications in bioactive papers, low-cost diagnostics, anti-counterfeiting devices and advanced packaging materials. These methods can create novel printing effects on commodity surfaces for advanced applications.

A hybrid technique based on a catalytic reaction carried out on the surface of a paper-based sorbent is proposed. It is shown that MnII exhibits its catalytic action in the oxidation of 3,3',5,5'-tetramethylbenzidine with periodate in aqueous solution as well as on filter-paper with or without attached diethylenetriaminetetraacetate (DETATA) groups. Optimum conditions differ for the reaction in solution and on filter-paper. For equal catalyst concentrations, higher initial reaction rates are attainable on the filter-papers. Preconcentration of manganese on the DETATA sorbent combined with the subsequent catalytic reaction improves the selectivity, reduces the limit of determination down to 5 x 10(-6) mg l-1 (as compared with 6 x 10(-5) mg l-1 in solution) and expands the linear range by an order of magnitude (to 5 x 10(-6)-2.5 x 10(-3) mg l-1). The precision of manganese determination on the sorbent is high (the RSDs areor = 5% foror = 6 x 10(-4) micrograms Mn). Samples of tap and river water were analyzed by use of the proposed sorption-catalytic technique. A rapid procedure for the determination of manganese with visual detection was also developed.

A simple and sensitive 3D origami multiple electrochemiluminescence immunodevice based on a novel silver nanoparticles modified porous paper working electrode as a sensor platform and multi-labeled nanoporous gold-carbon spheres as tracers has been demonstrated for the first time.

In this report, hierarchical ZnO nano- and microstructures were directly grown for the first time on a bacterial cellulose substrate and on two additional different papers by hydrothermal synthesis without any surface modification layer. Compactness and smoothness of the substrates are two important parameters that allow the growth of oriented structures.

A simple and sensitive 3D microfluidic origami multiplex electrochemical immunodevice was developed for the first time using a novel nanoporous silver modified paper working electrode as a sensor platform and different metal ion functionalized nanoporous gold-chitosan as a tracer.

A high-throughput, simple, fast, low-cost and sensitive paper-based electrochemical immunodevice has been demonstrated based on a functionalized 3D paper-based device for point-of-care diagnosis.

Paper strips containing DNA-conjugated microgels (MG) are used to achieve sensitive DNA detection in three steps: target DNA promoted ligation of a DNA primer to the MG-bound DNA, rolling circle amplification (RCA) between the primer and a circle DNA, and hybridization of the RCA products and a fluorescent DNA probe.