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Solution-processed bovine serum albumin conjugated with ZnO nanosphere (BCZ) have been synthesized for ultra-low level mercury ion detection. Simple drop casting technique was adopted to fabricate such a mercury ion (Hg 2+ ) detection scheme. Morphological and optical characterization of the BCZ was performed by Transmission Electron Microscopy (TEM), UV-Vis and Fluorescence spectroscopic technique prior to device fabrication. The working principle of the BCZ device for Hg 2+ detection depends upon the variation of conductance with various concentration of Hg 2+ . An extensive study was carried out to investigate the effect of Hg 2+ upon transport properties of BCZ. The ultra-low level of Hg 2+ sensing was performed using this electrical detection technique. More importantly, this proposed BCZ based detection technique is found to be simple, inexpensive and very fast in responding (response time  ∼ 2.5 s) to heavy metal ion with a limit of detection (LOD) 0.03 fg/ml (S/ [Formula: see text]3).

This work demonstrates a novel label free and sensitive approach for the detection of L-histidine. This is a simple and reliable method for ultra-low level detection of L-histidine. All solution processed synthesizing technique was utilized to develop such type of detection scheme. Silicon substrate was replaced by normal transparent sheet to make it more facile and cost-effective detection technique. Fabricated device for L-histidine detection works upon the variation of current through the ZnO nanorod with L-histidine concentration. Operation principle strongly depends upon the electron charge transfer between metal cation and L-histidine inside the chelating complex. Morphological, structural and optical characterization of solution processed synthesized ZnO nanorod (ZnO NR) was carried out prior to sensor device fabrication. Our sensor device exhibits the sensitivity around 0.86 nA/fM and lower limit of detection (LOD) ∼ 0.1 fM(S/N=3).

In this paper, we demonstrate an electrical detection technique based on solution processed zinc oxide nanosphere for ultra-low level detection of bovine serum albumin (BSA). Our sensor device works on the basis of the variation of conductance of the ZnO nanosphere with different concentration of BSA. The morphological and structural characterizations of ZnO nanosphere were carried out by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Circular dichroism (CD) spectroscopy was performed to investigate the chemical interaction between the BSA and zinc oxide nanosphere. Optical detection was performed using absorbance and Fourier transform infrared spectroscopy (FTIR) studies. Our device exhibits sensitivity 0.126 nA/pM, lower limit of detection (LOD) 10 pM and the fast response time around 5 s, confirming the highest sensitivity for BSA detection achieved so far. Sensing mechanism is governed on the basis of the charge transfer phenomenon between BSA and ZnO. All measurements were carried out at 1 V bias for low power operation.

Demand for the detection of poisonous arsenic ions in water is increasing due to uncontrolled industrial and human activities. Conventional detection methods are found to be very complex, cumbersome, and non-portable. This paper presents curcumin functionalized zinc oxide field effect transistor for selective detection of arsenic ions in water, with high sensitivity and stability. The operating voltage of the device is optimized to 2.9 V through output characteristics, which ensures low power consumption. The presence of curcumin on ZnO surface imparts high degree of selectivity toward arsenic ions, and ZnO nanorods ensures high surface to volume ratio for adsorption. The device is tested against eight metal ions commonly found in water and is found to be highly selective toward arsenic. The device exhibits a sensitivity of 102 nA/ppb at zero gate voltage, which is further amplified to 366 nA/ppb by applying 2.4 V gate bias. The application of gate bias plays a pivotal role for enhancing the device sensitivity by 266% for 5 ppb arsenic concentration. The sensor shows a response time of 67 s and is found to be highly stable against adverse conditions. The sensor shows high resilience in the degradation of sensing performance for a duration of 40 days. Therefore, curcumin functionalized zinc oxide field effect transistor with proper gate bias shows promising results to be used as a portable, low-cost, and user-friendly arsenic ion detector system in future. [ABSTRACT FROM AUTHOR]

A novel hierarchical heterostructure based on ZnO/ $\gamma $ -Fe2O3 nanorods decorated with nanoparticles has been synthesized via simple solvothermal approach followed by calcination at an elevated temperature. Considering the unique properties of both ZnO and $\gamma $ -Fe2O3 toward the sensing of reducing gases, the concept of forming a heterostructure between them has been conceived. The crystallinity, morphological structure, and defect states of nanostructures based on ZnO/ $\gamma $ -Fe2O3 composites were investigated by XRD, FESEM, TEM, and PL spectroscopy analysis. A flowerlike morphology was revealed with the coexistence of both ZnO and $\gamma $ -Fe2O3 leading to the formation of the heterostructure. The as-prepared ZnO/ $\gamma $ -Fe2O3 sensors display apparently enhanced sensing characteristics, including higher sensing response, quick response with recovery, and better selectivity toward acetone gas as compared to bare ZnO nanorods. The sensor showed selective detection of acetone among six VOC’s at an optimum temperature of 300°C. The response and recovery time of the sensor was found to be 12.5 and 26.9 s, respectively, compared to 51 and 80 s for bare ZnO nanorods, when exposed to 60-ppm concentration of acetone. This ultrafast and selective detection of acetone by ZnO/ $\gamma $ -Fe2O3 heterostructure shows potential to develop future commercial acetone sensor. [ABSTRACT FROM AUTHOR]

Hierarchical ZnO nanorods were synthesized via mild solvothermal approach followed by calcination at elevated temperatures (i.e. 250 °C and 450 °C) to induce surface defects. The defect induced nanostructures were utilized as resistive devices for low level acetone detection (~10–50 ppm). The porosity and the surface area of ZnO nanorods were seen to increase with increase in calcination temperature as evident from BET results (surface area of 450 °C calcined sample ~55.45 m2/g whereas for un-calcined sample ~38.63 m2/g). The 450 °C sample exhibited excellent acetone sensing (response ~705% at 20 ppm of acetone) with fast response and recovery time (25 s and 31 s respectively) in comparison to the other samples (i.e. 250 °C and un-calcined). The sensing performance was found to improve with increasing calcination temperature which was due to the formation of oxygen vacancies as evident from photoluminescence spectroscopy (enhancement of peak at ~538 nm). A higher surface area coupled with increased oxygen vacancies was responsible for enhanced sensing performance of the calcined nanostructures. The sensor was found to be repeatable and highly selective toward acetone compared to five other volatile organic compounds. Thus, the defect induced ZnO-based sensor shows potential to develop future commercial acetone sensor. [ABSTRACT FROM AUTHOR]

This paper describes a detail study of the synthesis of Bovine serum albumin (BSA) conjugated with ZnO nanosphere and its high speed humidity sensing applications. A simple and straight forward solution processed technique was used to synthesize BSA conjugated with ZnO nanosphere (BCZ). Most often used and easy drop casting technique was employed to make the humidity sensor using BCZ at room temperature. The morphological and optical characterization of the BCZ was performed by Transmission Electron Microscopy, ultraviolet-Vis, and fluorescence spectroscopic technique prior to sensor fabrication. The working principle of the BCZ humidity sensor depends upon the variation of conductance with the exposure of different humidity levels. The BCZ is generally formed through the self-assembly of donor and acceptor, which is involved in electron transfer between them. An electron charge transfer phenomenon in BCZ is highly affected by the exposure of different levels of humidity ranging from 40% to 85% RH. The response and recovery time of the BCZ humidity sensor are measured as 1.6 and 1.5 s, respectively. More importantly, BCZ may furnish a simple, inexpensive, and very fast response to the relative humidity detection. [ABSTRACT FROM PUBLISHER]

A Au/bovine serum albumin (BSA)–ZnO (n-type nanoparticles)/Au system is investigated for its transport properties using electrical ( $I$ – $V$ ) characterization in conjunction with spectroscopy techniques for cost-effective power-efficient biosensing. Temperature-dependent variation in different conduction mechanisms is observed with Au/ZnO/Au system as reference. Schottky emission dominates the carrier transport with defect-assisted tunneling and Poole–Frenkel hopping contributing peripherally. The distribution of defect states within the ZnO bandgap appears to be responsible for such low-field conduction characteristics along with the surface dipole effect of the BSA, which modulates barrier height and, consequently, carrier population in the ZnO nanoparticles. [ABSTRACT FROM PUBLISHER]