Multiwalled Carbon Nanotube-Templated Nickel Porphyrin Covalent Organic Framework for Pencil-Drawn Noninvasive Respiration Sensors.

Paper-integrated configuration with miniaturized functionality represents one of the future main green electronics. In this study, a paper-based respiration sensor was prepared using a multiwalled carbon nanotube-templated nickel porphyrin covalent organic framework (MWCNTs@COF) as an electrical identification component and pencil-drawn graphite electric circuits as interdigitated electrodes (IDEs). The MWCNTs@COF not only inherited the high gas sensing performance of porphyrin and the aperture induction effect of COFs but also overcame the shielding effect between phases through the MWCNT template.

Host-Guest Interaction Mediated Perovskite@Metal-Organic Framework Z-Scheme Heterojunction Enabled Paper-Based Photoelectrochemical Sensing.

Exploring the high-performance photoelectronic properties of perovskite quantum dots (QDs) is desirable for paper-based photoelectrochemical (PEC) sensing;however, challenges remain in improving their stability and fundamental performance. Herein, a novel Z-scheme heterostructure with host-guest interaction by the confinement of CHNHPbBr QDs within Cu(BTC) metal-organic framework (MOF) crystal (MAPbBr@Cu(BTC)) is successfully constructed on the paper-based PEC device for ultrasensitive detection of Ochratoxin A (OTA), with the assistance of the exciton-plasmon interaction (EPI) effect. The host-guest interaction is estabilished by encapsulating MAPbBr QDs as guests within Cu(BTC) MOF as a host, which prevents MAPbBr QDs from being damaged in the polar system, offering access to long-term stability with high-performance PEC properties.

Self-standing perylene diimide covalent organic framework membranes for trace TMA sensing at room temperature.

The unprecedented demand for highly selective, real-time monitoring and low-power gas sensors used in food quality control has been driven by the increasing popularity of the Internet of Things (IoT). Herein, the self-standing perylene diimide based covalent organic framework membranes (COFM) were prepared via liquid-liquid interfacial synthesis method. By incorporating the perylene diimide monomer into the COFM through molecular engineering, COFM based sensor demonstrated an outstanding trimethylamine (TMA)-sensing performance at room temperature.

Double-enzyme active MnO@BSA mediated lab-on-paper dual-modality aptasensor for di(2-ethylhexyl)phthalate.

Di(2-ethylhexyl)phthalate (DEHP), as an environmental endocrine disruptor, has adverse effects on eco-environments and health. Thus, it is crucial to highly sensitive on-site detect DEHP. Herein, a double-enzyme active MnO@BSA mediated dual-modality photoelectrochemical (PEC)/colorimetric aptasensing platform with the cascaded sensitization structures of ZnInS and TiO as signal generators was engineered for rapid and ultrasensitive detection of DEHP using an all-in-one lab-on-paper analytical device.

Rolling circle amplification assisted CRISPR/Cas12a dual-cleavage photoelectrochemical biosensor for highly sensitive detection of miRNA-21.

Background: MicroRNA-21 has been determined to be the only microRNA overexpressed in 11 types of solid tumors, making it an excellent candidate as a biomarker for disease diagnosis and therapy. Photoelectrochemical (PEC) biosensors have been widely used for quantification of microRNA-21. However, most PEC biosensing processes still suffer from some problems, such as the difficulty of avoiding the influence of interferents in complex matrices and the false-positive signals.

Potential-resolved electrochemiluminescence biosensor for simultaneous determination of multiplex miRNA.

The multi-target simultaneous detection strategy based on potential-resolved electrochemiluminescence (ECL) has still been a research hotspot in analytical science, but the limited selection of ECL luminophores hinders the development of this field. Herein, polyethyleneimine functionalized perylene derivatives (PTC-PEI) and luminol functionalized gold nanoparticles (Lu-Au NPs) possessed significantly resolved emission potentials as ECL luminophore. The ternary ECL system was constructed with MoS nanoflowers and KSO as the coreaction accelerator and coreactant respectively, which significantly improved the cathode ECL emission of PTC-PEI.

Flexible SERS strip based on HKUST-1(cu)/biomimetic antibodies composite multilayer for trace determination of ethephon.

A surface-enhanced Raman scattering (SERS) sensor based on the folding and assembly characteristics of the three-dimensional structure of paper fibers, the skeleton controllability of metal-organic framework materials (MOFs), and the morphology designability of plasmonic noble metal materials has been established for rapid on-site determination of ethephon in food. HKUST-1(Cu) was assembled onto a carbon-treated chromatographic paper matrix by electrodeposition, and its skeleton respiration and sponge effect were used to overcome the bottleneck problem of poor affinity of SERS substrate for target molecules. Further coupled with the targeted recognition specificity of biomimetic antibodies, a paper-based interface with high specificity of molecular sensitivity was constructed.

Electrochemiluminescence biosensor based on molybdenum disulfide-graphene quantum dots nanocomposites and DNA walker signal amplification for DNA detection.

Based on the prominent electrochemiluminescence (ECL) performances of molybdenum disulfide-graphene quantum dots (MoS-GQDs) nanocomposite and combined with enzyme-assisted recycling DNA walker signal amplification, an "on-off" switch ECL biosensor was proposed for sensitive assay of specific DNA sequences. Noticeably, MoS with two-dimensional nanosheet structure increased the loading capacity of GQDs to support abundant hairpin DNA (H). The composites of MoS and GQDs facilitated the charge transfer in ECL process, which significantly improved the ECL signal to achieve an "on" state.

Dual-Mode Aptasensor Assembled by a WO/FeO Heterojunction for Paper-Based Colorimetric Prediction/Photoelectrochemical Multicomponent Analysis.

The programed bimodal photoelectrochemical (PEC)-sensing platform based on DNA structural switching induced by targets binding to aptamers was innovatively designed for the simultaneous detection of mucin 1 (MUC1) and microRNA 21 (miRNA-21). To promote excellent current intensity as well as enhance the sensitivity of aptasensors, the evenly distributed WO/FeO heterojunction was prepared as a transducer material, notably reducing the background signal response and extending the absorption of light. The multifunctional paper-based biocathode was assembled to provide a visual colorimetric assay.

Paper-based electrochemiluminescence determination of streptavidin using reticular DNA-functionalized PtCu nanoframes and analyte-triggered DNA walker.

A paper-based electrochemiluminescence (ECL) biosensor characterized by the signal amplification of reticular DNA-functionalized PtCu nanoframes (DNA-PtCuTNFs) and analyte-triggered DNA walker was developed for sensitive streptavidin assay. Silver microflower functionalized paper-based sensing platform was prepared to fix the hairpin strand (S1). With addition of the streptavidin, plenty of DNA walkers consisting of the walking strands (S2) labeled with biotin and streptavidin were established, which protected S2 from digestion via the terminal protection mechanism.

Ultrasensitive Photoelectrochemical Detection of MicroRNA on Paper by Combining a Cascade Nanozyme-Engineered Biocatalytic Precipitation Reaction and Target-Triggerable DNA Motor.

Developing efficient strategies for sensitive detection of microRNAs, the noncoding bioactive molecules and well-established biomarkers, has aroused great interests due to its great potential values in genetic and pathological analyses. Herein, a highly selective and disposable paper-based photoelectrochemical (PEC) sensor was rationally designed for sensing microRNA based on simple self-assembly of a target-triggerable DNA motor and nanozyme-catalyzed multistage biocatalytic precipitation reaction. Specifically, a brand-new type II heterojunction of TiO-CeO nanotubes decorated with carbon fiber paper (CFP) was first prepared, which gave an enhanced photoreactive surface and realized fast electron transport and extraction, markedly accelerating photoelectric conversion efficiency of the sensor.

Paper-Based SERS Sensing Platform Based on 3D Silver Dendrites and Molecularly Imprinted Identifier Sandwich Hybrid for Neonicotinoid Quantification.

Real-time monitoring of neonicotinoid pesticide residues is of great significance for food security and sustainable development of the ecological environment. Herein, a paper-based surface-enhanced Raman scattering (SERS) amplified approach was proposed by virtue of multilayered plasmonic coupling amplification. The unique plasmonic SERS multilayer was constructed using three-dimensional (3D) silver dendrite (SD)/electropolymerized molecular identifier (EMI)/silver nanoparticle (AgNP) sandwich hybrids with multiple hotspots and a strong electromagnetic field in nanogaps.

Peptide cleavage-mediated photoelectrochemical signal on-off via CuS electronic extinguisher for PSA detection.

In this work, a peptide-based photoelectrochemical (PEC) biosensor was constructed based on CdTe/TiO sensitized structure as electrode and CuS nanocrystals as signal amplifier for the ultrasensitive detection of protein. After peptide was fixed to the CdTe/TiO electrode surface, the double-helix DNA (dsDNA) was immobilized at the end of the peptide and used as a carrier to immobilize the doxorubicin-copper sulfide nanocrystals (Dox-CuS) conjugates. As a proof of concept, prostate specific antigen (PSA) has been chosen as the model.

Donor/Acceptor-Induced Ratiometric Photoelectrochemical Paper Analytical Device with a Hollow Double-Hydrophilic-Walls Channel for microRNA Quantification.

Integrating ratiometric photoelectrochemical (PEC) techniques with paper microfluidics to construct a ratiometric PEC paper analytical device for practical application is often restricted by the grave dependence of ratiometric assay on photoactive materials and low mass-transfer rates of the paper channel. Herein, a universal donor/acceptor-induced ratiometric PEC paper analytical device with a hollow double-hydrophilic-walls channel (HDHC) was fabricated for high-performance microRNA-141 (miRNA-141) quantification. Concretely, a photoanode and photocathode were integrated on the paper-based sensing platform in which the photocathode served as a biosensing site for the pursuit of higher selectivity.

Triggerable HO-Cleavable Switch of Paper-Based Biochips Endows Precision of Chemometer/Ratiometric Electrochemical Quantification of Analyte in High-Efficiency Point-of-Care Testing.

In this work, a triggerable HO-cleavable fluid switch mediated paper-based biochip, being amenable to multiplexing and quantitative analysis with the dual-response output of visual screening and ratiometric electrochemistry, was developed for sensitive detection of target on-site. By properly implanting hydrophobic Ag-HO responsive material in specific zone to form a programmable fluid switch, the biochip could achieve different modes of blocking/connecting switching automatically. In order to improve the test performance, a ratiometric electrochemical signal readout was designed, which was enhanced by a secondary in situ growth method fabricating trepang-shaped Au modified paper working electrode.

Noninvasive and Wearable Respiration Sensor Based on Organic Semiconductor Film with Strong Electron Affinity.

Interventional medical detection techniques require expensive devices and cause inconvenience and discomfort to the human body, which restricts their application to the frequency and duration of measurements. A noninvasive respiration test is urgently required for the next-generation medical technologies in early disease warning and postoperative monitoring. This article describes a noninvasive and wearable sensing device that shows high sensitivity toward acetone in respiratory gases with excellent stability, low energy consumption, and reliable flexibility.

Visual distance readout to display the level of energy generation in paper-based biofuel cells: application to enzymatic sensing of glucose.

Biofuel cells (BFCs) based on anodic oxidation and cathodic oxygen reduction represent an attractive alternative to self-powered devices. A glucose/oxygen BFC is described for monitoring glucose. It is making use of a piece of paper carrying a glucose oxidase (GOx) based bioanode, and a bilirubin oxidase (BilOx) based biocathode.

Mimic peroxidase-transfer enhancement of photoelectrochemical aptasensing via CuO nanoflowers functionalized lab-on-paper device with a controllable fluid separator.

Inspired by the design of folding greeting cards and tissue drawing covers, a photoelectrochemical (PEC) lab-on-paper device with a controllable fluid separator, producing both reaction zone and detection zone, was explored for ultrasensitive detection of adenosine 5'-triphosphate (ATP) via mimic peroxidase-transfer enhancement of photocurrent response. To realize it, the DNA1, aptamer, and DNA2 as well as the mimic peroxidase of G-quadruplex/hemin modified Au nanocubes were linked on the graphene oxide-functionalized reaction zone via the DNA hybridization. Meanwhile, three-dimensional CuO nanoflowers (CuO NFs) as a photoactive material with outstanding electron transfer ability and absorption of light were grown in situ on the detection zone, providing a PEC active interface.

Paper based modification-free photoelectrochemical sensing platform with single-crystalline aloe like TiO as electron transporting material for cTnI detection.

By controlling target-induced signal quencher release, a label-free and modification-free microfluidic paper based photoelectrochemical analytical device (μ-PAD) for cardiac troponin-I (cTnI) detection was designed for the first time. To achieve it, cellulose paper based single-crystalline three-dimensional aloe like TiO arrays (PSATs) were firstly fabricated as the electron transporting material, providing direct pathways for the charge carriers transfer, and subsequently coupled with CdS to form PSATs/CdS heterojunction for extending the solar spectrum response. Meanwhile, positive charged mesoporous silica nanoparticles (PMSNs) were prepared as the nanocarrier to efficient entrap the Cu which could be regarded as signal quencher due to their reaction with CdS to form CuS.

Paper-Supported Self-Powered System Based on a Glucose/O Biofuel Cell for Visual MicroRNA-21 Sensing.

The exploitation of self-powered devices that get rid of the power source restriction represents the development tendency of sensing systems. Herein, a paper-supported glucose/O biofuel cell (BFC)-based self-powered sensing platform for visual analysis was developed. The BFC device utilized gold nanoparticle-modified paper fibers as the electrode to wire glucose oxidase (GOx) and bilirubin oxidase for the fabrication of bioanodes and biocathodes.

Double signal amplification based on palladium nanoclusters and nucleic acid cycles on a μPAD for dual-model detection of microRNAs.

MicroRNAs (miRNAs) are a class of significant biomarkers; however, it is still a huge challenge to express them accurately. Herein, a fluorescent/colorimetric dual-model biosensor based upon the quenching effect of graphitic carbon nitride on palladium nanoclusters (Pd NCs) on the platform of a microfluidic paper-based analytical device was built for the detection of miRNAs. On the one hand, Pd NCs could catalyze a chromogenic reaction so that preliminary detection was achieved by the naked eye.

Ag2S/CdS/TiO2 Nanotube Array Films with High Photocurrent Density by Spotting Sample Method.

Ag2S/CdS/TiO2 hybrid nanotube array films (Ag2S/CdS/TNTs) were prepared by selectively depositing a narrow-gap semiconductor-Ag2S (0.9 eV) quantum dots (QDs)-in the local domain of the CdS/TiO2 nanotube array films by spotting sample method (SSM). The improvement of sunlight absorption ability and photocurrent density of titanium dioxide (TiO2) nanotube array films (TNTs) which were obtained by anodic oxidation method was realized because of modifying semiconductor QDs.

2,6-Diaminopyridine-imprinted polymer and its potency to hair-dye assay using graphene/ionic liquid electrochemical sensor.

A new analytical approach for detecting diaminopyridine derivatives has been constructed using a molecular imprinting-electrochemical sensor. Opposed to the conventional strategy of employing diaminopyridine as the functional monomer and uracil derivatives as the target analyte, in the current study, the 2,6-Diaminopyridine-imprinted core-shell nanoparticles were synthesized with 2,6-Diaminopyridine as the template molecule and 6-aminouracil as the functional monomer. Graphene and ionic liquid which can assist 2,6-Diaminopyridine-imprinted core-shell nanoparticles in electrochemical reaction kinetics by increasing conductivity have been introduced to form one of the electrode modified layers.

Lysine-based chiral vesicles.

Uni-lamellar and multi-lamellar vesicles were prepared by the enantiomers of a biological molecule, L-lysine or D-lysine, with a double-tail weak monoacid, di-(2-ethylhexyl) phosphoric acid (abbreviated as DEHPA), in water. With the addition of DEHPA to lysine aqueous solutions, ion-pairs are formed through the acid-base reaction between the lysine cations and DEHP(-) anions. The self-assembled vesicles were proved to be driven by the hydrogen bonding between the side-chain amino groups in lysine molecules and the polar groups of DEHP(-) species.

Tert-butylhydroquinone recognition of molecular imprinting electrochemical sensor based on core-shell nanoparticles.

One novel electrochemistry-molecular imprinting sensor for determining tert-butylhydroquinone (TBHQ) in foodstuff was developed. TBHQ-imprinted core-shell nanoparticles (TICSNs) were fabricated using silica nanoparticles as core material. The silica nanoparticles were modified with (3-chloropropyl) trimethoxysilan and polyethylenimine, respectively, and polymerised to form the TICSNs with ethylene glycol dimethacrylate as cross-linker.