Effective Number Of Carriers Research Articles

Combinatorial Synthesis of Alkyl Chain-Capped Poly(β-Amino Ester)s for Effective siRNA Delivery.

Poly (β-amino ester) (PBAE) is a class of biodegradable polymers containing ester bonds in their main chain, extensively investigated as cationic polymer carriers for siRNA. Most current PBAE carriers rely on termination with hydrophilic or charged amines. In this study, a polymer platform consisting of 168 PBAE polymers with hydrophobic alkyl chain terminals is constructed through sequential aza-Michael addition. A large number of effective carriers are identified through in vitro screening of the PBAE platform for siLuc delivery to HeLa-Luc cells. Specifically, PA8-C6 and PA8-C8 achieve remarkable gene knockdown efficacies of up to 80% with low cytotoxicity. Certain materials from the PA2 and PA5 series demonstrate potent siRNA delivery capabilities associated with elevated cytotoxicity. The pKa value of PBAE is predominantly determined by the hydrophilic amine side chains rather than the end-capping groups. A pKa range of ≈6.2-6.5 may contribute to the excellent delivery capability for PA8 series carriers. The co-formulation of PBAE carriers with helper lipids leads to the reduced size and surface charges of the polyplex NPs with siRNA, consequently decreasing the cytotoxicity and enhancing siRNA delivery efficacy. These findings hold significant implications for the development of novel degradable polymer carriers for siRNA delivery.

Understanding the emergence of negative photoconductivity in CVD grown ReS2 thin films by invoking the trion generation mechanism.

Emerging from robust coulombic interactions and diminished dielectric screening, two-dimensional transition metal dichalcogenides (2D TMDs) manifest strongly bound excitons. While these pronounced many-body effects have been observed in 2D TMDs, their impact on the materials' intrinsic photoconductive characteristics remains relatively less explored. In this study, a considerable reduction in photoconductivity in chemical vapor deposited (CVD) ReS2 thin films has been observed. Through experimental and theoretical scrutiny, it is deduced that this anomalous phenomenon stems from the possible many-body interactions within the system, wherein photoexcited electron-hole pairs combine with excess electrons to generate trions. The formation of trions reduces the effective number of carriers contributing to photocurrent, thereby attenuating the photoconductivity. This study shows the profound influence of trions on the photoconductivity behaviour of ReS2 thin films, thereby elucidating their significance in modulating optical and electrical properties crucial for optoelectronic applications.

Enhanced catalytic activity of Molar-like BaTiO3 by oxygen vacancies

Oxygen vacancies are found to have significant effects on the piezo-photocatalytic performance. For this reason, Molar-like and Bamboo-like BaTiO3 with the same tetragonal phase are synthesized by a two-step hydrothermal method. Molar-like BaTiO3 exhibits a superior piezo-photocatalytic performance by degrading the organic dye indigo carmine (IC), whose kinetic constant of 0.099 min−1 is 1.80 times higher than that of Bamboo-like BaTiO3. The same conclusion is drawn while the differences in specific surface areas are eliminated. There are more oxygen vacancies in Molar-like BaTiO3 compared to Bamboo-like BaTiO3, as shown in XPS results. The oxygen vacancies are favorable for light adsorption and O2 activation, thus an excellent photocatalytic performance is achieved. XRD refinements show that Molar-like BaTiO3 has a slightly higher content of piezoelectric tetragonal phase and stronger lattice distortion than Bamboo-like BaTiO3. However, the piezoelectric polarization of Molar-like BaTiO3 is weakened and the number of effective carriers is reduced due to more oxygen vacancies. The presented work provides a profound reference for the structural design of catalysts.

Nanoscale Confinement Effects on Ionic Conductivity of Solid Polymer Electrolytes: The Interplay between Diffusion and Dissociation.

Solid polymer electrolytes (SPEs) are attractive for next-generation lithium metal batteries but still suffer from low ionic conductivity. Nanostructured materials offer design concepts for SPEs with better performance. Using molecular dynamics simulation, we examine SPEs under nanoscale confinement, which has been demonstrated to accelerate the transport of neutral molecules such as water. Our results show that while ion diffusion indeed accelerates by more than 2 orders of magnitude as the channel diameter decreases from 15 to 2 nm, the ionic conductivity does not increase significantly in parallel. Instead, the ionic conductivity shows a nonmonotonic variation, with an optimal value above, but on the same order as, its bulk counterparts. This trend is due to enhanced ion association with decreasing channel size, which reduces the number of effective charge carriers. This effect competes with accelerated ion diffusion, leading to the nonmonotonicity in ion conductivity.

Marker-assisted introgression of fecundity mutation into Barbarine sheep breed under low input production system

Fecundity gene introgression has become an economical method to improve sheep prolificacy in developing countries. The FecXBar and FecGHmutations are variants of the BMP15 and GDF9sheep genes,respectively, identified in Tunisian Barbarine sheep prolific line "W-INRAT," created through a prolificacy-based selection program. The firstmutation caused increased prolificacy in heterozygous state and sterility in homozygous ewes. The aim of this work was to increase the number of effective carriers by the introgression of fecundity mutation into non-carrier conventional flocks based on a marker-assisted breeding program. The genotyping was carried out to follow up on the segregation of prolificacy mutation. The conventional ewes, raised in state farms of Tunisia and inseminated by "W-INRAT" rams, yielded 100% carriers females at heterozygous state. These females were selected to be inseminated with conventional rams and produced carriers' lambs with 66.7% males and 33.3% females. The prolific males will be kept in breeding centers to disseminate the fecundity mutation in commercial flocks. This approach facilitates the dissemination of fecundity genes and contributes to livelihood improvement in communities raising Barbarine sheep.

Performance Enhancement of Moisture-driven Power Generators by Photofragmentation of Inorganic Salt Particles.

We developed a novel method based on the photofragmentation of inorganic salt particles for improving the moisture-electric energy transformation performance of a moisture-driven power generator (MPG). Infrared laser irradiation on cellulose nanofiber films (CNFs) prepared by a TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation of bleached pulp induced a photothermal conversion of CNFs to porous graphitic carbon films (GCFs) with the catalyst-derived Na2O2 particles. Since the laser beam was focused on the top surface of CNF, the gradients of the photothermal conversion of CNFs and Na2O2 concentration were created along the thickness direction. Subsequent irradiation with ultraviolet (UV) light induced the photofragmentation of the micrometer-sized Na2O2 particles into smaller ones, which increased the surface area of the salt particles in contact with the GCFs and consequently increased the number of effective dissociable charge carriers. When the GCF was exposed to moisture, the dissociated sodium ions migrated along the preformed concentration gradient, producing continuous outputs of current and voltage. At 90% relative humidity, the maximum voltage and current density outputs of the MPG increased from 0.91 V and 18.7 μA/cm2 before UV irradiation to 1.10 V and 56.2 μA/cm2 after UV irradiation, respectively. Additionally, we demonstrated that a green light-emitting diode could be turned on without capacitors or rectifiers during normal breathing while wearing a face mask with three GCF arrays attached (each 3 mm × 3 mm × 0.1 mm in size).

Effect of Nanoscale Confinement on Ultrafast Dynamics of Singlet Fission in TIPS-Pentacene.

Singlet fission (SF) is a phenomenon for the generation of a pair of triplet excitons from anexcited molecule in singlet electronic state interacting with another adjacent molecule in its ground electronic state. By increasing the effective number of charge carriers and reducing thermal dissipation of excess energy, SF is promised to enhance light-harvesting efficiency for photovoltaic applications. While SF has been extensively studied in thin films and crystals, the same has not been explored much within a confined medium. Here, we report the ultrafast SF dynamics of triisopropylsilylethynyl pentacene (TIPS-Pn) in micellar nanocavity of varying sizes (prepared from TX-100, CTAB, and SDS surfactants). The nanoparticles with a smaller size contain weakly coupled chromophores which are shown to be more efficient for SF followed by triplet generation as compared to the nanoparticles of larger size which contain strongly coupled chromophores which are less efficient due to the presence of singlet exciton traps. Through these studies, we delineate how a subtle interplay between short-range and long-range interaction among chromophores confined within nanoparticles, fine-tuned by the curvature of the micellar interface but irrespective of the nature of the micelle (cationic or anionic or neutral), play a crucial role in SF through and generation of triplets.

Comparison of the electronic transport of ThN against ThC

We compared the electronic heat capacity coefficient, thermal conductivity and resistivity of ThN and ThC. We found that the electronic heat capacity coefficient of both compounds was very low as evaluated using Quantum Espresso and GGA of the Perdew, Burke, and Ernzerhof (PBE) functional. The calculated electronic heat coefficient was further reduced (∼three times for ThN and four times for ThC) when the non-local hybrid functional (B3LYP) was used. QE combined with EPW code were used to calculate integrated electron-phonon coupling strength, the Eliashberg transport coupling function and electron-phonon scattering rates. The electronic resistivity was calculated using Ziman's formula for metals as implemented in EPW code and compared to the values derived from experimental data correlations. Furthermore, the effective number (neff) of electronic carriers was calculated. The electronic thermal conductivity was evaluated from the calculated electronic resistivity via Wiedemann-Franz law using the derived number of mobility electrons: nav (averaged over the temperature range 300 K–1000 K). We found that the only way to reproduce exactly the experimental electrical resistivity and electronic thermal conductivity in both ThN and ThC was to incorporate the number of electrons contributing to thermal mobility (neff), which increase with temperature. We estimated that in ThN the number of electronic carriers is two times larger and electron-phonon coupling strength lower by a factor ∼ two, which led to about five times higher electronic thermal conductivity than calculated for ThC.

Physical properties of rhodium retrieved from modeling its dielectric function by a simulated annealing approach

Optical, charge carriers transport, quantum mechanics, magnetic, thermal, and plasmonic properties of the transition metal rhodium are considered. An extended Drude-Lorentz (DL) model is applied to describe the dielectric function (DF) of rhodium in a spectral range going from the mid-infrared (12.4 μm) to the vacuum ultraviolet (32 nm). The Drude term of the DF includes, as optimization parameters, the inverse of the high frequency dielectric constant, the volume plasma frequency and scattering frequency of the electrons, the scattering frequency of holes relative to that of electrons, the ratio between the effective masses of electrons and holes, the number of holes per atom relative to that of electrons, and the renormalized times between grain boundary scattering events for electrons and holes. The Lorentz contribution to the DF includes the number of conduction electrons per atom, the oscillator strengths, the resonance energies, and the Lorentzian widths. Values of the parameters involved in the DF are optimized by an acceptance-probability-controlled simulated annealing method that minimizes spectral differences between the real and imaginary parts of the DF values obtained from the literature and those evaluated from the DL parametric formulation, accounting for the presence of electrons and holes as charge carriers. Once an optimized spectral description of the DF of rhodium is obtained, a large set of charge-transport, magnetic, thermal, plasmonic, and quantum mechanics derived quantities are evaluated: mobilities, relaxation times, Fermi velocities, effective masses, electrical and thermal conductivities, heat capacity coefficients, Hall coefficient, diamagnetic and paramagnetic susceptibilities, effective number of Bohr magnetons, Fermi energies and corresponding densities of states, energy loss functions, effective number of charge carriers participating in conduction, and effective number of electrons involved in inter-band transitions.

Statistical Analysis of the Photoelectric Characteristics for InGaN/GaN MQWs Solar Cells Following Proton Irradiation

The statistical photoelectric properties of InGaN/GaN MQWs solar cells under proton irradiation were studied. Three groups of devices were irradiated with 3 MeV proton beams with fluences of 1.0 × 1011 cm−2, 5.0 × 1011 cm−2, and 1.0 × 1012 cm−2. Averaged experiment results showed that the open circuit voltage (VOC) and fill factor (FF) always decreased. In contrast, the short circuit current density (JSC) and photoelectric conversion efficiency (η) increased first and then decreased with the increase of fluence. Firstly, the donor-like defects of InGaN layer in active region played a major role in increasing JSC and η when the fluence was relatively low. Due to the introduction of donor-like defects, extra free electrons were produced, which lead to an increase in the number of effective carriers. With the further increasing of proton fluence, the number of free electrons caused by donor-like defects in the used InGaN material (low indium component) increased slowly due to pinning effect. However, additional point defects (Ga vacancies) increased significantly. Ga vacancies can act as effective non-radiative recombination centers, thereby reducing the number of effective carriers. The combined effect of pinning effect and non-radiative recombination process is responsible for the first increase and subsequent decline of JSC and η.

Anomalous terahertz dielectric phase in charge-ordered La1/3Sr2/3FeO3 thin film

Orthoferrites are the model systems for understanding the origin of complex valance-skipping charge ordering (CO) associated with antiferromagnetic spin ordering as a sequence of Fe+3Fe+3Fe+5Fe+3Fe+3Fe+5 … along the pseudocubic (111) direction. Here, we have investigated the low-energy dynamics of one such system La1/3Sr2/3FeO3 along the (111) crystal orientation using terahertz (THz) time domain spectroscopy. The temperature dependent THz optical constants reveal a purely electronic semiconductor to a charge-ordered Mott insulator transition, which is contrary to the reported metal–insulator transition. Above the transition of ∼180 K, THz conductivity shows a thermally activated charge-carrier hopping type conduction with activation energy 92.7 meV (87.3 meV) when measured in cooling (heating). The dielectric constant also indicates that the charge ordering formation starts at 200 K, which exists down to 20 K. Further analysis shows a reduction in the effective number of carriers by a fraction of about six as temperature decreases from 300 K to the CO transition at 200 K; this depletion of carriers triggers the intersite interactions required for CO. These findings suggest that a high dielectric constant associated with charge order in the THz region could be useful for THz applications in communication.

Decoupling mobility and charge carrier concentration in AgR-AgPO3 glasses (R = Cl, Br, I)

Halide-containing silver phosphate glasses have been used as model systems for the study of the ionic conductivity of oxide glasses for the past 50 years, mostly due to the massive increase in conductivity observed as the halide concentration is increased, even if the molar ratio of silver is kept constant. Furthermore there is still no consensus if the increased conductivity is due to an enhancement of the number of effective charge carriers (glass as a weak electrolyte) or a higher charge carrier mobility (glass as a strong electrolyte). In this work we investigate the electrical properties of silver-halide-containing silver metaphosphate glasses through Impedance Spectroscopy. We find the glasses to follow the “canonical scaling”, which coupled with the diffusional nature of the conductivity allows us to show that the number of effective charge carriers remains constant with increasing halide concentration, and that the conductivity follows the same scaling as the ionic mobility.

Construction of Self‐Healing Internal Electric Field for Sustainably Enhanced Photocatalysis

AbstractThe construction of internal electric field is generally considered an effective strategy to enhance photocatalytic performance due to its significant role in charge separation. However, static internal electric field is prone to be saturated either by inner or outer shield effect, and thus its effect on the improvement of photocatalysis can easily vanish. Here, the self‐healing internal electric field is proposed and successfully endowed to a designed helical structural composite microfiber polyvinylidene fluoride/g‐C3N4 (PVDF/g‐C3N4) based on the bioinspired simple harmonic vibration. Importantly, the saturation and recovery of internal electric field are characterized by transient photovoltage and photoluminescence. The results indicate that the internal electric field could be saturated within about 10 min and refreshed with the assistance of rebuilt piezoelectric potential. The lifetime of photogenerated carriers is about 10−4 s and the number of effective carriers is greatly increased in the presence of self‐healing internal electric field. The results provide direct experimental evidence on the role of self‐healing internal electric field in charge transfer behavior. This work represents a new design strategy of photocatalysts, and it may open up new horizons for solving energy shortage and environmental issues.

Comments on the 2018 ESC/EACTS Guidelines for Myocardial Revascularization

A softening of bending mode and a hardening of stretching mode on cooling are observed in infrared spectra of La0.25Ca0.75MnO3 nanoparticles with particle sizes (D) of 40–1000 nm, indicating part of melting charge ordering in the samples. The particle size variations of the inverse of effective number of carriers neff∗ and optical gap show their maxima around D = 350 nm at T = 6 K and then decrease as D reduces from 350 nm to 40 nm. The signals of the decreasing localization of charge carriers provide the possible evidences for the suppression of charge ordering with the decreasing particle size. These observations are explained based on the model of disordered surface and bulk-like core.

Size effect on infrared spectra of La0.25Ca0.75MnO3 nanoparticles: Evidences of melting charge ordering

A softening of bending mode and a hardening of stretching mode on cooling are observed in infrared spectra of La0.25Ca0.75MnO3 nanoparticles with particle sizes (D) of 40–1000 nm, indicating part of melting charge ordering in the samples. The particle size variations of the inverse of effective number of carriers neff∗ and optical gap show their maxima around D = 350 nm at T = 6 K and then decrease as D reduces from 350 nm to 40 nm. The signals of the decreasing localization of charge carriers provide the possible evidences for the suppression of charge ordering with the decreasing particle size. These observations are explained based on the model of disordered surface and bulk-like core.

In situ synthesis and characterization of polyaniline/prussian blue/zinc oxide nanocomposite

A new ternary nanocomposite of polyaniline (PANI), prussian blue (PB) and zinc oxide (ZnO), i.e., PANI–PB–ZnO was successfully synthesized in one pot process through chemical oxidative polymerization of aniline using ammonium persulfate as oxidizing agent. The morphological studies showed the formation of PB nanocubes and agglomerated quasi-spherical ZnO nanoparticles over PANI matrix, and the elemental composition of PANI–PB–ZnO was analyzed with energy-dispersive X-ray spectroscopy. The XRD measurements reveal the semicrystalline structure of the PANI–PB–ZnO nanocomposite after the polymerization reaction. The various functional groups present in PANI–PB–ZnO were identified using FTIR spectroscopy which confirms the presence of ZnO, PB and PANI in the synthesized ternary nanocomposite. From thermogravimetric analysis, the thermal degradation mechanism of PANI–PB–ZnO nanocomposite was explored and the activation energy (EA) was calculated from Coats–Redfern plot and was found to be 14.33 kJ/mol. 38 wt% of PANI–PB–ZnO nanocomposite was obtained as a residue at 800 °C indicating the high thermal stability. The bulk ionic conductivity value of the synthesized nanocomposite was found to be 8.509 × 10−5 Ω−1 cm−1 at 30 °C and 1.22 × 10−4 Ω−1 cm−1 at 100 °C. The ionic conductivity was found to increase with temperature for the synthesized material which showed an increase in the number of effective charge carriers. The characteristic absorption bands were detected using UV–Vis spectroscopy that confirms the formation of PANI–PB–ZnO nanocomposite. X-ray photoelectron spectroscopy measurements confirmed the valence states of constituent elements in ZnO nanoparticles and ternary PANI–PB–ZnO nanocomposite. I–V studies revealed that hybrid PANI–PB–ZnO nanocomposite has higher conductivity (2.4 × 10−4 S cm−1) than ZnO nanoparticles (3.5 × 10−10 S cm−1).

Optical properties of body-centered tetragonal C4: Insights from many-body perturbation and time-dependent density functional theories

We study the electronic structure and optical properties of a body-centered tetragonal phase of carbon (bct-C4) within the framework of time-dependent density functional theory and Bethe-Salpeter equation. The results indicate that the optical properties of bct-C4 are strongly affected by the electron-hole interaction. It is demonstrated that the long-range corrected exchange-correlation kernels could fairly reproduce the Bethe-Salpeter equation results. The effective carrier number reveals that at energies above 30 eV, the excitonic effects are not dominant any more and that the optical transitions originate mainly from electronic excitations. The emerged peaks in the calculated electron energy loss spectra are discussed in terms of plasmon excitations and interband transitions. The results of the research indicate that bct-C4 is an indirect wide-band-gap semiconductor, which is transparent in the visible region and opaque in the ultraviolet spectral range.

Investigation of ionic conduction in PEO–PVDF based blend polymer electrolytes

We investigate the effect of blend host polymer on solid polymer electrolyte (SPE) films doped with ammonium iodide (NH4I) salt using a variety of experimental techniques. Structural studies on the composite SPEs show that the blending of Poly(ethylene oxide) (PEO)–Poly(vinylidene fluoride) (PVDF) polymers in a suitable ratio enhances the amorphous fraction of the polymer matrix and facilitates fast ion conduction through it. We observe that the addition of a small amount of PVDF in the PEO host polymer enhances the ion – polymer interaction leading to more ion dissociation. As a result, the effective number of mobile charge carriers within the polymer matrix increases. Systematic investigation in these blend SPEs shows that the maximum conductivity (1.01 × 10–3 S/cm) is obtained for PEO – rich (80 wt. % PEO, 20 wt. % PVDF) composites at 35 wt. % NH4I concentration at room temperature. Interestingly, at higher salt concentrations (above 35 wt. %), the conductivity is found to decrease in this system. The reduction of conductivity at higher salt concentrations is the consequence of decrease in the carrier concentration due to the formation of an ion pair and ion aggregates. PVDF–rich compositions (20 wt. % PEO and 80 wt. % PVDF), on the other hand, show a very complex porous microstructure. We also observe a much lower ionic conductivity (maximum ∼ 10–6 S/cm at 15 wt. % salt) in these composite systems relative to PEO-rich composites.

Exploration of channel width scaling and edge states in transition metal dichalcogenides

We explore the impact of edge states in three types of transition metal dichalcogenides (TMDs), namely metallic Td-phase WTe2 and semiconducting 2H-phase MoTe2 and MoS2, by patterning thin flakes into ribbons with varying channel widths. No obvious charge depletion at the edges is observed for any of these three materials, in contrast to observations made for graphene nanoribbon devices. The semiconducting ribbons are characterized in a three-terminal field-effect transistor (FET) geometry. In addition, two ribbon array designs have been carefully investigated and found to exhibit current levels higher than those observed for conventional one-channel devices. Our results suggest that device structures incorporating a high number of edges can improve the performance of TMD FETs. This improvement is attributed to a higher local electric field, resulting from the edges, increasing the effective number of charge carriers, and the absence of any detrimental edge-related scattering.

Infrared properties of perovskite manganites La1−xCaxMnO3 with 0.25 ≤ x ≤ 0.45

The systematical investigations of infrared phonon spectra were performed on the perovskite manganites La1−xCaxMnO3 with 0.25 ≤ x ≤ 0.45. Both frequency shift of stretching mode and effective number of carriers neff∗(T) change dramatically near the Curie temperature for all compounds. Moreover, Ca concentration dependences of variations of the phonon frequencies and neff∗(T) shows their extreme values around x = 0.35 and 0.40 respectively at the measuring temperatures. With the varying Ca concentration, the competition between the strong Jahn-Teller coupling and the magnetic double exchange interaction may be responsible for those results.