Showing papers in "Sensors and Actuators B-chemical in 2016"
TL;DR: In this article, the authors reviewed the humidity sensors based on ceramic materials and analyzed state-of-the-art techniques for producing ceramic sensors, and the key research and technological challenges in the field are discussed at the end of the review.
Abstract: We have reviewed the humidity sensors based on ceramic materials. We first discuss the operating principle of ceramic humidity sensors. This is followed by a section on the relationship between the conduction mechanism and microstructure characteristics of the sensing elements of ceramic humidity sensors. This part of the review is also focused on the methods for optimization of the microstructure of ceramic porous elements. The next section summarizes the information on the materials used for the ceramic humidity sensors fabrication and effect of dopants or hybrid compositions on the sensing ceramic-based materials. Then we analyze state-of-the-art techniques for producing ceramic sensors. The key research and technological challenges in the field are discussed at the end of the review. The review is based on 424 references published during from 1998–2013.
378 citations
TL;DR: SPR is a real-time, label-free measurement of binding kinetics and affinity and has been widely used in protein array technology and point-of-care (POC) testing as mentioned in this paper.
Abstract: SPR is a real-time, label-free measurement of binding kinetics and affinity. Success of SPR biosensor is evident by the growing number of commercially available instruments. In the current review, development in plasmon resonance techniques such as SPR, SPR-imaging (microscope, spectroscope, Electrochemical Impedance), nanoplasmonics and microfluidics, membrane proteins: receptor studies, sensors based on polarization and interferometery, PWR, SPR–MS, Signal locked SPR, FOPPR, Mid-IR SPR, trends in protein array technology and point-of-care (POC) testing over last decade are summarized. In addition, advancement over sensor configuration, mechanism and immobilization techniques are also discussed. Advantage and disadvantage of each methodology is provided along with some of the latest accomplishments.
373 citations
TL;DR: In this paper, a flexible humidity sensor based on tin dioxide/reduced graphene oxide (RGO) nanocomposite film was presented, which was fabricated on a polyimide substrate with microelectrodes by using a facile one-step hydrothermal route.
Abstract: This paper demonstrated a flexible humidity sensor based on tin dioxide/reduced graphene oxide (RGO) nanocomposite film. The humidity sensor was fabricated on a polyimide substrate with microelectrodes by using a facile one-step hydrothermal route. The hydrothermal synthesized SnO 2 nanoparticles and SnO 2 /RGO hybrid nanostructures were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The humidity sensing properties of the presented SnO 2 /RGO nano-hybrid sensor were investigated by exposing it to a broad humidity range of 11–97%RH at room temperature. Compared with traditional humidity sensors, the SnO 2 modified graphene sensor demonstrated an ultrahigh sensitivity and a rapid response/recovery characteristic over a full humidity range measurement, highlighting the unique advantages of hydrothermal synthesis for sensors fabrication. Finally, the possible humidity sensing mechanism of the proposed sensor was discussed by using complex impedance spectra and bode diagrams. These observed results demonstrate that RGO modified with metal oxide is promising nanomaterials for constructing high performance humidity sensors in widespread applications.
334 citations
TL;DR: In this article, the potential of spinel ferrites on gas sensor technology is discussed and a review highlights the recent developments and shows the potential for spinel-ferrite based gas sensors.
Abstract: The demand for portable gas sensors is increasing following the progress in the electronics industry; there is an equal need to increase the quality of gas sensors. Spinel ferrites have been used as electronic materials for more than 50 years and offer a suitable ceramic base for the gas sensor market. They are simple, low cost, and compared to other gas sensors have structural and compositional versatility. This review highlights the recent developments and shows the potential of the spinel ferrites on gas sensor technology. Sensing mechanisms for a range of gasses and humidity are explained for n-type, p-type, mixed and substituted spinel ferrite gas sensors. The change in conduction mechanism is discussed outlining electronic and chemical sensitization that both increase the conductivity. Some cation substitutions are shown to change the oxidation state, thereby increasing sensitivity, but noble metals are shown to chemically sensitize spinel ferrites. This review surveys synthesis methods for producing spinel ferrites and discusses future prospects for further improvements.
306 citations
TL;DR: In this paper, the electronic and transport properties of a MoS 2 monolayer transducer with some simple gas molecules, such as CO, CO 2 and NO, were investigated using nonequilibrium Green's function (NEGF) formalism based on the density functional theory.
Abstract: We investigate the electronic and transport properties of a MoS 2 monolayer transducer with some simple gas molecules, such as CO, CO 2 and NO to explore theoretically sensing capabilities of this monolayer. The calculations are performed using nonequilibrium Green's function (NEGF) formalism based on the density functional theory (DFT) as implemented in the TranSIESTA code. Exposure to the NO gas molecule influences dramatically the electron transmission and the current–voltage characteristics of the MoS 2 monolayer. The results predict that the MoS 2 monolayer transducer can monitor the NO gas molecule to 10 4 order among these molecules between ±0.9 V bias window using the current–voltage characteristic with high sensitivity and selectivity. Here, post-processed analyses predict that the sensing mechanism is based on the charge transfer, which it in turn causes remarkable electrostatic gating to occur for the NO adsorbate. The numerical results may be useful to engineer and design gas sensor based on the MoS 2 monolayer.
259 citations
TL;DR: In this paper, a review of the non-dispersive infrared (NDIR) gas sensors applied in an environmental field is presented, where the authors consider the advantages and disadvantages of these sensors, such as spectral interference and high detection limit.
Abstract: Non-dispersive infrared (NDIR) gas sensors applied in an environmental field are considered. Disadvantages of the non-dispersive infrared (NDIR) gas sensors include spectral interference and high detection limit. Efforts to improve these disadvantages are reviewed in this paper. Interference caused by water vapor and gas matrix has been partially solved using optical filters and interference correction factors. Limitations such as accuracy and sensitivity of the sensor were overcome by the improvements of inlet gas concentrations, infrared sources, optical designs (including optical filter and gas chamber) and detectors. These improvements are limited to a few gases, in particular, carbon dioxide. Drawbacks related to water vapor still remain and need to be addressed.
255 citations
TL;DR: Graphene as a novel material has laid a foundation for its applications in optical fiber sensors, due to its unique properties, especially the optical properties as mentioned in this paper, which has received world-wide attention due to their high sensitivity, small size, good anti-electromagnetic disturbance ability and other potential advantages.
Abstract: Graphene as a novel material has laid a foundation for its applications in optical fiber sensors, due to its unique properties, especially the optical properties. On the other hand, optical fiber sensors have received world-wide attention due to their high sensitivity, small size, good anti-electromagnetism disturbance ability and other potential advantages. In this paper, the developments of graphene in the applications of optical fiber sensors were reviewed from four aspects. Firstly, the common preparation methods of graphene were introduced. Next, the optical properties of graphene have been concluded. And then, some typical optical fiber chemical and biological sensors based on graphene, such as temperature sensors, biological sensors and gas sensors, were reviewed. It was shown that graphene had a great potential in the optical fiber sensing technology. Furthermore, the deficiencies and challenges of the graphene in the applications of optical fiber sensors were analyzed. In a whole, the unique advantages of graphene have present their versatility and importance in the application fields of optical fiber sensors.
252 citations
TL;DR: In this article, a reduced graphene oxide-zinc oxide (RGO-ZnO) composite was facilely fabricated by a spontaneous reduction of graphene oxide via zinc slice in one-pot approach at room temperature, and used to modify glassy carbon electrode (GCE) for developing of electrochemical biosensor.
Abstract: Reduced graphene oxide-zinc oxide (RGO–ZnO) composite was facilely fabricated by a spontaneous reduction of graphene oxide via zinc slice in one-pot approach at room temperature, and used to modify glassy carbon electrode (GCE) for developing of electrochemical biosensor (RGO–ZnO/GCE). The as-prepared RGO–ZnO was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM) and transmission electron microscope (TEM). It was revealed that the existence of ZnO in RGO–ZnO/GCE largely enhanced the electroactive surface area (EASA) and therefore the sensitivity for electrochemical sensing. In the mixtures of ascorbic acid (AA), dopamine (DA) and uric acid (UA), the biosensor exhibited three well-resolved voltammetric peaks (Δ E AA–DA = 236 mV, Δ E DA–UA = 132 mV, Δ E AA–UA = 368 mV) in the differential pulse voltammetry (DPV) measurements, allowing a simultaneous electrochemical detection of these biomolecules. The liner relationships between current intensities and concentrations were found to be 50–2350 μM, 1–70 μM and 3–330 μM, with detection limits of 3.71 μM, 0.33 μM and 1.08 μM for AA, UA and DA, respectively. The as-prepared RGO–ZnO/GCE biosensor displayed a good reproducibility and stability and was applied for detection of of AA, DA and UA in real plasma and urine samples with satisfying results.
243 citations
TL;DR: In this paper, a comprehensive report on the microwave-assisted synthesis of metal oxides for applications in the field of gas sensing is given, emphasizing the improved characteristics compared with materials produced by conventional synthesis procedures.
Abstract: This review gives a comprehensive report on the microwave-assisted synthesis of metal oxides for applications in the field of gas sensing. In recent years, microwave heating technology has gained importance in the synthesis of metal oxides because of its faster, cleaner and cost effectiveness than conventional thermal heating. Further, due to the peculiarity of microwave heating mechanism, the synthesis of metal oxides in different nanostructured forms by microwave-assisted methods has been widely pursued and the nanomaterials thus obtained have been applied as sensing elements in chemoresistive gas sensors. Their gas sensing performances are here described and discussed in detail, emphasizing the improved characteristics compared with materials produced by conventional synthesis procedures.
234 citations
TL;DR: In this paper, the application of beneficial physico-chemical properties of ZnO nanostructures for the detection of wide range of biological compounds is highlighted for medical diagnostics require accurate, fast and inexpensive biosensors, the advantages inherent optical methods of detection are considered.
Abstract: This review article highlights the application of beneficial physico-chemical properties of ZnO nanostructures for the detection of wide range of biological compounds. As the medical diagnostics require accurate, fast and inexpensive biosensors, the advantages inherent optical methods of detection are considered. The crucial points of the immobilization process, responsible for biosensor performance (biomolecule adsorption, surface properties, surface defects role, surface functionalization etc.) along with the interaction mechanism between biomolecules and ZnO are disclosed. The latest achievements in surface plasmon resonance (SPR), surface enhanced Raman spectroscopy (SERS) and photoluminescence based biosensors along with novel trends in the development of ZnO biosensor platform are presented.
230 citations
TL;DR: In this paper, a green method was developed for synthesis of fluorescent carbon dots (C-dots) from prawn shells, which possess many excellent features such as to eliminate blue fluorescence under UV light, high monodispersity, good stability, excellent water solubility and high quantum yield.
Abstract: A facile, economical and effective green method was developed for synthesis of fluorescent carbon dots (C-dots) from prawn shells The results showed that these C-dots (with an average diameter of 4 nm) possess many excellent features such as to eliminate blue fluorescence under UV light ( λ = 365 nm), with high monodispersity, good stability, excellent water solubility and high quantum yield (9%) We further explored these C-dots as effective sensing probes for Cu 2+ detection and found that they exhibit excellent selectivity and sensitivity toward Cu 2+ with a low detection limit of 5 nM We further demonstrated this novel sensing platform on Cu 2+ ions analysis from seawater samples This method is extremely rapid, low cost, ecofriendly, highly selective and sensitive for Cu 2+ ions sensing from various sources of environment such as drinking water, river water and sea water
TL;DR: In this paper, the authors highlight the strategies for design of heavy metal biosensors benefiting from the use of DNAzymes/DNA molecules and nanomaterials and summarize the advances in biosensing devices/chip based on this method for the detection of metal ions.
Abstract: Heavy metal pollution is one of the most serious concerns to human health because these substances are toxic and retained by the ecological system. Many efforts have been taken over the past few years for the detection of heavy metal ions in the environment. Incorporation of DNAzymes/DNA molecules (including T–T or C–C mismatches and G-quadruplexes) and nanomaterials into sensors can lead to significant improvement in the performance of sensors in terms of sensitivity, selectivity, multiplexed detection capability and portability. This review presents a recent advance in biosensors based on DNAzymes/DNA molecules functionalized nanostructures for heavy metal detection. Furthermore, advances in biosensing devices/chip based on this method for the detection of metal ions are summarized. This paper highlights the strategies for design of heavy metal biosensors benefiting from the use of DNAzymes/DNA molecules and nanomaterials.
TL;DR: In this article, ultralong MoO3 nanobelts are prepared by a facile hydrothermal method, which are flexible with an average length of 200μm and width of 200-400 nm.
Abstract: In the present work, ultralong MoO3 nanobelts are prepared by a facile hydrothermal method, which are flexible with an average length of 200 μm and width of 200–400 nm. Gas sensor based on ultralong MoO3 nanobelts shows a remarkable gas sensing properties towards trimethylamine (TMA) from 100 °C to 380 °C with a humidity level of about 55%. The optimum operating temperature is 240 °C with a response of 582 to 50 ppm TMA in static mode. The selectivity test among various reducing gases shows that the sensor has a quite good response towards TMA if compared with others gases, such as ethanol, ammonia, toluene, methanol and acetone. The probable gas sensing mechanism of the prepared MoO3 nanobelts is discussed as well. The results indicate that this kind of sensor has a promising application in TMA detection.
TL;DR: ZnO-modified In2O3 heterojunction with superior methanal (HCHO) sensing was synthesized by a simple and cost-efficient two-stage route.
Abstract: ZnO-modified In2O3 heterojunction with superior methanal (HCHO) sensing was synthesized by a simple and cost-efficient two-stage route, and the ZnO was promoted to uniformly attach on the surface of In2O3 nanostructure by using sonochemical synthesis. The In2O3 nanostructure modified with ZnO could remarkably enhance the gas response to HCHO and lower the detection limit respectively. Those were attributed to the fact that the electron transfer was modulated by the heterojunction in the interface between the ZnO and In2O3 nanostructure. The coalesced layer of the ZnO on the surface of In2O3 nanostructure facilitated to the formation of a heterojunction between the ZnO and In2O3 interface, which acted as a lever of electron transfer to increase the changes of resistance. Thus, a simple and cost-efficient method was reported here to modulate electron transfer and increase the variation amplitude of resistance in gas-sensing. The gas response of ZnO-modified In2O3 nanostructure was upgrade to more 6 times than intrinsic In2O3 for 100 ppm HCHO vapor at 300 °C. The results were valuable for great In2O3 nanostructure gas sensor applied to detecting toxic gas.
TL;DR: In this article, the interaction between NH 3 and O-terminated semiconducting MXenes with different charge states is considered by using first-principles simulations, and it is shown that NH 3 could be strongly adsorbed on M 2 CO 2 with apparent charge transfer, which renders them the potential candidates as the NH 3 sensor or capturer.
Abstract: NH 3 is one of the most common resources in chemical industry, which is very harmful to the human body. Thus, it becomes highly desirable to design advanced materials for efficient NH 3 sensor or capturer. However, one of the main challenge is the facile release of NH 3 gas from substrates due to the tendency of NH 3 strong interaction with many substrates. In this work, the interaction between NH 3 and O-terminated semiconducting MXenes (M 2 CO 2 , M = Sc, Ti, Zr, and Hf) with different charge states is considered by using first-principles simulations. Our results reveal that the NH 3 could be strongly adsorbed on M 2 CO 2 with apparent charge transfer, which renders them the potential candidates as the NH 3 sensor or capturer. In particular, the process of NH 3 release could be simply realized by tuning the electrons injected into M 2 CO 2 . Taking Zr 2 CO 2 as an example, it is highly selective towards NH 3 against other common gas molecules, and the adsorption energy dramatically increases from −0.81 eV to −0.20 eV when extra two electrons are injected into the 3 × 3 Zr 2 CO 2 sheet. Our study demonstrates that O-terminated semiconducting MXenes are excellent materials for NH 3 sensor or capturer, with highly reversible release and capture by controlling the charge states on the system.
TL;DR: In this paper, a fabricated sensor based on 3.8 wt% reduced graphene oxide/hexagonal WO3 (rGO/h-WO3) nanosheets composites was synthesized through hydrothermal method and post-calcination treatment.
Abstract: Reduced graphene oxide/hexagonal WO3 (rGO/h-WO3) nanosheets composites were synthesized through hydrothermal method and post-calcination treatment. The products were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), N2 adsorption-desorption, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric analysis (TGA). The results showed that two-dimensional (2D) h-WO3 nanosheets with porous structure were attached on rGO to construct 3D rGO/h-WO3 hybrid nanocomposites. This 3D hybrid nanostructure provided many channels for gas diffusion. The fabricated sensor based on 3.8 wt% rGO/h-WO3 composites showed good gas sensing response to H2S. The sensitivity of the sensor was about 168.58 toward 40 ppm H2S, which was 3.7 times higher than that of pure WO3, and the response time was 7 s when exposed to 10 ppm H2S. Moreover, the sensor showed low detection limit (10 ppb), wide linear range and high selectivity to H2S. The improved gas sensing properties of 3.8 wt% rGO/h-WO3 composites may be attributed to the formation of hetero-junctions, good accepting/transporting electrons properties of rGO and effective gas transport channels in 3D hybrid nanostructure.
TL;DR: In this paper, fluorescent nitrogen and sulfur co-doped carbon dots (N,S,C-dots) were synthesized by hydrothermal treatment of garlic and used for cell imaging.
Abstract: Novel fluorescent nitrogen and sulfur co-doped carbon dots (N,S,C-dots) were synthesized by hydrothermal treatment of garlic. It was confirmed that the prepared fluorescent nanodots were doped with nitrogen and sulfur in the format of pyridinic-N, pyrrolic-N and thiophene-S. The N,S,C-dots displayed strong fluorescence with quantum yield of 13%, and the fluorescence can be efficiently quenched by Fe3+. Based on the results, Fe3+ sensor was successfully developed and utilized to detect Fe3+ in environmental waters with excellent sensitivity and repeatability. Eventually, the carbon dots were applied for cell imaging, demonstrating their potential toward diverse applications.
TL;DR: Extracts from grape skins (EGS) were incorporated into tara gum (TG)/cellulose nanocrystal (CNC) matrix to prepare a colorimetric pH-sensing film.
Abstract: Extracts from grape skins (EGS) were incorporated into tara gum (TG)/cellulose nanocrystal (CNC) matrix to prepare a colorimetric pH-sensing film. The UV–vis spectra of EGS in the pH range of 1–10 were studied and the color clearly changed from bright red to dark green. Fourier transform-infrared spectroscopy, scanning electron microscopy and thermal analysis were used to characterize TG/CNC/EGS films, and the effects of EGS addition on mechanical properties, oxygen permeability and optical properties were also tested. The results revealed that EGS was successfully introduced into the TG/CNC matrix without obvious interactions. The EGS addition decreased the compact and continuous structure, thermal stability and barrier properties of the films. With EGS addition from 0 to 15 g/100 g TG, the tensile strength and light transmittance of films gradually decreased from 65.50 to 44.32 MPa and from 65.11 to 41.71% at 660 nm, respectively; however, the elongation at break of films increased significantly from 30.10 to 54.80%. The films were also immersed in different buffers to evaluate the response to pH changes. The color range of TG/CNC/EGS film varied from red (in acid pH) to slightly green (in alkali pH). The pH-sensing film was also evaluated by an activation test on milk, with evident change in the coloration of the film, indicating that the film could be applied in food packaging for information concerning the packaged food.
TL;DR: In this paper, a new rhodamine-derived Schiff base RH was synthesized and its sensing behavior toward various metal ions was investigated by UV-vis and fluorescence spectroscopic techniques.
Abstract: A new rhodamine-derived Schiff base RH was synthesized and its sensing behavior toward various metal ions was investigated by UV–vis and fluorescence spectroscopic techniques The sensor exhibited highly selective and sensitive colorimetric response to Cu2+ and Al3+, and “off–on” fluorescence response toward Fe3+ in semi-aqueous media The spectral changes obtained are large enough in the visible region of the spectrum and thus enable naked-eye detection Experimentally proved that the formation of RH–Al3+ complex is fully reversible and can sense to AcO−/F− via break the complex The results revealed that the sensor offers the sequential detection of Al3+ and AcO−/F−
TL;DR: In this article, a highly sensitive and selective fluorescent sensor, 1,4,8,11-tetraazacyclotetradecane (Cyclam)-functionalized carbon dots (CCDs), has been designed, synthesized and evaluated for Cu 2+ and S 2−.
Abstract: The detection of copper ion (Cu 2+ ) and sulfide anion (S 2− ) is of vital importance since the abnormal level of Cu 2+ or S 2− can lead to many diseases. Herein, a highly sensitive and selective fluorescent sensor, 1,4,8,11-tetraazacyclotetradecane (Cyclam)-functionalized carbon dots (CCDs), has been designed, synthesized and evaluated for Cu 2+ and S 2− . For this nanoprobe, a specific fluorescence resonance energy transfer (FRET) process can be effectively take place between carbon dots and the surface Cu 2+ -Cyclam complex, the as-prepared CCDs display high sensitivity (detection limit: 100 nM) and selectivity toward Cu 2+ among many other metal cations (such as Mg 2+ , Co 2+ , Pb 2+ , Ni 2+ , Mn 2+ , Hg 2+ , Fe 2+ , Ca 2+ and Zn 2+ ) in 100% aqueous solution. Moreover, it is worth to point out that the subsequent addition of S 2− can extract Cu 2+ from the CCDs-Cu 2+ complex and recover the fluorescence of carbon dots, the detection limit for S 2− can reach to 130 nM in the aqueous medium. And no statistically significant interference was observed among the other 10 anions (HCO 3 − , SO 4 2− , NO 3 − , Cl − , CO 3 2− , S 2 O 3 2− , F − , Br − , HPO 4 − , ClO 4 − ) for S 2− through the study. In addition, the novel type of multifunctional fluorescent sensor has a relatively wide pH range (pH 4–10). At the same time, it exhibited remarkable longterm fluorescence stability (≥35 days) for Cu 2+ detection. In addition, this nanoprobe exhibits very low cytotoxicity and can easily permeate the cell membrane and realize Cu 2+ and S 2− monitoring and imaging in live cells. Therefore, this novel approach can be used in various fields, such as the detection of multiplex analytes in biological applications and environment, and it will reveal great application prospects.
TL;DR: A facile strategy has been developed to fabricate silver nanoparticles (Ag NPs) through an electrochemical method with the assistance of metformin functionalized MWCNT (Ag@MH/MWCNT nanocomposite) as mentioned in this paper.
Abstract: A facile strategy has been developed to fabricate silver nanoparticles (Ag NPs) through an electrochemical method with the assistance of metformin functionalized MWCNT (Ag@MH/MWCNT nanocomposite). Investigations by field emission scanning electron microscopy (FESEM) confirmed that the prepared nanocomposite have a porous structure that is constructed by interconnecting functionalized MWCNT framework. Electrochemical studies show that the nanocomposite exhibits high stability and excellent activity for electrocatalytic oxidation of glucose in alkaline solutions, which allows the Ag@MH/MWCNT to be used in enzyme-free amperometric sensors for glucose determination. It was confirmed that the Ag@MH/MWCNT based glucose biosensor presents wide response window for glucose concentrations of 1.0 nM–350 μM, short amperometric response time (4 s), low detection limit of 0.0003 μM (S/N = 3), high sensitivity as well as good selectivity.
TL;DR: In this paper, the hierarchical hollow ZnO nanocages were synthesized by a facile strategy through the simple and direct pyrolysis of Zn-based metal-organic framework.
Abstract: The design and synthesis of nanostructured ZnO with high chemical sensing properties, especially towards ppb or sub-ppm level VOC gases is still highly desired and challengeable. Herein, the hierarchical hollow ZnO nanocages were synthesized by a facile strategy through the simple and direct pyrolysis of Zn-based metal-organic framework. The as-synthesized hollow ZnO products present the typical hierarchical structures with hollow interiors enveloped by interpenetrated ZnO nanoparticles as porous shell, providing structurally combined meso-/macro-porous channels for facilitating the diffusion and surface reaction of gas molecules. The gas-sensing experiments demonstrate that, in contrast with singular ZnO nanoparticles, the ZnO nanocages show significantly enhanced chemical sensing sensitivity and selectivity towards low-concentration volatile organic compounds, typically, acetone and benzene. Furthermore, the ZnO hollow nanocages perform sub-ppm level sensitivity with 2.3 ppm(-1) towards 0.1 ppm benzene, and ppb level sensitivity with 15.3 ppm(-1) towards 50 ppb acetone, respectively. The enhanced sensing performance of the MOF-derived ZnO nanocages is ascribed to the unique hierarchical structure with high specific surface area and abundant exposed active sites with surface-adsorbed oxygen. (C) 2015 Elsevier B.V. All rights reserved.
TL;DR: In this paper, a single electron transistor (SET) device made of two-dimensional single crystals is proposed as a low power device prototype for sensing purposes using density functional theory based Ab-initio calculations to understand their relative sensitivities towards sensing different gas molecules.
Abstract: Two dimensional single crystals like graphene, transition metal dichalcogenides, phosphorene, etc can be useful for sensing applications due to their enhanced surface to volume ratio A single electron transistor (SET) device made of such materials is proposed here as a futuristic low power device prototype for sensing purposes The operation and performance of these SET devices are investigated for the first time using Density functional theory based Ab-initio calculations to understand their relative sensitivities towards sensing different gas molecules The adsorption of CO, CO2, NH3 and NO2 on monolayers of graphene, MoS2 and phosphorene are investigated to find their most stable configurations and relative orientations on the host layers The structural and electronic properties of the host layers have been found to be unaffected as a result of the adsorption processes Phosphorene offers highest strength of physio-adsorption for all these molecules, indicating its superiority than the other two materials It is observed that Phosphorene and MoS2 are additionally sensitive towards the N-based molecules and magnetism could be induced in the presence of a paramagnetic molecule Present results indicate that the charge stability diagram of the SET is unique for a specific gas molecule on the Two-dimensional (2D) layer and this is sensitive up to the addition/removal of a single molecule from the island The wide temperature range of operation, extreme detection sensitivity and the versatility of the 2D materials for gas sensing make these SET devices very powerful candidates for practical application
TL;DR: Bright green luminescent graphitic carbon nitride quantum dots doped with oxygen and sulfur are prepared simply by microwave treatment of citric acid and thiourea and have great potential in bioanalysis and related fields.
Abstract: Herein, bright green luminescent graphitic carbon nitride quantum dots (GCNQDs) doped with oxygen and sulfur are prepared simply by microwave treatment of citric acid and thiourea. The as-obtained GCNQDs show excitation wavelength and pH dependent luminescence behaviors in the visible range. Besides, the GCNQDs exhibit high fluorescence quantum yield (31.67%), strong resistance to the interference of high ionic strength environment, and good biocompatibility as demonstrated by the cell viability assay. Thus, the resulting GCNQDs can be used as a promising fluorescent probe for HeLa cell imaging with low cytotoxicity, and have great potential in bioanalysis and related fields.
TL;DR: In this article, a molecularly imprinted polypyrrole/graphene quantum dots (MIPPy/GQDs) composite was developed for the detection of bisphenol A (BPA) in water samples.
Abstract: Bisphenol A (BPA) is an important endocrine disrupter in environments, for which sensitive and selective detection methods are highly necessary to carry out its recognition and quantification. Here a novel electrochemical sensor was developed based on molecularly imprinted polypyrrole/graphene quantum dots (MIPPy/GQDs) composite for the detection of bisphenol A (BPA) in water samples. A MIPPy/GQDs composite layer was prepared by the electropolymerization of pyrrole on a glassy carbon electrode with BPA as a template. The MIPPy/GQDs composite could specifically recognize BPA in aqueous solutions, which resulted in the decrease of peak currents of K 3 [Fe(CN) 6 ] at the MIPPy/GQDs) modified electrode in cyclic voltammetry (CV) and differential pulse voltammetry (DPV). There was a linear relationship between BPA concentrations ranging from 0.1 μM to 50 μM and the response value ( ΔI DPV ) in DPV, with a limit of detection of 0.04 μM (S/N = 3). The sensor was applied for the detection of BPA in tap and sea water samples, with recoveries of 94.5% and 93.7%, respectively. The proposed method provides a powerful tool for rapid and sensitive detection of BPA in environmental samples.
TL;DR: In this article, the performance of nanosensors based on a single nanowire of silver-doped zinc oxide (ZnO:Ag) was investigated and an increase in current value of about two orders in magnitude I UVON / I UVOFF was observed under exposure to UV light.
Abstract: Enhanced performances were obtained for nanosensors based on a single nanowire of silver-doped zinc oxide (ZnO:Ag). Arrays of crystalline ZnO:Ag nanowires were synthesized by electrodeposition on F-doped tin oxide coated substrates and studied by SEM, EDX, TEM, HRTEM, SIMS, XPS, PL and micro-Raman spectroscopy. Integration of a single nanowire or a single microwire on the chip was performed by employing metal maskless nanodeposition in the dual beam focused electron/ion beam instrument. The ultraviolet (UV) response and hydrogen (H 2 ) gas response were studied for nanodevices and microdevices based on a single ZnO:Ag nanowire. We found that ZnO:Ag nanowire based nanosensor possesses a much faster response/recovery time and a higher response to UV radiation and hydrogen gas (∼50%) than those reported in literature. An increase in current value of about two orders in magnitude I UVON / I UVOFF was observed under exposure to UV light. Faster response/recovery times of about 0.98 s/0.87 s were observed. The ZnO:Ag nanowires and microwires can serve as nano-building materials for ultrasensitive and ultra-fast sensors with reduced power consumption. The mechanisms for such improved responses to UV and H 2 were discussed. The developed nanomaterial is of great scientific interest for further studies as promising candidates for fabricating multifunctional nano-sensors, LEDs and photodetectors by bottom-up and hybrid nanotechnologies.
TL;DR: In this article, a label-free fluorescence based method using graphene quantum dots (GQDs) as effective probes was developed for sensitive and selective detection of dopamine (DA).
Abstract: A label-free fluorescence based method using graphene quantum dots (GQDs) as effective probes was developed for sensitive and selective detection of dopamine (DA). The initial strong blue fluorescence of the GQDs in aqueous solution was effectively quenched upon addition of DA. The quenching mechanism may involve transfer of electrons from the photoexcited GQDs to dopamine–quinine, which was produced via the oxidization of DA by ambient O 2 in alkaline solution. The quenching efficiency was linearly proportional to the concentration of DA within the range of 0.25–50 μM with a low detection limit down of 0.09 μM. The proposed sensing system is simple and low-cost with facile experimental operations, and has a high selectivity for DA over a number of possible interfering species. Additionally, this method was successfully applied to the determination of DA in biological samples with satisfactory recoveries (98.8–106.4%).
TL;DR: In this article, a chemo-resistive gas sensor has been developed consisting of flame-made nanostructured α-MoO3, a promising phase for selective detection of breath NH3.
Abstract: Ammonia is an important breath marker for non-invasive detection and monitoring of end-stage renal disease (ESRD). Here, a chemo-resistive gas sensor has been developed consisting of flame-made nanostructured α-MoO3, a promising phase for selective detection of breath NH3. A key novelty is the thermal stabilization of α-MoO3 by Si-doping inhibiting sintering and crystal growth at the operational conditions of such sensors. Therefore, pure and Si-doped MoOx nanoparticles were made by flame spray pyrolysis (FSP) and directly deposited onto sensor substrates forming highly porous films with ribbon-like and nanoparticle/needle-like morphologies, respectively. In situ XRD analysis of the MoOx phase dynamics revealed a thermally induced recrystallization of β-MoO3 at 300–350 °C and optimal annealing at 450 °C for synthesis of highly nanocrystalline α-MoO3. For selective NH3 sensing, however, the optimum SiO2 content was 3 wt% and the operational temperature 400 °C. This sensor showed superior NH3 selectivity toward acetone, NO and CO, and accurately detected breath-relevant NH3 concentrations down to 400 ppb under 90% relative humidity (RH). As a result, a stable and inexpensive sensor for NH3 is presented which has the potential for further development toward a hand-held device for the early-stage diagnosis and monitoring of ESRD.
TL;DR: In this paper, an innovative flexible ammonia sensor based on S and N co-doped graphene quantum dots (S, N: GQDs)/polyaniline (PANI) hybrid loading on flexible polyethylene terephthalate thin film by chemical oxidative polymerization was presented.
Abstract: Here we present an innovative flexible ammonia (NH3) sensor based on S and N co-doped graphene quantum dots (S, N: GQDs)/polyaniline (PANI) hybrid loading on flexible polyethylene terephthalate thin film by chemical oxidative polymerization. The sensor exhibited not only excellent response, good selectivity and fast response and recovery time at room temperature but also flexibility, low cost and wearable characteristics. The experimental results reveal that the response of S, N: GQDs/PANI hybrid was about 5 fold higher than that of pure PANI at 100 ppm of NH3 and the attained gas-sensing performance may be attributed to the increased hole like carriers by S, N: GQDs and enhanced interactions between the hybrid sensing film and NH3 molecules via π electron networks. The NH3-sensing mechanisms of the flexible S, N: GQDs/PANI gas sensor based on acid-base doping/de-doping process, carriers mobility, and swelling process are highlighted.
TL;DR: In this paper, a single-armed Salamo-type bisoximes (H 3 L) was designed and synthesized firstly, which can act as a relay-sensor for ratiometric recognition of Zn 2+ /Cu 2+ with high selectivity and sensitivity.
Abstract: A novel single-armed Salamo-type bisoximes (H 3 L) has been designed and synthesized firstly. A new application of Salamo-type bisoximes in ion recognition is investigated in detail. H 3 L can act as a relay–sensor for ratiometric recognition of Zn 2+ /Cu 2+ with high selectivity and sensitivity. The Zn 2+ and Cu 2+ complexes behave successive sensing of H + /OH − through fluorescence intensity increasing (ON) and decreasing (OFF). Meanwhile, the crystal structures of the Zn 2+ and Cu 2+ complexes based on H 3 L, [Zn(L)( μ -OAc)Zn] and [Cu(L)(μ-OAc)Cu], have been determined by X-ray crystallographic analyses, respectively.