Dynamic behavior of a nematic liquid crystal mixed with CoFe₂O₄ ferromagnetic nanoparticles in a magnetic field

• Emil Petrescu,
• Cristina Cirtoaje and
• Cristina Stan

Beilstein J. Nanotechnol. 2017, 8, 2467–2473, doi:10.3762/bjnano.8.246

• relaxation times for this mixture were calculated using experimental results and the theoretical model described above. They are presented in Table 1 where τon is the relaxation time after the field is switched on, and τoff is the relaxation time after the field is switched off. In pure nematic substances

• , the relaxation time τoff does not depend on the applied field as long as it is higher than the Fréedericksz transition threshold. As it can be observed from Table 1, when ferro-particles are added, the relaxation time decreases with increase of the applied field. Conclusion A new alignment was

• sample and improves the stability, proving to provide important benefits for magneto-optic devices. We obtained a stable structure with controllable phase modulation without backflow effect, and fast response. An important step was made to reduce the relaxation time, a major problem in magnetic devices

Material property analytical relations for the case of an AFM probe tapping a viscoelastic surface containing multiple characteristic times

• Enrique A. López-Guerra and
• Santiago D. Solares

Beilstein J. Nanotechnol. 2017, 8, 2230–2244, doi:10.3762/bjnano.8.223

• , which is its high scanning speed. At the same time, knowing that the observation of viscoelasticity demands agreement between the material timescale (e.g., relaxation time) and the experimental timescale (ca. 1/ω), we expect that in tapping mode AFM the observables are mainly governed by the elements of

Spin-dependent transport and functional design in organic ferromagnetic devices

• Guichao Hu,
• Shijie Xie,
• Chuankui Wang and
• Carsten Timm

Beilstein J. Nanotechnol. 2017, 8, 1919–1931, doi:10.3762/bjnano.8.192

• hyperfine interactions in organic materials are usually weak [4], which induces a long spin relaxation time and makes organic materials ideal for spin-polarized transport applications. Organic molecules may form a soft interface with metals and ferromagnets via chemical adsorption. The interfacial orbital

• interlayer has been studied in many experiments, motivated by the long spin relaxation time [4]. Examples are the giant magnetoresistance (GMR) and the room-temperature tunneling magnetoresistance (TMR) in LSMO/Alq3/Co junctions [6][7][8]. The MR in the ferromagnet/OF/ferromagnet junction Co/poly-BIPO/Co has

Stick–slip boundary friction mode as a second-order phase transition with an inhomogeneous distribution of elastic stress in the contact area

• Iakov A. Lyashenko,
• Vadym N. Borysiuk and
• Valentin L. Popov

Beilstein J. Nanotechnol. 2017, 8, 1889–1896, doi:10.3762/bjnano.8.189

• dependence of the friction force with monotonically decreasing coefficient A according to the relaxation law where A0 is the initial value of coefficient A at time t = 0, while is the relaxation time. Equation 18 relates to the increase of the lubricant temperature. The temperature of the lubricant can vary

Calcium fluoride based multifunctional nanoparticles for multimodal imaging

• Marion Straßer,
• Joachim H. X. Schrauth,
• Sofia Dembski,
• Daniel Haddad,
• Bernd Ahrens,
• Stefan Schweizer,
• Bastian Christ,
• Alevtina Cubukova,
• Marco Metzger,
• Heike Walles,
• Peter M. Jakob and
• Gerhard Sextl

Beilstein J. Nanotechnol. 2017, 8, 1484–1493, doi:10.3762/bjnano.8.148

• Gd3+ ions on the surface, the NPs reduce the MR T1 relaxation time constant as a function of their concentration. Thus, the NPs can be used as a MRI CA with a mean relaxivity of about r = 0.471 mL·mg−1·s−1. Repeated MRI examinations of four different batches prove the reproducibility of the NP

• CaF2:(Tb3+,Gd3+) NPs with concentrations in the range from 0.4 to 18.2 mg·mL−1 is shown in Figure 4a. Due to the different concentrations of the samples, the T1 relaxation time constants vary and therefore, different signal intensities are observable at different time points. To evaluate the potential

• values of the NPs vary from 137 to 1633 ms with decreasing concentrations. Plotting the relaxation rate R1 (inverse relaxation time T1) over the concentration of the samples, the relaxivity r arises from the slope of the linear fit (cf. Equation 1, Figure 4c). The relaxivity indicates the efficiency of

BTEX detection with composites of ethylenevinyl acetate and nanostructured carbon

• Santa Stepina,
• Astrida Berzina,
• Gita Sakale and
• Maris Knite

Beilstein J. Nanotechnol. 2017, 8, 982–988, doi:10.3762/bjnano.8.100

• varies as shown in Figure 2. The highest peak of this curve is marked as ΔR/R0 max. This is the maximal relative change of the electrical resistance at the end of the exposure time, for example, at 60 s. By changing the exposure time, the value of ΔR/R0 max and the relaxation time will change. If the

Tuning the spin coherence time of Cu(II)−(bis)oxamato and Cu(II)−(bis)oxamidato complexes by advanced ESR pulse protocols

• Ruslan Zaripov,
• Evgeniya Vavilova,
• Iskander Khairuzhdinov,
• Kev Salikhov,
• Violeta Voronkova,
• Mohammad A. Abdulmalic,
• Francois E. Meva,
• Saddam Weheabby,
• Tobias Rüffer,
• Bernd Büchner and
• Vladislav Kataev

Beilstein J. Nanotechnol. 2017, 8, 943–955, doi:10.3762/bjnano.8.96

• chosen such, so that the last n-th echo could not be observed anymore above the noise level. For example, at T = 10 K it was possible to apply 250 π-pulses, whereas the number of echoes reduced down to n = 25 at 80 K. To evaluate the longitudinal relaxation time the stimulated echo (SE) decay was

• resolved 14N HF structure due to the presence of four instead of two N-donor ligands, were obtained for P2 (not shown). Measurements of the phase relaxation time Tm of both complexes with the primary echo and CPMG pulse sequences have revealed that Tm does not depend on the choice of the peak of the ESR

• , including those inside the diffusion barrier, contribute to the shortening of Tm. In addition, also the nuclear spin-lattice relaxation time depends on the distance between a particular nucleus and the paramagnetic center. This circumstance, as well freezing of the motion of the propyl groups may be

First examples of organosilica-based ionogels: synthesis and electrochemical behavior

• Andreas Taubert,
• Ruben Löbbicke,
• Barbara Kirchner and
• Fabrice Leroux

Beilstein J. Nanotechnol. 2017, 8, 736–751, doi:10.3762/bjnano.8.77

• of MBA40IL. The peak maximum in intensity (ω·τ = 1) is the relaxation time (Figure 14a) [54], and their positions are plotted against the inverse of the temperature (Figure 14b). Once again, an Arrhenius-type behavior with the presence of two defined slopes is observed. The associated energy of

• conductive dynamics [52] but as there are no data available for the present system we prefer to not speculate about the details of the kink observed in some of the data. The experiments are, however, highly reproducible. Variation of (A) tan δ vs log f and (B) relaxation time vs 1000/T for MBA40. The

Formation and shape-control of hierarchical cobalt nanostructures using quaternary ammonium salts in aqueous media

• Ruchi Deshmukh,
• Anurag Mehra and
• Rochish Thaokar

Beilstein J. Nanotechnol. 2017, 8, 494–505, doi:10.3762/bjnano.8.53

• ferromagnetic materials because of distinctive magnetic properties such as an exponential dependence of the magnetization relaxation time on the volume of a particle [4], high susceptibility, many available crystal structures [5] and the uniaxial magnetic axis in hexagonal close-package (hcp) cobalt [6], which

Microwave synthesis of high-quality and uniform 4 nm ZnFe₂O₄ nanocrystals for application in energy storage and nanomagnetics

• Christian Suchomski,
• Ben Breitung,
• Ralf Witte,
• Michael Knapp,
• Sondes Bauer,
• Tilo Baumbach,
• Christian Reitz and
• Torsten Brezesinski

Beilstein J. Nanotechnol. 2016, 7, 1350–1360, doi:10.3762/bjnano.7.126

• frequency dependence of the peak temperature can also be described by a critical power law according to ν = ν0 × [(Tmax – T0)/T0]zυ with τ0 = 1/2πν0 and Tr = (Tmax – T0)/T0, where τ0 is the microscopic spin relaxation time, Tr is the reduced temperature and zυ is the dynamical exponent [39][41]. The best

Multiwalled carbon nanotube hybrids as MRI contrast agents

• Nikodem Kuźnik and
• Mateusz M. Tomczyk

Beilstein J. Nanotechnol. 2016, 7, 1086–1103, doi:10.3762/bjnano.7.102

• relaxation, could be registered by a receiver as two separate magnetization vector components, i.e., a longitudinal verctor along B0 described by the relaxation time T1 and a transverse vector, T2, perpendicular to B0. The decay of the NMR signal is observed in two separate processes: T1 called also spin

• –lattice relaxation time describes signal intensity disappearance, while T2, the spin–spin relaxation time is associated with the loss of frequency coherence among spins. MRI incorporates a gradient modification of the static external field B0 allowing for a three-dimensional image to be recorded. T1 and

• on their specificity of targeting to desired organs [49][50]. However, the negative CAs, routinely represented by SPIOs [46], also have their targets. The acceleration efficiency is expressed by the relaxivities r1 and r2, which are calculated as the reciprocal relaxation time effect caused by a unit

Phenalenyl-based mononuclear dysprosium complexes

• Yanhua Lan,
• Andrea Magri,
• Olaf Fuhr and
• Mario Ruben

Beilstein J. Nanotechnol. 2016, 7, 995–1009, doi:10.3762/bjnano.7.92

• -of-phase component in ac susceptibilities suggests that 1 might be a SMM. The relaxation time plotted in Figure 5 was extracted with an Arrhenius law by fitting the frequency sweeping data between 11 and 13 K. In doing so, we estimated the characteristic energy gap Δ for the thermally activated

• suppressed quantum tunneling of the magnetization (QTM) [52]. Lastly, ac susceptibilities as a function of the temperature have been measured under a dc field of 200 Oe to estimate the effective relaxation time (Figure 5). The data were fitted with an Arrhenius law function in the temperature range between

• 10 and 14 K. The characteristic SMM energy gap Δ is 49.4 K and the pre-exponential factor is τ0 is 2.9 × 10−6 s. Additionally, a quantum relaxation time of 1 × 10−3 s is observed below 7 K. Compared to the data calculated in zero-field, the energy gap Δ and its corresponding pre-exponential factor τ0

Dielectrophoresis of gold nanoparticles conjugated to DNA origami structures

• Anja Henning-Knechtel,
• Matthew Wiens,
• Mathias Lakatos,
• Andreas Heerwig,
• Frieder Ostermaier,
• Nora Haufe and
• Michael Mertig

Beilstein J. Nanotechnol. 2016, 7, 948–956, doi:10.3762/bjnano.7.87

• pristine DNA origami can be explained by the difference in polarizability of the metallic nanoparticles and the DNA nanostructure, i.e., the dipole relaxation time and the nature of the dipole. A dipole in gold nanoparticles is induced due to direct polarization of the electron cloud, whereas polarization

Single-molecule magnet behavior in 2,2’-bipyrimidine-bridged dilanthanide complexes

• Wen Yu,
• Frank Schramm,
• Eufemio Moreno Pineda,
• Yanhua Lan,
• Olaf Fuhr,
• Jinjie Chen,
• Hironari Isshiki,
• Wolfgang Wernsdorfer,
• Wulf Wulfhekel and
• Mario Ruben

Beilstein J. Nanotechnol. 2016, 7, 126–137, doi:10.3762/bjnano.7.15

• = (6.73 ± 0.4) × 10−7 s. The nonthermally activated regime is clearly marked in the Arrhenius plot at low temperatures range between 4 and 2 K, where the relaxation time is temperature independent with a tunneling frequency of 1.1 Hz, corresponding to a tunneling time τQTM of 0.145 ms. Cole–Cole fittings

Charge injection and transport properties of an organic light-emitting diode

• Peter Juhasz,
• Juraj Nevrela,
• Michal Micjan,
• Miroslav Novota,
• Jan Uhrik,
• Lubica Stuchlikova,
• Jan Jakabovic,
• Ladislav Harmatha and
• Martin Weis

Beilstein J. Nanotechnol. 2016, 7, 47–52, doi:10.3762/bjnano.7.5

• the 2C-SCLC region, the major charge relaxation phenomenon should be related to the charge transport. Hence, in regions of a high applied voltage the relaxation time trelax obtained from the impedance spectra analysis has been assigned to the transit time ttr across the organic film as ttr 0.72trelax

A simple and efficient quasi 3-dimensional viscoelastic model and software for simulation of tapping-mode atomic force microscopy

• Santiago D. Solares

Beilstein J. Nanotechnol. 2015, 6, 2233–2241, doi:10.3762/bjnano.6.229

• additional springs and dampers connecting adjacent SLS elements, through the use of 1D models with more than one relaxation time, or through the use of nonlinear elements [11]. (a) Schematic of AFM tip interacting with the standard linear solid model; (b) example of force curve for monomodal AFM; (c) example

An adapted Coffey model for studying susceptibility losses in interacting magnetic nanoparticles

• Mihaela Osaci and
• Matteo Cacciola

Beilstein J. Nanotechnol. 2015, 6, 2173–2182, doi:10.3762/bjnano.6.223

• : Néel relaxation and Brownian relaxation. Results: Since a consistent theory for the Néel relaxation time that is applicable to systems of interacting nanoparticles has not yet been developed, we adapted the Coffey theoretical model for the Néel relaxation time in external magnetic fields in order to

• consider local dipolar magnetic fields. Then, we obtained the effective relaxation time. The effective relaxation time is further used for obtaining values of specific loss power (SLP) through linear response theory (LRT). A comparative analysis between our model and the discrete orientation model, more

• superparamagnetic behaviour [15]. The typical time between two flips is called relaxation time, and the reversal process is called relaxation process. In nanofluids, the superparamagnetic nanoparticles have two associated relaxation processes: the Néel relaxation process and Brownian relaxation process. The former

Nonconservative current-driven dynamics: beyond the nanoscale

• Brian Cunningham,
• Tchavdar N. Todorov and
• Daniel Dundas

Beilstein J. Nanotechnol. 2015, 6, 2140–2147, doi:10.3762/bjnano.6.219

• can also use the above estimates to independently verify the balance between friction and NC forces in the dynamical steady state. For estimation purposes, we use the analytical result for the friction coefficient, and corresponding energy relaxation time, τfrict, for atomic Einstein oscillators [17

Large-voltage behavior of charge transport characteristics in nanosystems with weak electron–vibration coupling

• Tomáš Novotný and
• Wolfgang Belzig

Beilstein J. Nanotechnol. 2015, 6, 1853–1859, doi:10.3762/bjnano.6.188

• power balance equation [10][12] enables one to identify the inverse oscillator relaxation time τ−1≡γ↓ − γ↑ = 2αω/π and its stationary mean occupation number characterizing the geometric distribution of the asymptotic state [19]. Equation for the current cumulant generating function The above master

• damping of the oscillator mode) as we briefly discuss in the concluding section. In the case specified above, we can obtain the large-V asymptotics of the CGF by identifying the known leading contributions of the constituent parts. From the definitions and with the voltage-independent relaxation time

Metal hydrides: an innovative and challenging conversion reaction anode for lithium-ion batteries

• Luc Aymard,
• Yassine Oumellal and
• Jean-Pierre Bonnet

Beilstein J. Nanotechnol. 2015, 6, 1821–1839, doi:10.3762/bjnano.6.186

• ) Mg2FeH6-10% Ct,z electrodes prepared by reactive grinding as a function of the mole fraction of Li (x) Inset: Potential profile of a) b) c) and d) obtained during GITT (rate: one equivalent of Li in 10 h, relaxation time: 10 h). Adapted from [13] (copyright 2013 Elsevier) and [19]. The evolution of the

Nonlinear optical properties of near-infrared region Ag₂S quantum dots pumped by nanosecond laser pulses

• Li-wei Liu,
• Si-yi Hu,
• Yin-ping Dou,
• Tian-hang Liu,
• Jing-quan Lin and
• Yue Wang

Beilstein J. Nanotechnol. 2015, 6, 1781–1787, doi:10.3762/bjnano.6.182

• laser pump energy increased. In a two-level system, such as this, when the laser pulse width is much larger than the particle relaxation time, multiple absorption will occur in the QDs. For Ag2S QDs, a large Ag protrusion is formed in the nanogap when the laser pump energy increased. Both electronic and

Radiation losses in the microwave K_u band in magneto-electric nanocomposites

• Talwinder Kaur,
• Sachin Kumar,
• Jyoti Sharma and
• A. K. Srivastava

Beilstein J. Nanotechnol. 2015, 6, 1700–1707, doi:10.3762/bjnano.6.173

• adjacent atoms is related to the relaxation time and can be calculated from value of ∆H by using following relation: where β is the Bohr magneton (9.274 × 10−21 erg·G−1), ΔH1/2 is half of peak to peak width, and is the reduced Planck constant with a value of 1.055 × 10−34 J·s. The relaxation time is

Attenuation, dispersion and nonlinearity effects in graphene-based waveguides

• Almir Wirth Lima Jr.,
• João Cesar Moura Mota and
• Antonio Sergio Bezerra Sombra

Beilstein J. Nanotechnol. 2015, 6, 1221–1228, doi:10.3762/bjnano.6.125

• vector of the GSPP TM modes, we can see from the lower part of Figure 2 that Lp remains constant for wavelengths up to 1.7 μm. Also note that in this wavelength range, the value of the ratio Re(q)/Im(q) = ωτ (where τ is the relaxation time) varies very little. After the transfer of graphene onto a

Silica micro/nanospheres for theranostics: from bimodal MRI and fluorescent imaging probes to cancer therapy

• Shanka Walia and
• Amitabha Acharya

Beilstein J. Nanotechnol. 2015, 6, 546–558, doi:10.3762/bjnano.6.57

• found that the NPs emitted green light at 510 nm. The magnetic studies suggested that the nanocomposites exhibited typical property of superparamagnetic iron oxide by shortening the relaxation time T2. The cell uptake experiment of these nanocomposites was performed with human mesenchymal stem cells

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

• particular, if the measurement timescale >> relaxation time of the system, the system will be in equilibrium with the double layer fully formed, whereas for a measurement timescale << the relaxation time of the system, the system will behave similar to a linear dielectric. Finally, intermediate relaxation

• response is observed for all biases measured. The relaxation could be well-described by a double exponent decay having a fast relaxation time (τ1) of 1.2 ms to 6.3 ms and a slower relaxation time (τ2) between 11 ms and 47 ms (see Supporting Information File 1, Figure S1 for full fitting results). For milli