Dependence Of Interparticle Distance Research Articles

Screening length in dusty plasma crystals

Particles interaction and value of the screening length in dusty plasma systems are of great interest in dusty plasma area. Three inter-particle potentials (Debye potential, Gurevich potential and interaction potential in the weakly collisional regime) are used to solve equilibrium equations for two dusty particles suspended in a parabolic trap. The inter-particle distance dependence on screening length, trap parameter and particle charge is obtained. The functional form of inter-particle distance dependence on ion temperature is investigated and compared with experimental data at 200-300 K in order to test used potentials applicability to dusty plasma systems at room temperatures. The preference is given to the Yukawa-type potential including effective values of particle charge and screening length. The estimated effective value of the screening length is 5-15 times larger than the Debye length.

Surface plasmon near-field resonance characteristics of silver shell nanocylinders arranged in triangular geometry

The optical near-field surface plasmon effects of a triangular system of silver nanoshell cylinders are numerically studied using the two-dimensional finite difference time domain method. The dependence of interparticle distance, shell thickness of the cylinder, dielectric constant of shell core as well as embedding medium, and orientation of the optical source plane on the plasmonic resonances of the nanocylinder shells is studied. The plasmonic resonances are found to have strong dependence on the interparticle distance. As the size of the particle is increased, the field intensity peak shows a redshift. The resonance condition varies with the dielectric constant of the environment as well as the core. In addition, the orientation of the incident source plane has a significant role in the near-field intensity distribution. Since the near-field intensity has the same trend as that of the scattering cross section, the results can be used in the design of various applications like sensing, antennas, and waveguides.

Tunable SERS in Gold Nanorod Dimers through Strain Control on an Elastomeric Substrate

In this Letter we provide experimental verification of the interparticle distance dependence of the SERS enhancement factor in 1 μm gold gapped nanorods. Au dimers are fabricated from electrochemically grown heterogeneous Au-Ag-Au nanorods and deposited on a stretchable elastomer film which allows active and reversible tuning of the interparticle gap on the sub-5-nm level. Significantly, this technique allows the distance dependence to be tracked using a single dimer, thereby avoiding enhancement factor reproducibility issues arising from morphological differences in disparate nanoparticle pairs.

Gold and magnetic oxide/gold core/shell nanoparticles as bio-functional nanoprobes

The ability to create bio-functional nanoprobes for the detection of biologicalreactivity is important for developing bioassay and diagnostic methods. Thispaper describes the findings of an investigation of the surface functionalization ofgold (Au) and magnetic nanoparticles coated with gold shells (M/Au) byproteins and spectroscopic labels for the creation of nanoprobes for use insurface enhanced Raman scattering (SERS) assays. Highly monodispersed Aunanoparticles and M/Au nanoparticles with two types of magnetic nanoparticle cores(Fe2O3 and MnZn ferrite) were studied as model systems for the bio-functionalization and Ramanlabeling. Comparison of the SERS intensities obtained with different particle sizes(30–100 nm) and samples in solution versus on solid substrates have revealed importantinformation about the manipulation of the SERS signals. In contrast to the salt-induceduncontrollable and irreversible aggregation of nanoparticles, the ability to use acentrifugation method to control the formation of stable small clustering sizes ofnanoparticles was shown to enhance SERS intensities for samples in solution as comparedwith samples on solid substrates. A simple method for labeling protein-capped Aunanoparticles with Raman-active molecules was also described. The functionalized Au andM/Au nanoparticles are shown to exhibit the desired functional properties for the detectionof SERS signals in the magnetically separated reaction products. These results arediscussed in terms of the interparticle distance dependence of ‘hot-spot’ SERS sites and thedelineation of the parameters for controlling the core–shell reactivity of the magneticfunctional nanocomposite materials in bio-separation and spectroscopic probing.

Supertoughness and critical interparticle distance dependence in poly(butylene terephthalate) and poly(ethylene‐co‐glycidyl methacrylate) blends

AbstractSupertough poly(butylene terephthalate) (PBT)‐based blends were obtained by the melt blending of PBT with 0–30 wt % poly(ethylene‐co‐glycidyl methacrylate) (EGMA). The reaction between PBT and EGMA was detected by torque measurements. The particle size was almost constant with increasing EGMA content, and this indicated that compatibilization occurred. The minimum EGMA content for achieving supertoughness (i.e., an impact strength 16 times greater than that of PBT) was 20 wt %. The interparticle distance was the parameter controlling toughness in these PBT/EGMA blends. The dependence of the critical interparticle distance (τc) on the modulus of the dispersed phase appeared only at low τc values, and the primary dependence of τc on the ratio of the modulus of the matrix to the modulus of the rubbery dispersed phase was proposed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2236–2247, 2003

Critical inter-particle distance dependence and super-toughness in poly(butylene terephthalate)/grafted poly(ethylene-octene) copolymer blends by means of polyarylate addition

New super-tough poly(butylene terephthalate) (PBT) materials were obtained modifying with 10 wt% polyarylate (PAr) a PBT/maleic anhydride grafted poly(ethylene-octene) copolymer (mPEO) blend with mPEO contents from 0 to 30 wt%. PAr was fully miscible in the PBT phase. The presence of mPEO did not influence either the nature or the crystallinity of the PBT–PAr matrix. The decrease in interfacial tension and particle size upon grafting of PEO, indicated that compatibilization took place. The maximum toughness obtained was very high (impact strength more than twenty-fold that of the PBT–PAr matrix). Moreover, it was attained with only 7.5% PEO maleinized at 0.63%, and was accomplished by an increase in stiffness of the blends. The successful modification of the matrix consolidates this method as a new one to improve impact toughness. The critical inter-particle distance ( τ c) appears as the parameter that control super-toughness in these blends, and it is proposed to depend on adhesion measured by means of the interfacial tension.

Electrophoretic and Structural Studies of DNA-Directed Au Nanoparticle Groupings

Discrete Au nanoparticle/DNA conjugates have been isolated by electrophoresis and used to form small groupings of particles, such as dimers and trimers. The use of purified conjugates leads to a higher yield of the target structure, and it has allowed us better control and understanding of the system. Newly accessible questions, such as the electrophoretic mobility of nanoparticle/DNA hybrids and the critical role of particle surface charge on mobility, have been studied. Detailed characterization by transmission electron microscopy (TEM) has now been done because of the higher quality of the samples. A computer program to generate pair distribution functions from TEM images was developed, pointing out the dependence of interparticle distance with DNA length on dimers of particles.

The mystery of colloidal crystal formation — novel aspects obtained by ultra-small-angle X-ray scattering

We describe our recent ultra-small-angle X-ray (USAXS) data for the structure of colloidal crystals. Information on the three dimensional ‘bulk’ structure of colloidal crystals can be obtained using USAXS, and the interparticle distance estimated from the Bragg peak in the USAXS profile shows a maximum as a function of added salt concentration (i.e. ionic strength). Since all types of latex particles used in the experiments show a similar trend, this phenomenon, i.e. the existence of ‘a maximum’, can be said to be universal. This maximum position appears at κa=1.3 ( κ −1: the Debye length, a: the particle radius). By theoretically analyzing the USAXS profiles, we have quantitatively estimated the distortion of the lattice structure of colloidal crystals. This analysis revealed that the maximum point corresponds to the ‘melting’ point of colloidal crystals. The dependence of interparticle distance on added salt at κa>1.3, where colloidal particles form liquid-like structures, can be explained by the classical theories, such as the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, but that at κa<1.3, where colloidal particles form solid-like crystals, can not be accounted for by current theories and concepts. We also found by USAXS that the colloidal crystal structure is affected largely by the counterion species: when the counterions are changed from H + to Na + without changing ionic strength, the interparticle distance and the distortion of crystals increase. These USAXS results, which appear to be quite mysterious but interesting, lead to a possible new mechanism underlying the colloidal crystal formation. Colloidal crystal formation might still have mysterious aspects but our USAXS data will certainly help solve this mystery and will open the door to a new world of colloid science.

Exact Evaluation of the Salt Concentration Dependence of Interparticle Distance in Colloidal Crystals by Ultra-Small-Angle X-ray Scattering. 4. Effect of Counterion Species and the Possibility of New Factors for Colloidal Crystal Formation

In our previous papers (Langmuir 1994, 10, 4423; 1996, 12, 5588; 1999, 15, 573), we have reported the salt concentration dependence of interparticle distance in colloidal crystals formed in highly charged colloidal dispersion by performing ultra-small-angle X-ray scattering (USAXS). We found that the interparticle distance−salt concentration relationship had a maximum at κa = 1.3 (κ-1, Debye length; a, particle radius). This result could not be explained by current theories proposed for colloidal stability, such as the Derjaguin−Landau−Verwey−Overbeek (DLVO) theory. From the results of our previous USAXS study, we thought that the interpenetration of ionic clouds around particles and counterion sharing effect play an important role for the formation of colloidal crystal. In this study, we have investigated the added NaOH dependence, i.e., the degree of neutralization dependence of strong acid group at particle surface (a), on the nearest interparticle distance (2Dexp) in colloidal crystals by the USAXS te...

An Exact Evaluation of Salt Concentration Dependence of Interparticle Distance in Colloidal Crystals by Ultra-Small-Angle X-ray Scattering. 3. Confirmation of Solid−Liquid Transition by Three-Dimensional Paracrystal Analysis

In our previous works (Langmuir 1994, 10, 4423; 1996, 12, 5588), we performed a systematic ultra-small-angle X-ray scattering (USAXS) study for structure and its change as a function of salt concentration very carefully and found that the interparticle distance in colloidal crystal showed a maximum at κa = 1.3 (κ-1, Debye length; a, radius of particle). This observation could not be explained by present concepts and theories for colloidal interaction like Derjaguin−Landau−Verwey−Overbeek (DLVO). However, it was confirmed that this phenomenon is universal by experiments for various latex particles which were different in size and charged state. By the analysis of the interparticle structure factor, S(q), it was suggested that the point at κa = 1.3 is the solid−liquid transition point. In this study, the USAXS data have been further analyzed by three-dimensional (3D) paracrystal theory to obtain more quantitative information about this curious, unexpected phenomenon. The S(q) profiles obtained by USAXS were excellently reproduced by the 3D-paracrystal lattice factor, Z(q), for face-centered cubic symmetry. The g-factor, which represents the degree of distortion, was found to be about 0.1−0.15 near the transition point, which was in good agreement with α*-law for solid−liquid transition. Possible new factors, which should be taken into account to explain this phenomenon, were duly discussed.

Exact Evaluation of the Salt Concentration Dependence of Interparticle Distance in Colloidal Crystals by Ultra-Small-Angle X-ray Scattering. 2. The Universality of the Maximum in the Interparticle Distance−Salt Concentration Relationship

We have investigated the salt concentration dependence of the interparticle distance in colloidal crystals in dispersion by the ultra-small-angle X-ray scattering (USAXS) technique. USAXS gives us ...