Stiffness of sphere–plate contacts at MHz frequencies: dependence on normal load, oscillation amplitude, and ambient medium

• Jana Vlachová,
• Rebekka König and
• Diethelm Johannsmann

Beilstein J. Nanotechnol. 2015, 6, 845–856, doi:10.3762/bjnano.6.87

• related to the dissipation factor, D, by D = Γ/(2f). fF is the fundamental frequency, which is often 5 MHz. Zq = 8.8 × 106 kg∙m−2s−1 is the shear wave impedance of AT-cut quartz. is the area-averaged complex amplitude of the tangential stress at the resonator surface, and u0 is the amplitude of

• oscillation. The ratio of stress and velocity (where the latter is equal to iωu0) is the complex load impedance, ZL. In the second step in Equation 1, the stress was converted to force by area. The force, in turn, was expressed as tangential stiffness times amplitude (that is, as κu0). n is the overtone order

• Equation 3 and the principle of operation of lock-in amplifiers. Δf and ΔΓ are proportional to the in-phase and the out-of-phase components of the force. Underlying both Equation 1 and Equation 3 is the small load approximation, which states that the load impedance (often called ZL, the ratio of σ0 and

Entropy effects in the collective dynamic behavior of alkyl monolayers tethered to Si(111)

• Christian Godet

Beilstein J. Nanotechnol. 2015, 6, 583–594, doi:10.3762/bjnano.6.60

• Technologies). The sample holder was inserted in a two terminal active cell with the impedance converter mounted directly above the sample. The junction was placed into a cryostat under dry nitrogen flow to avoid extensive water condensation and to minimize surface oxidation during electrical measurements [39

Electrical response of liquid crystal cells doped with multi-walled carbon nanotubes

• Amanda García-García,
• Ricardo Vergaz,
• José F. Algorri,
• Xabier Quintana and
• José M. Otón

Beilstein J. Nanotechnol. 2015, 6, 396–403, doi:10.3762/bjnano.6.39

• characteristic impedance has been studied at different frequencies and excitation voltages. The results demonstrate alterations in the anisotropic conductivity of the samples with the applied electric field, which can be followed by monitoring the impedance evolution with the excitation voltage. Results are

• consistent with a possible electric contact between the coated substrates of the LC cell caused by the reorientation of the nanotubes. The reversibility of the doped system upon removal of the electric field is quite low. Keywords: carbon nanotubes; Cole–Cole diagrams; impedance; liquid crystal; PEDOT:PSS

• LC cells under different conditions seems to be missing. This could be achieved by studying the impedance evolution of the doped cells with voltage and frequency. Indeed, the electrical response may be fairly complex since dielectric and anisotropic conductive elements are present in the system. The

Comparative evaluation of the impact on endothelial cells induced by different nanoparticle structures and functionalization

• Lisa Landgraf,
• Ines Müller,
• Peter Ernst,
• Miriam Schäfer,
• Christina Rosman,
• Isabel Schick,
• Oskar Köhler,
• Hartmut Oehring,
• Vladimir V. Breus,
• Thomas Basché,
• Carsten Sönnichsen,
• Wolfgang Tremel and
• Ingrid Hilger

Beilstein J. Nanotechnol. 2015, 6, 300–312, doi:10.3762/bjnano.6.28

• monolayers around the CdSe core of QDs showed that the lowest impact on cell metabolism (cellular dehydrogenase activities) was present when QDs were coated with two monolayers (Figure S1, Supporting Information File 1). Impedance measurements (electric cell–substrate impedance sensing, ECIS) revealed a

• nanoparticles and nearly absent for the D-penicillamine (DPA)-coated QDs. These effects most certainly depend upon the positive charge of CyA, which resulted in an electrostatic attraction to the negatively charged cell membranes. Beyond impedance measurements, the MTS assay with endothelial cells (SVEC4-10

• , Germany) after a 4 h incubation period at 37 °C. The production of light was measured with a luminescence plate reader (BMG LABATECH GmbH, Germany). Relative cellular dehydrogenase and ATP levels were expressed as relative values to the untreated control. Measuring cell viability through impedance

The effect of surface charge on nonspecific uptake and cytotoxicity of CdSe/ZnS core/shell quantum dots

• Vladimir V. Breus,
• Anna Pietuch,
• Marco Tarantola,
• Thomas Basché and
• Andreas Janshoff

Beilstein J. Nanotechnol. 2015, 6, 281–292, doi:10.3762/bjnano.6.26

• -Planck-Institute for Dynamics and Self-Organization (MPIDS), Laboratory for Fluid Dynamics, Pattern Formation and Biocomplexity, Am Fassberg 17, 37077 Goettingen, Germany 10.3762/bjnano.6.26 Abstract In this work, cytotoxicity and cellular impedance response was compared for CdSe/ZnS core/shell quantum

• -particle tracking), was shown to compromise the integrity of the cytoskeletal and plasma membrane dynamics, as evidenced by electric cell–substrate impedance sensing. Keywords: biocompatibility; CdSe/ZnS; cytotoxicity; ECIS; quantum dots; single-particle tracking; Introduction Quantum dots (QDs) are

• membrane permeability assays. We demonstrate that these methods, however, can overlook other more subtle impacts on cell viability and metabolism caused by binding of QDs to cellular compartments, without release of Cd2+ ions. In the present study, we use a noninvasive and label-free impedance setup to

Mechanical properties of MDCK II cells exposed to gold nanorods

• Anna Pietuch,
• Bastian Rouven Brückner,
• David Schneider,
• Marco Tarantola,
• Christina Rosman,
• Carsten Sönnichsen and
• Andreas Janshoff

Beilstein J. Nanotechnol. 2015, 6, 223–231, doi:10.3762/bjnano.6.21

• enzymes. More advanced techniques, like electric cell-substrate impedance sensing (ECIS) or quartz crystal microbalance measurements monitor the vertical cell motility, i.e., dynamic changes of the cell-substrate distance, as a reporter for cell viability [1][10][11][12][13][14][15]. Mechanical properties

• epithelial cells was shown to be corrupted by gold-nanoparticle exposure in these previous publications, we decided to monitor viscoelastic changes and metabolically driven shape fluctuations in real-time by means of acoustic and impedance-based sensors like QCM and ECIS; the latter furthermore enabled us to

Kelvin probe force microscopy in liquid using electrochemical force microscopy

• Liam Collins,
• Stephen Jesse,
• Jason I. Kilpatrick,
• Alexander Tselev,
• M. Baris Okatan,
• Sergei V. Kalinin and
• Brian J. Rodriguez

Beilstein J. Nanotechnol. 2015, 6, 201–214, doi:10.3762/bjnano.6.19

• effects, which cannot be obtained using linear bias sweeps (e.g., CV measurements), ultimately requiring either pulsed electrochemical or impedance measurements [57]. To achieve this goal, a multidimensional spectroscopic strategy was implemented, which is capable of probing both the bias- and time

• electronic charge and z is the ion valence. At low biases (Vdc < kT/e ≈ 25 mV) and in the absence of Faradaic reactions, this RC time is the relevant timescale of the transient response, e.g., in high-frequency impedance spectroscopy experiments or induced charge electrokinetics, where high-frequency

Mammalian cell growth on gold nanoparticle-decorated substrates is influenced by the nanoparticle coating

• Christina Rosman,
• Sebastien Pierrat,
• Marco Tarantola,
• David Schneider,
• Eva Sunnick,
• Andreas Janshoff and
• Carsten Sönnichsen

Beilstein J. Nanotechnol. 2014, 5, 2479–2488, doi:10.3762/bjnano.5.257

• polymer induced a reduction by 30% and 40%, respectively, which is absent for the carboxy-terminated polymer. Furthermore, interface-sensitive impedance spectroscopy (electric cell–substrate impedance sensing, ECIS) was employed in order to investigate the micromotility of cells added to substrates

• nanorods, which were applied to the basolateral side of the cells, has a recognizable influence on the growth behavior and thus the coating should be carefully selected for biomedical applications of nanoparticles. Keywords: basolateral application; cytotoxicity; electric cell–substrate impedance sensing

• properties of the coating agent and its reactive group. The impact on surfactant-induced cell behavior was investigated in more detail by interface-sensitive impedance spectroscopy (electric cell–substrate impedance sensing, ECIS). Studies on the uptake and influence on metabolic activity with respect to

High-frequency multimodal atomic force microscopy

• Adrian P. Nievergelt,
• Jonathan D. Adams,
• Pascal D. Odermatt and
• Georg E. Fantner

Beilstein J. Nanotechnol. 2014, 5, 2459–2467, doi:10.3762/bjnano.5.255

• mirror based readout has two major advantages over a conventional, purely operational amplifier based readout. The large increase in speed is achieved by the very low input impedance of current mirrors, thus countering the negative impact of diode parasitics on the total bandwidth. Additionally, the

Gas sensing properties of nanocrystalline diamond at room temperature

• Marina Davydova,
• Pavel Kulha,
• Alexandr Laposa,
• Karel Hruska,
• Pavel Demo and
• Alexander Kromka

Beilstein J. Nanotechnol. 2014, 5, 2339–2345, doi:10.3762/bjnano.5.243

• Figure 5, exposure of the sensor elements to 100 ppm of ammonia gas led to increased impedances from 4.4 to 5.4 MΩ and from 3.9 to 5.4 MΩ for the samples nucleated for 1 min and 5 min, respectively. It should be noted that a variation (shift) in the starting impedance value was observed. The starting

• impedance varied by nearly an order of magnitude in some cases. The origin for this difference can be attributed to several factors, for example, low quality ohmic contacts or memory effects of the surface state of NCD. It was concluded that technological optimization is still required for achieving better

• conductive electrodes (Figure 7, cross-sectional view). Moreover, the impedance measurements showed that the gap between the interdigitated electrodes is one of the most important geometric parameters of the sensor and should carefully be considered when enhancing the sensing response (Figure 3 and Figure 5

Low cost, p-ZnO/n-Si, rectifying, nano heterojunction diode: Fabrication and electrical characterization

• Vinay Kabra,
• Lubna Aamir and
• M. M. Malik

Beilstein J. Nanotechnol. 2014, 5, 2216–2221, doi:10.3762/bjnano.5.230

• Equations 4–6 [9][10] as follows: where Vbi is the built-in voltage, Xn and Xp are the depletion width for the n- and p-side, and εn and εp are the dielectric constants of n-Si and p-ZnO, respectively. The dielectric constants εp and εn were found to be 7 and 11.7, respectively, as derived from impedance

• crystalline phase of the p-ZnO nanoparticles. The Hall effect measurement system (ECOPIA, model HMS-3000) was used for electrical characterization of the sample. An electrometer (KEITHLEY, 6517B) was used for the current–voltage (I–V) measurements of the diode and an impedance analyzer (WAYNE KERR, 6500B) was

Effect of channel length on the electrical response of carbon nanotube field-effect transistors to deoxyribonucleic acid hybridization

• Hari Krishna Salila Vijayalal Mohan,
• Jianing An,
• Yani Zhang,
• Chee How Wong and
• Lianxi Zheng

Beilstein J. Nanotechnol. 2014, 5, 2081–2091, doi:10.3762/bjnano.5.217

• contribution of charge-trapping mechanism to the observed behavior [27][28]. Similar DNA detection studies using CNTs based on the principle of impedance exhibited detection limits as low as 100 aM [29]. To verify whether the source of the signal is from the CNT channel, ID–VG curves of FETs with only the

Carbon-based smart nanomaterials in biomedicine and neuroengineering

• Antonina M. Monaco and
• Michele Giugliano

Beilstein J. Nanotechnol. 2014, 5, 1849–1863, doi:10.3762/bjnano.5.196

• smaller microelectrodes, reducing the electrode surface exposed to the electrolyte or in close proximity to neuronal cell membranes, has been shown to lead to a significant electrochemical impedance of the interface, decreased injected charge limits and poor S/N properties. CNTs, by their excellent

• ionic and electronic conductivity of poly(3,4-ethylenedioxythiophene) (PEDOT), a conductive polymer, with the high mechanical stability of CNTs. This combination, employed as a coating layer of conventional MEAs, resulted in reduced impedance, and thus in improved performances not only when compared

Experimental techniques for the characterization of carbon nanoparticles – a brief overview

• Wojciech Kempiński,
• Szymon Łoś,
• Mateusz Kempiński and
• Damian Markowski

Beilstein J. Nanotechnol. 2014, 5, 1760–1766, doi:10.3762/bjnano.5.186

• be attributed to the strained nano-graphite appearing in the sample. There are also other ways to determine the dimensions of the CNs. Among them are impedance measurements [32] and the EPR technique performed on the conducting electrons [33]. A more detailed analysis is provided in the next section

Growth and structural discrimination of cortical neurons on randomly oriented and vertically aligned dense carbon nanotube networks

• Christoph Nick,
• Sandeep Yadav,
• Ravi Joshi,
• Christiane Thielemann and
• Jörg J. Schneider

Beilstein J. Nanotechnol. 2014, 5, 1575–1579, doi:10.3762/bjnano.5.169

• stimulate neural activity. CNTs do have a high capacity and low impedance, e.g., compared to IrO2 which is widely used as electrical interface for cells, as has been manifested by cyclic voltammetry and impedance spectroscopy [9]. Thus CNTs allow to minimise the stimulation voltage as well as the electrode

Methods for rapid frequency-domain characterization of leakage currents in silicon nanowire-based field-effect transistors

• Tomi Roinila,
• Xiao Yu,
• Jarmo Verho,
• Tie Li,
• Pasi Kallio,
• Matti Vilkko,
• Anran Gao and
• Yuelin Wang

Beilstein J. Nanotechnol. 2014, 5, 964–972, doi:10.3762/bjnano.5.110

• -response measurements of switched-mode power supplies, and applied the IRS to analyze the output impedance. The design steps of the excitation sequence can also be applied for the application in this paper. Results and Discussion The presented methods were applied, and the leakage current was characterized

• amplifier. The upper operational amplifier in the schematic works as an excitation voltage buffer, which drives the ground-referred unknown impedance Zx through a current sense resistor Rsense. The measured current causes a voltage drop in this resistor, which is then amplified with the lower

• instrumentation amplifier. Cc and Rc are added to prevent oscillation in case Zx is highly capacitive. Excitation voltage scaling, power supplies, filtering, and additional amplifier stages are not included. The amplifier has a selectable gain of −1.1 mV/nA or −4.5 mV/nA. The bandwidth depends on the impedance to

Optical modeling-assisted characterization of dye-sensitized solar cells using TiO₂ nanotube arrays as photoanodes

• Jung-Ho Yun,
• Il Ku Kim,
• Yun Hau Ng,
• Lianzhou Wang and
• Rose Amal

Beilstein J. Nanotechnol. 2014, 5, 895–902, doi:10.3762/bjnano.5.102

• parameters of the DSSCs, electrochemical impedance spectroscopy (EIS) offers valuable information. Figure 4 shows the Bode phase plots and the Nyquist plots obtained from electron transfer at the TiO2 and electrolyte interface under a solar simulator of AM 1.5. Figure 4a shows the negative shift of the

• for about 40 min. The absorbance measurement was performed using UV–vis spectrophotometer (Cary 300, Varian). The electrochemical impedance spectroscopy (EIS) measurements were performed by illuminating the DSSCs with a AM 1.5 solar simulator calibrated at 100 mW·cm−2 at open-circuit conditions

Enhancement of photocatalytic H₂ evolution of eosin Y-sensitized reduced graphene oxide through a simple photoreaction

• Weiying Zhang,
• Yuexiang Li,
• Shaoqin Peng and
• Xiang Cai

Beilstein J. Nanotechnol. 2014, 5, 801–811, doi:10.3762/bjnano.5.92

• photoreaction. This further indicates the restoration of the sp2 π-conjugated network for RGO after the photoreaction. Due to restoration of the sp2 π-conjugated network in RGOx, its conductivity is expected to increase [42]. To verify this enhancement, the electrochemical impedance spectroscopy (EIS) of GO

• -resolution TEM (HRTEM) images were taken on a JEOL JEM-2010 (TEM) equipped with an energy dispersive spectrometer (EDS). Electrochemical impedance spectroscopy (EIS) was measured on an IVIUMSTAT electrochemical workstation (Netherlands). The electrochemical experiments were performed in a 3-compartment cell

Electrochemical and electron microscopic characterization of Super-P based cathodes for Li–O₂ batteries

• Mario Marinaro,
• Santhana K. Eswara Moorthy,
• Jörg Bernhard,
• Ludwig Jörissen,
• Margret Wohlfahrt-Mehrens and
• Ute Kaiser

Beilstein J. Nanotechnol. 2013, 4, 665–670, doi:10.3762/bjnano.4.74

• (trifluoromethane)sulfonimide lithium salt (LiTFSI)/tetraglyme electrolyte were investigated by galvanostatic cycling and electrochemical impedance spectroscopy measurements. Ex-situ X-ray diffraction and scanning electron microscopy were used to evaluate the formation/dissolution of Li2O2 particles at the cathode

• side during the operation of Li–O2 cells. Keywords: aprotic electrolyte; impedance spectroscopy; Li–O2 batteries; scanning electron microscopy; Introduction The development of new types of electrochemical power sources is nowadays considered a key factor for further development of hybrid and fully

• electrolyte. The electrochemical behaviors of the batteries were investigated by galvanostatic cycling and electrochemical impedance spectroscopy. The physico–chemical investigation of the lithium-oxide phases that form and dissolve at the cathode side upon discharge and charge of Li–O2 batteries has been

Novel composite Zr/PBI-O-PhT membranes for HT-PEFC applications

• Mikhail S. Kondratenko,
• Igor I. Ponomarev,
• Marat O. Gallyamov,
• Dmitry Y. Razorenov,
• Yulia A. Volkova,
• Elena P. Kharitonova and
• Alexei R. Khokhlov

Beilstein J. Nanotechnol. 2013, 4, 481–492, doi:10.3762/bjnano.4.57

• were examined by means of SAXS, thermomechanical analysis (TMA), and were tested in operating fuel cells by means of stationary voltammetry and impedance spectroscopy. The new membranes showed excellent stability in a 2000-hour fuel cell (FC) durability test. The modification of the PBI-O-PhT films

• reduced conductivity due to an excessively high degree of crosslinking. Keywords: composite; high temperature polymer-electrolyte fuel cells (HT-PEFC); impedance spectroscopy; polybenzimidazole (PBI); zirconium; Introduction Polymer-electrolyte fuel cells (PEFC) based on polybenzimidazole (PBI

• . The current step was 2 mA·cm−2. After setting each current value the system was allowed to reach a steady state for about 10 s before measuring the voltage. Impedance measurements The impedance of the fuel cells with membranes of different types was measured in a galvanostatic mode at frequencies from

Zeolites as nanoporous, gas-sensitive materials for in situ monitoring of DeNO_x-SCR

• Thomas Simons and
• Ulrich Simon

Beilstein J. Nanotechnol. 2012, 3, 667–673, doi:10.3762/bjnano.3.76

• sensor at the same time. By means of temperature-dependent impedance spectroscopy we found that the thermally induced NH3 desorption in H-form and in Fe-loaded zeolite H-ZSM-5 follow the same process, while a remarkable difference under DeNOx-SCR reaction conditions was found. The Fe-loaded catalyst

• elementary catalytic process promoting a full description of the NH3-SCR reaction system. Keywords: DeNOx-SCR; gas sensing; in situ; impedance spectroscopy; zeolite; Introduction Zeolites are crystalline, nanoporous aluminosilicates composed of [TO4] tetrahedra (T = Si, Al). In H-form zeolites protons

• also applied in gas sensors [12][13][14][15][16][17]. They are proton conductors due to the mobility of the charge-compensating protons. By means of impedance spectroscopy (IS) [18][19][20][21] and quantum chemical calculations on H-ZSM-5 [22][23], we showed in previous works that protons can move

A facile approach to nanoarchitectured three-dimensional graphene-based Li–Mn–O composite as high-power cathodes for Li-ion batteries

• Wenyu Zhang,
• Yi Zeng,
• Chen Xu,
• Ni Xiao,
• Yiben Gao,
• Lain-Jong Li,
• Xiaodong Chen,
• Huey Hoon Hng and
• Qingyu Yan

Beilstein J. Nanotechnol. 2012, 3, 513–523, doi:10.3762/bjnano.3.59

• high current densities are supported by the impedance studies. The electrodes at the fifth fully discharged state are tested under identical conditions. Figure 7 shows the Nyquist plots of the LMO/G and pure LMO electrodes. The pure LMO electrode displays a larger semicircular diameter than that of LMO

• hybrid sample helps to reduce the dissolution of Mn into the electrolyte further. The superior electrochemical performance of LMO/G electrodes is ascribed to three aspects. First, the LMO/G exhibits fast kinetics of Li-ion and electron diffusion, as examined by the electrochemical impedance spectroscopy

• theoretical capacity of 148 mAh·g−1. The electrochemical impedance was performed on the aforementioned CR2032 coin cells with lithium foil as the counter and reference electrode. All cells were measured at the fifth fully discharged state. INPHAZETM EIS system was employed to measure the electrochemical

Reduced electron recombination of dye-sensitized solar cells based on TiO₂ spheres consisting of ultrathin nanosheets with [001] facet exposed

• Hongxia Wang,
• Meinan Liu,
• Cheng Yan and
• John Bell

Beilstein J. Nanotechnol. 2012, 3, 378–387, doi:10.3762/bjnano.3.44

• consisting of ultrathin nanosheets with 100% of the [001] facet exposed was employed to fabricate dye-sensitized solar cells (DSCs). Investigation of the electron transport and back reaction of the DSCs by electrochemical impedance spectroscopy showed that the spheres had a threefold lower electron

• also observed after TiCl4 treatment. The synergistic effect of the variation of the TiO2 conduction band and the electron recombination determined the open-circuit voltage of the DSC. Keywords: dye-sensitized solar cells; electrochemical impedance spectroscopy; electron recombination; TiO2 [001] facet

• transport and back reaction of the DSCs with the spheres were investigated by electrochemical impedance spectroscopy. In addition, the effect of treatment by an aqueous solution of TiCl4 on the performance of the DSCs with the TiO2 spheres was discussed. Experimental Synthesis of TiO2 nanosheet particles

Functionalised zinc oxide nanowire gas sensors: Enhanced NO₂ gas sensor response by chemical modification of nanowire surfaces

• Eric R. Waclawik,
• Jin Chang,
• Andrea Ponzoni,
• Isabella Concina,
• Dario Zappa,
• Elisabetta Comini,
• Nunzio Motta,
• Guido Faglia and
• Giorgio Sberveglieri

Beilstein J. Nanotechnol. 2012, 3, 368–377, doi:10.3762/bjnano.3.43

• innovations in the semiconductor gas-sensing field are still in demand [1][2][3]. Impedance-semiconductor gas sensors typically operate at temperatures greater than 200 °C [4][5]. High operating temperatures are generally required to maximise the sensor response to target gases, either to activate the

• of detail. Coating of the semiconductor with a sensitising molecule layer could enhance surface reactions or modify the surface chemistry and, hence, improve sensor sensitivity and specificity to a particular gas. Although such chemical functionalisation of impedance-based gas sensor surfaces is

Junction formation of Cu₃BiS₃ investigated by Kelvin probe force microscopy and surface photovoltage measurements

• Fredy Mesa,
• William Chamorro,
• William Vallejo,
• Robert Baier,
• Thomas Dittrich,
• Alexander Grimm,
• Martha C. Lux-Steiner and
• Sascha Sadewasser

Beilstein J. Nanotechnol. 2012, 3, 277–284, doi:10.3762/bjnano.3.31

• -impedance buffer with a dual-phase lock-in amplifier. Spectral SPV experiments were performed on untreated Cu3BiS3 samples. XPS measurements on Cu3BiS3 and Cu3BiS3 etched in NH3. (a) Overview spectrum showing that Na, oxides, and C contamination are effectively reduced by the NH3 etch. (b) Detailed spectrum