Carboxymethyl Cellulose Biopolymer Research Articles

Turning trash into treasure: conversion of agroresidue rice straw into carboxymethylcellulose biopolymer

AbstractIn the present study, rice straw‐derived cellulose was converted into carboxymethylcellulose (CMC) using alkalization followed by an etherification reaction. The synthesis conditions for this chemical modification were optimized such that CMC with a high degree of substitution (1.02) was obtained. Infrared spectra of the synthesized CMC clearly showed an increased intensity of the C═O bond at 1600 cm−1, confirming successful carboxymethylation. Further, X‐ray diffraction analysis demonstrated a decrease in cellulose crystallinity owing to partial rearrangement from a crystalline to an amorphous phase during initial alkalization reaction. The obtained CMC biopolymer was subsequently cross‐linked to form a composite hydrogel matrix reinforced with bentonite clay. The hydrogel showed about 91% adsorption capacity for methylene blue dye as a model contaminant in aqueous media. Therefore, this study shows that lignocellulosic agrowaste is a rich source of cellulose, and its derivatives such as CMC possess the potential to realize the waste to wealth sustainability goal.

Biopolymer Film Embedded ZnO Nanoparticles for Antimicrobial Application and Fresh Fruit Preservation

In this study, we reported on the synthesis of carboxymethyl cellulose biopolymer film containing ZnO nanoparticles (CMC – ZnO), oriented for antibacterial, and fruit preservation applications. The SEM and TEM image results show that the ZnO nanoparticles (ZnO NPs) on the CMC biopolymer film have a spherical structure that is irregularly agglomerated with each other. The CMC - ZnO biopolymer film has been proven to effectively inhibit the growth of E. coli. At the same time, it is considered a promising application in packaging and preserving fruits and foods. As a proof of concept, we used this CMC biopolymer film containing zinc oxide for avocado preservation. The results show that its freshness could be maintained for up to 35 days.

Chemical and Resistive Switching Properties of Elaeodendron buchananii Extract-Carboxymethyl Cellulose Composite: A Potential Active Layer for Biodegradable Memory Devices.

Biodegradable electronic devices play a crucial role in addressing the escalating issue of electronic waste accumulation, which poses significant environmental threats. In this study, we explore the utilization of a methanol-based extract of the Elaeodendron buchananii plant blended with a carboxymethyl cellulose biopolymer to produce a biodegradable and environmentally friendly functional material for a resistive switching memory system using silver and tungsten electrodes. Our analyses revealed that these two materials chemically interact to generate a perfect composite with near semiconducting optical bandgap (4.01 eV). The resultant device exhibits O-type memory behavior, with a low ON/OFF ratio, strong endurance (≥103 write/erase cycles), and satisfactory (≥103) data retention. Furthermore, through a comprehensive transport mechanism analysis, we observed the formation of traps in the composite that significantly improved conduction in the device. In addition, we established that altering the voltage amplitude modifies the concentration of traps, leading to voltage amplitude-driven multiple resistance states. Overall, our findings underscore the potential of functionalizing polymers that can be functionalized by incorporating plant extracts, resulting in biodegradable and nonvolatile memory devices with promising performance metrics.

Bioengineered Carboxymethylcellulose-Peptide Hybrid Nanozyme Cascade for Targeted Intracellular Biocatalytic-Magnetothermal Therapy of Brain Cancer Cells.

Glioblastoma remains the most lethal form of brain cancer, where hybrid nanomaterials biofunctionalized with polysaccharide peptides offer disruptive strategies relying on passive/active targeting and multimodal therapy for killing cancer cells. Thus, in this research, we report for the first time the rational design and synthesis of novel hybrid colloidal nanostructures composed of gold nanoparticles stabilized by trisodium citrate (AuNP@TSC) as the oxidase-like nanozyme, coupled with cobalt-doped superparamagnetic iron oxide nanoparticles stabilized by carboxymethylcellulose ligands (Co-MION@CMC) as the peroxidase-like nanozyme. They formed inorganic–inorganic dual-nanozyme systems functionalized by a carboxymethylcellulose biopolymer organic shell, which can trigger a biocatalytic cascade reaction in the cancer tumor microenvironment for the combination of magnetothermal–chemodynamic therapy. These nanoassemblies were produced through a green aqueous process under mild conditions and chemically biofunctionalized with integrin-targeting peptide (iRDG), creating bioengineered nanocarriers. The results demonstrated that the oxidase-like nanozyme (AuNP) was produced with a crystalline face-centered cubic nanostructure, spherical morphology (diameter = 16 ± 3 nm), zeta potential (ZP) of −50 ± 5 mV, and hydrodynamic diameter (DH) of 15 ± 1 nm. The peroxide-like nanostructure (POD, Co-MION@CMC) contained an inorganic crystalline core of magnetite and had a uniform spherical shape (2R = 7 ± 1 nm) which, summed to the contribution of the CMC shell, rendered a hydrodynamic diameter of 45 ± 4 nm and a negative surface charge (ZP = −41 ± 5 mV). Upon coupling both nanozymes, water-dispersible colloidal supramolecular vesicle-like organic–inorganic nanostructures were produced (AuNP//Co-MION@CMC, ZP = −45 ± 4 mV and DH = 28 ± 3 nm). They confirmed dual-nanozyme cascade biocatalytic activity targeted by polymer–peptide conjugates (AuNP//Co-MION@CMC_iRGD, ZP = −29 ± 3 mV and DH = 60 ± 4 nm) to kill brain cancer cells (i.e., bioenergy “starvation” by glucose deprivation and oxidative stress through reactive oxygen species generation), which was boosted by the magneto-hyperthermotherapy effect when submitted to the alternating magnetic field (i.e., induced local thermal stress by “nanoheaters”). This groundwork offers a wide avenue of opportunities to develop innovative theranostic nanoplatforms with multiple integrated functionalities for fighting cancer and reducing the harsh side effects of conventional chemotherapy.

Parameters Affecting Lithium Ion Conductivity of Carboxymethyl Cellulose Binders

In an effort to minimize green house gas emissions, the development of renewable energy storage has become important, especially for the transportation industry.(I) Currently, the most effective energy storage solution is Li-ion batteries due to their long cycle life and high energy density.(I) However, this current technology uses highly reactive and flammable liquid electrolytes which are both limited by their limited charging speed through a liquid medium and their unsafe nature.(II) For this reason, many large companies such as Hyundai and Samsung have heavily invested in the development of all-solid-state batteries (ASSB), seen as the next step in safe fast-charging energy storage.(III)However, problems remain that need to be solved before ASSBs can become commercially viable. One of these problems is cycling stability, where battery performance significantly drops after a few charge/discharge cycles, notably through mechanical degradation and interfacial contact issues caused by volume changes of the active material against a rigid solid electrolyte.(I) For this reason, there is growing interest in increasing the system’s mechanical flexibility thus preventing degradation by the use of ionically conductive polymers as soft binders and volume buffers.(IV) One potential choice for such materials are environmentally friendly natural biopolymers such as cellulose derivatives like carboxymethyl cellulose (CMC), whose functional groups coordinate cations during transport. CMC has already been shown to act as a binder that increases mechanical stability for electrodes of current Li-ion technology and exhibits proton conductivity in fuel cell applications. It is also being investigated for its potential in ASSBs, Na-ion, and Zn batteries where it has been shown to have high durability and that it combines well with a variety of other polymers when used as binders or as a solid electrolyte in these batteries.(IV-VII)To further our understanding of incorporating this biopolymer in batteries, we are studying the effects of various aspects of CMC film preparation on their ionic conductivity such as salt concentration and film homogeneity. In addition, to the preparation parameters, we investigated the activation energy of ion transport for CMC films of differing concentrations through temperature dependence measurements. Furthermore, we investigated the structure of these materials with infrared spectroscopy and differential scanning calorimetry to see the effects of salt concentration on the microstructure. This data is of importance in assessing the impact of CMC binders and will lay a foundation for optimizing binder choice for cheap and biodegradable components in both current and next-generation battery technology. References (I) Li, L.; Deng, Y.; Chen, G. Status And Prospect Of Garnet/Polymer Solid Composite Electrolytes For All-Solid-State Lithium Batteries. Journal of Energy Chemistry 2020, 50, 154-177.(II) Zheng, Y.; Li, X.; Li, C. A Novel De-Coupling Solid Polymer Electrolyte Via Semi-Interpenetrating Network For Lithium Metal Battery. Energy Storage Materials 2020, 29, 42-51.(III) Eckhouse, B. Samsung Venture, Hyundai Investing in Battery Producer. https://www.bloomberg.com/news/articles/2018-09-10/samsung-and-hyundai-investing-in-solid-state-battery-producer.(IV) Shetty, S.; Ismayil; Shetty, G. Enhancement Of Electrical And Optical Properties Of Sodium Bromide Doped Carboxymethyl Cellulose Biopolymer Electrolyte Films. Journal of Macromolecular Science, Part B 2020, 59 (4), 235-247.(V) Darjazi, H.; Staffolani, A.; Sbrascini, L.; Bottoni, L.; Tossici, R.; Nobili, F. Sustainable Anodes For Lithium- And Sodium-Ion Batteries Based On Coffee Ground-Derived Hard Carbon And Green Binders. Energies 2020, 13 (23), 6216.(VI) Dueramae, I.; Okhawilai, M.; Kasemsiri, P.; Uyama, H.; Kita, R. Properties Enhancement Of Carboxymethyl Cellulose With Thermo-Responsive Polymer As Solid Polymer Electrolyte For Zinc Ion Battery. Scientific Reports 2020, 10 (1).(VII) Sasso, C.; Beneventi, D.; Zeno, E.; Petit-Conil, M.; Chaussy, D.; Belgacem, M. Carboxymethylcellulose: A Conductivity Enhancer And Film-Forming Agent For Processable Polypyrrole From Aqueous Medium. Synthetic Metals 2011, 161 (5-6), 397-403.

Cellulose-based nanocomposite for ultrasonic assisted dispersive solid phase microextraction of triazole fungicides from water, fruits, and vegetables samples

Herein, an ultrasound-assisted dispersive solid phase microextraction (UA-DSPME) approach has been described for trace level analysis of triazole fungicides in real samples. For this purpose, a new nanosorbent was prepared through modification of carboxymethylcellulose biopolymer with zinc-based metal–organic framework and graphene oxide, and fully characterized. Then, the effect of extraction parameters on extraction efficiency was optimized for the microextraction process. Finally, desorbed triazole fungicides with ethanol were determined using gas chromatography equipped with flame ionization detector. This technique provided good linearity (R2 > 0.99), low detection limits (0.3–1.5 ng mL−1), high preconcentration factors (419–426), good relative recoveries (91.6–102 %), and high repeatability (RSD < 4.1 %) at optimized conditions (amount of sorbent: 15 mg; pH of solution: 7.0; and extraction time; 4 min). Ultimately, this approach was applied to determine triazole fungicides in different water and food samples.

Effect of new crystalline phase on the ionic conduction properties of sodium perchlorate salt doped carboxymethyl cellulose biopolymer electrolyte films

Dopant induced modifications in the microstructure of sodium carboxymethyl cellulose (NaCMC) were characterized by FTIR, XRD, DSC and EIS techniques. FTIR analysis exhibited a considerable microstructural modification in NaCMC upon NaClO4⋅H2O doping invoked through complex formation via Lewis acid-base interaction and hydrogen bond formation between ions and dipoles. This resulted in the modification in the orderliness/disorderliness of polymer chains as observed from XRD deconvolution. At higher salt concentrations, the complexity of the network causes the formation of new amorphous and crystalline phases as reflected in the XRD studies. DSC analysis showed an increase in Tg as the salt concentration increased, indicating a reduction in polymer chains flexibility. The contribution of free ions has masked over the enhancement in amorphous content to conductivity at a lower concentration of salt in the matrix, later on, the formation of a new crystalline phase due to transient crosslinks by Na+…ClO4−…Na+ has affected the ion transport process.

Facile synthesis of Zn-based metal-organic framework in the presence of carboxymethyl cellulose: A safe carrier for ibuprofen

Fabrication of porous materials with a high surface area affords a great interest to achieve a system with a prolonged drug release manner. In this context, the subject of this work is to describe a novel green one-pot synthesis route for the growth of metal-organic framework (MOF) from zinc metal (Zn) and 1, 4-benzene dicarboxylic acid (BDC) in the vicinity of the carboxymethyl cellulose (CMC), which homogeneously confined in the biopolymeric chains. The synthesized Zn (BDC)@CMC was characterized and confirmed using different analyses. N2 adsorption/desorption isotherms determined the mean diameter of pore size of about 2.3993 nm. Ibuprofen (IBU) as a model drug was highly loaded to the Zn(BDC)@CMC by immersing in the drug solution; 50.95%. The in vitro IBU release study indicated that the Zn(BDC)@CMC has more attractive performances than pristine Zn(BDC). The IBU release occurred via the Fickian mechanism. Isotherm studies showed that the IBU adsorption on obeys from Langmuir isotherm; R2 0.9623. The MTT results revealed the HEK 293A cell viability of higher than 90% for Zn(BDC)@CMC that confirms its cytocompatibility. Overall, obtained results confirm the functionality of CMC biopolymer for in situ growth of MOF in the presence of it due to having the reactive nature.

Estimation of pressure drop of single-phase flow in horizontal long pipes using artificial neural network

Large- pressure drop and drag along the pipe route is one of the problems with fluid transfer lines. For many years, various methods have been employed to reduce the drag in fluid transmission lines. One of the best ways for this purpose is reducing friction coefficients by utilizing drag lowering materials. Experimentally by adding minimal amounts of this material at the ppm scale to the lines and reducing the drag of the flow, fluid can be pumped without the need to change the size of the pipe. In this study, the effect of carboxymethylcellulose biopolymer on the water flow reduction in a 12.7- and 25.4-mm galvanized pipe was investigated. In order to have a comprehensive analysis of process conditions, experiments were carried out with three different levels of concentrations, flow rate and temperature. Also, as a new innovation in this investigation, the outputs of the experimental data were evaluated and analyzed using the Taguchi method and neural network system, and optimized through a genetic algorithm. In this study, the highest rate of drag reduction will be achieved at 39 ° C and at a concentration of 991.6 ppm and flow rate of 1441.1L/h was 59.83% at 12.7-mm diameter.

Cu-In-S/ZnS@carboxymethylcellulose supramolecular structures: Fluorescent nanoarchitectures for targeted-theranostics of cancer cells

Although the field of oncology nanomedicine has shown indisputable progress in recent years, cancer remains one of the most lethal diseases, where the early diagnosis plays a pivotal role in the patient's prognosis and therapy. Herein, we report for the first time, the synthesis of biocompatible nanostructures composed of Cu-In-S and Cu-In-S/ZnS nanoparticles functionalized with carboxymethylcellulose biopolymer produced by a green aqueous process. These inorganic-organic colloidal nanohybrids developed supramolecular architectures stabilized by chemical functional groups of the polysaccharide shell with the fluorescent semiconductor nanocrystal core, which were extensively characterized by several morphological and spectroscopical techniques. Moreover, these nanoconjugates were covalently bonded with folic acid via amide bonds and electrostatically conjugated with the anticancer drug, producing functionalized supramolecular nanostructures. They demonstrated nanotheranostics properties for bioimaging and drug delivery vectorization effective for killing breast cancer cells in vitro. These hybrids offer a new nanoplatform using fluorescent polysaccharide-drug conjugates for cancer theranostics applications.

Enhancement of Electrical and Optical Properties of Sodium Bromide Doped Carboxymethyl Cellulose Biopolymer Electrolyte Films

Biodegradable ion conducting solid polymer electrolyte films of carboxymethyl cellulose (CMC) doped with sodium bromide (NaBr) with various weight percentages were prepared by a solution casting technique. Their structural, optical and electrical properties were studied by various experimental techniques in order to understand the impact of the sodium metal salt on the biopolymer CMC’s properties. The optical parameters namely the optical bandgap energy and the refractive index, showed a significant variable variation with the metal salt concentration. The maximum dc conductivity was found to be ∼5.15 × 10−4 S cm−1 at room temperature for the sample with 20 wt% of NaBr content in the CMC matrix. The ionic conductivity and dielectric constant in general, increased with increase in metal salt content, affirming the increase in ion concentration. The calculated transference number showed that the conductivity was mainly due to ions. The increase in conductivity was due to an increase in degree of amorphousness of the polymer upon doping, as analyzed by their XRD spectra.

Nano micelles of cellulose-graft-poly (l-lactic acid) anchored with epithelial cell adhesion antibody for enhanced drug loading and anti-tumor effect

Biocompatibility and targeted therapy are the demand by modern chemotherapy drugs. Meanwhile, the utilizations of biopolymer or environmentally friendly polymer are also the key issues for sustainable development. We have constructed a new drug delivery system with targeted and controlled release capabilities. It has been confirmed that an environmentally friendly polymer (CMC-g-PLA) obtained by grafting polylactic acid on a carboxymethyl cellulose biopolymer has an amphiphilic property and is easy to form micelles, thereby being useful as a hydrophobic drug carrier. In order to have the function of targeted therapy, anti-EpCAM antibody was anchored on the polymer chain of carboxymethyl cellulose by amidation reaction. Doxorubicin and HepG2 cells were used as the model anticancer drug and tumor targeting cells, respectively. The nano scale core-shell structure, critical micelle concentration, drug loading and encapsulation efficiency were studied by TEM, pyrene fluorescent probe method and ultraviolet standard curve method, respectively. Furthermore, the pH induced release function experiments, cytotoxicity experiments and in vivo tumor treatments experiments on mice. The results show that the drug carrier with antibody prepared by us can effectively deliver hydrophobic drugs to specific tumor sites and increase the effect of tumor treatment. This versatile design provides a new solution for future cancer treatments.

Effect of sodium carboxymethylcellulose biopolymer on sedimentation properties of trimagnesium, tricalcium and tristrontium phosphates precipitates

Sedimentation data of bioactive materials are essential in formulation of suspension with desirable requirements. Batch-wise precipitation and sedimentation tests were conducted to evaluate the effect of sodium carboxymethylcellulose (Na-CMC) biopolymer solution on the sedimentation properties (rate and compaction) of trimagnesium phosphate (TMP), tricalcium phosphate (TCP) and tristrontium phosphate (TSP) precipitates. Fixed volume (1ml) of different concentrations (200ppm - 2000ppm) of Na-CMC solution was mixed with fixed volume (50ml) of 0.5M, 0.05M Na3PO4 solutions. Accordingly, the resulting solutions were separately mixed with fixed volumes (50ml) of 0.5M Mg (NO3)2, 0.05M CaCL2 and 0.05M SrCL2 solutions and settling of the precipitates formed monitored. The results showed that whereas for TCP, Na-CMC exhibited a curvilinear relationship with precipitate sedimentation, non-linear relationships were observed for TMP and TSP precipitates. Between 200ppm and 2000ppm of Na-CMC addition, sedimentation rate and compaction of TCP precipitate increased by 187% and 18.5%, whereas for TMP and TSP precipitates, they increased by only (19.89% and 1%) and (30% and 0%), respectively. The results suggest that Na-CMC biopolymer is not the preferred suspending medium for suspension formulations containing TCP. For TMP and TSP precipitates, further study is needed in the light of the fact that magnesium and strontium resemble calcium.Keywords: sedimentation rate, compaction, precipitates, sodium carboxymethylcellulose

Design and Development of Polysaccharide-Doxorubicin-Peptide Bioconjugates for Dual Synergistic Effects of Integrin-Targeted and Cell-Penetrating Peptides for Cancer Chemotherapy.

Polymer-drug conjugation is an attractive approach for target delivering insoluble and highly toxic drugs to tumor sites to overcome the side-effects caused by cancer chemotherapy. In this study we designed and synthesized novel polymer-drug-peptide conjugates for improved specificity on targeting cancer cells. Chemically modified polysaccharide, carboxymethylcellulose (CMC), was conjugated with doxorubicin (DOX) anticancer drug by amide bonds and dually biofunctionalized with integrin-target receptor tripeptide (RGD) and l-arginine (R) as cell-penetrating amino acid for synergistic targeting and enhancing internalization by cancer cells. These bioconjugates were tested as prodrugs against bone, breast, and brain cancer cell lines (SAOS, MCF7, and U87) and a normal cell line (HEK 293T, reference). The physicochemical characterization showed the formation of amide bonds between carboxylates (-RCOO-) from CMC biopolymer and amino groups (-NH2) from DOX and peptides (RGD or R). Moreover, these polymer-drug-peptide bioconjugates formed nanoparticulate colloidal structures and behaved as "smart" drug delivery systems (DDS) promoting remarkable reduction of the cytotoxicity toward normal cells (HEK 293T) while retaining high killing activity against cancer cells. Based on cell viability bioassays, DNA-staining, and confocal laser microscopy, this effect was assigned to the association of physicochemical aspects with the difference of the endocytic pathways and the drug release rates in live cells caused by the biofunctionalization of the macromolecule-drug systems with RGD and l-arginine. In addition, chick chorioallantoic membrane (CAM) assay was performed as an in vivo xenograft model test, which endorsed the in vitro results of anticancer activities of these polymer-drug systems. Thus, prodrug nanocarriers based on CMC-DOX-peptide bioconjugates were developed for simultaneously integrin-targeting and high killing efficacy against cancer cells, while preserving healthy cells with promising perspectives in cancer chemotherapy.

A comprehensive investigation on electrical characterization and ionic transport properties of cellulose derivative from kenaf fibre-based biopolymer electrolytes

The invention of a new biopolymer electrolyte based on carboxymethyl cellulose from Hibiscus cannabinus or kenaf fibre has been accomplished by doping ammonium acetate to the polymer–salt system by a solution cast technique. The optical micrograph of all films indicated that the addition of ionic salt enhances the amorphosity of the films. The conductivity values were determined via impedance spectroscopy. The maximum ionic conductivity in the order of 5.77 × 10−4 S cm−1 has been obtained for 20 wt% ammonium acetate-doped carboxymethyl cellulose biopolymer electrolyte. This proved that the insertion of ionic salt into the biopolymer materials successfully improved the conductivity. The prepared films were ionic conductors since the cationic transference number of the biopolymer electrolyte film was ~ 0.99. Transport studies confirmed that the ionic conductivity was influenced by the ionic mobility and diffusion coefficient.

Development of novel carboxymethyl cellulose/k-carrageenan blends as an enteric delivery vehicle for probiotic bacteria

This study reports a novel carrier based on blends of carboxymethyl cellulose (CMC) and k-carrageenan (k-Carr) for probiotic colon delivery. Lactobacillus plantarum ATCC:13643 (L. plantarum) cells were encapsulated in CMC/k-Carr blends by extrusion method. k-Carrageenan was used as a coating agent to improve encapsulation of L. plantarum cells in carboxymethyl cellulose biopolymer. K-Carrageenan and carboxymethyl cellulose were ionically cross-linked with K+ and Ca2+ ions, respectively. Optical and scanning electron microscopy obviously showed the random distribution of L. plantarum cells throughout the blend network. The viability of encapsulated cells in simulated gastric fluid (SGF) and bile salt solution were conducted. Results indicated that CMC/k-Carr blends could successfully protect L. plantarum cells against adverse conditions of the gastro–intestinal tract and bile salt solution. After sequential exposure to SGF for 2h almost complete death of free cells was observed. However, the number of surviving cells was 5.20 and 7.30 Log CFU/g for uncoated free CMC and CMC/k-Carr blends, respectively. Cumulatively the results of this research offer a suitable media to potentially deliver probiotics to colon site.

Potential study of biopolymer-based carboxymethylcellulose electrolytes system for solid-state battery application

ABSTRACTThis paper focused on study of potential biopolymer carboxymethylcellulose (CMC) as electrolyte system for application in solid-state battery, which was prepared via solution casting technique. The highest conducting CMC biopolymer electrolytes (BE) was achieved at 1.12 × 10−4 Scm−1 with addition of 25 wt% NH4Br and was improved to 3.31 × 10−3 Scm−1 when plasticized with 8 wt% EC. The solid-state battery was assembled using both systems with the configuration Zn +ZnSO4.7H2O // highest conducting BE // MnO2 and showed promising performance at room temperature. This work implies that the possible practical application of the present biopolymer CMC as a new invention of electrolytes system in the fabrication of electrochemical devices.

Study of the ionic conduction mechanism based on carboxymethyl cellulose biopolymer electrolytes

Biodegradable carboxymethyl cellulose (CMC) doped with various compositions of NH4Br biopolymer electrolytes (BE) were successfully prepared via a solution-cast technique. The ionic conductivity for the CMC-NH4Br BE system was measured by using impedance spectroscopy, and the highest ambient temperature conductivity was observed to be 1.12 × 10−4 S cm−1 for the sample containing 25-wt.% NH4Br. The temperature dependence of the ionic conductivity revealed that the BE system followed an Arrhenius behavior. Jonscher’s universal power law was applied to analyze the AC conductivity of the highest conducting sample in the BE system, and the results indicate that the conduction is due to small polaron hopping (SPH) caused by a non-adiabatic mechanism.