Showing papers in "Sensors and Actuators B-chemical in 2013"
TL;DR: In this article, the state of the art for electrical gas sensors employing carbon nanomaterials, identifies the bottlenecks that impair their commercialisation and also some recent breakthroughs.
Abstract: Carbon nanomaterials have been attracting a great deal of research interest in the last few years. Their unique electrical, optical and mechanical properties make them very interesting for developing the new generation of miniaturised, low-power, ubiquitous sensors. In the particular case of gas sensing, some carbon nanomaterials such as nanofibres, nanotubes and graphene are threatening the dominance position of other well established (nano)materials, yet the commercial exploitation of carbon nanomaterials is still a way off. This paper reviews the state of the art for electrical gas sensors employing carbon nanomaterials, identifies the bottlenecks that impair their commercialisation and also some recent breakthroughs. Finally an outlook in which challenges and opportunities are identified is given.
550 citations
TL;DR: In this article, conductometric sensors based on graphene/PANI nanocomposites, which were synthesized using chemical oxidative polymerization, for NH3 sensing were reported, which exhibited much higher sensitivity (ca. 5 times) than that of PANI, and showed approximate linearity over a wide range of concentrations from 1 to 6400 ppm.
Abstract: In this paper, we report conductometric sensors based on graphene/PANI nanocomposites, which were synthesized using chemical oxidative polymerization, for NH3 sensing. The experimental result reveals that the graphene/PANI sensor exhibits much higher sensitivity (ca. 5 times) than that of PANI, and shows approximate linearity over a wide range of concentrations from 1 to 6400 ppm. The detection limit of graphene/PANI sensor (ca. 1 ppm) is lower than that of PANI (ca. 10 ppm) for NH3. This shows that sensitivity of graphene/PANI sensor for NH3 detection is enhanced by the graphene added into PANI. The result is partially supported by experimental data that the NH3 adsorption of quartz crystal microbalance (QCM) coated graphene/PANI is larger than that of PANI. Meanwhile, the structure and morphology of the synthesized products are characterized by Fourier transform infrared spectroscopy (FTIR), brunauer emmett tellerand (BET), ultraviolet–visible spectroscopy (UV–vis), photoluminescence (PL), X-ray photoemission spectroscopy (XPS) and scanning electron microscopy (SEM), respectively.
408 citations
TL;DR: In this article, the authors give an overview on the recent process of the development of nanotechnology and nanowire-based gas sensors and compare two basic approaches, top-down and bottom-up, for synthesizing nanowires.
Abstract: Gas sensors fabricated with nanowires as the detecting elements are powerful due to their many improved characteristics such as high surface-to-volume ratios, ultrasensitivity, higher selectivity, low power consumption, and fast response. This paper gives an overview on the recent process of the development of nanotechnology and nanowire-based gas sensors. The two basic approaches, top-down and bottom-up, for synthesizing nanowires are compared. The conduction mechanisms, sensing performances, configurations, and sensing principles of different nanowire gas sensors and arrays are summarized and discussed. Meanwhile, an emerging nanowires fabrication method and a self-powered nanowire pH sensor are highlighted. The scientific and technological challenges in the field are discussed at the end of the review. © 2012 Elsevier B.V. All rights reserved.
346 citations
TL;DR: In this article, a graphene oxide (GO) modified glassy carbon electrode (GCE) was prepared by covalent coupling method, which was characterized by atomic force microscope (AFM), cyclic voltammetry (CV) and electrochemical impedance spectra (EIS), and the results showed that the electrochemistry of dopamine (DA) is greatly enhanced, while that of ascorbic acid (AA) is totally impressed.
Abstract: A graphene oxide (GO) modified glassy carbon electrode (GCE), namely GO/GCE was prepared by covalent coupling method, which was characterized by atomic force microscope (AFM), cyclic voltammetry (CV) and electrochemical impedance spectra (EIS). On this modified electrode, it is found that the electrochemistry of dopamine (DA) is greatly enhanced, while that of ascorbic acid (AA) is totally impressed, showing that the modified layer of GO has completely different impact on the electrochemical response of DA and AA. The probable mechanism to cause the different impact was proposed. GO/GCE was further applied as a biosensor for the determination of DA in the presence of with AA, and the results showed that the coexisted AA has no interference toward the electrochemistry of DA. The oxidation peak currents of DA present a good linear relationship with the concentrations in the range from 1.0 μM to 15.0 μM with a detection limit of 0.27 μM. The electrochemical parameters such as the electron transfer rate constant, catalytic rate constant, diffusion coefficient, and electron/proton transfer number of DA on GO/GCE were also studied.
266 citations
TL;DR: Results suggest that RF may be a promising pattern recognition method for E-tongue data processing, because it can deal with classification problems of unbalanced, multiclass and small sample data without data preprocessing procedures.
Abstract: Random forest (RF) has been proposed on the basis of classification and regression trees (CART) with “ensemble learning” strategy by Breiman in 2001. In this paper, RF is introduced and investigated for electronic tongue (E-tongue) data processing. The experiments were designed for type and brand recognition of orange beverage and Chinese vinegar by an E-tongue with seven potentiometric sensors and an Ag/AgCl reference electrode. Principal component analysis (PCA) was used to visualize the distribution of total samples of each data set. Back propagation neural network (BPNN) and support vector machine (SVM), as comparative methods, were also employed to deal with four data sets. Five-fold cross-validation (CV) with twenty replications was applied during modeling and an external testing set was employed to validate the prediction performance of models. The average correct rates (CR) on CV sets of the four data sets performed by BPNN, SVM and RF were 86.68%, 66.45% and 99.07%, respectively. RF has been proved to outperform BPNN and SVM, and has some advantages in such cases, because it can deal with classification problems of unbalanced, multiclass and small sample data without data preprocessing procedures. These results suggest that RF may be a promising pattern recognition method for E-tongues.
265 citations
TL;DR: In this article, a comprehensive review of the organic/inorganic hybrid sensors is provided, where several suggestions related to future development of organic and inorganic hybrid sensing materials are also made.
Abstract: Due to the synergetic or complementary effects between organic and inorganic components, which could result in improved properties or performances, the organic/inorganic hybrid materials have recently gained extensive interest in many fields. Up to date, many reports have been published based on the organic/inorganic hybrid materials for the sensor applications. The paper provided a comprehensive review about recent progress of the organic/inorganic hybrid sensors. The organic/inorganic hybrid sensing materials could be fabricated in several configuration types such as intercalating type, core–shell type, coating type and mixed type. The sensing form of the hybrid sensors could be presented in thin-film, thick-film or pellet form, and the sensing performances could by measured in the flowing or static-state system. The hybrid sensing materials have been applied in gas sensors, humidity sensors, ultraviolet sensors, strain sensors, electrochemical immunosensors and fluorescent chemosensors. Finally, several suggestions related to future development of organic/inorganic hybrid sensing materials were also made.
238 citations
TL;DR: In this article, the use of a carbon paste electrode modified by ethynylferrocene (EF) and NiO/MWCNT nanocomposite prepared by a simple and rapid method was described.
Abstract: In the present study, the use of a carbon paste electrode modified by ethynylferrocene (EF) and NiO/MWCNT nanocomposite prepared by a simple and rapid method was described. The modified electrode showed an excellent character for electrocatalytic oxidization of glutathione (GSH) and acetaminophen (AC). For the mixture containing GSH and AC, the peaks potential well separated from each other. Their square wave voltammetrics peaks current increased linearly with their concentration at the ranges of 0.01–200 and 0.8–600 μM, respectively with the detection limits of 0.006 and 0.5 μM, respectively. The modified electrode was successfully used for the determination of the analytes in real samples with satisfactory results.
215 citations
TL;DR: In this paper, the upconversion quantum efficiency of Ho3+/Yb3+ codoped CaWO4 phosphor was evaluated under 980-nm diode laser excitation.
Abstract: Under 980 nm diode laser excitation, efficient upconversion emissions from the Ho3+/Yb3+ codoped CaWO4 phosphor were obtained. The upconversion quantum efficiency was evaluated to be about 3.3% when the power density of the excitation laser was 47 W/cm2. Additionally, temperature dependent blue emissions from the 5F2,3/3K8 and 5G6/5F1 states of Ho3+ ions were studied in the range of 303–923 K. The result demonstrated that using the ratio between the blue luminescence intensities of Ho3+ ions, the sensitivity and the accuracy for optical thermometry achieved here are superior to the previously reported Er3+ green fluorescence based optical temperature sensors.
215 citations
TL;DR: In this article, the microwave assisted rapid green synthesis of photoluminescent carbon nanodots (C-dots) with diameters in the range of 1-4nm using flour as the carbon source was reported.
Abstract: The article reports on the microwave-assisted rapid green synthesis of photoluminescent carbon nanodots (C-dots) with diameters in the range of 1–4 nm using flour as the carbon source. It suggests that the resultant C-dots exhibit high sensitivity and selectivity toward Hg 2+ with a detection limit as low as 0.5 nM and a linear range of 0.0005–0.01 μM. The practical use of this system for Hg 2+ determination in real lake water samples is also demonstrated successfully.
213 citations
TL;DR: In this paper, the structural, morphological and optical properties of as-deposited and annealed samples were investigated for various concentration levels of ammonia at dry air and humidity conditions.
Abstract: Nanostructured ZnO thin films were deposited on glass substrates at 503 K using spray pyrolysis technique and the films were post annealed at 673 K in air atmosphere for 3 h. The structural, morphological and optical properties of as-deposited and annealed samples were investigated. The annealed films showed uniform spherical morphology in contrast with as-deposited films. XRD patterns of both the annealed and as-deposited films confirmed the polycrystalline nature of the films with hexagonal wurtzite structure. Room temperature ammonia sensing characteristics of annealed films were studied for various concentration levels of ammonia at dry air and humidity conditions. A highest room temperature response of 233 was achieved at 25 ppm of NH3 with a response and recovery times of 20 and 25 s respectively. The response of the sensor to other gases such as methanol, ethanol, 2-propanol, benzyl alcohol and acetone indicated a high selectivity towards ammonia gas. The room temperature (303 K) operation, with high selectivity, repeatability and fast transition times of the sensor together with the low deposition cost suggests suitability for developing a low power cost-effective ammonia sensor.
211 citations
TL;DR: In this article, a label-free Mach-Zehnder interferometer (MZI) biosensor based on a silicon nitride slot waveguide was proposed for the detection and quantification of the methylation of DAPK (deathassociated protein kinase ) gene.
Abstract: We demonstrate a highly sensitive label-free Mach–Zehnder interferometer (MZI) biosensor based on silicon nitride slot waveguide. Unlike the conventional MZI sensors, the sensing arm of the sensor consists of a slot waveguide while the reference arm consists of a strip waveguide. Thanks to the slot waveguide's property to provide high optical intensity in a subwavelength-size low refractive index region (slot region), which allows high light–analyte interaction, higher sensitivity can be obtained as compared to conventional waveguides using the slot waveguide as sensing region. The bulk refractive index sensitivity of the slot waveguide MZI sensor was found to be 1864 π /RIU (refractive index unit) with 7 mm long slot waveguide sensing arm, which shows higher sensitivity compared to the conventional MZI device based on silicon nitride. The biosensing capability of the developed slot waveguide MZI was investigated using biotin–streptavidin binding as a model system. The sensitivity of the system was demonstrated down to 18.9 fM or 1 pg/ml of streptavidin solution and to the best of our knowledge, it is the best reported experimental value for the limit of detection of a MZI sensor. Furthermore, we investigated the specific detection and quantification of the methylation of DAPK ( Death-associated protein kinase ) gene, which is a widely used biomarker for human cancers. We have shown that methylation sequences of DAPK gene of various methylation densities (100%, 50%, and 0% of methylation sites) can be quantified and discriminated even at a concentration as low as 1 fmol/μl or 1 nM.
TL;DR: This article reviews biosensors that use optical, electrochemical and piezoelectric transduction mechanisms for the detection of foodborne contaminants and concludes that, in spite of the promising approaches demonstrated, much work still needs to be done before they become a viable alternative to conventional methods.
Abstract: Rapid detection of foodborne pathogens is important for reducing diseases caused by food contaminated with pathogens and toxins. Current methods rely on conventional culture-based techniques which are time-wise lengthy and require trained personnel, and are not effective for on-site use. On the other hand biosensors can detect pathogens in a much shorter time with sensitivity and selectivity comparable to the conventional methods, but with a slightly lower reliability. Since they are low-cost and high-throughput devices and do not require trained personnel, they potentially can be used in future as stand-alone devices for on-site monitoring. This article reviews biosensors that use optical, electrochemical and piezoelectric transduction mechanisms for the detection of foodborne contaminants. After a brief discussion of the transduction principles, specific examples of foodborne pathogen detection using biosensors are presented and critically reviewed. We conclude by noting that, in spite of the promising approaches demonstrated thus far, much work still needs to be done before they become a viable alternative to conventional methods.
TL;DR: In this paper, the electronic sensitivity of pristine, Al and Si-doped BC3 nanosheets to formaldehyde (H2CO) molecule was investigated by utilizing density functional theory.
Abstract: Electronic sensitivity of pristine, Al- and Si-doped BC3 nanosheets to formaldehyde (H2CO) molecule was investigated by utilizing density functional theory. It was found that H2CO is weakly adsorbed on the sheet, releasing energy of 11.35 kcal/mol, and electronic properties of the sheet are not significantly changed. Although both Al and Si dopings make the sheet more reactive and sensitive to H2CO, Si doping seems to be a better strategy to manufacture H2CO chemical sensors due to the shorter recovery time and higher sensitivity of the Si-doped sheet. Our calculations show that the HOMO/LUMO gap of the Si-doped sheet is significantly decreased from 2.20 to 1.58 eV upon H2CO adsorption, which may increase the electrical conductance of the sheet. Therefore, the doped sheet might convert the presence of H2CO molecules to electrical signal. Moreover, the shorter recovery time of the Si-doped sheet is due to middle adsorption energy of −26.49 kcal/mol in comparison with −40.50 kcal/mol for the Al-doped sheet.
TL;DR: Analysis has shown that engineering approaches in a number of cases can eliminate some intrinsic disadvantages of conductometric gas sensors, can give significant improvement of gas sensors performances and expand their application in various fields.
Abstract: Engineering approaches designed to improve the parameters of conductometric gas sensors, are considered in this short survey. In particular, in the first part of the paper we analyze the engineering approaches used for the improvement of sensor sensitivity and selectivity. Analysis has shown that engineering approaches in a number of cases can eliminate some intrinsic disadvantages of conductometric gas sensors, can give significant improvement of gas sensors performances and expand their application in various fields.
TL;DR: The excellent performance of biosensor is attributed to large surface-to-volume ratio and good electrochemical activity of graphene oxide, and good biocompatibility of chitosan, which enhances the DNA immobilization and facilitate electron transfer between DNA and electrode surface (ITO).
Abstract: Graphene oxide (GO)-Chitosan (CHI) nano-composite is employed for the development of DNA based electrochemical biosensor for diagnosis of typhoid. Biosensor has been prepared by covalent immobilization of Salmonella typhi specific 5′-amine labeled single stranded (ss) DNA probe on GO-CHI/ITO via glutaraldehyde. Differential pulse voltammetry (DPV) studies revealed good specificity and ability of ssDNA/GO-CHI/ITO biosensor to distinguish complementary, non-complementary and one base mismatch sequences. The ssDNA/GO-CHI/ITO biosensor showed detection range of 10 fM to 50 nM and LOD 10 fM within 60 s hybridization times for complementary sequence. Further, ssDNA/GO-CHI/ITO bioelectrode is able to detect complementary target present in serum samples with LOD of 100 fM at 25 °C. The excellent performance of biosensor is attributed to large surface-to-volume ratio and good electrochemical activity of graphene oxide, and good biocompatibility of chitosan, which enhances the DNA immobilization and facilitate electron transfer between DNA and electrode surface (ITO).
TL;DR: In this paper, the room temperature gas sensing properties of the Co3O4 intercalated reduced graphene oxide (rGO) based thin film semiconductor sensors were investigated and two possible reasons have been discussed including the increased surface area of the rGO thick film by the intercalation of Co 3O4 nanocrystals and the Co 3+-carbon coupling effect for the rapid response.
Abstract: The room temperature gas sensing properties of the Co3O4 intercalated reduced graphene oxide (rGO) based thick film semiconductor sensors were investigated. The Co3O4–rGO composite based sensors showed a much higher response to NO2 at room temperature compared to the rGO based sensors. However, with an increase in the rGO concentration from 5 wt% to 30 wt%, the response showed a decreasing tendency. The sensor response to NO2 was not fully recovered within the measurement time (∼20 min) due to the much strong adsorption of NO2 at the defective sites of rGO. In contrast, the sensors using rGO showed a fast response and full recovery to methanol. This has been proposed to be exclusively due to the interaction of methanol with the sp2 bonding of the carbon. Similarly, with Co3O4 intercalated rGO, the response was significantly enhanced and the response/recovery time was within 1–2 min. Two possible reasons have been discussed including the increased surface area of the rGO thick film by the intercalation of Co3O4 nanocrystals and the Co3+-carbon coupling effect for the rapid response.
TL;DR: In this article, a room temperature H 2 S sensor based on pure and Au modified ZnO nanowires has been demonstrated, which is attributed to the alteration of barrier properties by the adsorption or desorption of adsorbed species and/or H 2S gas molecules.
Abstract: A room temperature H 2 S sensor based on pure and Au modified ZnO nanowires has been demonstrated. Modification of ZnO nanowires with Au resulted in a remarkable 16-fold increase in the sensor response over pure ZnO NWs toward 5 ppm H 2 S at room temperature. A sensing mechanism based on the formation of nano-Schottky type barrier junction at the interface between Au and ZnO has been proposed. The enhanced response is attributed to the alteration of barrier properties by the adsorption or desorption of adsorbed species and/or H 2 S gas molecules. Observance of higher resistivity and a higher work function (0.2 eV) for Au modified samples further corroborates the finding. Low temperature resistivity measurements indicate that the charge transport is governed by the thermal conduction and the nearest neighbor hopping mechanism.
TL;DR: In this article, a planar paper-based electrochemical cell was used to evaluate the performance of an electrode platform printed on a recyclable low-cost paper substrate, where the working and counter electrodes were directly printed goldstripes, while the reference electrode was a printed silver stripe onto which an AgCl layer was deposited electrochemically.
Abstract: An electrode platform printed on a recyclable low-cost paper substrate was characterized using cyclic voltammetry. The working and counter electrodes were directly printed gold-stripes, while the reference electrode was a printed silver stripe onto which an AgCl layer was deposited electrochemically. The novel paper-based chips showed comparable performance to conventional electrochemical cells. Different types of electrode modifications were carried out to demonstrate that the printed electrodes behave similarly with conventional electrodes. Firstly, a self-assembled monolayer (SAM) of alkanethiols was successfully formed on the Au electrode surface. As a consequence, the peak currents were suppressed and no longer showed clear increase as a function of the scan rate. Such modified electrodes have potential in various sensor applications when terminally substituted thiols are used. Secondly, a polyaniline film was electropolymerized on the working electrode by cyclic voltammetry and used for potentiometric pH sensing. The calibration curve showed close to Nerstian response. Thirdly, a poly(3,4-ethylenedioxythiophene) (PEDOT) layer was electropolymerized both by galvanostatic and cyclic potential sweep method on the working electrode using two different dopants; Cl− to study ion-to-electron transduction on paper-Au/PEDOT system and glucose oxidase in order to fabricate a glucose biosensor. The planar paper-based electrochemical cell is a user-friendly platform that functions with low sample volume and allows the sample to be applied and changed by e.g. pipetting. Low unit cost is achieved with mask- and mesh-free inkjet-printing technology.
TL;DR: In this paper, a novel electrochemical sensor was proposed for detecting acetaminophen with a detection limit of 2.0 × 10 −8 −8 µm (S/N = 3) and linear range of 0.1 −100 µm.
Abstract: Layered MoS 2 –graphene composites were synthesized by a modified l -cysteine-assisted solution-phase method, and were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (TEM). The electrochemical properties of the nanocomposite film were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Acetaminophen as model molecular was employed to study its electrochemical responses at the MoS 2 –graphene modified electrode, which shows more favorable electron transfer kinetics than graphene modified glassy carbon and bare glassy carbon electrodes. This novel electrochemical sensor exhibits excellent analytical performance for acetaminophen detection with detection limit of 2.0 × 10 −8 M (S/N = 3) and linear range of 0.1–100 μM. The superior electrochemical performances of MoS 2 –graphene composites are attributed to their robust composite structure and the synergistic effects between layered MoS 2 and graphene, and it may hold great promise for electrochemical sensors and biosensors design.
TL;DR: In this paper, the electrochemical oxidation of dopamine (DA) and serotonin (ST) have been investigated by application of Nafion/Ni(OH) 2 -multiwalled carbon nanotubes modified glassy carbon electrode (Nafion and Ni(OH)-MWNTs/GCE) using cyclic voltammetry (CV), differential pulse voltammetmetry (DPV) and chronoamperometry (CA) methods.
Abstract: The electrochemical oxidation of dopamine (DA) and serotonin (ST) have been investigated by application of Nafion/Ni(OH) 2 -multiwalled carbon nanotubes modified glassy carbon electrode (Nafion/Ni(OH) 2 -MWNTs/GCE) using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA) methods. The modified electrode worked as an efficient electron-mediator for DA and ST in the presence of ascorbic acid (AA). Voltammetric techniques separated the anodic peaks of DA and ST, and the interference from AA was effectively excluded from DA and ST determination. The DPV data showed that the obtained anodic peak currents were linearly proportional to concentration in the range of 0.05–25 μmol L −1 with a detection limit (S/N = 3.0) of 0.015 μmol L −1 for DA and in the range of 0.008–10 μmol L −1 and with a detection limit of 0.003 μmol L −1 for ST. The proposed sensor was used for determination of ST and DA in human blood serum with satisfactory results.
TL;DR: In this paper, a novel sensing graphene/polypyrrole (PPy) material was prepared by a chemical oxidative polymerization method with various weight percentages of graphene and the results indicated that the sample with 10% graphene/PPy had better humidity sensing properties than the other samples at relative humidity (RH) in the range 12-90%.
Abstract: A novel sensing graphene/polypyrrole (PPy) material was prepared by a chemical oxidative polymerization method with various weight percentages of graphene. The structure and morphology were characterized by XRD (X-ray diffraction), FTIR (Fourier transform infrared), TEM (transmission electron microscopy), UV–vis spectrometry and TGA (thermo-gravimetric analysis). The humidity sensing properties were measured by using an LCR (inductance, capacitance and resistance) analyzer. The results indicate that the sample with 10% graphene/PPy had better humidity sensing properties than the other samples at relative humidity (RH) in the range 12–90%. The response and recovery times were approximately 15 s and 20 s, respectively. The prepared sensor has a higher sensitivity (S = 138) than those developed elsewhere and the humidity hysteresis value was very small at all humidities (<0.16%). The results herein demonstrate the potential of graphene/PPy composite for use in fabricating high-performance humidity sensors.
TL;DR: In this paper, high-ordered TiO 2 nanotube arrays (TiO 2 NTs) evenly modified by Ni-Cu nanoparticles were successfully prepared by potential step method.
Abstract: Highly ordered TiO 2 nanotube arrays (TiO 2 NTs) evenly modified by Ni–Cu nanoparticles were successfully prepared by potential step method. Their morphologies, structures, and alloy composition were characterized by FESEM, XRD and EDS, respectively. The as-prepared Ni–Cu/TiO 2 NTs electrodes were employed for non-enzymatic glucose detection in alkaline electrolyte and showed better electro-catalytic activity compared with Ni/TiO 2 NTs and Cu/TiO 2 NTs electrodes. Factors that affected the electrocatalysis of the electrodes were examined and optimized. Consequently, a sensitive amperometric electrode of glucose was achieved under 0.6 V vs. Ag/AgCl with a high sensitivity (1590.9 μA mM −1 cm −2 ), low detection limit (5 μM) and wide linear range from 10 μM to 3.2 mM ( R 2 = 0.993). Furthermore, the oxidable species such as ascorbic acid and uric acid showed no significant interference in determination of glucose. The experiment results revealed a very good reproducibility and high stability for the proposed Ni–Cu/TiO 2 NTs electrodes.
TL;DR: A green approach for the synthesis of silver nanoparticles (Ag NPs) by using locust bean gum (LBG) polysaccharide and its application to detect hydrogen peroxide (H2O2) was reported in this paper.
Abstract: Green synthesis of nanoparticles and their applications in sensing area is of great interest to the research community. Herein we report a green approach for the synthesis of silver nanoparticles (Ag NPs) by using locust bean gum (LBG) polysaccharide and its application to detect hydrogen peroxide (H2O2). Ag NPs were synthesized by mixing optimized weight percent of LBG with a known quantity of silver nitrate (AgNO3) at 55–60 °C. Synthesized Ag NPs were characterized by UV–vis spectroscopy and atomic force microscopy (AFM). The size of synthesized Ag NPs was in the range of 18–51 nm depending upon the concentration of LBG and AgNO3. Further, a low cost and portable optical fiber based sensor using LBG stabilized Ag NPs was developed for monitoring the H2O2 concentration as low as 0.01 mM.
TL;DR: In this paper, a one-pot microwave-assisted non-aqueous sol-gel method was used to synthesize n-SnO2/reduced graphene oxide (RGO) nanocomposites, in which partially reduction of the graphene oxide and nanoparticle formation occurs simultaneously.
Abstract: Crystalline SnO2/reduced graphene oxide (RGO) nanocomposites were synthesized by a one-pot microwave-assisted non-aqueous sol–gel method, in which partially reduction of the graphene oxide and nanoparticle formation occurs simultaneously. Composite samples with different SnO2 loadings on the RGO were prepared and characterized by TEM, XRD, TGA-DSC and FT-IR. Chemoresistive devices, consisting of a thick layer of the samples synthesized on alumina substrates provided with Pt interdigitated electrodes, were fabricated and their electrical and NO2 sensing characteristics investigated. The results obtained have shown the possibility of a fine tuning of the sensing characteristics of the devices fabricated by simply controlling the amount of metal oxide nanoparticles loaded onto the reduced graphene oxide sheets. This was explained on the basis of the critical role played by the n-SnO2/p-RGO heterojunction formed on the composite materials.
TL;DR: In this article, a gas sensing device based on cupric oxide (CuO) nanowires which are synthesized on-chip by thermal oxidation of electroplated copper microstructures is presented.
Abstract: We report on novel gas sensing devices based on cupric oxide (CuO) nanowires which are synthesized on-chip by thermal oxidation of electroplated copper microstructures. This technique enables the direct integration of a multitude of CuO nanowires, which bridge the electrical contacts of a conductometric gas sensor. The CuO nanowire bridges exhibit a huge surface-to-volume ratio and are entirely surrounded by the gas atmosphere, which is a highly favorable gas sensor configuration. As a result, the CuO nanowire gas sensor devices are able to detect carbon monoxide (CO) down to a concentration of 10 ppm and exhibit extraordinary sensitivity to hydrogen sulfide (H 2 S) where concentrations down to 10 ppb have been detected, even in the presence of humidity. For characterization of the CuO nanowires, X-ray diffraction measurements, transmission electron microscopy and electron energy loss spectroscopy are employed. As no process temperatures higher than 400 °C are required for the fabrication of the CuO nanowire devices, our approach can be employed in a CMOS backend process enabling the realization of a fully silicon integrated CuO nanowire gas sensing device.
TL;DR: In this article, the impact of spherical gold nanoparticles (Au NPs) with diameters of 40-80mm for the enhancement of surface plasmon resonance (SPR) sensing signals is presented, and numerical analysis is given to simulate the perturbation of evanescent field in the presence of Au NPs.
Abstract: The impact of spherical gold nanoparticles (Au NPs) with diameters of 40–80 nm for the enhancement of surface plasmon resonance (SPR) sensing signals is presented. Numerical analysis is given to simulate the perturbation of evanescent field in the presence of Au NPs. The results indicate that Au NPs with 40 nm possess the highest coupling effect when the separation of Au NP and SPR sensing film is fixed at 5 nm. For experimental demonstrations, colloidal Au NPs with different sizes but unified extinction coefficient (optical density) are immobilized onto SPR sensing films respectively through a spacer, dithiothreitol (DTT). Phase changes of the reflected SPR signals, which are associated with the plasmonic coupling between the NPs and sensing film, are monitored using a differential phase SPR sensor. Results obtained from the experiments show good agreement with the theoretical studies. This work can considerably serve as a solid guidance for future development of Au NPs-enhanced SPR sensors.
TL;DR: In this article, polyaniline (PANI) and carboxylic acid functionalized multi-walled carbon nanotube (c-MWCNT) nanocomposites were synthesized by in situ chemical oxidation polymerization of aniline monomer using ammonium persulfate in the presence of CNTs.
Abstract: Polyaniline (PANI) nanocomposites doped with carboxylic acid functionalized multi-walled carbon nanotube (c-MWCNT) were synthesized by in situ chemical oxidation polymerization of aniline monomer using ammonium persulfate in the presence of c-MWCNT. Different techniques like Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscope, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to evaluate the interaction between PANI and c-MWCNTs as well as the nature of chain growth on the CNT surfaces. The response of the prepared PANI/c-MWCNT nanocomposite to different chlorinated methane vapor was examined and compared with that of the pure PANI. The nanocomposites showed better response to chloroform vapor as compared to pure PANI. The sensing performances of the formulated nanocomposites were compared in terms of their responses, response time and reproducibility for different vapor concentrations. It was found that the PANI/c-MWCNT nanocomposite sensors exhibited good selectivity toward chloroform vapor over the other chlorinated methane vapor. The nanocomposite containing 2 wt% c-MWCNT exhibited better sensing performance to chloroform detection. The UV–vis analysis was used to explain the sensing mechanism.
TL;DR: In this article, the capabilities and development prospects of nanostructured metal oxides (MOX) representing the most versatile and richest class of materials in terms of electronic structure and structural, chemical, and physical properties are discussed.
Abstract: a b s t r a c t This paper focuses on the capabilities and development prospects of nanostructured metal oxides (MOX) representing the most versatile and richest class of materials in terms of electronic structure and structural, chemical, and physical properties. MOX nano-materials with controlled composition, surface terminations, and crystalline structures to be used as chemical sensors as a new area in analytical chemistry and instrument engineering are discussed. Their principles of operation, and basic characteristics are outlined and main applications of MOX sensor technology are presented.
TL;DR: In this paper, a simple benzimidazole-based fluorescent chemosensor (1) was designed and synthesized to realize highly selective relay recognition of Cu2+ and sulfide ions.
Abstract: To realize highly selective relay recognition of Cu2+ and sulfide ions, a simple benzimidazole-based fluorescent chemosensor (1) was designed and synthesized. Sensor 1 displays rapid, highly selective and sensitive recognition to Cu2+ in 100% water solution at pH 6.0. The in situ generated 1-Cu2+ complex solution exhibit a fast response and high selectivity toward sulfide anion via Cu2+ displacement approach. The detection limits of sensor 1 to Cu2+ and 1-Cu2+ complex to sulfide anion were estimated to be 3.5 × 10−7 M and 1.35 × 10−6 M, respectively. Proof-of-concept experiment results demonstrate that sensor 1 has potential utilities for Cu2+ and sulfide ion concentration evaluation in real water samples. This successive recognition feature of sensor 1 makes it has a potential utility for Cu2+ and sulfide anion detection in water.
TL;DR: In this paper, the effects of graphene mixing weight and solvothermal temperature on the gas-sensing response, the selectivity and reproducibility, and the response of the sensor based on 0.125%G-ZnFe2O4 to acetone in various concentrations.
Abstract: In order to study the gas-sensing properties of graphene-ZnFe2O4 composite, graphene-mixed ZnFe2O4 with different mixing ratios are prepared via solvothermal method and characterized by X-ray diffraction using CuKα. Before preparing graphene-ZnFe2O4 composite, graphene is firstly prepared by reduction of graphene oxide with hydrazine hydrate and identified by FT-IR and Raman spectrometer. The gas-sensing experiments include the effects of graphene mixing weight and solvothermal temperature on the gas-sensing response, the selectivity and reproducibility, and the response of the sensor based on 0.125%G-ZnFe2O4 to acetone in various concentrations. The experimental results reveal that the mixing of graphene into ZnFe2O4 can lower the operating temperature of the sensors to acetone vapor, and the sensor based on 0.125%G-ZnFe2O4 (180 °C, 10 h) exhibits good selectivity and reproducibility to 10 ppm acetone vapor at 275 °C. So, the sensor based on 0.125%G-ZnFe2O4 (180 °C, 10 h) may be applied to detect diabetes mellitus via measuring the acetone vapor at low temperature if the selectivity and response are improved further and the amount relation of sensing response versus concentration of acetone is found.