Electric Polarizability Anisotropy Research Articles

Optimization of particle size for high birefringence and fast switching time in electro-optical switching of graphene oxide dispersions.

In order to use graphene oxide (GO) dispersions for electro-optical applications, both a high GO concentration and a high electrical sensitivity are essential; however, these have not been achieved to date. Here, we report that by optimizing the mean size of GO particles to approximately 0.5 μm, one can obtain a high GO concentration of up to 2 wt% and high electrical sensitivity simultaneously. By reducing the mean GO-particle size, the interparticle interaction and the rotational viscosity can be significantly reduced, and a high-concentration isotropic phase can be obtained. As a result, the maximum birefringence increases and the dynamic response becomes faster. However, further decrease of the mean size below 0.1 μm causes a decrease in the anisotropy of electrical polarizability, resulting in the reduction of the electrical sensitivity of GO dispersions.

Electric dipole moments of particle aggregates in magnetite colloidal solutions in liquid dielectrics

The permanent electric moments and the electric polarizability anisotropy of particle aggregates are determined from the results of measuring the birefringence of a magnetite colloidal solution in kerosene subjected to constant and pulsed electric fields. A possible mechanism of generating an induced dipole moment in the aggregates is analyzed. The moment is characterized by a long relaxation time and, according to the results of optical experiments, is interpreted as permanent. The calculated dipole moments are consistent with the experimental data in the order of magnitude.

Electrooptical measurements for monitoring metabolite fluxes in acetone–butanol–ethanol fermentations

Anisotropy of electrical polarizability in Clostridium acetobutylicum cells during pH 5 controlled acetone butanol ethanol fermentations was observed. Cell length was determined from the electrooptical data. Mean length was determined as being 2.5 microm in the growth phase and 3.5 microm in the early stationary phase. Based on the obtained frequency dispersion of polarizability anisotropy (FDPA) in the range of 190 to 2,100 kHz, the switch from the acidogenic to the solventogenic phase could be monitored. The slope of polarizability versus the frequency made it possible to differentiate between phases of dominating acid and solvent production. Metabolite fluxes determined from concentration measurements correlated well to the polarizability. A partial least-squares (PLS) model was established and validated by applying data from several fermentations. The root mean square error of calibration (RMSEC) was 0.09 for the acid fluxes and 0.11 for the solvent fluxes. The root mean square error of prediction (RMSEP) was 0.20 for acid fluxes and 0.24 for solvent fluxes. The ratio of polarizability at high and low frequencies correlated to the ongoing sporulation process. At ratios below 0.25, spore formation in the cells became visible under the microscope. The advantage of using electrooptical measurements is the ability to observe metabolite fluxes rather than concentrations, which provides useful information on productivity during a bioprocess.

Reversing-pulse electric birefringence of multicomponent systems: The formulation and signal simulation for two axially symmetric components in equilibrium and the appearance of unusual signal patterns

This paper consists of two parts on reversing-pulse electric birefringence (RPEB) signal patterns. The first is the theoretical formulation of two axially symmetric models coexisting in equilibrium in solution. The present RPEB theory is based on the original Tinoco–Yamaoka theory with classical electric dipole moments, which was recently modified and extended by Yamaoka, Sasai, and Kohno to include various electric and optical parameters and most importantly the ion-fluctuation dipole moment 〈 m 3 2 〉 1 / 2 along the longitudinal direction of axially symmetric molecules. The theory contains the electric polarizability anisotropy Δ α′, which can be either positive or negative in relation to the shape of components. The overall signal can be expressed as the sum of the fractions of two components in proportions to the coefficient F 1 or F 2 (=1 − F 1). The second part is the simulation of theoretical RPEB curves for the two-component system with various sets of electric and hydrodynamic parameters for hypothetical but interesting cases. In consideration of the decay behavior, calculated decay curves were compared with experimentally conceivable signals, classifying them into three categories according to cases: F 1 > 1, 0 < F 1 < 1, and F 1 < 0. Showing humps and/or dips in profiles the simulated RPEB signal in buildup and reverse transients reveals the mechanism of field orientation and electro-optic properties of molecules in solution. The ratio q = 〈 m 3 2 〉 / k t Δ α ′ is the crucial factor that controls the pattern of RPEB signals. If q value of one component is positive and the other is negative, the simulated RPEB curves are characterized by three cases: q > 0, q < −1, and −1 < q < 0. If q > 0 or q < −1, the resultant patterns are often encountered with experimental signals. If −1 < q < 0, many anomalous signal patterns appears.

Anomalous electric birefringence behavior of sonicated DNA fragments as observed in reversing-pulse transients and steady-state sign reversal: A multicomponent approach

Anomalous electric birefringence signals of a sonicated and column-fractionated medium-size calf thymus DNA sample (bp = 570) in Na + solutions were measured at 7 °C. The reversing-pulse electric birefringence (RPEB) signal pattern was theoretically calculated in the low electric field region for two axially symmetric models coexisting in equilibrium in solution. The RPEB theory is based on the electric dipole moment due to ion-fluctuation along the longitudinal direction and the electric polarizability anisotropy (Δ α′), together with various electric and optical parameters assigned to the models. An analytical method was developed for the steady-state birefringence of the two-component system in a wide range of electric fields. The NaDNA samples exhibit complex RPEB patterns mixed with negative- and positive-going profiles. An experimental RPEB signal of NaDNA at an absorbance ( A 260) of 8 was fitted to theoretical curve at weak electric fields. The anomalous RPEB signal was attributed to the component 2, which shows a dip in the buildup and another in the reverse processes with a positive sign and a larger relaxation time. For the component 1, a normal DNA profile with negative sign is associated with a narrow dip in the reverse and a faster relaxation time in the decay signal. The field-strength dependence of observed steady-state birefringence δ(∞) could be fitted for NaDNA at A 260 = 8 by the SUSID orientation function with saturated ionic and electronic moments. An apparent positive maximum and the sign reversal in δ(∞) at weak electric fields is an interplay between the positive component 2 with positive optical factor Δ g and negative Δ α′ and the negative component 1 with negative Δ g and positive Δ α′. Possible conformation of two DNA components involved in solution was estimated.

Electric birefringence and streaming-electric birefringence of synthesized imogolite: The anisotropy of electric polarizability

Imogolite synthesized from sodium orthosilicate and aluminum trichloride was fractionated into four fractions by centrifuging at 12,000 × g (1 h). The supernatant, which did not deposit by three times centrifugations, was used for all measurements. The signal of birefringence under a reversing electric pulse showed that the permanent dipole moment is negligibly small at low fields. The electric birefringence under a rectangular electric pulse is positive. The saturated value is proportional to the concentration of imogolite in the range of 0–0.1 mg/ml and decreases rapidly with an increase of added salt concentration for NaCl and AgNO 3. It slightly depends on the pH of solution and is biggest in pure water. Then we have determined the anisotropy of electric polarizability (Δ α) for imogolite in pure water at 0.05 mg/ml. Δ α we obtained from the method decreases rapidly at low fields and slowly at high fields as shown in references [M. Matsumoto, Colloids Surf. A 148 (1999) 75, M. Matsumoto, Biophys. Chem. 58 (1996) 173]. It is approximately shown by the following expression, Δ α = Δ α ∞ + (Δ α 0 − Δ α ∞)/(1 + KE), (Δ α 0:Δ α at E = 0, Δ α ∞:Δ α at E = ∞). Using this relation we can draw the curve of electric birefringence as a function of electric field and compare it with experimental values. The results, when Δ α 0 = 1.17 × 10 −28 F m 2, Δ α ∞ = 0.005 × 10 −28 F m 2 and K = 0.00031 m/V, are in good agreement with each other. In order to explain the reason why the anisotropy of electric polarizability rapidly decreases with an increase of electric field we propose that the difference of electrophoretic mobility between parts of colloidal particle causes the orientation of a rod like particle. The theoretical electric birefringence as a function of electric field we obtained is considerably in good agreement with the experimental values.

Cotton–Mouton effect, magnetizability anisotropy and molecular charge distribution of boron trichloride

Abstract Measurements of the magneto-optical Cotton–Mouton effect of gaseous BCl3 over a range of temperature (295.6–361.9 K) are analyzed in conjunction with the known electric polarizability anisotropy, mean magnetizability, molecular quadrupole moment and molecular geometry to obtain the magnetizability anisotropy (Δχ=χzz−χxx) and related magnetic properties (χzz, χxx, Δχd, Δχp, gzz− 1 2 gxx) of this species. The observation that Δχ is negative in sign is consistent with Pauling's view of the molecular structure in terms of pπ–pπ interactions, ionic–covalent resonance, partial double bond character and electron delocalization.

Transient electric birefringence of colloidal particles immersed in shear flow: Part III: A preliminary report on determination of anisotropy of electric polarizability

We have constructed an electric birefringence apparatus having a flow cell with parallel platinum electrodes to measure the initial values and initial slopes of the transmitted light intensity in two cases. One is the case that the polarizer is at 0° to the electric field and 90° to the direction of flow; the other is the case that the polarizer is at 45° to the electric field and the direction of flow. By using theoretical relationships derived previously, we tried to estimate the anisotropy of electric polarizability, the axial ratio, the optical anisotropy factor and the velocity gradient for a fractionated bentonite solution. The signs of the optical anisotropy factor and parameter R related to the axial ratio as ( P 2−1)/( P 2+1) were easily determined. However, we could not obtain reliable values of the axial ratio and the optical anisotropy factor because it was difficult to maintain the same conditions in two different observations. On the other hand, it is easy to estimate the anisotropy of electric polarizability at various electric fields because it can be evaluated from one signal. The anisotropy of electric polarizability of bentonite particles had the same negative sign as Shah's conclusion. However, it was unexpected that its magnitude at low fields (<200 V/cm) increased rapidly with a decrease of electric field. The dependence of the steady-state birefringence on electric field also supports this result.

Anisotropy of Electrical Polarizability of a DNA Fragment

Abstract Metropolis Monte Carlo Brownian dynamics simulations are performed on model DNA solutions. It is shown that the induced dipole moment responsible for the orientation of a DNA fragment in an applied electric field may have its origin in the displacement of Manning’s condensed counterions along DNA rod axis.

Transient electric birefringence of colloidal particles immersed in shear flow. Part II. The initial response under the action of a rectangular electric pulse and the behavior at a low alternating electric field

The time-dependent rotational diffusion equation for rigid macromolecules in solution has been approximately solved for two cases in order to extend the electric birefringence technique to streaming-electric birefringence. One is for the initial period through the application of a rectangular electric pulse to the solution immersed in a low shear flow. The purpose of this is expansion of the distribution function into a function series made by the product of the powers of reduced time (= Θt) and hydrodynamic field α ( = G Θ , G: velocity gradient, Θ: rotary diffusion constant) and a surface harmonic P i j cos jφ. The solution for the build-up process at arbitrary electric field strength is found, but is limited to low hydrodynamic fields. The other is for the response when an alternating electric field is applied to the solution in a shear flow. Here, instead of reduced time, the maximum electric field E 0 is chosen as a parameter for the expansion. The expressions for the intensity of the transmitted light through crossed Nicols are derived in two optical systems where the polarizer is set at an angle of 45° and 0° to the direction of the electric field. The results in the former case show that we can determine four parameters, the ratio of velocity gradient to rotary diffusion constant, the axial ratio of a particle, the anisotropy of electric polarizability, and the optical anisotropy factor, from four values observed in two optical systems, namely, two light intensities before applying an electric field and two initial slopes of the build-up after applying an electric field. On the other hand, when a low alternating electric field with extremely high frequency is applied, the build-up of the light intensity in the former case is the same as that of electric birefringence for pure induced dipole orientation. The build-up for the latter optical system is the same as the expression for pure induced dipole orientation of Eq. (38) shown in a previous work.

Radio frequency spectra of chloroacetylene in v=0 and v=1 of the C–H stretching vibration

Radio frequency spectroscopy has been carried out on molecular beams of chloroacetylene to yield Stark and chlorine hyperfine properties for the ground and excited C–H stretching vibrational states. For HCC35Cl v=0, μ=0.440 079(1) D, eQq=−79 733.59(4) kHz, and CCl=1.412(4) kHz. For HCC35Cl v=1, μ=0.462 792(1) D, eQq=−79 744.59(5) kHz, and CCl=1.398(3) kHz. For HCC37Cl v=0, μ=0.439 954(1) D, eQq=−62 839.68(9) kHz, and CCl=1.142(6) kHz. For HCC37Cl v=1, μ=0.462 778(1) D, eQq=−62 848.64(10) kHz, and CCl=1.127(8) kHz. The above results are for J=1 levels, while J=1 and J=2 Stark data for the ground state were combined to give an electric polarizability anisotropy, α∥–α⊥=3.87(2) Å3.

Dielectric behavior of polyelectrolytes. IV. Electric polarizability of rigid biopolymers in electric fields.

The equilibrium Kerr effect of a system of mobile charges constrained to the surface of biomacromolecules is calculated. Cylindrical and spherical geometries are considered. For the cylinder we determine the anisotropy of electric polarizability as a function of length, temperature, and number of charged species in the low-field regime, and the fraction of the maximum induced dipole in the field direction for higher electric fields. The results are compared to experimental data for DNA oligomers taken from the literature. With spherical geometry we calculate the fractional induced dipole moment as a function of electric field strength and from this deduce the orientation function. The field dependence of the orientation function is compared to experimental data in the literature for bovine disk membrane vesicles.

Reversing‐pulse electric birefringence of poly (γ‐benzyl‐L‐glutamate). II. Field‐strength dependence of steady‐state and decay signals of well‐fractionated samples

AbstractThe electric field dependence (up to 21 kV/cm) of the steady‐state and decay signals has been examined on the four well‐fractionated samples of poly(γ‐benzyl‐L‐glutamate), [Glu(OBzl)]n, in N,N‐dimethylformamide at 535 nm and 20°C. Together with the data previously obtained from the reversing‐pulse electric birefringence [Ueda, K., Nomura, M. &amp; Yamaoka, K. (1983) Biopolymers 22, 2077–2090], the steady‐state birefringence and field‐free relaxation time were analyzed by a method that takes into account the polydispersity of the chain length. The weight‐average chain length, (lw), permanent dipole moment, (μw), electric polarizability anisotropy, (Δαw), and the length‐independent optical anisotropy factor were evaluated. The axial translation per residue was calculated for the [Glu(OBzl)]n helix, but the uncertainly involved in the weight‐average molecular weights, determined from light scattering by different investigators, makes the determination of the exact conformation of [Glu(OBzl)]n difficult. The contribution of Δαw to electric field orientation was found to be significant, since Δαw was approximately proportional to lw. A linear relationship also exists between μw and lw, when the [Glu(OBzl)]n helix is shorter than about 1200 Å.

Reversing‐pulse electric birefringence of poly(γ‐benzyl‐L‐glutamate). I. Transient behavior of fractionated samples in the low electric field region

AbstractReversing‐pulse electric birefringence (RPEB) was measured for the first time for four fractionated poly(γ‐benzyl‐L‐glutamate), [Glu(OBzl)]n, samples in N,N‐dimethylformamide (DMF) at 20°C and at 535 nm. The RPEB signal showed a deep minimum for each sample on reversal of an applied electric field. The profiles of the reverse‐transient signal were analyzed by taking into account the polydispersity for the continuous distribution of molecular lengths. The best set of three quantities (lw, lw/ln, (βw)2/2γw), which determine a signal profile, was evaluated for each sample. By combining the experimental data of intrinsic viscosity and RPEB, the diameter of a cylinder, which is assumed for the [Glu(OBzl)]n helix, was found to be 17 Å. The value (βw)2/2γw, which is related to the ratio of weight‐average permanent dipole moment μw, and electric polarizability anisotropy Δαw, was found to be in the range of 20–45. This indicates that the former contributes predominantly to electric field orientation, but the latter also should not be ignored. With the three parameters from the reverse portion, the rise and decay curves were regenerated theoretically in excellent agreement with experimental signals.

Electric Field Orientation of Poly(p-styrenesulfonate) and Its 9-Aminoacridinium Complex as Studied by Square-pulse Transient Electric Birefringence

Abstract Electric birefringence was measured at 20 °C and at 535 nm for sodium poly(p-styrenesulfonate) (NaPSS), with and without added sodium chloride, and the 9-aminoacridinium (AA) complex in aqueous solutions. The field strength dependence of both the steady-state EB (Δn(∞)) the field-free decay time (〈τ〉EB) was examined. Charge suppression by added Na+ ions or neutralization by strongly bound AA decreased both Δn(∞) and 〈τ〉EB considerably, altering not only the optical factor Δg and electric moments, but also the backbone chain length. The weight-average values of chain length (lw), pseudopermanent dipole moment (μw), counterion-induced electric polarizability anisotropy (Δαw), and the length-independent values of Δg were estimated by analyzing the experimental data on the basis of the “classical” orientation function which takes into account the continuous distribution of chain length for the polydisperse NaPSS sample. The electric field orientation of NaPSS and the AA-complex could be described by the interaction between an applied field and the electric moment which transforms from counterion-induced type in the extremely low field region (&amp;lt;1.5 kV/cm) to saturated induced permanent type at higher fields.

Electric and optical anisotropy and their osmotically induced changes of photoreceptor disk membrane vesicles.

Electro-optical characterization of the photoreceptor disk membrane vesicle is performed by examining the electric field and concentration dependence of the study-state birefringence of aqueous suspensions of the vesicles. The electric polarizability anisotropy is found to be negative and of large magnitude: alpha 1 - alpha 2 = -(1-3) X 10 cm3. The optical anisotropy is determined to be also negative but of small magnitude: g 1 - g 2 = -1 X 10(-7). The specific Kerr constant deduced from the concentration dependence of the Kerr constant is found to be very large: Ksp = 7 X 10(-4) e.s.u. Upon deforming the vesicles osmotically from the spherical shell to the disk structure, the steady-state birefringence increases by an order of magnitude which is attributed solely to the increase in optical anisotropy attending the corresponding change in the geometric eccentricity of the vesicle. A plausible birefringence mechanism based on the known structural features of the vesicles is proposed, which would account for these findings.

Stark hyperfine structure of hydrogen bromide

The ν=0, J=1,2 hyperfine spectra of hydrogen bromide have been measured with a molecular beam electric resonance spectrometer at electric fields of 1500–3500 V/cm. The hyperfine structure parameters were determined for H 79.81Br and D 79.81Br. The quadrupole interaction ratios are The distance derivative of the electric field gradient at the site of the bromine nucleus was determined to be d (q/qe)/d ([R−Re]/Re) =1.556(3). The magnetic octupole interaction of the bromine nucleus was negligible ‖ewΩ‖&amp;lt;0.5 Hz. The electric polarizability anisotropy was measured to be (α∥−α⊥) =0.37(9) Å3. The same technique was used for DCl with the result (α∥−α⊥) = 0.23(3) Å3. Numbers in parenthesis are uncertainties in the final figures.

The microwave stark effect in oxygen

The Stark effect of the 118 GHz oxygen transition has been observed. From measured frequency shifts in strong electric fields, the sign and magnitude of the electric polarizability anisotropy were found to be α‖ - α⊥ = 1.12 ± 0.07 A 3.

Electric and hydrodynamic properties of polypeptides in solution. 3. Aggregation of poly(L-glutamic acid) in aqueous methanol solvents studied by electric birefringence.

AbstractThe rise and decay of electric birefringence for poly(L‐glutamic acid) (PLGA) in aqueous solvents containing 20 and 10 vol % methanol have been found to be unusual. The decay curves have been analyzed on the assumption that there exist two kinds of particles, namely, one (component I) with a shorter relaxation time exhibiting positive birefringence and the other (component II) with a longer relaxation time exhibiting negative birefringence at low fields. From the field strength dependence of the steadystate birefringence the permanent dipole moment, the anisotropy of electric polarizability, and the saturation value of birefringence have been determined for each component. Furthermore, from the relaxation time the length of component I and the diameter of component II have been computed on the models of cylindrical rod and oblate ellipsoid, respectively. The dipole moment, the anisotropy of electric polarizability, and the relaxation time of component II are much larger than those of component I. Both the anisotropy of electric polarizability and the optical anisotropy factor are positive in sign for component I and negative for component II. It is concluded that component I is the helical PLGA molecule itself and component II is the side‐by‐side (antiparallel) aggregate composed of many helical PLGA molecules. The optical anisotropy factor of each component has been discussed on the basis of Peterlin‐Stuart theory.

Electrooptical study of the electric polarizability of rodlike fragments of DNA.

AbstractThe anisotropy of electrical polarizability of rodlike fragments of DNA has been studied by a number of electro‐optical methods: Kerr effect (combined with flow birefringence), light scattering, diehroism, and fluorescence in an electric field. The most sensitive technique (Kerr effect) has been used to study the variation of the polarizability with the nature and concentration of counteroins. DNA fragments constitute a truly rigid polyelectrolyte of known structure. The value obtained can then be quantitatively compared to the predictions of those of the theories of the longitudinal polarizability of rigid polyelectrolytes which are based on true molecular parameters. The comparison emphasizes the role of the counterion–counterion repulsion. Oosawa's theory seems to represent the best approach but fails to explain the differences observed between monovalent and divalent ions.