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Abstract: This paper focuses on the gas sensing properties of the mixed-potential-type NO2 sensor based on yttria stabilized zirconia (YSZ) and NiO electrode. The sensing performance of the sensor was improved by modifying the three-phase boundary (TPB). Hydrofluoric acid with different concentrations (10%, 20% and 40%) was used to corrode YSZ substrate to obtain large superficial area of TPB. The scanning electron microscope and atomic force microscopic images showed that the 40% HF could form the largest superficial area at the same corroding time (3h). The sensitivity of the sensor using the YSZ plate corroded with 40% hydrofluoric acid to 20–500ppm NO2 was 76mV/decade at 850°C, which was the largest among the examined HF concentrations. It was also seen that the sensor showed a good selectivity and speedy response kinetics to NO2. On the basis of the measurements of anodic and cathodic polarization curves, as well as the complex impedance of the device, the sensing mechanism was confirmed to involve a mixed potential at the oxide sensing electrode. [Copyright &y& Elsevier]

Incompatible cross-platform detection technologies adopted for different medical scenarios has caused several problems in the clinical detection of disease biomarkers. Here, we developed a unified platform with hierarchical performance for biomarker detection. A hexagonal star-nanostructured DNAzyme was constructed. It shows excellent catalytic activity towards the deposition of polydopamine, which is capable of presenting colorimetric signals directly and is also scalable to present fluorescent and electrochemical signals by conjugating with quantum dots. This scalable detection system is validated for the detection of both nucleic acid biomarkers (miRNAs) and protein biomarkers (carcinoembryonic antigen and platelet-derived growth factor). Results show that the detection system can adapt to the current colorimetric, fluorescent and electrochemical equipment, possess the advantage of high efficiency and low-cost, and present hierarchical performance in terms of operability and sensitivity, making it possible to verify the results in a unified system and to switch the detection methods according to different scenarios. [Display omitted] • The unified platform showed excellent advantages in efficiency and cost of biomarker detection. • A nanostructured DNAzyme was constructed to realize efficient deposition of dopamine. • The scalable platform is validated for the detection of both nucleic acid and protein biomarkers. [ABSTRACT FROM AUTHOR]

Aminopeptidase N (APN) is an important ectopeptidase involved in many physiological functions e.g. tumor angiogenesis, and the detection of APN activity thus facilitates the early diagnosis and elucidation of tumor development. Herein we propose a one-pot and one-step colorimetric sensing method for detecting APN activity based on a peptide functionalized gold nanoparticles/cucurbit[8]uril (pep-AuNPs/CB[8]) supramolecular structure. In principle, a peptide that comprises both the recognition sequence of APN and binding motif of CB[8] is first functionalized onto the surface of AuNPs. Because CB[8] can interact with two binding motifs simultaneously, the assembly of pep-AuNPs and CB[8] consequently take place, leading to the formation of pep-AuNPs/CB[8] supramolecular structure. However, in the presence of APN, the peptide will be hydrolyzed by APN, resulting in the breach of binding motifs of CB[8] as well as the prevention of the formation of pep-AuNPs/CB[8] supramolecular structure. In this way, the activity of APN can be determined through the absorbance changes based on the assembly/disassembly of AuNPs. Under optimized conditions, the detection of APN activity is achieved in a linear range from 5 μg/mL to 15 μg/mL with a detection limit of 0.42 μg/mL, which is also available directly in serum samples. Because of the simplicity and the cost-efficient materials, the method is competent for practical applications. [ABSTRACT FROM AUTHOR]

Abstract: A series of mixed W/Cr oxides with different ratio of W and Cr (1:6, 1:2 and 3:2) have been prepared by using polymeric precursor method. By comparing their sensitivities to 20–300ppm NO2, it was found that the sensor using oxide with 3:2 W/Cr gave the largest response value. For 3:2 W/Cr oxide, the effect of the sintering temperature on the electrode microstructure was also investigated. As a result, the device sintered at 1000°C showed the best performance. The response value to 100ppm NO2 is 51.6mV, the response time is within 20s and the sensing device also shows an excellent selectivity against other coexisting gases. The characteristics of SEM and TEM revealed that the special microstructure of oxide electrode formed by sintering plays a significant role in better sensing performance. [Copyright &y& Elsevier]