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In this paper, new frequency equations of a shear mode c-axis tilted FBAR (Film Bulk Acoustic Wave Resonator) sensor operating in viscous liquid media are derived by using the transfer matrix method to predict the frequency shift (FS) induced by fluid viscosity. Top and bottom electrodes of FBAR are considered as a superposition of a pure elastic model and a perfectly conducting model. Employing the perturbation method and developed frequency equations, an approximate FS expression is obtained to study the effects of viscous liquid properties on frequency shifts for the sensor operating in water-glycerol solutions. Numerical results by the developed frequency equations are compared with the published experimental results and those predicted by the traditional Stockbridge-Kanazawa equation, which was originally derived for quartz crystal microbalances (QCMs). Meanwhile, the influence of the electrode material and thickness on FS is also discussed to demonstrate the outperformance of the developed equations over the Stockbridge-Kanazawa equation. Results show that the analytical equations for frequency shift analysis have more potential than the well-known Stockbridge-Kanazawa equation to predict frequency shift characteristics of FBAR sensors in terms of accuracy and efficiency.

With large accelerations, the mechanical vibrations of device structures can be driven to nonlinear states yielding strong variations of vibration characteristics such as frequency change and modes...

Mode-coupled vibrations in a thickness-shear (TSh) mode and laterally finite film bulk acoustic resonator (FBAR) with one face in contact with Newtonian (linearly viscous and compressional) liquid are investigated. With boundary conditions and interface continuity conditions, exact dispersion curves in FBAR sensors contacting with two kinds of liquids are obtained, and they are compared with the dispersion curves in a bare sensor without liquid contact. Frequency spectra, describing mode couplings between the main TSh modal branch and undesirable modal branches, are calculated by employing weak boundary conditions at lateral free edges constructed based on the variational principle. Mode shapes of mechanical displacements in both the sensor and liquid layer are presented, and mode transformations are observed due to the liquid contact and lateral edge effect. The effect of liquid thickness on frequency spectra is also studied. Numerical results reveal that the generation of shear wave in the liquid layer results in the shifts of spectrum curves along the frequency axis and hence it is the main factor of frequency shifts of FBAR sensors. The compressional wave causes the shifts of spectrum curves along the lateral aspect ratio axis. Then for a given FBAR sensor, the liquid thickness changes could also cause frequency shifts. Therefore, desirable vibration modes should be chosen based on the frequency spectra to avoid strong mode couplings and to eliminate frequency shifts induced by the liquid thickness changes in real applications.

Tubular mesoporous silica (T-mSiO2) was facilely synthesized through a co-template method by using cetyltrimethylammonium bromide and α-Fe2O3 as the dual templates, and then disulfide (–SS–) bonds and carboxyl groups (–COOH) were introduced to the resultant T-mSiO2 via the reaction with 2-carboxyethyl 2-pyridyl disulphide. The obtained –SS– grafted T-mSiO2 (SS-T-mSiO2) was then grafted with chitosan (CS) via the amidation reaction between the –COOH groups on SS-T-mSiO2 and the –NH2 groups on CS. The CS grafted SS-T-mSiO2 (CS-SS-T-mSiO2) was fully characterized by various technologies such as transmission electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. Finally, the as-synthesized CS-SS-T-mSiO2 was used as the carrier for redox and pH dual-triggered delivery of 5-fluorouracil (5-FU), an anti-cancer drug, and the results indicate that the developed CS-SS-T-mSiO2 might be a potential responsive carrier for redox and pH dual-triggered drug delivery.

The second (H2) and third (H3) harmonic generations in surface acoustic wave (SAW) resonators based on the YZ-cut LiNbO 3 operating in both longitudinal leaky SAW (LLSAW) mode and Rayleigh SAW mode were investigated and compared. For the Rayleigh SAW mode, the patterns and trends of nonlinearly excited harmonics in the YZ-cut LiNbO 3 were the same as those of 128° YX LiNbO 3 except that the peaks of nonlinear harmonic responses in YZ-cut LiNbO 3 were denser than the latter. However, for the YZ-cut LiNbO 3 LLSAW resonators, the peaks of the nonlinear harmonic responses would be 20 to 30 dBm lower than those in the Rayleigh SAW resonators. For the YZ-cut LiNbO 3 LLSAW resonators, we found that the quasi-periodic peaks in the nonlinear harmonics response would disappear at a substrate thickness of 500 μm. Results showed that the nonlinear harmonic generation concerns in SAW filters and duplexers may be substantially reduced by the use of longitudinal leaky SAW based on YZ-cut LiNbO 3 .

Ionic chiral selectors have been received much attention in the field of asymmetric catalysis, chiral recognition, and preparative separation. It has been shown that the addition of ionic chiral selectors can enhance the recognition efficiency dramatically due to the presence of multiple intermolecular interactions, including hydrogen bond, π-π interaction, van der Waals force, electrostatic ion-pairing interaction, and ionic-hydrogen bond. In the initial research stage of the ionic chiral selectors, most of work center on the application in chromatographic separation (capillary electrophoresis, high-performance liquid chromatography, and gas chromatography). Differently, more and more attention has been paid on the spectroscopy (nuclear magnetic resonance, fluorescence, ultraviolet and visible absorption spectrum, and circular dichroism spectrum) and electrochemistry in recent years. In this tutorial review as regards the ionic chiral selectors, we discuss in detail the structural features, properties, and their application in chromatography, spectroscopy, and electrochemistry.

In this study, a sensitive and selective electrochemical sensing platform for the detection of Sudan I was developed with CuO nanoparticles-decorated 3D N-doped porous carbon (CuO/3DNPC). 3D N-doped porous carbon (3DNPC) was first prepared by calcining the precursors of 3D integrated polysaccharides, and then it was decorated with CuO nanoparticles by hydrothermal method. The CuO/3DNPC modified electrode showed high sensitivity and wide linear range for the detection of Sudan I due to the excellent electrocatalytic activity of CuO and the accelerated electron transfer by 3DNPC. In addition, the proposed CuO/3DNPC also exhibited high selectivity, high reproducibility and stability in the detection of Sudan I. Finally, the CuO/3DNPC based Sudan I sensor was applied in the detection of Sudan I in ketchup and chilli sauces, and the results demonstrated the potential of the developed CuO/3DNPC as a promising electrode material for accurate assay of Sudan I in food samples.

Poly(acrylic acid-co-acrylamide) (P(AA-co-AM)) hydrogels with upper critical solution temperature (UCST) were synthesized via radical copolymerization technology, which were then incorporated with SiO2@polypyrrole (SiO2@PPy) for the construction of light-, thermo- and pH-responsive drug delivery system. The synthesized SiO2@PPy@P(AA-co-AM) hydrogels were then examined by Fourier transform infrared (FT-IR) spectrometry, field emission scanning electron microscopy (FESEM), thermogravimetry (TG) and differential thermogravimetric (DTG). Finally, the designed SiO2@PPy@P(AA-co-AM) hydrogels were used for controlled delivery of 5-fluorouracil (5-FU), an anti-cancer drug. An encapsulation ratio of up to 92.2% was obtained when 5-FU was encapsulated in the SiO2@PPy@P(AA-co-AM) hydrogels, and the cumulative release of 5-FU could reach 83.9% with the near-infrared (NIR) irradiation of 6 h at pH 7.4. During the controlled release of 5-FU, PPy in the system could convert the NIR irradiation to heat as a photo-thermal transducer while maintaining the temperature in the UCST range of P(AA-co-AM). In addition, SiO2 in the hydrogels acted as a gatekeeper to prevent the burst release of 5-FU.

A novel ultraviolet (UV)- and visible-light-active 3D graphene aerogels (3DGA)/Sb2WO6 hybrid photocatalyst was prepared by electrostatic self-assembly (ESSA) method. The photocatalytic activity of the 3DGA/Sb2WO6 hybrid was studied by monitoring the change in the concentration of methyl orange (MO) under UV-light and visible-light irradiation. The results demonstrated that the as-prepared hybrid exhibited significantly enhanced efficiency for the photodegradation of MO in comparison with pure Sb2WO6. This was ascribed to the efficient separation of the photogenerated electrons (e–) and holes (h+) with the aid of 3DGA as well as the generated reactive superoxide radical anions (O2•–). Moreover, the 3DGA/Sb2WO6 hybrid exhibited high recyclability, because the highly hydrophobic 3DGA in the hybrid was very advantageous to the separation of the hybrid photocatalyst from the MO solutions.

In order to study the effect of mechanical-stress on the quartz filter output, based on the elasto-optical effect of quartz crystal, the relationship between berifringent difference of quratz plate and mechanical-stress is deduced, the experimental system is set up by using Ultra-6600 UV spectrophotometer, and received the transmission spectrum of Lyot quartz birefringence filter, the transmission spectrum was investigated theoretically and experimentally in detail. The results show that when applied different mechanical stresses, the center wavelength of quartz birefringent filter changed, and the drifting direction of the center wavelength is related to the size of applied mechanical stress, the drifting size of the center wavelength is related to the direction of applied mechanical stress. It is helpful for the manufacturing, correct design and application of quartz birefringence filter.

The heterostructures made of magnetostrictive and piezoelectric layers have been recently investigated for the application of magnetic sensors and antenna. In this paper we investigate the possibility of FeGaB thin film on quartz crystal substrate with different orientations of quartz layer. Response of magnetic FeGaB/AlN nanoplate resonator under RF magnetic excitation was simulated by finite element program COMSOL. The results were compared with available experiment and confirmed the validity of available material properties of FeGaB thin film and current simulation method. Quartz/FeGaB composite resonator structures based on different modes of vibration were studied. Quartz/FeGaB resonator based on in-plane extensional modes was found to have a large magnetoelectric coupling effect. These findings can be used to design RF magnetic sensors based on Quartz/FeGaB bilayer plate.

Mode-coupled vibrations in an ultra-high frequency (UHF) ZnO thin film bulk acoustic resonator (FBAR) operating at thickness-extensional (TE) mode are studied by employing weak boundary conditions (WBCs), constructed based on Saint-Venant’s principle and mixed variational principle in the piezoelectric theory. The frequency spectra, describing the lateral size-dependence of mode couplings between the main mode (TE) and undesirable eigen-modes, for clamped lateral edges are compared with the existing frequency spectra for free lateral edges to illustrate the boundary influence. The displacement and stress variations in FBAR volume are also presented to intuitionally understand and distinguish the difference of frequency spectra between these two different lateral edges, and then we discuss how to select outstanding lateral sizes to weaken the mounting effect. The frequency spectra predicted from our approximate WBCs are also compared with and agree well with those predicted by the finite element method (FEM) using COMSOL, which proves the correctness and accuracy of our theoretical method. These results indicate that the WBCs could have potentials in the valid predictions of lateral size-dependence of mode couplings in piezoelectric acoustic wave devices.

The effect of pretilt and twisted angle on twisted nematic liquid crystal filter (TNLCF) is studied theoretically and experimentally in this paper, based on the birefringence and distortion characteristic of twisted nematic liquid crystal, the output performance of TNLCF has been analyzed through numerical simulation firstly, then the corresponding experiment results verify the correctness of the simulation results, which show that the output performance of TNLCF is indeed related to pretilt angle and twisted angle of liquid crystal–with the increasing of the twisted angle the central wavelength of TNLCF will shift to the long wavelength, with the increasing of pretilt angle for the top glass substrate and the decreasing of pretilt angle for the bottom glass substrate the central wavelength of TNLCF will shift to the short wavelength, and if the pretilt angle of the bottom glass substrate is increased and the pretilt angle of the top glass substrate is reduced at the same time in some certain value or otherwise the shift trend of the central wavelength will be not evident. These results will offer an important reference value for the design and application of TNLCF as we believe.

The nonlinear intermodulation effect in piezoelectric devices was studied By using the three-dimensional equations of nonlinear piezoelectricity and the method of harmonic balance, we have formulated and derived coupled sets of nonlinear piezoelectric equations in the frequency domain for intermodulation effects. The coupled sets of equations could be embedded in COMSOL FEM models. In order to check the validity and accuracy of the FEM models we studied the third order intermodulation effects in AT-cut quartz resonators. Our three-dimensional FEM model results compared well with the analytical one-dimensional results by Tiersten and with the experimental results by Smythe. The FEM models could be used for simulating intermodulation effects in BAW and SAW piezoelectric devices provided that the nonlinear material constants are available and are accurate.

We report on a 32-MHz quartz temperature compensated crystal oscillator (TCXO) fully integrated with commercial CMOS electronics and vacuum packaged at wafer level using a low-temperature MEMS-after quartz process. The novel quartz resonator design provides for stress isolation from the CMOS substrate, thereby yielding classical AT-cut f/T profiles and low hysteresis which can be compensated to±0.2 parts per million over temperature using on-chip third-order compensation circuitry. The TCXO operates at low power of 2.5 mW and can be thinned to as part of the wafer-level eutectic encapsulation. Full integration with large state-of-the-art CMOS wafers is possible using carrier wafer techniques.

Rational design and synthesis of high performance active materials is one of the most challenging tasks in supercapacitors. Herein, a new three-dimensional (3D) reduced graphene oxide (RGO)/carbon nanospheres (CNS)/polyaniline (PANI) ternary nanocomposites were prepared facilely and applied as supercapacitor electrode materials. The as-prepared RGO/CNS/PANI ternary nanocomposites were characterized by field-emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectra and X-ray powder diffraction (XRD), respectively. An enhanced specific capacitance was demonstrated compared with other binary nanocomposites RGO/PANI, RGO/CNS and pure RGO or PANI. The RGO/CNS/PANI exhibited a high specific capacitance of 583 F g −1 at a current density of 1 A g −1 and excellent cyclic stability with 86% of its initial capacitance at a large current density of 10 A g −1 after 1000 charge/discharge cycles. In addition, high rate capability (72% capacity retention from 1 to 10 A g −1 ) was obtained due to the synergistic effects of RGO/CNS and PANI. The results indicated that the ternary nanocomposites of RGO/CNS/PANI could be a promising material for supercapacitor electrodes.

Hierarchical mesoporous Co3O4/C@MoS2 core-shell structured materials are synthesized via a two-step calcination and a solvothermal method using cobalt metal-organic frameworks (cobalt-MOFs, ZIF-67) and (NH4)2MoS4 as the precursors of Co3O4/C and MoS2, respectively, which is a new class of core-shell materials as supercapacitor electrode materials. The obtained Co3O4/C@MoS2 exhibits high specific capacitance (1076 F g−1 at 1 A g−1), rate capability (76.9% capacitance retention at 10 A g−1) and cyclic stability (64.5% capacitance retention after 5000 cycles at 10 A g−1). Moreover, the content of MoS2 greatly influences the electrochemical performances of the obtained core-shell materials. The results demonstrate that the as-synthesized ZIF-67 can be used as a promising candidate for designing Co3O4 based core-shell materials used in supercapacitors.

Sulfur-doped titanium dioxide (S-TiO2) was hydrothermally synthesized using thiourea as the sulfur source, and then it was successfully integrated to the three-dimensional graphene aerogels (3DGA). The obtained nanocomposites of S-TiO2 and 3DGA (S-TiO2-3DGA) were characterized by XRD, SEM, TEM, XPS and UV–vis diffuse reflectance spectroscopy. When the nanocomposites were applied for the photodegradation of methyl orange (MO), the photocatalytic activity of TiO2 was significantly improved by doping of S and integration with 3DGA, which might be due to the narrowed bandgap of S-TiO2 and the good conductive ability and 3D structure of 3DGA. More importantly, the hydrophobic property of 3DGA makes it easy to separate the S-TiO2-3DGA from the water phase, resulting in excellent recyclability and high stability of the photocatalyst.

Near-infrared (NIR) light has great potential in biomedical applications due to its advantages of deep penetration depth and low photodamage to biological tissues. In this paper, we constructed a novel core-shell structured drug nanocarrier, Fe3O4@Au@SiO2, for the controlled delivery of etoposide (VP16), a chemotherapeutic drug for cancer patients. The novel core-shell structured drug delivery platform is composed of a mesoporous silica shell and a magnetic Fe3O4 core using Au nanoparticles (AuNPs) as the interlayer, which is characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, N2 adsorption/desorption isotherms and the magnetic measurements with vibrating-sample magnetometer (VSM). The synergistic effects of AuNPs, mesoporous silica and Fe3O4 make the core-shell structured nanocomposites an excellent candidate for targeted and NIR light irradiation-controlled drug delivery. For the proposed nanocarrier of VP16, the mesopores in silica can enhance the encapsulation capacity of the nanocarrier and the AuNPs can effectively convert the NIR light into heat to speed up the drug deliver; meanwhile, the incorporation of Fe3O4 with high magnetization to the drug delivery platform realize drug targeting under an applied external magnetic field.

We report the facile synthesis of N-doped carbon-graphene-manganese oxide (N/C-G-MnO) that can serve as precious metal-free electrocatalysts for oxygen reduction reaction (ORR). The N/C-G-MnO is synthesized via polymerization of m -phenylenediamine adsorbed on graphene using KMnO 4 as the oxidant, followed by pyrolyzation of the resulting N- and MnO 2 -containing poly( m -phenylenediamine). That is, poly( m -phenylenediamine) plays multi-roles in the synthesis of the ORR catalysts: (i) Serving as interlayer spacer to prevent graphene sheets from restacking during the thermal annealing, (ii) Function as the source of N-doped carbon (N/C) and MnO for the simultaneous doping of graphene. The N/C-G-MnO exhibits better ORR activity, long-term stability and methanol tolerance than those of the commercial Pt (5%)/C catalyst.

Recent research work on the theoretical and experimental possibilities of acoustically actuated MEMS RF magnetoelectric antennas using piezoelectric-magnetostrictive multilayers have been published, for example in ref. [1], [2]. A mechanism of electromagnetic-acoustic coupling was achieved in the composite ferromagnetic/piezoelectric heterostructure. The magnetostrictive thin film provided the function of converting the RF magnetic signal to acoustic vibration of the composite resonator while the piezoelectric body realized the transduction of acoustic wave to electric signal. In this paper, we proposed a novel MEMS RF FeGaB/Quartz receiver sensor where FeGaB had a relatively stronger piezomagnetic coefficient compared to other ferromagnetic materials such as nickel. The quartz resonator had the advantages of high Q, low resistance, and high frequency-temperature stability. Experiments were set up to measure the remnant magnetization state of FeGaB thin film deposited on AT- and SC-cut quartz wafers. Consistent comparison results were obtained between the simulated and measured magnetization curves of FeGaB thin films. A 10 MHz AT-cut quartz resonator coated with 200-nm-thick FeGaB layer was fabricated and tested. The frequency response of a similar uncoated quartz resonator was also tested so that the difference between the responses of coated and uncoated resonator respectively could yield a qualitative view of the magnetic field response. A special setup of experiments were taken to reduce the electric field effect of the RF signal. The simulated frequency responses of the coated and uncoated resonators showed trends that were consistent with the experimental results.

The characteristics of nonlinear harmonic generation of bulk acoustic wave (BAW) modes in surface acoustic wave (SAW) devices were studied and presented. Specifically the BAW modes were nonlinearly generated ($f$-2$f$-3$f$) by the fundamental SAW mode in a 128° YX LiNO 3 temperature compensated SAW (TC-SAW) resonator. These BAW modes interfered with the desired SAW mode of the TC-SAW resonator. The method and formulation of nonlinear frequency response of piezoelectric BAW and SAW was presented, and FEM was used to solve three sets of coupled nonlinear equations in the frequency domain. For SAW devices, nonlinearly excited BAW waves in 128° YX LiNO 3 TC-SAW devices had been observed experimentally and reported [1]. We demonstrated our formulation/method for this nonlinear harmonic generation problem, and we obtained good, consistent simulation results. The 2nd harmonic (H2) generation was due to a nonlinearly excited bulk wave mode polarized and travelling along the thickness direction of substrate. The mode was almost normal to the top and bottom surfaces of substrate, forming a standing wave between top and bottom surfaces. Therefore, the substrate thickness, and bottom surface roughness had effects on the H2 response. The H3 response was due to a similar type of nonlinearly excited BAW wave.

Forced mode coupling vibration of ZnO thin film resonator with its c-axis along thickness direction operating at thickness-extensional mode is studied in this paper. The zone dispersion curve is obtained since the mechanical damping of ZnO thin film is considered in this case. The displacement solutions are constructed based on the zone dispersion curve and the Mason model solution, which are then substituted into weak boundary conditions at the left and right edges determining the undetermined constants. The effect of lateral electrode size on suppressing spurious modes is particularly studied. The results show that with lateral electrode size increasing, more spurious modes occurs in the band between fs and fp but their amplitude strength become weaker. Therefore, in realistic resonators a larger lateral boundary is more desirable and then the band between fs and fp would become smoother.

This study focused on the searching of new cuts for SAW substrates of triply-rotated quartz with cubic frequency-temperature (f-T) relationship by solving the equations of the first and second derivatives of the f-T function. First we established the f-T function of SAW, which was presented in matrix form and was based on the thermal incremental field theory. Next the wave velocity was obtained by the golden search method. Then the first two derivatives of the f-T function were calculated by multi-point finite difference formula. Finally, solving the nonlinear equations of the first two derivatives in the whole range of triply-rotated quartz, we obtained some new cuts with high inflection temperature Ti about 85°C.

The thickness-extensional mode in layered piezoelectric plates can be inevitably interfered by some undesirable eigen-modes due to the lateral edge effect. A reported theoretical method to predict high-frequency coupled vibrations is the 2D high-order plate theory derived based on approximate dispersion relations. In this paper, based on accurate dispersion relations a novel approach called Frequency Spectrum Quantitative Prediction (FSQP) is developed to quantitatively investigate coupled vibration behaviors in piezoelectric multilayered plates operating at ultra-high frequency. Two significant sub-goals need to be achieved: one is the accurate dispersion relations of the layered structure; the other is the variational formulation for the layered plates with piezoelectric and/or elastic phases. Lastly, the objective equation, i.e., frequency spectra, describing coupling strengths between the thickness-extensional mode and unwanted eigen-modes, is derived. A reported numerical example of a piezoelectric thin-film resonator is considered to demonstrate the correctness and superiority of the proposed methodology. Mode shapes of mechanical displacements are investigated in detail to illustrate the application of frequency spectra to suppress the undesirable eigen-modes. Numerical results show that the proposed approach FSQP is efficient and more accurate than the existing 2D high-order plate theory in quantitative predictions of high-frequency coupled vibrations in layered piezoelectric plates.

Poly(aniline- co - m -aminophenol)(PANMA)/graphene/NiO nanocomposite was synthesized and applied as a supercapacitor electrode for the first time. Graphene/NiO nanocomposite was first synthesized via a hydrothermal synthesis method from Ni(NO 3 ) 2 ·6H 2 O, urea, and graphite oxide. NiO nanoparticles were distributed uniformly on both sides of the graphene. Then, PANMA was deposited in situ on the surface of the graphene/NiO nanocomposite via the copolymerization of aniline and m -aminophenol. The obtained nanocomposite has a similar porous morphology with that of PANMA. Experimental results indicate that the synergistic contributions from PANMA, graphene and NiO enable the composite electrode with substantially improved energy storage performance metrics. The nanocomposite shows a high specific capacitance of 562 F g −1 at a current density of 0.5 A g −1 , a good rate capability even at high current densities and a better long-term cycling stability.

Graphene–polyaniline–MnO 2 (G–P–Mn) hybrids were synthesized via a facile approach that includes the reduction of graphene oxide (GO) to graphene (G) by aniline and then followed by oil–water interfacial polymerization of aniline to polyaniline (PANI) using a binary oxidant of KMnO 4 and (NH 4 ) 2 S 2 O 8 . PANI was orderly nanofibered and MnO 2 -doped due to interfacial polymerization and the use of binary oxidant. The hybrids conclude electrical double layer capacitance of G and pseudo capacitance of PANI and MnO 2 , showing enhanced specific capacitance of 800.1 F g −1 at 0.4 A g −1 with good cycling stability.

ZnO and CuO co-decorated porous carbon spheres (PCS) were prepared via a simple hydrothermal method, denoted as ZnO-CuO/PCS. An electrochemical sensor based on the ZnO-CuO/PCS was fabricated for simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). Three well-resolved anodic peaks along with greatly increased peak currents were obtained at the ZnO-CuO/PCS modified glassy carbon electrode (GCE) on the differential pulse voltammograms. The anodic peak separations at the ZnO-CuO/PCS/GCE were 204 mV between AA and DA and 132 mV between DA and UA. Notably, the analytical performances of the ZnO-CuO/PCS outperform those of ZnO/PCS and CuO/PCS, which can be attributed to the synergistic effect of the two metallic oxides, i.e., the formation of p-n heterojunctions between p-type CuO and n-type ZnO allows sensitive transduction into remarkable changes in the electrochemical signals. The ZnO-CuO/PCS/GCE also presented high anti-interference ability, storage stability and repeatability in the determination of AA, DA and UA. Finally, the practical applicability of the prepared sensor was successfully demonstrated by the simultaneous determination of AA, DA and UA in human urine samples.

Incremental piezoelectric equations for small vibrations superposed on initial deformations are presented. The equations are implemented in COMSOL finite element models (FEA). Equations are validated by comparing the results for the force sensitivity coefficient Kf of a circular quartz plate subjected to a pair of diametrical forces with measured data. The model results show a consistent trend with the experimental results, and the relative difference between our FEA results and Ballato's measured result is about 13%. A detailed study of the acceleration sensitivity of a rectangular AT-cut quartz plate is presented. The plate resonator is fixed along one edge as a cantilever. For AT-cut quartz resonators with the crystal digonal X-axis perpendicular to plate X-axis, the in-plane acceleration sensitivity is found to be negligible compared with the out-of-plane (Y-axis) acceleration sensitivity. For AT-cut quartz resonators with the crystal digonal X-axis parallel to plate X-axis, the Y-axis acceleration sensitivity is found to be rectified, that is the fractional change in frequency is positive with respect to both positive and negative Y-axis accelerations. The Y-axis acceleration sensitivity is small in comparison with the in-plane acceleration sensitivity for small body forces. However, for large body forces, the Y-axis acceleration sensitivity dominates because it increases nonlinearly with the Y-axis acceleration. The resonator rectified acceleration sensitivity is confirmed by phase noise measurements. For reduced acceleration sensitivity, two pairs of electrodes along the plate edges reduce the bending of the plate resonator and subsequently reduce acceleration sensitivity. We present a new method using these edge electrodes in which a dc bias field is employed to control the resonant frequency of resonator subjected to g body forces. A dc bias field with an appropriate dc bias voltage could potentially yield a reduction of acceleration sensitivity in Y-axis direction of about two orders of magnitude.

A simple method to synthesize Zn 2+ doped poly(aniline- co - m -aminophenol) (PANMA), Zn-PANMA, for supercapacitors is reported. Capacitive behaviors of the copolymer based supercapacitor in 1 M H 2 SO 4 electrolyte were examined by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge/discharge. The morphological characteristics of Zn-PANMA and PANMA doped with Fe 3+ and Cu 2+ were investigated by field emission scanning microscopy (FESEM), explaining the different capacitive behaviors of these transition metal ions doped PANMA. A specific capacitance of Zn-PANMA as high as 631 F g −1 was achieved at a current density of 0.5 A g −1 , due to the enhancement of the electrochemical properties of the copolymer by Zn 2+ doping. Moreover, the specific capacitance still remained 71.7% after cycling for 800 times, exhibiting a good cycling performance and structure stability of Zn-PANMA.

The behavior of vibrating crystal plates under the action of external forces was studied. The plates were respectively subjected to diametrical compression force and bending force in different configurations: (a) a clamped cantilever, (b) a cantilever with displaced knife edges, and (c) a dual support mounting with displaced knife edge applied midway between. Finite element models were developed using the theory of small deformations superposed on finite initial deformations in Lagrangian formulation. The model results compared well with the experimental results by Mingins, Ballato, et. al., [3, 4]. For the AT-cut plate, the azimuth Ψ angles of frequency insensitivity due to compressional force were found at Ψ∼65° and 115°. For the plate bending in a clamped cantilever configuration a W-shaped plot of negative frequency deviations was observed when Ψ was varied from 0° to 180°, while the maximum positive frequency deviations occurred at Ψ∼270°. For the plate bending of cantilever with displaced knife edges, the results were similar to the plate bending in a clamped cantilever configuration. For the plate bending of dual support mounting with displaced knife edge applied in midway, the results for Ψ = 0° to 180° were very similar to Ψ = 180° to 360°. By searching out the effects of frequency deviations, optimal angles can be obtained to minimize or eliminate them.

A series of 3 wt% Ru embedded on ordered mesoporous carbon (OMC) catalysts with different pore sizes were prepared by autoreduction between ruthenium precursors and carbon sources at 1123 K. Ru nanoparticles were embedded on the carbon walls of OMC. Characterization technologies including power X-ray diffraction (XRD), nitrogen adsorption-desorption, transmission electron microscopy (TEM), and hydrogen temperature-programmed reduction (H2-TPR) were used to scrutinize the catalysts. The catalyst activity for Fischer-Tropsch synthesis (FTS) was measured in a fixed bed reactor. It was revealed that 3 wt% Ru-OMC catalysts exhibited highly ordered mesoporous structure and large surface area. Compared with the catalysts with smaller pores, the catalysts with larger pores were inclined to form larger Ru particles. These 3 wt% Ru-OMC catalysts with different pore sizes were more stable than 3 wt% Ru/AC catalyst during the FTS reactions because Ru particles were embedded on the carbon walls, suppressing particles aggregation, movement and oxidation. The catalytic activity and C5+ selectivity were found to increase with the increasing pore size, however, CH4 selectivity showed the opposite trend. These changes may be explained in terms of the special environment of the active Ru sites and the diffusion of products in the pores of the catalysts, suggesting that the activity and hydrocarbon selectivity are more dependent on the pore size of OMC than on the Ru particle size.

Chitosan (CTS)-stabilized bimetallic nanoparticles were prepared at room temperature (rt.) in aqueous solution. Palladium (Pd) and platinum (Pt) were selected as the first metals while iron (Fe) and nickel (Ni) functioned as the second metals. In order to obtain the noble metal core-transition metal shell structures, bimetallic nanoparticles were prepared in a two-step process: the preparation of mono noble metallic (Pd or Pt) nanoparticles and the deposition of transition metals (Fe or Ni) on the surface of the monometallic nanoparticles. The structures of the nanoparticles were studied using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The XPS results show that Pd and Pt exist mainly in zero valences. The presence of Fe and Ni in the bimetallic nanoparticles affects the binding energy of Pd and Pt. Moreover, the studies of O 1s spectra indicate the presence of Fe or Ni shells. The analyses of TEM micrographs give the particle size and size distributions while the high-resolution TEM (HRTEM) micrographs show the existence of noble metal core lattices. The results confirm the formation of noble metal core-transition metal shell structures.

The experimental studies of temperature coefficient of frequency (TCF) of SAW resonators were usually modeled by TCF models first proposed by Bechmann, Ballato and Lukaszeck[1]. These models unfortunately were not frame invariant with regards to the material property tensors of the crystal substrate and metal interdigital transducers (IDTs). Furthermore the models did not have the 3rd order nonlinear elastic constants that were needed to account for the effects of thermal strains from mountings, boundary constraints, and material interfaces. We employed a Lagrangian model of TCF of SAW resonators wherein governing equations for incremental vibrations superposed on thermal strains were implemented in a finite element program. The model used material coordinates referred to a fixed reference frame at a reference temperature, therefore the material property tensors were frame invariant. In addition it had a term that was a product of the 3rd order nonlinear elastic constants and thermoelastic strains. This product could account for the thermoelastic strains from interfacial stresses and boundary conditions. The objective of our study was to provide an accurate and detailed finite element model of the effects of the crystal substrate, metal IDTs, and stack layers on the TCF of SAW resonators. Good comparisons of model results with the experimental results were found for the 1 GHz lithium tantalate YXl 42° shear horizontal SAW resonator. Characterization of the electrode film properties was found to be important, especially when the film thickness was increased from 2000 A to 4000 A.

The acceleration sensitivity and its related problem of force-frequency in quartz resonators were studied. We studied the effects of initial nonlinear strains versus the effects of nonlinear elastic constants on the force-frequency problem of quartz resonators subjected to bending forces. We found that for quartz thickness shear resonators subjected to bending, the force frequency effect could be described primarily by the effects of nonlinear elastic constants with negligible effects from initial nonlinear strains. Since the acceleration sensitivity of quartz resonators is due mainly to bending forces, we proposed a set of simplified equations for these problems which were easier to implement in commercial finite element software.

The langasite crystal has the capability of no phase change at temperatures exceeding 600°C for high temperature applications. Since the material properties of langasite were measured usually at 25 0C as the reference temperature they are no longer accurate at high temperature environments. We employ a Lagrangian formulation to investigate the temperature behavior of thickness vibrations of langasite in a wide temperature range from 25°C to 600°C. The analysis only requires the elastic constants and their effective temperature derivatives of elastic constants and thermal expansion coefficients to predict the material constants at any given temperature. Based on the new values of the elastic constants and thermal expansion coefficients, the zero-valued temperature coefficients of frequency are investigated. The presently identified temperature compensated crystal cuts of the thickness-shear modes of langasite at different temperatures were compared with those at reference temperature and also with some cuts found in the literature.

We present a new method in which the electrode stress can be used to improve the frequency-temperature (f-T) behavior of ultra-high frequency (UHF) quartz resonators. The electrode films are treated as composite layers of different metals in a plate resonator. A FEM model for the effects of non-homogeneous thermal stress on the f-T behavior of quartz resonators was developed. For our 1 GHz AT-cut resonator, the use of chromium-aluminum electrodes yields improved frequency-temperature behavior compared to the case where aluminum electrodes are used alone. The UHF quartz resonators must be treated as composite plates of quartz and electrode film since the ratio of electrode thickness to quartz plate thickness is significant. The quartz-aluminum composite plate rotates the f-T curve clockwise while the quartz-chromium composite plate rotates the f-T curve counter-clockwise. The titanium was found to be a good electrode metal due to its small effect on the f-T curve.

A series of Ce -incorporated structure of cubic large mesoporous molecular sieves, KIT-6, with different Ce contents were synthesized by a direct hydrothermal process. A sample of Ce -loaded KIT-6 material was synthesised by incipent wetness impregnation. Similarly, catalysts with 15 wt.% Co loading on the above supports were also synthesized by incipient wetness impregnation. The supports and catalysts were characterized by X-ray diffraction, diffuse reflectance UV-vis, solid-state 29Si magic-angle spinning nuclear magnetic resonance, H2 -temperature programmed reduction, H2 -temperature programmed desorption and oxygen titration. The structure of the KIT-6 support was well retained after Ce incorporation. Small amounts of Ce in the Co catalyst were found to improve the activity and increase the selectivity to C5+ hydrocarbons for Fischer–Tropsch synthesis, while larger amounts of Ce had the reverse effect. Meanwhile, methane selectivity shows an opposite trend as compared with that of C5+ selectivity. Ce -loaded KIT-6 supported Co catalyst showed lower activity than KIT-6 supported Co catalyst.

We investigate the properties of shear horizontal surface acoustic wave propagation in layered functionally graded piezoelectric material structures loaded with viscous liquid. The piezoelectric material is polarized in the z-direction and the material properties change gradually along the thickness of the layer. Interfacial mechanical conditions are continuity of particle velocity and stress components at the interface. We here assume that the liquid is electrically insulated and its permittivity is much less than that of the piezoelectric material. The solutions of dispersion relations are obtained for insulated liquid with electrically open or shorted conditions by means of transfer matrix method. The effects of the gradient variation of material constants on the phase velocity and attenuation are presented and discussed in detail. The analytical method and the results are useful for the design of the resonators and sensors.

Ruthenium catalysts supported on multiwalled carbon nanotubes (MCNTs) with different loadings (1% wt, 3% wt, 5% wt) were prepared by reduction with H2 or NaBH4 for selective hydrogenation of soybean oil at 338 K and initial pressure of 1.066 MPa. These catalysts were characterized using transmission electron microscopy (TEM), X-ray powder diffraction (XRD), N2 adsorption–desorption, and H2-temperature programmed desorption (TPD) techniques. Ru particles were dispersed more homogeneously on the surface of the nanotubes after being reduced with H2 than with NaBH4. The catalysts with 3% and 5% Ru loadings had higher hydrogenation activity. The NaBH4-reduced catalyst had higher cis-isomer selectivity.

Theoretical analyses and designs of high-Q, quartz thin film resonators are presented. The resonators operate at an ultra-high frequency of 3.4 GHz for application to high-frequency timing devices such as cesium chip-scale atomic clocks. The frequency spectra for the 3.4-GHz thin film quartz resonators, which serve as design aids in selecting the resonator dimensions/configurations for simple electrodes, and ring electrode mesa designs are presented here for the first time. The thin film aluminum electrodes are found to play a major role in the resonators because the electrodes are only one third the thickness and mass of the active areas of the plate resonator. Hence, in addition to the material properties of quartz, the elastic, viscoelastic, and thermal properties of the electrodes are included in the models. The frequency-temperature behavior is obtained for the best resonator designs. To improve the frequency-temperature behavior of the resonators, new quartz cuts are proposed to compensate for the thermal stresses caused by the aluminum electrodes and the mounting supports. Frequency response analyses are performed to determine the Q-factor, motional resistance, capacitance ratio, and other figures of merit. The resonators have Q's of about 3800, resistance of about 1300 to 1400 ohms, and capacitance ratios of 1100 to 2800.

The quartz resonator Q with aluminum electrodes was studied with respect to its fundamental thickness shear mode frequency and its viscoelastic, viscopiezoelectric, and viscopiezoelectromagnetic behaviors. The governing equations for viscoelasticity, viscopiezoelectricity, and viscopiezoelectromagnetism were implemented for an AT-cut quartz resonator. To simulate the radiation conditions at infinity for the viscopiezoelectromagnetic model, perfectly matched layers over a surface enclosing the resonator were implemented to absorb all incident electromagnetic radiation. The shape of the radiation spectrum of a 5.6 MHz AT-cut quartz resonator was found to compare relatively well the measured results by Campbell and Weber. The mesa-plate resonator was studied for a frequency range of 1.4 GHz to 3.4 GHz. The resonator Q was determined to be influenced predominantly by the quartz viscoelasticity; however at frequencies greater than 2.3 GHz, the quartz electromagnetic radiation had an increasingly significant effect on the resonator Q. At 3.4 GHz, the electromagnetic radiation accounted for about 14% of the loss in resonator Q. At frequencies less than 2 GHz, the calculated resonator Q compared well with the intrinsic Q(x) provided by the formula Q(x) = 16 x 10(6)/f where f was in MHz. At frequencies higher than 2.3 GHz, the aluminum electrodes had significant effects on the resonator Q. At 3.4 GHz, the electromagnetic radiation loss in the electrodes was an order of magnitude greater than their viscoelastic loss; hence, the vibrating aluminum electrodes became an efficient emitter of electromagnetic waves. The effects of electrical resistance in both the electrodes and quartz were determined to be negligible.

Co particles were synthesized with mean particle sizes in the range of 3.2–171.4 nm in ambient atmosphere by reduction of cobalt salt with sodium borohydride as the reducing reagent, a combination of alcohols as solvents and a triblock copolymer P123 (EO 20 PO 70 EO 20 ) as the surfactant. The particle size and its distribution were controlled by varying the synthesis parameters such as the viscosity of the medium, the amount of alcohols or P123 in the reaction system. FT-IR and X-ray photoelectron spectroscopy (XPS) measurements confirmed the interaction between the oxygen atoms of P123 and Co 2+ or Co 0 . Detailed surface analyses by XPS and HRTEM revealed that the synthesized particles consisted of Co 0 metal surrounded by amorphous CoO, Co 2 B and chemisorbed P123.

Using two different methods, Ru nanoparticles have been synthesized by chemical reduction of ruthenium nitrosyl nitrate in ethylene glycol using Poly (N-vinyl-2-pyrrolidone) (PVP) as a stabilizer. In a one-step reaction, the average diameters of Ru nanoparticles were controlled in the range of 1.2–6.5 nm with narrow size distributions by changing the synthesis procedure and reaction conditions. In the seeding growth reaction, the Ru nanoparticle size was also precisely controlled by varying the seeds to Ru3+ ions ratio, ruthenium particles with different sizes (3.8–7.3 nm) were synthesized.

This paper investigates the photorefractive properties of iron doped lithium niobate with different [Li]/[Nb] ratios. The experimental results show two photorefractive centres for iron doped near-stoichiometric lithium niobate crystal. Besides Fe2+ and Fe3+ ions, small polarons and bipolarons are considered as another photoactive centre.

The frequency–temperature characteristics of quartz crystal resonators, particularly the frequency stability in a specific temperature range in which the vibration modes are strongly coupled, has been an important requirement in most applications. The analytical work on frequency–temperature relations has been done over the last decades in many aspects, ranging from the fundamental theory for the thermal effect on vibrations of elastic solids to simplified plate equations of a few strongly coupled vibration modes. However, it has been clearly observed that due to complications of the resonator structures such as the presence of a mounting structure and electrodes, simple and analytical solutions will not be able to consider all the factors which will have inevitable and noticeable effects. In this paper, we incorporate the frequency–temperature theory for crystal plates based on the incremental thermal field formulation by Lee and Yong into our finite element analysis implementation, which is then used to analyze the free vibrations of crystal plates with the higher-order Mindlin plate theory. The effect of electrodes on the frequency–temperature relation is also considered. The computational results are compared with experimental ones from actual products. The satisfactory agreement demonstrates the precise prediction of the frequency–temperature behavior and practical applications of the finite element analysis in product modeling and development.