Kourosh Kalantar-Zadeh | RMIT University (original) (raw)

Papers by Kourosh Kalantar-Zadeh

Nature Communications, 2020

The predicted strong piezoelectricity for monolayers of group IV monochalcogenides, together with... more The predicted strong piezoelectricity for monolayers of group IV monochalcogenides, together with their inherent flexibility, makes them likely candidates for developing flexible nanogenerators. Within this group, SnS is a potential choice for such nanogenerators due to its favourable semiconducting properties. To date, access to large-area and highly crystalline monolayer SnS has been challenging due to the presence of strong inter-layer interactions by the lone-pair electrons of S. Here we report single crystal across-the-plane and large-area monolayer SnS synthesis using a liquid metal-based technique. The characterisations confirm the formation of atomically thin SnS with a remarkable carrier mobility of ~35 cm2 V−1 s−1 and piezoelectric coefficient of ~26 pm V−1. Piezoelectric nanogenerators fabricated using the SnS monolayers demonstrate a peak output voltage of ~150 mV at 0.7% strain. The stable and flexible monolayer SnS can be implemented into a variety of systems for effic...

2006 IEEE International Frequency Control Symposium and Exposition, 2006

In this work a Surface Acoustic Wave (SAW) gas sensor based on a 64° YX LiNbO 3 substrate has bee... more In this work a Surface Acoustic Wave (SAW) gas sensor based on a 64° YX LiNbO 3 substrate has been developed. The sensitive layer consists of electropolymerized polyaniline nanofibers. Device was tested towards hydrogen gas.

Sensors and Actuators B-chemical, 2005

Layered surface acoustic wave (SAW) devices are investigated for sensing hydrogen (H2) concentrat... more Layered surface acoustic wave (SAW) devices are investigated for sensing hydrogen (H2) concentrations less than 1% in air. Platinum (Pt) and gold (Au) catalyst activated tungsten trioxide (WO3) selective layers are investigated. The SAW sensors consist of two thin film metal interdigital transducers (IDTs) on a 36° Y-cut, X-propagating LiTaO3 substrate. A ZnO guiding layer is used to confine the acoustic energy at the active surface of the device for increased sensitivity. In this paper, the fabrication of an Au–WO3 and a Pt–WO3 based layered SAW device are described. The sensor response have been analysed in terms of frequency shift as a function of different hydrogen concentrations and operating temperatures. The responses of the catalyst activated WO3 sensors show much higher sensitivity when compared against a layered SAW sensor employing only a bare WO3 selective layer. Frequency shifts of 705 and 118 kHz towards 1% H2 in air were observed for the Au–WO3 and Pt–WO3 sensors, respectively. Characterization by scanning electron microscope (SEM) of the Au catalyst activated tungsten trioxide sensor is also presented.

A gas sensor was developed by depositing polythiophene nanofibers on the surface of ZnO/36° YX Li... more A gas sensor was developed by depositing polythiophene nanofibers on the surface of ZnO/36° YX LiTaO3 layered surface acoustic wave (SAW) transducer and tested towards different concentrations of hydrogen gas in synthetic air. Polythiophene nanofibers were synthesized by using a template-free method through the introduction of an initiator into the reaction mixture of a rapidly mixed reaction between the monomer (thiophene) and the oxidant. The yield of the reaction was characterized using scanning electron microscopy (SEM) as well as Ultraviolet-visible (UV-vis) and Fourier Transform Infrared (FTIR) spectroscopies. The frequency shift due to the sensor response was ~17 kHz towards 1% of H2. All tests were conducted at room temperature. The sensor performance was assessed over a two day period and a high degree of repeatability was obtained.

Titanium oxide nanotubes Schottky diodes were fabricated for hydrogen gas sensing applications. T... more Titanium oxide nanotubes Schottky diodes were fabricated for hydrogen gas sensing applications. The TiO2 nanotubes were synthesized via anodization of RF sputtered titanium films on SiC substrates. Two anodization potentials of 5 V and 20 V were used. Scanning electron microscopy of the synthesized films revealed nanotubes with avarage diameters of 20 nm and 75 nm. X-ray diffraction analysis revealed that the composition of the oxide varied with the anodization potential. TiO2 (anatase) being formed preferentially at 5 V and TiO (no anatase) at 20 V. Current-voltage characteristics of the diodes were studied towards hydrogen at temperatures from 25°C to 250°C. At constant current bias of -500 μA and 250°C, the lateral voltage shifts of 800 mV and 520 mV were recorded towards 1% hydrogen for the 5 V and 20 V anodized nanotubes, respectively.

A layered Surface Acoustic Wave (SAW) device based on an InOx/Si3N4/36° YX LiTaO3 structure is in... more A layered Surface Acoustic Wave (SAW) device based on an InOx/Si3N4/36° YX LiTaO3 structure is investigated for sensing ozone in air at different operating temperatures and concentrations. These concentrations are between 25 ppb and 150 ppb. Layered SAW devices are of a great interest as they show a remarkable performance for liquid and gas sensing applications. This structure is a single delay line SAW device with 64 input and output finger pairs, having periodicity of 24 μm. They were fabricated on a 36° Y-cut X-propagating lithium tantalate (LiTaO3) piezoelectric substrate. A 1 μm thick silicon nitride (Si3N4) layer was deposited over the finger pairs and a 100 nm indium oxide (InOx) sensing layer was deposited over the Si3N4 layer. Both layers were deposited by RF magnetron sputtering. InOx was chosen as it has a remarkable sensitivity towards ozone. Si3N4 was chosen as it is inert and has stable characteristics at high temperature. The sensor performance is analysed in terms of response time, recovery time and response magnitude as a function of operational temperature. The operational temperature ranges between 185°C and 205°C. The sensor shows repeatability, reversibility, fast response and recovery time. At approximately 190°C the highest sensitivity was observed. A frequency shift of 5.0 kHz at 25 ppb, 6.5 kHz at 50 ppb ozone was recorded. The presented results show this structure is promising for gas sensing applications.

Poly‐vinyl‐pyrrolidone (PVP)∕ Multiwall Carbon Nanotubes (MWNTs) based Surface Acoustic Wave (SAW... more Poly‐vinyl‐pyrrolidone (PVP)∕ Multiwall Carbon Nanotubes (MWNTs) based Surface Acoustic Wave (SAW) sensors are fabricated and characterized, and their performances towards hydrogen gas are investigated. The PVP∕ MWNTs fibers composite are prepared by electrospinning of the composite aqueous solution deposited directly onto the active area of SAW transducers. Via scanning electron microscopy (SEM), the morphology of the deposited nanostructure material is observed. From the dynamic response, frequency ...

Journal of The Acoustical Society of America, 1998

MoO3-WO3 thin films have been fabricated via the sol-gel method. FESEM, TEM, RBS and SIMS analysi... more MoO3-WO3 thin films have been fabricated via the sol-gel method. FESEM, TEM, RBS and SIMS analysis techniques have been employed to analyse the films and material properties for use as gas sensors to detect CO and NO2. FESEM shows the film made up of segregated molybdenum crystals. TEM highlights the nano-sized grains sructure and crystallinity. RBS analysis confirmed the films are stoichimetric and that the Mo component of the system decreases as the annealing temperature is increased. SIMS illustrates the interesting elemental depth profiles of the films. The films were exposed to CO and NO2. MoO3-WO3 shows better NO2 sensitivity and selectivity compared to its single metal oxide constituents.

Layered Surface Acoustic Wave (SAW)immunosensors based on a substrate crystal cut that allows the... more Layered Surface Acoustic Wave (SAW)immunosensors based on a substrate crystal cut that allows the propagation of Surface Skimming Bulk Wave (SSBW)have been fabricated. SiO2 and ZnO films with different thicknesses deposited onto the substrate to form the SAW device. The layered SAW device developed is a gravimetric sensor.Upon exposures to solutions containing IgG, the operational frequency of the system incorporating the sensor changes. In this paper, the sensitivity of the SAW devices with different film thicknesses will be compared. Their response to the biochemical components will be investigated.

Nano Letters, 2011

An initiator is applied to synthesize single-walled carbon nanotube/polyaniline composite nanofib... more An initiator is applied to synthesize single-walled carbon nanotube/polyaniline composite nanofibers for use as high-performance chemosensors. The composite nanofibers possess widely tunable conductivities (10 -4 to 10 2 S/cm) with up to 5.0 wt % single-walled carbon nanotube (SWCNT) loadings. Chemosensors fabricated from the composite nanofibers synthesized with a 1.0 wt % SWCNT loading respond much more rapidly to low concentrations (100 ppb) of HCl and NH 3 vapors compared to polyaniline nanofibers alone (120 s vs 1000 s). These nanofibrillar SWCNT/polyaniline composite nanostructures are promising materials for use as low-cost disposable sensors and as electrodes due to their widely tunable conductivities.

A multi-layered surface acoustic wave (SAW) transducer employing an R.F. magnetron sputtered tung... more A multi-layered surface acoustic wave (SAW) transducer employing an R.F. magnetron sputtered tungsten trioxide (WO3) thin film as a selective layer, for low concentration nitrogen dioxide (NO2) gas sensing is presented. The layered SAW device structure is fabricated on a 36° Y-cut, X-propagating LiTaO3 substrate with a zinc oxide (ZnO) guiding layer. The dominant mode of acoustic propagation in the sensor is a combination of mainly a shear and a longitudinal displacement types. Such a structure has the advantage of confining the acoustic wave energy to the surface of the device, which increases the sensitivity of the system. A frequency shift of 30 kHz is shown for a concentration of 500ppb of NO2 in synthetic air, highlighting the possibility of such a sensor being targeted towards the sub-ppb levels of NO2.

Pathological thrombus formation is initiated by the interaction of blood platelets to immobilized... more Pathological thrombus formation is initiated by the interaction of blood platelets to immobilized proteins at the vessel wall. Platelet surface adhesion leads to biochemical activation and structural reorganization resulting in spreading of the platelet across the adhesive surface. Extensive studies have been carried out to examine platelet spreading responses on continuous substrates but little is known about the impact of protein surface distribution on platelet function. This paper describes the development of a micro-contact printing technique to establish defined 2-dimensional arrays of the thrombogenic protein fibrinogen at the surface of glass substrates, with the aim of investigating the impact of protein surface distribution on platelet biochemical signaling events associated with the adhesion/spreading process.

Procedia Chemistry, 2009

Here we report on a layered Surface Acoustic Wave (SAW) gas sensor featuring polyethylaniline nan... more Here we report on a layered Surface Acoustic Wave (SAW) gas sensor featuring polyethylaniline nanofibers as the active layer. A rapidly-mixed reaction was employed to synthesize polyethylaniline nanofibers. The product was deposited on a microfabricated ZnO/36° YX LiTaO3 SAW transducer. Scanning Electron Microscopy (SEM) and Ultraviolet-visible spectroscopy (UV-vis) were utilized to characterize the nanomaterials. The novel sensor was tested towards different concentrations of hydrogen at room temperature. It was observed that the sensor maintained a stable baseline with good repeatability. Hence, the sensor is expected to be potentially attractive for industrial applications.

Sensors and Actuators B-chemical, 2010

Conductometric, optical and surface acoustic wave gas sensors based on sol–gel silica porous film... more Conductometric, optical and surface acoustic wave gas sensors based on sol–gel silica porous films doped with NiO and Au nanoparticles are studied. The nanocomposite films are characterized by optical absorption in the visible and near-infrared region, spectroscopic ellipsometry, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) analysis and X-ray photoemission spectroscopy (XPS). They show poor conductometric gas sensing response toward CO and H2. However, both optical and surface acoustic wave (SAW) responses are reversible and stable to H2. Moreover, exploiting the wavelength dependence of the optical sensor response it is possible to selective recognition of H2. Choosing the appropriate wavelength, almost no variation in absorption is observed when introducing different gases into the testing chamber.

Smart Materials & Structures, 2006

Abstract A comparison between the performance of conductometric and layered surface acoustic wave... more Abstract A comparison between the performance of conductometric and layered surface acoustic wave (SAW) hydrogen sensors is presented. Both sensor structures employ an RF magnetron sputtered tungsten trioxide (WO3) thin film as a selective layer for hydrogen (H2) sensing applications. The conductometric device is based on an alumina substrate, while the layered SAW device structure is fabricated on a 36◦ Y-cut, X-propagating LiTaO3 substrate with a zinc oxide (ZnO) guiding layer. The sensors were investigated for different ...

Electrophoresis, 2009

This paper presents the development and experimental analysis of a dielectrophoresis (DEP) system... more This paper presents the development and experimental analysis of a dielectrophoresis (DEP) system, which is used for the manipulation and separation of microparticles in liquid flow. The system is composed of arrays of microelectrodes integrated to a microchannel. Novel curved microelectrodes are symmetrically placed with respect to the centre of the microchannel with a minimum gap of 40 μm. Computational fluid dynamics method is utilised to characterise the DEP field and predict the dynamics of particles. The performance of the system is assessed with microspheres of 1, 5 and 12 μm diameters. When a high-frequency potential is applied to microelectrodes a spatially varying electric field is induced in the microchannel, which creates the DEP force. Negative-DEP behaviour is observed with particles being repelled from the microelectrodes. The particles of different dimensions experience different DEP forces and thus settle to separate equilibrium zones across the microchannel. Experiments demonstrate the capability of the system as a field flow fraction tool for sorting microparticles according to their dimensions and dielectric properties.

Abstract Novel layered Surface Acoustic Wave (SAW) sensors, based on a ZnO/90 rotated ST-cut quar... more Abstract Novel layered Surface Acoustic Wave (SAW) sensors, based on a ZnO/90 rotated ST-cut quartz crystal structure, were fabricated. They were employed as gravimetric sensor&amp;amp;#x27;s for immunosensing applications and as SAW conductometric sensors for gas sensing applications. These sensors are able to sense oxygen gas concentrations as low as 0.2 ppm in nitrogen gas. Their mass detection limit in liquid media is as low as 100 pgr/cm 2

Crystal Growth & Design, 2010

Highly crystalline nanostructured tungsten oxides were produced via an extremely simple and inexp... more Highly crystalline nanostructured tungsten oxides were produced via an extremely simple and inexpensive novel aqueous sol− gel technique. By altering the deposition parameters and the postdeposition treatment, these nanostructures can be tuned into anhydrous or partially or fully hydrated tungsten oxides. Additionally, we will demonstrate the suitability of the developed WO3 for NO2 gas sensing.

In this paper, the design of a thin film thermoelectric microcooler module is examined. The modul... more In this paper, the design of a thin film thermoelectric microcooler module is examined. The module consists of n-type bismuth telluride and p-type antimony telluride thermoelectric materials. The commercial software CFD-ACE+ is used to implement and analyse the model. A two-dimensional coupled electrical and thermal synthesis was performed. The influence of the thickness of the thermoelectric materials on the change in temperature has been investigated. The thickness of the thermoelements was varied between 0.5 and 20 μm. The device performance in terms of change in temperature with and without a load has been studied. The optimal thickness for the thermoelements was found to be 2μm. At 30mA, a temperature difference of 3K below ambient was obtained.