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• Biosensor based on Pt nanoparticles modified MXene is developed for analysis of pyruvate. • Pyruvate oxidase oxidizes pyruvate to produce H 2 O 2. • H 2 O 2 was detected by PtNPs-modified MXene to generate electrochemical signals. • The sensor was applied for determination of pyruvate in human serum. In this study, we developed a biosensor based on Pt nanoparticles (PtNPs) modified 2D MXene for sensitive analysis of pyruvate in human serum. The pyruvate oxidase oxidizes pyruvate to produce H 2 O 2 , which is catalyzed by PtNPs-modified MXene, generating electrochemical signals for pyruvate detection, with a linear range of 10–1000 μM and a detection limit of 0.7 μM. The practical application of the sensor was verified by the determination of pyruvate in human serum. The utilization of MXene as biosensing materials may find wide application in the design of different biosensors. [ABSTRACT FROM AUTHOR]

Co 3 O 4 /NiCo 2 O 4 double-shelled nanocages (DSNCs) were successfully prepared through a metal-organic frameworks (MOFs) route. The strategy includes the synthesis of zeolite imidazolate framework-67 (ZIF-67)/Ni-Co layer doubled hydroxides precursor and subsequent transformation to Co 3 O 4 /NiCo 2 O 4 DSNCs by thermal annealing of the as-prepared precursor in air. Various techniques such as XRD, SEM/EDS, BET and TEM were employed for the characterization of microstructure and morphology of the as-prepared Co 3 O 4 /NiCo 2 O 4 DSNCs. The use of as-prepared Co 3 O 4 /NiCo 2 O 4 DSNCs as a gas sensing material in a gas sensor gave an enhanced sensitivity to acetone compared with result obtained in Co 3 O 4 nanocages (NCs). In addition, excellent reversibility and selectivity of the sensor were observed. These properties make the Co 3 O 4 /NiCo 2 O 4 DSNCs a good candidate for acetone detection. [ABSTRACT FROM AUTHOR]

• Photoelectrochemical immunosensor for detection of cancer biomarker. • Organic semiconductor Y6 and gold nanoparticles were utilized as photoactive material. • ZnPO 4 nanoparticles with horseradish peroxidase embedded was used as signal probe. • Horseradish peroxidase catalyzed the formation of insulating film on electrode. • The insulating film resulted in suppression of photoelectrochemical current intensity. Photoelectrochemical (PEC) sensor was prepared for detection of cancer biomarker carcinoembryonic antigen (CEA), which is strongly associated with diagnosis and prognosis of different cancer. Organic semiconductor Y6 combined with gold nanoparticles (Au NPs) formed organic–inorganic heterojunction and the heterojunction was utilized as photoactive material. ZnPO 4 nanoparticles with horseradish peroxidase (HRP) embedded inside the nanoparticle and antibody absorbed on nanoparticle surface were synthesized and utilized as signal probe. After formation of sandwich structure on electrode surface, HRP can catalyze 3,3′-dimethoxybenzidine (DB) in solution to form insulating polymer film, poly(3,3′-dimethoxybenzidine) (PDB) onto the electrode surface. The formed PDB film on electrode surface resulted in the suppression of PEC current intensity, achieving sensitive and selective detection of CEA with linear range from 1 pg/mL to 1 ng/mL and limit of detection of 0.5 pg/mL. [ABSTRACT FROM AUTHOR]

• Electrochemical sensor for the detection of uric acid in serum was reported. • Platinum nanoparticles were synthesized within the porous structure of ZIF-8. • ZIF-8 was carbonized to form platinum nanoparticles modified porous carbon. • The modified porous carbon was able to detect uric acid selectively and sensitively. In this study, we prepared an electrochemical sensor for the detection of uric acid (UA) in serum. Platinum nanoparticles (PtNPs) were synthesized within the porous structure of ZIF-8 and the nanocomposite was then carbonized at high temperatures to improve the adhesion rate of PtNPs in porous carbon. The synthesized materials were characterized by scanning electron microscopy and transmission electron microscopy. The sensor was able to detect uric acid in serum sensitively with good selectivity and stability. [ABSTRACT FROM AUTHOR]

• Photoelectrochemical sensor for the detection of neurofilament light chain is reported. • Organic semiconductor Y6 is utilized as photoelectrochemical active material. • Magnetic Fe 3 O 4 nanospheres was employed for capture of target analyte. • Gold nanoparticles modified with polycytosine DNA sequence was used for signal amplification. • The formed molybdophosphate suppressed photoelectrochemical current intensity. Sensitive photoelectrochemical sensor based on organic semiconductor Y6 as photoactive material is reported for the detection of neurofilament light chain in human serum. Magnetic Fe 3 O 4 nanospheres modified with capture antibodies were employed for highly efficient capture of neurofilament light chain from serum sample, and gold nanoparticles modified with detection antibodies as well as polycytosine DNA sequence were used for signal amplification. The reaction of polycytosine sequence with molybdate formed molybdophosphate precipitate on electrode surface, leading to decrease of photoelectrochemical current intensity. [ABSTRACT FROM AUTHOR]

• Copper peroxide nanodot was utilized as signal nanoprobe for photoelectrochemical sensor. • The nanodots were encapsulated in metal-organic frameworks. • The nanoprobe can self-supply H 2 O 2 by encapsulated CPNs under acidic condition. • The produced H 2 O 2 can help generate insoluble precipitation onto sensor surface. • The formed precipitation resulted in decrease of photoelectrochemical current intensity. Signal nanoprobe based on copper peroxide nanodots (CPNs) embedded within metal–organic frameworks (ZIF-8) was applied for developing photoelectrochemical (PEC) sensor for detection of circulation tumor cells (CTC). The nanoprobe can self-supply H 2 O 2 by encapsulated CPNs under acidic condition. The produced H 2 O 2 can help generate insoluble precipitation onto sensor surface in the presence of horseradish peroxidase (HRP), leading to suppressed PEC current intensity. MCF-7 was selected as model CTC, which was enriched and separated from samples by antibody modified magnetic beads (MB). Organic semiconductor BTA-C4Ph and PM6 were chosen to form n-p heterojunction on sensor surface with enhanced PEC current intensity. The PEC sensor was constructed based on "sandwich" protocol, which has a linear range from 5 cell/mL to 100 cell/mL and a limit of detection (LOD) of 3 cell/mL (S/N = 3) for MCF-7. What more, the sensor was successfully applied for detection of MCF-7 in whole blood samples. [ABSTRACT FROM AUTHOR]

• Electrochemical sensor for detecting circulating tumor cells is reported. • Fe 3 O 4 magnetic nanospheres were utilized to capture MCF-7 cell. • LiFePO 4 particles were chosen as electrochemical label. • Electrochemical signals are generated by reaction of LiFePO 4 with molybdate. • The sensor was applied for detection of tumor cells in blood sample. In this study, we reported an electrochemical assay for detecting circulating tumor cells (CTCs) in whole blood. Breast cancer cell MCF-7 was chosen as a model for study. Fe 3 O 4 magnetic nanospheres (MNs) modified with anti-epithelial cell adhesion molecule (EpCAM) antibody were utilized to capture MCF-7 from samples and gold nanoparticles modified LiFePO 4 (LiFePO 4 /Au) particles were chosen as electrochemical label. Aptamer can be linked onto LiFePO 4 /Au via Au-S bond, and then the LiFePO 4 /Au-aptamer complex can specifically bind to the MUC1 protein that is over-expressed on the cell surface of MCF-7. Electrochemical signals are generated by the reaction of phosphate in LiFePO 4 with molybdate to form redox molybdophosphate. The utilization of LiFePO 4 for signal probe may expand the application of LiFePO 4 in biosensing fields. [ABSTRACT FROM AUTHOR]

The mesoporous Co 3 O 4 with shape of fans has been successfully synthesized by a simple hydrothermal approach from cobalt nitrate, urea, gelation and subsequent calcination process. Powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and nitrogen adsorption/ desorption analysis are characterized to demonstrate the crystal structure, morphology, and microstructure of Co 3 O 4 nanofans (Co 3 O 4 NFs). When applied as a gas sensing material, the sensitivity of as-prepared Co 3 O 4 is obviously higher than the Co 3 O 4 nanosheets (Co 3 O 4 NSs).The well gas sensing performances to xylene properties make this mesoporous fan-like Co 3 O 4 be a good candidate for xylene sensors. [ABSTRACT FROM AUTHOR]

The rational designs of metal oxides with well exposed facets have stimulated tremendous attentions due to their vital importance for practical applications. In 2 O 3 microcubes (In 2 O 3 MCs) were synthesized by a simple hydro-thermal method with cubic structure and high surface area. Various techniques were employed for characterization of the structure and morphology of the as-prepared In 2 O 3 MCs. The as-synthesized In 2 O 3 MCs, when utilized as gas sensing material, exhibited high sensitivity and selectivity towards ethanol vapor. Such outstanding gas sensing performance of In 2 O 3 MCs benefits from their large specific surface area and exposure of {1 0 0} facets. [ABSTRACT FROM AUTHOR]

Ordered In 2 O 3 nanoparticles (In 2 O 3 NPs) were successfully prepared via a template-free method. The synthesis was conducted in a water-glycerol-ethylene glycol mixed solvent without any templates, and the ultra-fine nanostructured In 2 O 3 has a uniform size of about 20–30 nm. The In 2 O 3 nanoparticles exhibited improved sensitivity, fast response, and high selectivity to acetone. The enhanced acetone performance results from a large surface area with enough sensing active sites, and small particle size for effective electron depletion. [ABSTRACT FROM AUTHOR]

The presence of low-valent Nb-based point defects and low surface area are common issues within niobium oxynitrides. Herein, La 3 NbO 7 which has richer basic oxide and lower positive Mulliken charge on Nb(V) than LaNbO 4 , was prepared via NaCl-KCl mixed flux synthesis and converted to perovskite-type LaNbON 2 via thermal ammonolysis. Removal of secondary product La 2 O 3 from ammonolysis of La 3 NbO 7 gives rise to additional nanopores in LaNbON 2 besides the pores resulted from nitridation. This makes a bigger specific surface area (23 m 2 /g) than conventional LaNbON 2 prepared from LaNbO 4 (11 m 2 /g). Moreover, UV–vis spectrum of LaNbON 2 from La 3 NbO 7 reveals much lower defect absorption than LaNbON 2 from LaNbO 4 ; thermogravimetric analysis shows that the mass-gain stage attributed to oxidation of low-valent Nb is present in curve of LaNbON 2 from LaNbO 4 while absent in that of LaNbON 2 from La 3 NbO 7 . These indicate that the formation of low-valent Nb defects in LaNbON 2 is inhibited when using La 3 NbO 7 as precursor. [ABSTRACT FROM AUTHOR]

Molecularly imprinted electrochemical sensor for ascorbic acid detection was prepared based on MXene modified glassy carbon electrode. • Molecularly imprinted electrochemical sensor detection was prepared. • MXene was utilized to modify glassy carbon electrode. • Mxene with layered structure was prepared by chemical etching method. • O-phenylenediamine was electrochemically polymerized onto MXene modified electrode. • The imprinted polymer provides binding sites for target analytes. Molecularly imprinted electrochemical sensor for ascorbic acid (AA) detection was prepared based on MXene modified glassy carbon electrode (MIPs/MXene/GCE). MXene with layered structure was synthesized by chemical etching method and the o-phenylenediamine (o-PD) polymer was electrochemically polymerized onto MXene modified electrode surface. With the binding of AA molecules onto electrode, the current response of the sensor was decreased. Under the optimized experimental conditions, the current response change of the sensor was in linear with the concentration of AA in the range from 0.5 μM to 10 μM with detection limit of 0.27 μM. The sensor has good selectivity, which was applied to the determination of AA in vitamin C tablets. [ABSTRACT FROM AUTHOR]