Search

Photoexcitation is an effective method to promote specific gas sensing performance of semiconductor for electronic device. In this work, an interlayered Ti 3 C 2 T X /TiO 2 /ZnO ternary nanoarchitecture was successfully prepared via sequential etching-intercalation and pyrolysis methods, for which the ZIF-8 nanoparticles were initially incorporated into the adjacent interlayers of laminated Ti 3 C 2 T X MXene derived from HF-etching of Ti 3 AlC 2 MAX phase. The resultant multilayered Ti 3 C 2 T X /ZIF-8 nanocomposite was pyrolyzed at 400 oC to form Ti 3 C 2 T X /TiO 2 /ZnO ternary heterostructure, showing high triethylamine (TEA) sensing performance with R a /R g = 98 at 270 oC under 620 nm red-light irradiation, which is 3.1 times higher than that of the value measured under darkness. A rapid response/recovery time of 17 s/86 s is achieved, and it shows excellent TEA sensing selectivity and long-term cyclic stability. The close-stacked nano-/microstructure of Ti 3 C 2 T X /TiO 2 /ZnO effectively contribute to the diffusion and permeation of gas molecules, as well as the photogeneration and migration of charge carriers, leading to its outstanding photoactivated TEA sensing performance. This work provides a feasible approach to exploring high-performance Mxene hybrids for ultrasensitive TEA monitoring. [Display omitted] • Accordion-like Ti 3 C 2 T x /TiO 2 /ZnO nanocomposite was prepared via etching and pyrolysis. • The Ti 3 C 2 T x /TiO 2 /ZnO nanocomposite exhibits excellent triethylamine sensing ability. • The response under 620 nm excitation was 3.1 times higher than that under darkness. • Construction of ternary heterojunction positively modulates the band gap structure. • Synergistic effect of photoactivation and charge carrier migration was investigated. [ABSTRACT FROM AUTHOR]

The repeated outbreaks of coronavirus disease 2019 (COVID-19) have seriously threatened human health and economic development. Therefore, it is still significant to explore an efficient method for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection. Herein, we designed a dual-mode colorimetric and fluorescent immunosensor based on Fe2+ doped ZIF-67 derivatives-based composites, Pt nanoparticles loaded on CoFe nanoparticles embedded porous carbon-nitrogen hexahedron (CoFe/NC@Pt), for detecting SARS-CoV-2 nucleocapsid protein. The doping of Fe2+ generated bimetallic CoFe nanoparticles and formed more defects after pyrolysis. Meanwhile, the peroxides-like activity significantly improved owning to the synergistic effect of Co and Fe nanoparticles. Furthermore, loaded Pt nanoparticles not only provided more active sites, but also could couple antibodies by modifying functional groups. CoFe/NC@Pt exhibited good peroxidase-like activity and could catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxides in the presence of H 2 O 2 , generating visible color signals. While the oxTMB could quench the fluorescence of carbon dots through inner filter effect, thereby providing fluorescent signals. The limit of detection were 0.022 ng/mL (colorimetric) and 0.018 ng/mL (fluorescent). And the specificity of the immunosensor was verified by comparing with other interferents. Therefore, this dual-mode immunosensor with good performance provided a reliable strategy for diagnosis of COVID-19. [Display omitted] • A dual-mode colorimetric and fluorescent immunosensor based on CoFe/NC@Pt nanozyme. • CoFe/NC@Pt exhibited good peroxidase-like activity. • The quenching mechanism of CDs was inner filter effect. • The accuracy of the sensor was improved by mutual authentication of double signals. [ABSTRACT FROM AUTHOR]

Doping noble metals into semiconductor based gas sensors was proved to be an effective strategy in improving gas response properties. Here, we report a silver/silver (II) oxide nanoparticles (Ag/AgO NPs) modified highly porous ZnO nanocomposite. Firstly, the Ag NPs were evenly deposited on the surface of flower-like ZnCO 3 precursors through a simple photochemical reduction method, which was then heated at 400 °C to give highly porous Ag/AgO/ZnO nanocomposite, accompaning with the dissociation of ZnCO 3 after release of CO 2. The interleaving ultrathin and porous sheet-like features of Ag/AgO/ZnO nanocomposite afford it excellent triethylamine (TEA) sensing performance with R a /R g = 90.3 at an operating temperature of 240 °C, and the response sensitivity is 5.5-fold higher than that of pure ZnO. Specifically, the porous Ag/AgO/ZnO nanocomposite exhibited a fast response/recovery time of 53 s/8 s and oustanding long-term cyclic stability. The enhanced gas sensing performance can be attributed to the sensitization of Ag/AgO NPs, significantly increasing the number of oxygen vacancies and thus providing more reactive sites. The synergistic interaction between Ag/AgO NPs and porous ZnO nanosheets also facilitates a fast electron transport and a high permeability for gas molecules. This work displays a feasible way of coupling photochemical reduction and pyrolysis strategy to develop highly porous ZnO nanosheets functionalized by noble metal NPs with remarkably enhanced gas response property. [Display omitted] • Ag/AgO NPs were loaded on porous ZnO microspheres by photochemical reduction method. • Ag/AgO NPs increase the oxygen vacancy concentration and provide more active sites. • It shows excellent triethylamine (TEA) response (R a /R g = 90.3) perfromance at 240 °C. • It has fast response/recovery time (53 s/8 s), good selectivity and high stability. • The TEA sensing mechanism of highly porous Ag/AgO/ZnO nanocomposites is discussed. [ABSTRACT FROM AUTHOR]

Increasing demands for detection of toxic gases in ambient atmosphere have attracted much attention to design and fabricate gas sensors with high sensitivity, good selectivity and low operating temperature. Herein, porous ZnFe 2 O 4 nanosheets (NSs) have been successfully synthesized using graphene sheets as hard templates. The as-fabricated ZnFe 2 O 4 NSs are composed of small particles with a diameter of approximately 10–20 nm and the pore size in the NSs is in range of 5–50 nm. In comparison with the Fe 2 O 3 NSs, ZnO NSs and ZnFe 2 O 4 nanoparticles (NPs), the gas sensors based on ZnFe 2 O 4 NSs exhibit superior H 2 S sensing performance, including high sensor response at a low working temperature (85 °C), relatively fast response and recovery times, and good selectivity. Furthermore, the sensors based on ZnFe 2 O 4 NSs show good repeatability and long-term stability. Our results demonstrate that the porous ZnFe 2 O 4 NSs are very promising for the fabrication of high-performance H 2 S gas sensors. The work highlights the possibility to develop a novel high performance gas sensor for practical applications. [ABSTRACT FROM AUTHOR]

A turn-on fluorescent probe based on terthienyl for CN − has been constructed and CN − was detected by taking advantage of aggregation-induced emission (AIE) behavior of terthienyl units in aqueous solutions. The probe displayed a high selectivity and sensitivity for CN − against other analytes, and the detection limit was measured to be 0.1 μM. The aggregation behavior confirmed by DLS and SEM caused fluorescence enhancement in the sensing environment. A simple paper test strip system for the rapid monitoring of CN − was developed. Moreover, the probe could be employed to detect CN − in biological samples. [ABSTRACT FROM AUTHOR]

The reasonable chiral discrimination has been achieved using silver nanoparticles technique while improving the sensitivity of chiral recognition is essential and remains a challenging task. Dynamic light scattering (DLS), is expected to be a feasible method for improving the sensitivity of analyte discrimination. In this article, by capping Ag NPs with a novel chiral R-mandelic acid-derived calix[4]arene (R-MAC4), the intriguing optical and other properties of the structures can be modified via self-assembly. A method of dynamic light scattering (DLS) was used to recognize the N-Fmoc- d/l -aspartic acid ( d/l -FAA). Using this dynamic light-scattering technique, the detection sensitivity was improved almost 500-fold, with detection limit of 5.0 × 10 −8 M, compared with Ag NPs methods. [ABSTRACT FROM AUTHOR]

A new ratiometric fluorescent probe for hydrazine based on a 4-hydroxynaphthalimide fluorophore was developed. The selective deprotection of the acetate group of the probe by hydrazine led to a prominent fluorescence ratiometric change, as well as a remarkable color change which could be distinguished by naked-eye. The reaction between the probe and hydrazine completed in 5 min under the analytical system, and displayed a high selectivity and sensitivity for hydrazine against other primary amines and environmental and/or biological abundant ions. Moreover, the probe could be applied for hydrazine detection both in water samples and in vivo . [ABSTRACT FROM AUTHOR]

Periodontitis, as one of the most universal chronic inflammatory diseases worldwide, has raised numerous attentions since its tremendous destructive force against alveolar bone and soft tissue, ultimately leading to the tooth loss. Hydrogen peroxide (H 2 O 2) is a major byproduct during the pathogenesis of periodontitis, which hints that direct and in-situ detection of H 2 O 2 provides an effective way for early diagnosis of periodontitis. Herein, a non-enzymatic and highly electrocatalytic H 2 O 2 biosensor was proposed by using a novel electrode composed of copper oxide nanoparticles (CuO NPs), black phosphorus nanosheets (BP NSs) and chitosan. Owing to the remarkable electrochemical redox capability of CuO NPs and marvelous conductivity of BP NSs, such heterostructure attained enhanced surface adsorption and efficient electron transfer, contributing to ultrasensitive determination of H 2 O 2 in a real-time manner. The synergistic effects of CuO and BP demonstrated supreme electrocatalytic ability with a low practical detection limit (30 nM), excellent sensitivity (138.00 μA mM−1 cm−2), extraordinary selectivity, splendid reusability and long-term stability. In terms of biofluid level, this biosensor achieved feasible detection of H 2 O 2 in saliva and gingival crevicular fluid samples and effectively differentiated patients of periodontitis from healthy people, which lay solid foundation for diagnosis of periodontitis. Referring to cellular scale, such device was successfully implemented to detect H 2 O 2 released from macrophages and gingival fibroblasts, presenting favorable biosensing capability in living cells. Looking forward, this design of CuO/BP sensor could be extended to broader applications in monitoring physiological and dynamic in-clinic pathological processes in other inflammatory diseases. [Display omitted] • An electrochemical sensor for H 2 O 2 was developed based on the CuO/BP nanohybrid. • The as-designed electrode showed excellent sensitivity and desirable detection limit. • The proposed electrode easily recognized H 2 O 2 in saliva or gingival crevicular fluid. • The biosensor successfully determined H 2 O 2 released from fibroblasts or macrophages. • This protocol provides smart strategy for early diagnosis of periodontitis. [ABSTRACT FROM AUTHOR]

Abstract: A new fluorescent turn-on probe for HSO3 − bearing a benzo[e]indolium moiety was developed. The HSO3 − undergoes 1,4-addition reaction with the C-4 atom in the ethylene group, resulting in a prominent fluorescence enhancement and a fluorescent color change. The reaction could be completed in 1min in PBS buffer, and displayed a high selectivity and sensitivity for HSO3 − against other anions, including CN−. Moreover, the practical value of the probe was confirmed by application to detect the level of HSO3 − in sugar samples. [Copyright &y& Elsevier]

Abstract: A new ratiometric fluorescent cyanide probe bearing a benzo [e] indolium moiety as a fluorophore and binding site was developed. The detection of cyanide was performed via the nucleophilic attack of cyanide toward the benzo [e] indolium group of the probe, resulting in a prominent fluorescence ratiometric change and a color change. The probe was invested in water with high selectivity and sensitivity for cyanide. A simple paper test strip system for the rapid monitoring of cyanide was developed. [Copyright &y& Elsevier]

Abstract: Two highly selective cyanide probes with a salicylaldehyde hydrazone functionality as binding site were reported with fast response. The detection of cyanide was performed via the nucleophilic attack of cyanide anion on the imine group of the probes with a 1:1 binding stoichiometry, which could be confirmed by 1H NMR and MS studies. The specific reaction results in a prominent fluorescence enhancement for one of the probes and a color change from pale yellow to dark red for the other. The cyanide detection method described here should have potential application as a new family of probes for detecting cyanide in aqueous solution. [Copyright &y& Elsevier]

• A sensitive and selective SERS aptasensor was developed for atrazine detection. • A nitrile-mediated molecule (MMBN) was utilized as optical interference-free Raman tag. • Fe 3 O 4 @Au core/shell nanoparticles were used as SERS substrate for rapid enrichment. • Reliable measurements of atrazine were well established in real samples. A novel aptasensor based on the combination of surface-enhanced Raman scattering (SERS) and magnetic separation is presented for sensitive and selective determination of atrazine. 4-(Mercaptomethyl) benzonitrile (MMBN), providing a prominent peak (2227 cm−1) in the Raman-silent spectral window (1800–2800 cm−1), is selected as Raman tag to eliminate optical interference from biomolecules in sensing system. The MMBN and atrazine-binding aptamer are assembled on silver nanoparticles (AgNPs) to serve as Raman probe (MMBN-AgNPs-aptamer). Meanwhile, Fe 3 O 4 @Au core/shell nanoparticles conjugated with the complementary DNA (Fe 3 O 4 @Au-cDNA) are prepared as Raman substrate to extract the Raman probe with magnetic separation. Atrazine specifically binds to aptamer, and hinders the formation of Fe 3 O 4 @Au-cDNA-aptamer-AgNPs-MMBN (expressed as "Fe 3 O 4 @Au-AgNPs") complex. Therefore, the Raman intensity of MMBN on substrate decreases with the increment of atrazine concentration. Under optimal SERS conditions, the proposed aptasensor is used to detect atrazine in the laboratory and real samples. The as-prepared atrazine sensor demonstrates a broad dynamic range of 1–50 nM, as well as a low detection limit of 0.67 nM (S/N = 3). For real sample test, the recovery rate ranges from 98.7%–106.6%. The fabricated aptasensor shows superior interference-free performance for atrazine determination in the presence of analogs at high levels. [ABSTRACT FROM AUTHOR]

• In-MIL-68 derived porous lacunaris structure In 2 O 3 for triethylamine sensor was synthesized by a simple method. • In 2 O 3 -500 sensor shows excellent sensing performance, the response of 32 when exposed to 100 ppb TEA at 120 °C. • Gas sensitivity mechanism about the improvement of gas sensitivity performance has been studied and discussed in this work. Gas sensors with high sensitivity, selectivity, stability, moisture resistance and reliable fabrication potency for detection of toxic and harmful gases have been now expected for many applications in the environment. Herein, a kind of triethylamine (TEA) gas sensors can quantitatively detect on ppb level gases is reported. The sensors were fabricated with porous lacunaris structure In 2 O 3 derived from metal-organic frameworks In-MIL-68 by annealing at a suitable temperature 500 °C. It exhibited the highest response of 32 when exposed to 100 ppb TEA gas at the optimal operation temperature 120 °C, and the response and recovery time is 9 s and 36 s respectively. Furthermore, it also demonstrated outstanding selectivity, stability (without any change after 40 days) and moisture resistance (kept 86.2 % response at 90 % relative humidity). In addition, the good response linearity within a wide TEA concentration range of 0.1 ppm–5 ppm and lower detection limit are other advantages of the sensor. Considering these advantages, In-MIL-68 derived In 2 O 3 sensor is a promising candidate for TEA detection. The gas sensing mechanism is also explored here. [ABSTRACT FROM AUTHOR]

We describe a biomimetic strategy via supramolecular host-guest chemistry for constructing artificial nanochannels to detect N-acetylglucosamine analogues. The functional nanochannels exhibited a high selectivity and good reversibility towards N-acetylglucosamine. • The pillararene decorated with tryptophan was designed and synthesized for binding the N-acetylglucosamine analogues. • Artificial nanochannels constructed by host-guest chemistry can detect N-acetylglucosamine with a high selectivity and good reversibility. • The functional nanochannel can further achieve the detection of N-acetylglucosamine in the serum sample. N-acetylglucosamine analogues exist in nature as an important saccharide in human body and can regulate a variety of life activities captured through biological nanochannels. Herein we describe a biomimetic strategy via supramolecular host-guest chemistry for constructing artificial nanochannels to detect N-acetylglucosamine analogues. The functional nanochannels exhibited a high selectivity and good reversibility towards N-acetylglucosamine. Further studies indicate that the detecting behaviors was probably due to the multiple hydrogen bonding interactions and an appropriately fitting the functional and geometric requirements between the tryptophan-decorated pillararenes and N-acetylglucosamine, leading to the change of the surface charge and wettability within the nanochannels. These studies can give interesting insight for the research of biological processes caused by N-acetylglucosamine-sensitive ion channels, and also help to develop the platform for detecting N-acetylglucosamine in vitro. [ABSTRACT FROM AUTHOR]

Herein, a spectrum-resolved differential strategy was proposed to enhance further the selectivity of photoelectrochemical (PEC) sensors, demonstrated by the simultaneous determinations of ascorbic acid (AA) and uric acid (UA). Molecularly imprinted polymer (MIP) membranes for AA (MIP AA) and UA (MIP UA) were fabricated on the surface of TiO 2 nanotubes via electropolymerization, using pyrrole as functional monomer, AA and UA as templates, respectively. It was shown that the increase in absorbance from AA or UA within the MIP membranes resulted in an intense decrease in the photocurrent of the PEC sensors. In the spectrum-resolved differential mode, Δ RI AA = (I AA / I AA0 − I UA / I UA0) 310 and Δ RI UA = (I UA0 / I UA − I AA0 / I AA) 275 were used in the simultaneous determinations of AA and UA, respectively. Where I AA , I AA0 , I UA and I UA0 are the photocurrents of MIP AA and MIP UA in sample and blank, the subscripts of 275 and 310 stand for the excitation wavelength (nm), respectively. The interference levels in the differential mode were reduced by one order of magnitude compared with the normal MIP mode. The spectrum-resolved differential PEC MIP sensors were used in the simultaneous determination of AA and UA in serum and urine samples, with the detection limits of 0.019 and 0.036 μM, respectively. [Display omitted] • Spectrum-resolved molecularly imprinted photoelectrochemical sensors were reported. • The wavelength-dependent photocurrent response was investigated. • Photocurrents at 275 and 310 nm were used to determine uric acid and ascorbic acid. • Interference to sensor A was corrected from sensor B at its insensitive wavelength. • The anti-interference ability of the sensor was much enhanced in differential mode. [ABSTRACT FROM AUTHOR]

Highlights • Microfluidic based isolating of circulating fetal nucleated red blood cells is proposed. • The enhanced isolation can be achieved by the microfluidic chaotic chip with multifunctional nanoparticle deposited. • The platform shows sensitivity in detection fNRBCs from maternal blood during early pregnancy. • Early diagnostic application of fNRBCs for fetal chromosomal disorders by our platform was confirmed. Abstract Fetal nucleated red blood cells (fNRBC) in maternal peripheral blood has the potential for non-invasive prenatal diagnostics (NIPD), given its intrinsic nature carrying total genetic information of the fetus. Unfortunately, the scarcity of fNRBCs in maternal blood circulation greatly hinders the effective isolation of fNRBCs and its further uses for clinical prenatal diagnostics. Herein, we developed a gelatin nanoparticles (GNPs) decorated microchip that modified with anti-CD147 as specific capture antibody to efficiently isolate fNRBCs from maternal peripheral blood. The corrugated GNP nanocoating on the walls of the channel, together with herringbone grooves in the continuous curved channel design, produced enhanced interactions between fNRBC and the device for better cell capture performance. Furthermore, the captured cells could be gently released for subsequent off-chip analyses, using an enzymatic treatment to dissolve the biodegradable GNP nanocoating. Significant target cell capture efficiency (>80%), release efficiency (∼89%) and purity (∼85%) as well as a high viability of >90% were achieved using simulated spiked samples. fNRBCs were detected from a series of maternal peripheral blood samples ranging from 7 to 13 weeks of gestation, and the diagnostic application for fetal chromosomal disorders was demonstrated. Our strategy may provide new insights into developing an approach to recover fNRBCs from early pregnancy for improved cell-based NIPD. [ABSTRACT FROM AUTHOR]

• Bilayer films were developed using agar, anthocyanins, gellan gum and TiO 2. • TiO 2 improved the illumination stability of the film. • Gellan gum-TiO 2 contributed to the electrochemical writing on the film. • The bilayer film was sensitive to NH 3 , trimethylamine and dimethylamine. • The bilayer film showed color changes during spoilage of pork and silver carp. Amine-responsive bilayer films were developed by using agar (AG), anthocyanins (AN), gellan gum (GG) and TiO 2 nanoparticles for visual monitoring of meat spoilage. The AG-AN layer worked as the sensing layer to volatile amines, while GG-TiO 2 layer served as the light barrier layer and simultaneously the conducting layer to improve the illumination stability and electrochemical writing ability of the AG-AN layer, respectively. The Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) spectra indicated the successful fabrication of bilayer films. Illumination experiments showed that the incorporation of TiO 2 in the GG-TiO 2 layer significantly improved the illumination stability of AN in the AG-AN layer. Meanwhile, electrochemical writing process could be easily conducted on the AG-AN layer in the presence of GG-TiO 2 layer, indicating the feasibility of ink-free printing on bilayer biopolymer films. The AG-AN/GG-2%TiO 2 film presented a limit of detection of 0.018 mM to trimethylamine (TMA), a typical basic gas generated during meat spoilage. Based on its good illumination stability and sensing ability to basic gases, the AG-AN/GG-2%TiO 2 film exhibited rose red-to-green color changes along with the spoilage of pork and silver carp, indicating its great potential for monitoring meat spoilage in intelligent food packaging. [ABSTRACT FROM AUTHOR]