Imaginary Conductivity Research Articles

Capturing In Situ Glyphosate (De)sorption Kinetics in Floodplain Aquifer Sediment Columns: Geophysical Measurements and Reactive Transport Modeling.

Glyphosate, an ionizable organic herbicide, is frequently detected in soils and groundwater globally despite its strong retention via sorption. Understanding its apparent mobility hinges on our ability to quantify its system-specific sorption behavior, hindered by its affinity to adsorb onto sediments, yielding very low aqueous concentrations. Here, we present findings from a saturated flow-through column experiment in which we monitored glyphosate sorption onto a natural calcareous aquifer sediment, using the noninvasive geophysical method spectral induced polarization (SIP). Our kinetic sorption reactive transport model predicted the strong nonlinear reversible retention of glyphosate and reproduced the spatial profile of retained glyphosate in the sediment, with a measured maximum of 0.06 mg g-1. The strong contribution of sorption to pore fluid conduction masked the expected variations in imaginary conductivity, σ″. However, time constants derived from a Cole-Cole model matched the timing and spatial distribution of model-predicted sorbed concentration changes, increasing from 0.8 × 10-3 to 1.7 × 10-3 s with an increase in sorbed glyphosate of 0.1 mg g-1. Thus, glyphosate sorption modified the surface charging properties of the sediment proportional to the solid-bound concentrations. Our findings link SIP signal variations to sorption dynamics and provide a framework for improved monitoring of charged organic contaminants in natural sediments.

Exploring microstructural, optical, electrical, and DFT/TD-DFT studies of boron subphthalocyanine chloride for renewable energy applications

Microstructural, optical and electrical properties of boron subphthalocyanine chloride (B- SubPc-Cl) were investigated in order to use it in energy applications. Field emission scanning microscopy (FE-SEM) was used to investigat the surface morphology and the structural nature of B- SubPc-Cl evaporated thin films. The diffuse reflectance spectra of the as-deposited and annealed B-subPc-Cl thin films were investigated based on Kubelka-Munk (K-M) function. The optical characteristics (specular transmission and reflection) were determined from the analysis the spectrophotometric measurements. Organic/inorganic B- SubPc-Cl / n-Si heterojunction diode was successfully fabricated by means of the conventional thermal evaporation technique of B- SubPc-Cl thin film onto n-Si substrates of (110) preferred orientation. The current density–voltage (J–V) of Au/ B- SubPc-Cl / n-Si/Al heterojunction device was measured at selected temperatures. The essential electrical parameters of the device such as the series resistance, ideality factor, and barrier height were estimated from the analysis of current-voltage characteristics of heterojunction diode according to the Cheung-Cheung and Norde methods. The Complex dielectric functions such as the real and imaginary dielectric parts, dielectric modulus, and electrical conductivity of Au/ B- SubPc-Cl / n-Si/Al heterojunction device were carried out with the applied frequency in the range 20 Hz to 1 MHz and selected temperatures from 298 K to 473 K. DFT/TD-DFT calculations with B3LYP/6–31 G level of theory were used to study the optimized geometry and some important parameters of B-SubPc-Cl.

The mechanisms and monitoring of zeolite remediating chemical oxygen demand, NH4+, and Pb2+

Zeolite is utilized as an effective filling material in a permeable reactive barrier (PRB) at contaminated sites. Evaluation of the long-term performance of such barrier demands thorough understanding of the remediation mechanisms and real-time monitoring technique. In this study, the processes of zeolite remediation of three typical major contaminants from municipal solid waste sites (Chemical Oxygen Demand (COD), NH4+, and Pb2+, respectively) were simulated with column test, analyzed with microscopic methods (MIP, BET, SEM, XPS, FTIR, and XRD) and monitored with the spectral induced polarization (SIP) technique. Zeolite remediates COD simulant, KC8H5O4, through cation exchange of K+ and surface complexation of C8H5O4−. Patchy distribution of K+ with size range of 16–60 μm was both observed and calculated from the peak frequency of imaginary conductivity of SIP responses, which was attributed to the preferential complexation of C8H5O4− at low velocity regions (dents) on zeolite surfaces. Zeolite remediates NH4+ mainly through ion exchange due to the higher affinity of NH4+ to zeolite surfaces than that of Na+. Zeolite remediates Pb2+ mainly through surface complexation, with clusters of complexed Pb (II) of wide size range (a few μm to 25 μm) residing on zeolite particle surfaces. The real conductivity of SIP responses for zeolite under contaminant flow-through is primarily sensitive to the ionic strength of influx fluid. A mean size of near 270 μm was calculated from SIP responses in all three cases, which was attributed to the pore throat of zeolite. Spectral induced polarization demonstrated its capability of monitoring three processes of zeolite remediating COD, NH4+, and Pb2+, respectively, and held promise of non-invasively monitoring of long-term performance of contaminant containing barriers.

Evaluation of aqueous Cd2+ and Pb2+ removal by natural loess using spectral induced polarization and microscopic characterization.

Mining and landfill activities can cause serious soil and groundwater contamination with lead (Pb) and cadmium (Cd). Loess soils are common and have been reported as effective for the removal of heavy metals. The spectral induced polarization (SIP) technique has been approved for its nondestructive ability to characterize the contaminant transport process and surface geochemical properties in porous media. In the present study, SIP was applied to monitor Pb2+ and Cd2+ removal processes using loess through column flow-through experiments. The outflow aqueous geochemical analyses indicated a better retention capability of loess for Pb2+, which was through precipitation induced by calcite dissolution and aqueous pH increment, as confirmed by SEM-EDS and XRD results. Cd retention took place mainly through ion exchange with Ca2+ and Mg2+ on the loess surface. The SIP signals showed a continuous decrement on the magnitude of imaginary conductivity during both Pb2+ and Cd2+ flow-through, which was attributed to the total surface area and decrement of polarizable surface charges. The SIP signals differentiated the interactions between loess and Pb2+/Cd2+ by displaying a peak shift to a higher frequency on the imaginary conductivity spectra during Pb2+ flow-through, which was attributed to calcite dissolution and proved by the high correlation (R2 = 0.9366) between the estimated dissolved calcite mass and the peak of imaginary conductivity. The above results suggest that loess has a great potential for field heavy metal remediation applications, and the SIP technique displays a promising capability of monitoring the remediation performance.

Real-time monitoring of organic contaminant adsorption in activated carbon filters using spectral induced polarization

Real-time, in-situ monitoring of adsorption processes in activated carbon (AC) filters may advance the effectiveness, reliability and economical value of such systems. In this study, the applicability of spectral induced polarization (SIP) as a real-time monitoring tool was examined. The adsorption of anionic and cationic organic dyes to commercial-AC filter was examined using a set of breakthrough experiments combined with continuous SIP monitoring. The imaginary part of the complex electrical conductivity decreased in the range of 0.25−2.5Hz for both dyes. During the adsorption of the cationic dye, a new peak developed in the range of 7−40Hz, suggesting the dominance of surface processes that are not explained by the classic stern-layer polarization theory. The recorded imaginary conductivity values were used as a proxy for adsorbed dye concentration in the calibration process of a reactive transport model. The model confirmed that SIP can successfully be used for real-time monitoring of the dye progression through the filter. The applicability of SIP as an effective monitoring tool was also shown for cyclic operation (adsorption-desorption cycles).

Paraquat sorption- and organic matter-induced modifications of soil spectral induced polarization (SIP) signals

SUMMARY Quantifying the capacity of soils to immobilize sorbing contaminants of concern relies on batch sorption experiments, typically performed at skewed solid-to-liquid ratios. The geophysical method spectral induced polarization (SIP) provides a powerful non-invasive monitoring alternative that can capture changes in soil electrical properties driven by contaminant sorption, yielding an approach whereby immobilization can be monitored in situ. Here, we present SIP signals obtained from a series of columns packed with a water saturated natural sandy-loam soil, with and without solid organic matter (SOM) amendment, contaminated with increasing concentrations of the herbicide paraquat. Our results highlight that soil polarization drops proportional to increasing amounts of sorbed paraquat in the SOM-free soil, exhibiting a Langmuir-type leveling-off behaviour. The addition of 8 percent-SOM yielded an increase in both the real ($\sigma ^{\prime}$) and imaginary ($\sigma ^{\prime\prime}$) conductivity of the uncontaminated treatment, driven by the contribution of charged sites in the SOM. Further, SOM modified the dependence between $\sigma ^{\prime\prime}$ and sorbed paraquat, likely driven by continued polarization within the polydisperse SOM with continued paraquat addition. However, the time constant ($\tau $), derived using the Cole–Cole model, shed light on a saturation-type dependence governed by a drop in ion mobility with increasing sorption. Thus, aiding the interpretation of sorption-driven SIP signals.

Relaxation behavior in low-frequency complex conductivity of sands caused by bacterial growth and biofilm formation by Shewanella oneidensis under a high-salinity condition

Complex electrical conductivity is increasingly used to monitor subsurface processes associated with microbial activities because microbial cells mostly have surface charges and thus electrical double layers. Although highly saline environments are frequently encountered in coastal and marine sediments, there are limited data available on the complex conductivity associated with microbial activities under a high-salinity condition. Therefore, we have developed the spectral responses of complex conductivity of sand associated with bacterial growth and biofilm formation under a highly saline condition of approximately 1% salinity and approximately 2 S/m pore water conductivity with an emphasis on relaxation behavior. A column test is performed, in which the model bacteria Shewanella oneidensis MR-1 are stimulated for cell growth and biofilm formation in a sand pack, whereas the complex conductivity is monitored from 0.01 Hz to 10 kHz. The test results indicate that the real conductivity increases in the early stage due to the microbial metabolites and the increased surface conduction with cell growth but soon begin to decrease because of the reduction of charge passages due to bioclogging. However, the imaginary conductivity significantly increases with time, and clear bell-shaped relaxation behaviors are observed with the peak frequency of 0.1–1 Hz, associated with the double-layer polarization of cells and electrically conductive pili and biofilms. The Cole-Cole relaxation model appears to capture such relaxation behaviors well, and the modeling results indicate gradual increases in normalized chargeability and decreases in relaxation time during bacterial growth and biofilm formation in the highly saline condition. Comparison with previous literature confirms that the high-salinity condition further increases the normalized chargeability, whereas it suppresses the phase shift and thus the imaginary conductivity. Our results suggest that the complex conductivity can effectively capture microbial biomass formation in sands under a highly saline condition.

Polaron assisted electrical transport and fertile field emission response in polycrystalline LiNi0.33Co0.33Mn0.33O2 with theoretical insight by density functional theory

Polycrystalline LiCo0.33Ni0.33Mn0.33O2 compounds were prepared via a sol-gel auto combustion synthesis route to examine its conduction mechanism with thermal assessment and a new window of its application as a field emitter is explored. The structural modules and molecular footmarks have been confirmed by XRD, Raman, FTIR, XPS and FESEM techniques. The Nyquist plots (Z′vs.Z′′) exhibits significant contribution of electrode solid interface effect with compared to intra and inter granular contribution. The variation of real and imaginary impedance, modulus, and conductivity spectra with thermal evolution is attributed with the creation of a quasi-particle called “polaron” and the migration of small polaron by tunneling/hopping creates localized state in high temperature. However, a weak crossover between small polaron hopping (SPH) and Mott’s variable range hopping (VRH) is observed near 323 K. The colossal dielectric permittivity (ɛr′)~5 × 106 is originated from inhomogeneous electronic conduction process in LiNi0.33Co0.33Mn0.33O2 due to the creation of absorption current in the flimsy grain boundary which leads to the stockpile of charge carriers in the external-electrode sample interface and induces Maxwell-Wagner electrode interfacial polarization. The exquisite field emission properties were discovered in LiNi0.33Co0.33Mn0.33O2 with low turn-on field@ 1 µA/cm2~2.75 V/µm and threshold field@ 10 µA/cm2~4.39 V/µm with field enhancement factor (β)~4251. The structural and electronic properties of LiNi0.33Co0.33Mn0.33O2 and the local work function (φ)~4.94 eV is computed employing the Density functional theory (DFT). It further supports the conduction mechanism due to self-trapping electrons and strong spin polarization of the O-2p state under applied electric field.

Classification of slag material by spectral induced polarization laboratory and field measurements

Historical slag dumps are of increasing interest due to economic, environmental or archaeological reasons. Geophysical investigations can help accessing the potential reuse of slag material to recover metallic raw material or for the estimation of the hazard potential of the buried slag material due to dissolution occurrence.In our study, we have investigated various slag material in the laboratory with the spectral induced polarization (SIP) method, obtained from different historical slag dumps, located in the Harz Mountains, Germany. We also present SIP results from field measurements at a historical slag dump where most of the slag samples reveal high amounts of iron, zinc, silica, and barium.Our results reveal a discrimination between three different slag grades (low, medium, high) by using the imaginary conductivity σ″ at a medium frequency (1–10 Hz) in both laboratory and field. Furthermore, additional information is obtained by a classification based on the spectral polarization behaviour and considering the field frequency range (0.1 Hz – 100 Hz). Five different types of spectra (ascending, descending, constant, maximum and minimum type) can be discriminated and recognized in the laboratory and in distinct areas of the slag dump. Even though a direct comparison between the laboratory and field results still needs to be proven, the buried slag material can be differentiated from the surrounding material by the polarization magnitude.

Surface Phonon Polariton Modes in Suspended Monolayer Hexagonal Boron Nitrides

Dispersion properties and characteristics of transverse magnetic (TM) and transverse electric (TE) surface phonon polaritons (SPhP) in suspended monolayer hexagonal boron nitrides (hBN) was studied extensively. The analytical results show that the hBN based TM (TE) phonon polaritons exist in restsrahlen bands when imaginary surface conductivity is positive. The effective mode index of TM phonon polaritons is much higher than that of TE phonon polaritons with respective values of ~3000 and ~1.0002 which makes TM SPhP more promising in the practical realization. In addition, the propagation length of TE SPhP is less lossy and surpass that of TM SPhP by factor of 104. This study compares these important properties and sheds more insight into their applications in optical communications, photonics and optoelectronics devices.

Complex conductivity signatures of compressive deformation and shear failure in soils

The mechanical properties of soils play a crucial role in site assessment for construction and infrastructure. Soils with low shear strength can become unstable as a result of natural and/or anthropogenic induced forces. Standard geotechnical methods, such as compressive strength tests, quantify the mechanical properties of soils, but these methods have low spatiotemporal resolution and may involve disruption of existing infrastructure. In contrast, the complex conductivity geophysical method can provide information on spatiotemporal changes in the subsurface in a minimally invasive manner. We investigated complex conductivity signatures resulting from soil deformation and failure during an unconfined compression test. A synthetic soil composed of silica sand (98%) and kaolin powder (2%) was saturated below its liquid limit and packed inside a flexible sample holder custom-equipped with four electrodes under zero confining stress to simulate an unconfined condition. This soil sample underwent a constant and slow rate of compression. Soil stress, strain, effluent volume, along with the frequency dependent real and imaginary parts of the complex conductivity were recorded over distinct time intervals. The first experiment focused on the sensitivity of complex conductivity to soil failure. Imaginary conductivity (equivalent to surface conductivity) abruptly decreased at the failure point (similar to the decrease in stress) compared to the real conductivity signal. The square of the dominant geophysical length scale L determined from the complex conductivity spectra (related to pore size) exhibits an inverse linear dependence on compression. The second experiment focused on the complex conductivity during shearing (beyond failure). In this case, the imaginary (or surface) conductivity closely tracked changes in the sample stress. In both experiments, imaginary (or surface) conductivity is highly sensitive to changes caused by rearrangement of soil structure under stress (i.e., deformation and failure). In contrast, the real conductivity is minimally sensitive, and the electrolytic conductivity is insensitive to these changes. Our findings indicate that complex conductivity is capable of tracking mechanical changes of soils under stress and during failure foremost through the surface conductivity.

Complex optical conductivity of Bi2Se3 thin film: Approaching two-dimensional limit

Two-dimensional Bi2Se3 thin films have attracted widespread attention as an ideal platform of high-performance optoelectronic applications. Understanding the intrinsic optical/electronic properties of Bi2Se3 thin films is vital for Bi2Se3-based optoelectronic applications. Here, the complex optical conductivities of a series of Bi2Se3 thin films with a varying number of quintuple layers are investigated by combining spectroscopic ellipsometry with the classical slab model over a broad spectral range of 0.73–6.43 eV. Results show that the zero-cross point of the imaginary complex optical conductivity exhibits a blueshift trend due to the enhanced coupling between the surface states as the thickness of Bi2Se3 thin film approaches the two-dimensional limit. Five feature peaks (A–E) are identified in the complex optical conductivity spectra, and their center energies exhibit interesting thickness dependencies, which are mainly attributed to the increased surface state gap due to the finite-size effects when the Bi2Se3 thin film gradually approaches the two-dimensional limit. Our work not only gives insights into the tunable optical properties of Bi2Se3 thin films but also reveals its intrinsic physical origin, which are essential and imperative for accurate modeling and design of Bi2Se3-based optoelectronic devices.

First principle study on structural and optoelectronic properties and band-gap modulation in germanium incorporated tin (IV) oxide

First principle calculations on pure and germanium (Ge) incorporated tin (IV) oxide (SnO2) are performed to understand their structural, electronic, and optical properties at the microscopic level. The optimized ground state structures exhibited a reduction in their lattice parameters as well as total energy with increasing germanium concentration. From the band structures of the pristine and doped SnO2, we have observed a reduction in the energy gap due to the incorporation of germanium into stannic oxide (SnO2). As conduction band minimum near Fermi level reaching a lower energy level with an increase in doping concentration, the electron affinity is increasing. The calculated band gaps of pure, 6.25 %, 12.5 % and 25 % ‘Ge’ incorporated tin (IV) oxides are 1.76, 1.73, 1.56 and 1.53 eV, respectively, and all are direct in nature. Further, the calculated electron effective mass at the conduction band minimum is lower than the hole effective mass at the valence band maximum. Hence, the mobility of electrons is found to be higher, suggesting the n-type semiconducting property. The contributions of different atoms on valence and conduction band are studied by calculating the density of states spectra. Optical properties, such as real and imaginary dielectric constants, absorption, reflectivity, refraction and extinction coefficient, loss function, real and imaginary optical conductivity are calculated. The calculated optical absorption shows that both un-doped and doped materials preserve the optical transparency in the infra-red region. Our analysis shows that Ge-doped SnO2 has a tunable band gap and work function, which makes it suitable for applications in photovoltaic devices.

Structural, Optical and Acoustical Characterization of Polyvinyl Alcohol Dispersed Cadmium Selenide Nanocomposites

Nanosized semiconducting cadmium selenide particles were successfully distributed within the polymer matrix of polyvinyl alcohol (PVA) utilizing the method of heat induced chemical synthesis. The structural characterization of the prepared nanocomposite was conducted using X-ray diffraction for the phase analysis of the nanocrystallites, Transmission electron microscopy (TEM) was used for size and shape determination of the nanoparticles and Fourier transform infrared (FTIR) spectroscopy for identification of the various chemical functional groups possessed by the PVA/CdSe nanocomposites. Various properties of hybrid nanocomposites have been widely scrutinized by researchers during the past few decades because of their unique properties and versatility. The present study involved the behavioral analysis of various optical properties, such as optical absorbance (A), transmittance (T), optical band gap (Eg), refractive index (n), extinction coefficient (k), real and imaginary dielectric constants (ε1 and ε2) and optical conductivity (σopt), of nanocomposite thin films produced by solution casting at temperatures ranging from 303 K to 343 K. The present study also deals with the evaluation of various ultrasonic acoustical properties, like adiabatic compressibility (βad), acoustic impedance (Z), intermolecular free length (Lf), relaxation time (τ) and attenuation coefficient, α, as a function of the square of the frequency (ƒ 1 ), i.e., (α/ƒ 1 ), to permit detailed understanding of behavioral changes in particle-fluid interactions with variation in the solution temperature of the nanocomposite.

Dielectric Properties of Coronene Film Deposited onto Silicon Substrate by Spin Coating for Optoelectronic Applications

To determine the electrical modulus, dielectric properties, and ac conductivity of Coronene semiconductor layer, we have produced Al/Coronene/n-Si structure by using the thermally evaporation and spin coating method. The variation of dielectric constant (e′), dielectric imaginary part (e″), tangent loss (tanδ), electrical modulus (M′ and M″), and ac electrical conductivity (σac) with voltage and frequency of Coronene semiconductor layer have been investigated in the frequency range of 1 kHz – 1 MHz and at the selected voltages (0.0–0.4 V with steps 0.02 V). It is found that thee′ande″values decrease with increasing frequency while an increase is observed in tanδ, σac, and the real (M′) and the imaginary (M″) of the electrical modulus. The e′, e″, tanδ, σac, M′, and M″ values have been determined as 6.53, 8.58, 1.31, 0.0477 S/cm, 0.0561 and 0.0477 for 1 kHz and 0.0046, 0.129, 2.78, 7.17 S/cm, 0.278, and 7.74 for 1 MHz at 0.0 V, respectively.

Characterizing Physical Properties of Streambed Interface Sediments Using In Situ Complex Electrical Conductivity Measurements

AbstractStreambed sediment physical properties such as surface area, are difficult to quantify in situ but exert a high‐level control on a wide range of biogeochemical processes and sorption of contaminants. We introduce the use of complex electrical conductivity (CC) methods (also known as spectral‐induced polarization (SIP)) that measure both real and imaginary conductivity to noninvasively and efficiently characterize shallow streambed sediments. We explore the method through synthetic modeling, laboratory, and field measurements to demonstrate the sensitivity of imaginary conductivity to sediment surface area, controlled in part by fine‐grained iron oxides produced by anoxic groundwater discharge. Laboratory measurements verify expected relationships between CC parameters and sediment properties. Synthetic modeling using a 1D analytical model illustrates the influence of water layer depth and conductivity on the field CC measurements made at the streambed‐stream water interface. Specifically, the inverted sediment imaginary conductivity is less impacted by uncertainty in the water layer depth and conductivity relative to the real conductivity and phase shift. Field CC measurements along a landfill‐impacted river reveal discrete streambed zones with enhanced bulk surface area generally corresponding to anoxic groundwater discharge zones with high concentrations of fine‐grained iron oxide precipitates.

Spatiotemporal geo-electrical sensing of a Pluronic-coated cobalt ferrite nanoparticle slug in natural sand flow-through columns

Rising industrial interest in the application of nanomaterials for the remediation of contaminated sites has led to concern over the environmental fate of the nanoremediation agents used. A critical requirement in evaluating and understanding nanoparticle (NP) behaviour in porous media is the development of analytical methods capable of in situ monitoring of complex NP transport dynamics. Spectral induced polarization (SIP), a non-invasive geo-electrical technique, offers a promising tool for detecting and quantifying NPs in soil and aquifer media. However, its application for monitoring the spatial migration and attachment behaviour of NPs remains uninvestigated. Here, we present results from flow-through experiments where we monitored the transport of cobalt ferrite nanoparticles (CoFe-NPs) coated with Pluronic, an amphiphilic polymer, in natural aquifer sand columns. We coupled concentration breakthrough curve analysis with SIP monitoring and reactive transport modeling to relate spatiotemporal NP concentration distributions to geo-electrical signals. Changes in the real (σ′) conductivity at three different locations along the columns closely correlated with model-computed total (solid plus aqueous phase) NP concentrations during the propagation of a NP slug. The imaginary conductivity (σ″) correlated closely with the arrival of the NP-slug. However, during the receding front, bimodal σ″-signal peak behaviour was observed propagating through the columns, indicating the existence of complex in situ NP transport dynamics, potentially revealing the rupture of nanoclusters upon straining and their effect on bulk charge storage that may not be obvious from breakthrough curve data alone. Fitting of a double Cole-Cole relaxation model yielded distinct shifts in relaxation time (τ) associated with the polarization of smaller length-scale particles. Post-NP pulse τ and σ″ did not return to pre-injection values; these lingering signals were caused by retained NP concentrations as low as 8.8 mg kg−1. Our results support the applicability of SIP for spatial and temporal monitoring of NP distributions, with implications for the investigation of NP transport and nanoremediation strategies.

Content and morphology of lead remediated by activated carbon and biochar: A spectral induced polarization study

Soil and groundwater contamination with lead (Pb) poses serious challenges for the environment. Activated carbon (AC) and biochar have huge potential application in the in-situ remediation processes through permeable reactive barriers (PRB). Spectral induced polarization (SIP) technique recently showed promises in nondestructively monitoring the spatio-temporal characteristics of physical, chemical and biological processes in porous media. In this study SIP technique was used for monitoring Pb remediation by AC and biochar in column scale. The calculated characteristic grain/pore size evolutions from SIP signals on AC, agreed well with the size of precipitates measured by SEM and mercury intrusion porosimetry (MIP) methods. The content increment process of the retained Pb on AC was also recorded via the magnitude increment of the imaginary conductivity. The mechanisms of Pb–AC and Pb-biochar interactions were investigated using SEM-EDS, TEM, FTIR, XRD, and XPS measurements. It showed that AC immobilizes through physical adsorption and precipitation, whereas complexation with functional groups is the remediation mechanism for biochar. Furthermore, the observed SIP responses of both AC and biochar are two orders of magnitude higher than those of typical natural soils or silica materials. This distinct difference is an additional advantage for the field application of SIP technique in PRB scenarios.

Optical characterizations and dielectric performance of 5,10,15,20-Tetrakis(pentafluorophenyl)-21H,23H-porphine palladium(II) for photodetector applications

Photodetector application of organic-based device like porphine palladium (II) substitution, 5,10,15,20-Tetrakis (pentafluorophenyl)-21H,23H-porphine palladium (II), (TPPFT) thin films was investigated. A high quality and adherent films over various substrates were prepared using a low-cost spin coating method. The HR-TEM images confirm the nanofiber-like structure of TPPFT with a length of up to 2 μm and width in the range 20–30 nm. The X-ray diffraction pattern confirms that the deposited films were amorphous nature, which was further verified by the SAED pattern. The analysis of the absorption properties through the band edge revealed a direct allowed optical gap of about 2.87 eV. The oscillator and dispersion energies of 2.16 and 7.12 eV, respectively were extracted from the analysis of the dispersion curve using the typical single oscillator-based supported by the Wemple Didomenico relationship. . The measurements of the dielectric properties of TPPFT-based devices in a wide range of frequency up to 20 MHz under influence of DC-bias (−3 to 3 V) and temperature in the range 303–343 K the diodes indicate the effectiveness of the interface states at the device barriers. The real and imaginary parts of the impedance are found to be frequency dependence and interpreted via interfacial dipole time which is decreased with increasing the frequency within the desired bias range. The real and imaginary AC conductivities recorded a higher value of about 6 × 10−4 and 1.7 × 10−4 sm−1at 0.1 MHz under the bias of 3 V. The prepared junction device-based TPPFT presented a high rectification performance with a rectification ratio up to 103 at ±1 V. The responsivity, detectivity, and external quantum efficiency of the TPPFT-based devices under the illumination of 100 mW/cm2 was investigated under reverse bias and found to be 2.75 × 10−6 A/w, 9 × 10−9 Jones, and 7.8% at the bias of 1 V, respectively. The obtained results recommended that TPPFT-based devices can be utilized for the prospect photodetector application.

Synthesis, structural, optical and dispersion parameters of La-doped spinel zinc ferrites ZnFe2-xLaxO4 (x = 0.00, 0.001, 0.005, 0.01 and 0.015)

We investigate the structural and optical properties of ZnFe2-xLaxO4 spinel ferrite (0 ≤ x ≤ 0.015) prepared using sol-gel route. The lattice parameter increases and the crystallite size decreases by La3+ replacements as was demonstrated by X-ray diffraction. UV–visible spectroscopy was used to study the optical properties. The optical band gap increases from 1.8714 to 1.9557 eV, with the increase in La3+ concentration up to x = 0.015. On the contrary, Urbach energy (band tail width), EU was found to be decreased from 0.6027 to 0.4247 eV. In addition, different optical parameters were extracted and associated with the change of La amount such as the absorption coefficient, refractive index, the extinction coefficient, real and imaginary dielectric constant, conductivity optical and electrical conductivity. Finally, the dependency of the refractive index to the wavelength was fitted to Wemple-DiDomenico single oscillator model and the parameters like dispersion energy, single oscillator energy, oscillator length strength, and average oscillator wavelength were also determined.