Surface Groups Research Articles

Ordered self-assembled monolayers terminated with different chemical functional groups direct neural stem cell linage behaviours

Neural stem cells (NSCs) have been a promising candidate for stem cell-based nerve tissue regeneration. Therefore, the design of idea biomaterials that deliver precise regulatory signals to control stem cell fate is currently a crucial issue that depends on a profound understanding of the interactions between NSCs with the surrounding micro-environment. In this work, self-assembled monolayers of alkanethiols on gold with different chemical groups, including hydroxyl (−OH), amino (−NH2), carboxyl (−COOH) and methyl (−CH3), were used as a simple model to study the effects of surface chemistry on NSC fate decisions. Contact angle measurement and x-ray photoelectron spectroscopy (XPS) examination implied that all types of alkanethiols self-assembled on gold into a close-packed phase structure with similar molecular densities. In this study, we evaluated NSC adhesion, migration and differentiation in response to different chemical functional groups cultured under serum-free conditions. Our studies showed that NSCs exhibited certain phenotypes with extreme sensitivity to surface chemical groups. Compared with other functional groups, the SAMs with hydroxyl end-groups provided the best micro-environment in promoting NSC migration and maintaining an undifferentiated or neuronal differentiation state. −NH2 surfaces directed neural stem cells into astrocytic lineages, while NSCs on −COOH and −CH3 surfaces had a similar potency to differentiate into three nerve lineages. To further investigate the possible signaling pathway, the gene expression of integrin β1 and β4 were examined. The results indicated that a high expression of β1 integrin would probably have a tight correlation with the expression of nestin, which implied the stemness of NSCs, while β4 integrin seemed to correspond to the differentiated NSCs. The results presented here give useful information for the future design of biomaterials to regulate the preservation, proliferation and differentiation of NSCs for central nervous tissue engineering.

Deceleration of single-stranded DNA passing through a nanopore using a nanometre-sized bead structure.

DNA sequencing with a solid-state nanopore requires a reduction of the translocation speeds of single-stranded DNA (ssDNA) over 10 μs/base. In this study, we report that a nanometre-sized bead structure constructed around a nanopore can reduce the moving speed of ssDNA to 270 μs/base by adjusting the diameter of the bead and its surface chemical group. This decelerating effect originates from the strong interaction between ssDNA and the chemical group on the surface of the bead. This nanostructure was simply prepared by dip coating in which a substrate with a nanopore was immersed in a silica bead solution and then dried in an oven. As compared with conventional approaches, our novel method is less laborious, simpler to perform and more effective in reducing ssDNA translocation speed.

An investigation of phase transformation of titania slag using microwave heating

The influences of microwave heating on the phase transformation of titania slag were systematically investigated. The thermal stability, surface chemical functional groups and microstructure of the titania slag before and after microwave heating, at a temperature of 950 °C for 60 min, were also analyzed using thermogravimetry and differential thermal analysis (TG-DSC), Fourier transform infrared spectroscopy (FT-IR) spectrum and scanning electron microscope (SEM), respectively. The TG-DSC analysis revealed that the phase transformation of the titania slag from anatase TiO2 to rutile TiO2 occurred between 750 and 1000 °C. The FT-IR rustles demonstrate that the banding form of Ti4+, Ti3+ and Ti2+ ions and the methyl groups on the surface of the titania slag has changed and a new chemical bond Ti–OH was formed. The results of SEM showed that a large number of regulation rutile TiO2 crystals were found on the surface of the microwave-treated samples and the synthetic rutile has been synthesized successfully using microwave heating.

Investigation of equilibrium and kinetics of Cr(VI) adsorption by dried Bacillus cereus using response surface methodology

In this study, response surface methodology (RSM) based on three-variable-five-level central composite rotatable design was used to analyze the effects of combined and individual operating parameters (biomass dose, initial concentration of Cr(VI) and pH) on the Cr(VI) adsorption capacity of dried Bacillus cereus. A quadratic polynomial equation was obtained to predict the adsorbed Cr(VI) amount. Analysis of variance showed that the effect of biomass dose was the key factor in the removal of Cr(VI). The maximum adsorbed Cr(VI) amount (30.93 mg g(-1)) was found at 165.30 mg L(-1), 2.96, and 3.01 g L(-1) for initial Cr(VI) concentration, pH, and biosorbent dosage, respectively. The surface chemical functional groups and microstructure of unloaded and Cr(VI)-loaded dried Bacillus cereus were identified by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. Besides, the results gained from these studies indicated that Langmuir isotherm and the second-order rate expression were suitable for the removal of Cr(VI) from wastewater. The results revealed RSM was an effective method for optimizing biosorption process, and dried Bacillus cereus had a remarkable performance on the removal of Cr(VI) from wastewater.

Chemical-activated carbons from peach stones for the adsorption of emerging contaminants in aqueous solutions

Activated carbons from peach stones by chemical activation with H3PO4(s) have been prepared, leading to high surface area and well-developed mesoporous materials. Further oxidation and gas phase treatments were applied in order to analyze the influence of the chemical surface groups on the adsorption behavior. The adsorption of three emerging compounds: a stimulant (caffeine), an anti-inflammatory drug (diclofenac) and a psychiatric drug (carbamazepine) from ultrapure water through batch and dynamic tests was investigated. The characterization of the adsorbents was conducted by N2 adsorption–desorption isotherms, scanning electron microscopy (SEM), infrared spectrometry (FTIR), thermal programmed decomposition (TPD), zero charge and isoelectric points (pHZPC, pHIEP) determination and the evaluation of the total acidity by potentiometric titration with n-butylamine. TPD profiles and FTIR spectra revealed the presence of carboxylic, phenolic, carbonyl and quinonic functionalities in the carbonaceous surfaces. S-type adsorption isotherms, as Giles classification, were obtained, indicating a competitive effect between aqueous solution and the target adsorbates. Carbamazepine adsorption capacity was higher than caffeine and diclofenac, reaching 335mg/g, attributed to its hydrophobic character and water solubility properties. The oxidation of the activated carbon greatly enhanced the hydrophilic character of the material, decreasing the adsorption capacity and highly affecting on the breakthrough times and adsorption capacity values in the fixed-bed adsorption process.

Interaction of paracetamol and 125I-paracetamol with surface groups of activated carbon: theoretical and experimental study

The selection of activated carbon (AC) filters for water decontamination is currently carried out empirically. The low concentrations of drugs in the environment make the radioisotope labeling a valuable tool for physical and chemical studies of the adsorption process. A theoretical study of paracetamol and 125I-paracetamol adsorption onto AC was performed to evaluate the interactions between pollutants and surface groups (SG) of AC. Paracetamol was labeled with 125I and adsorption isotherms were obtained using radioanalytical and spectrophotometric techniques. The radioanalytical method overestimates the paracetamol adsorption. The validity of the chosen approach for qualitative assessment of SG influence over the adsorption process was demonstrated.

Surface or full cementation of the tibial component in total knee arthroplasty: a matched-pair analysis of mid- to long-term results.

Despite the clinical success of cemented TKA, aseptic loosening of the tibial component remains a potential long-term complication. Considering the constantly growing revision burden, there is a need for clarification regarding controversial views on primary fixation techniques. In this retrospective analysis, surface (SC) or full cementation (FC) of tibial components was compared in a matched-pair and long-term setting. Matching pairs were identified in a patient series from 1989 to 1994. Hence, 25 primary TKA (SC) were compared to 42 TKA (FC). The study population included 34 patients with rheumatoid arthritis. Patients were matched in a 1:1.7 fashion according to age, gender and initial diagnosis. Outcome was assessed by multiple clinical parameters, detailed radiographic evaluation and survivorship analysis. Clinical follow-up (FU) was at 10.3 years (range 1.5-15.6) for the SC and 12 years (range 0.2-16.2) for the FC group. Survivorship at 10 years was 100 % for the surface cemented trays and 93.3 % (95 % CI 80.5-100) for the fully cemented implants considering aseptic loosening as endpoint (p = 0.3918). Improvement of the AKS Score was greater in the SC group (p = 0.044) and patients in this group were more satisfied (p = 0.013). For any other clinical parameter, no difference could be observed (p > 0.05). Results of this study showed no statistically significant difference regarding long-term survivorship for the two cementing techniques. This finding questions the claimed advantage of full cementation for tibial components. The presented data do not support the concern that surface cementation results in insufficient fixation in patients with rheumatoid arthritis.

Three-dimensionally plotted MBG/PHBHHx composite scaffold for antitubercular drug delivery and tissue regeneration.

A suitable drug-loaded scaffold that can postoperatively release an antituberculosis drug efficiently in a lesion area and help repair a bone defect is very important in the clinical treatment of bone tuberculosis (TB). In this study, a composite drug-loaded cylindrical scaffold was prepared by using three-dimensional printing technology in combination with the mesoporous confinement range, surface chemical groups, and gradual degradation of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). This achieves the slow release of a drug for as long as possible. We implanted the drug-loaded compound scaffold into New Zealand rabbits' femur defect model to study the in vivo drug release performance and osteogenic ability. The in vivo release of isoniazid and rifampicin from the prepared composites could be effectively sustained for 12weeks in local tissues, whereas these drugs were sustained for just 2weeks in a control group. The blood drug concentrations were very low and most concentrations were below 5μg/ml. Therefore, the systemic toxic adverse effect is very low. In addition, the composite exhibits good osteogenic potential in a rabbit bone defect model. The results of this study indicate that this composite has great potential for treating osteoarticular TB.

Synthesis of carbon xerogels and their application in adsorption studies of caffeine and diclofenac as emerging contaminants

This work involves the application of carbon xerogels in the removal of two emerging contaminants, caffeine and diclofenac, from aqueous solutions. Textural characterization of the carbon xerogels prepared by polycondensation of resorcinol with formaldehyde (with a molar ratio of 1:2) has been investigated using N2 adsorption–desorption at −196°C. Chemical surface groups were analyzed by FTIR spectroscopy, elemental microanalysis and determination of isoelectric point. The equilibrium tests were carried out using different weights of adsorbent and the experimental data were best correlated by Sips isotherm equation. The kinetic experimental data were described using pseudo-first and pseudo-second order kinetic models, being well described by a pseudo-second order model. The maximum adsorption capacity was observed for adsorption of caffeine onto a xerogel treated with urea solution (182.5mgg−1), due to the presence of Lewis bases on its surface, which increase the adsorption affinity for organic compounds. On the other hand, the higher extent of diclofenac adsorption was obtained with a carbon xerogel treated with sulfuric acid (80.0mgg−1), mainly due to electronic interactions. Comparing these results with other data reported in the literature, the carbon xerogels employed in our study were found to exhibit comparable adsorption capacities and higher kinetic properties.

Hygroscopicity and Characterization of Wood Fibers Modified by Alkoxysilanes with Different Chain Lengths

As the main raw material for fiberboard, the hygroscopicity of wood fibers is of great concern. In this study, three alkoxysilanes with different chain lengths—methyl trimethoxy silane (MTMS), octyl trimethoxy silane (OTMS), and dodecyl trimethoxysilane (DTMS)—were used respectively to treat wood fibers to reduce their hygroscopicity and surface hydrophilicity. After alkoyxilane properties were evaluated, the chemical structures, surface groups, and morphology and distribution of alkoxysilanes within modified wood fibers were characterized using scanning electron microscopy (SEM) coupled with energy-dispersed X-ray analyzer (EDXA), Fourier Transform Infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The study found that after modification, the moisture adsorption rate of wood fibers had decreased and the surface hydrophobicity of the fibers had been promoted. The fibers modified with MTMS adsorbed the least amount of moisture. The study also found that while hydrolyzed silane penetrated into wood fibers and reacted with their chemical components, long chains of the silane hindered the degree of that penetration.

Toxicology of chemically modified graphene-based materials for medical application.

This review article aims to provide an overview of chemically modified graphene, and graphene oxide (GO), and their impact on toxicology when present in biological systems. Graphene is one of the most promising nanomaterials due to unique physicochemical properties including enhanced optical, thermal, and electrically conductive behavior in addition to mechanical strength and high surface-to-volume ratio. Graphene-based nanomaterials have received much attention over the last 5 years in the biomedical field ranging from their use as polymeric conduits for nerve regeneration, carriers for targeted drug delivery and in the treatment of cancer via photo-thermal therapy. Both in vitro and in vivo biological studies of graphene-based nanomaterials help understand their relative toxicity and biocompatibility when used for biomedical applications. Several studies investigating important material properties such as surface charge, concentration, shape, size, structural defects, and chemical functional groups relate to their safety profile and influence cyto- and geno-toxicology. In this review, we highlight the most recent studies of graphene-based nanomaterials and outline their unique properties, which determine their interactions under a range of environmental conditions. The advent of graphene technology has led to many promising new opportunities for future applications in the field of electronics, biotechnology, and nanomedicine to aid in the diagnosis and treatment of a variety of debilitating diseases.

Optimization of preparation conditions of activated carbon from the residue of desilicated rice husk using response surface methodology

Activated carbon could be prepared from residue of rice husk using physical activation with steam as activating agent. Response surface methodology (RSM) was applied to optimize the effects of processing parameters, and regression analysis was performed on the data obtained. The optimal conditions for adsorption capacity of activated carbon from the residue of rice husk were activation temperature of 946 °C, activation time of 31 min and water (18 g) which changed to steam by heating, resulting in 970.06 mg·g−1 of iodine adsorption capacity and 31.36% of activated carbon yield. The activated carbon prepared under optimum condition was mesoporous with BET surface area of 1,004.296 m2·g−1, total pore volume of 0.9388 cm3·g−1 and average pore diameter of 2.043 nm. The surface chemical functional groups of activated carbon were identified by FT-IR, and its microstructure was examined by scanning electron microscopy (SEM). We concluded that the process of physical activation with steam could be an environmentally harmonious and effective method for preparing activated carbon from residue of desilicated rice husk.

Alginate encapsulated mesoporous silica nanospheres as a sustained drug delivery system for the poorly water-soluble drug indomethacin

We applied a combination of inorganic mesoporous silica material, frequently used as drug carriers, and a natural organic polymer alginate (ALG), to establish a sustained drug delivery system for the poorly water-soluble drug Indomethacin (IND). Mesoporous silica nanospheres (MSNs) were synthesized using an organic template method and then functionalized with aminopropyl groups through postsynthesis. After drug loading into the pores of aninopropyl functionalized MSNs (AP-MSNs), IND loaded AP-MSNs (IND-AP-MSNs) were encapsulated by ALG through the ionic interaction. The effects of surface chemical groups and ALG layer on IND release were systematically studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, zeta-potential analysis and TGA analysis. The surface structure and surface charge changes of the ALG encapsulated AP-MSNs (ALG-AP-MSNs) were also investigated. The results showed that sustained release of IND from the designed drug delivery system was mainly due to the blockage effect from the coated ALG. We believe that this combination will help designing oral sustained drug delivery systems for poorly water-soluble drugs.

Theoretical study of γ-hexachlorocyclohexane and β-hexachlorocyclohexane isomers interaction with surface groups of activated carbon model

Activated carbon (AC) is employed in drinking water purification without almost any knowledge about the adsorption mechanism of persistent organic pollutants (POPs) onto it. Hexachlorocyclohexane (HCH) is an organochlorinated contaminant present in water and soils of banana crops production zones of the Caribbean. The most relevant isomers of HCH are γ-HCH and β-HCH, both with great environmental persistence. A theoretical study of the influence of AC surface groups (SGs) on HCH adsorption is done in order to help to understand the process and may lead to improve the AC selection process. A simplified AC model consisting of naphthalene with a functional group was used to assess the influence of SGs over the adsorption process. The Multiple Minima Hypersurface (MMH) methodology was employed to study γ-HCH and β-HCH interactions with different AC SGs (hydroxyl and carboxyl) under different hydration and pH conditions. The results obtained showed that association of HCH with SGs preferentially occurs between the axial protons of HCH and SG's oxygen atom, and the most favorable interactions occurring with charged SGs. An increase in carboxylic SGs content is proposed to enhance HCH adsorption onto AC under neutral pH conditions. Finally, this work presents an inexpensive computer aided methodology for preselecting activated carbon SGs content for the removal of a given compound.

Controlling the Surface Chemistry of Multiwalled Carbon Nanotubes for the Production of Highly Efficient and Stable Laccase‐Based Biocatalysts

AbstractLaccase was immobilized over multiwalled carbon nanotubes (MWCNTs) with diameters ranging from 10 to 100 nm and different surface chemical groups. Oxygen‐containing groups were introduced selectively or removed by liquid‐phase oxidation and thermal treatments. The effect of pH on the immobilization efficiency and catalytic activity of laccase has been evaluated. Pristine MWCNTs show excellent immobilization capacity (100 %) and high enzyme activity, but low thermal stability (at 50 °C) owing to weak interaction (mostly hydrophobic) between laccase and the support. Immobilization capacity and catalytic activity of laccase on the modified MWCNTs were related to the surface electric charge of both the support and the enzyme. MWCNTs oxidized with HNO3 and posteriorly heated at 400 °C, mostly presenting hydroxyl surface groups, provided the best compromise between laccase activity and thermal stability, which has been attributed to the formation of hydrogen bonds between the support and the enzyme.

Hydrothermal synthesis of TiO2–yeast hybrid microspheres with controllable structures and their application for the photocatalytic reduction of Cr (VI)

AbstractBACKGROUNDNanoparticle TiO2 and biological yeast cells have been investigated in previous work. However, the formation of TiO2–yeast hybrid materials with controllable structures is rarely reported. In the present study, the hydrolysis of titanium tetrabutoxide (TBOB) on the surface of yeast cells was proposed to prepare controllable structures of TiO2–yeast hybrid microspheres. It also develops and widens the applications of TiO2–yeast hybrid microspheres for removal of Cr(VI).RESULTSFE‐SEM and EDS revealed that the TiO2–yeast hybrid microspheres have rough surface morphology and uniform diameter. The XRD pattern indicated anatase phase TiO2 nanoparticles with amorphous yeast. FT‐IR spectroscopy demonstrated that the formation of controllable TiO2–yeast composite microspheres was related to surface chemical functional groups of yeast. The composite microspheres possessed enhanced light response over the wide range 250–435 nm. The photocatalytic performance of TiO2–yeast (1.3 mL TBOB) composite microspheres exhibited a maximum removal rate of 99% for the reduction of Cr(VI) under UV light irradiation.CONCLUSIONSTiO2–yeast hybrid microspheres with controllable structures were successfully synthesized via a hydrothermal method. The diameter of TiO2–yeast microspheres decreased with increase of the amount of TBOB. No significant decrease in photo‐activity was found when used for the reduction of Cr(VI) and the composites could be re‐used repeatedly without other treatment. © 2014 Society of Chemical Industry

Chemical surface modified‐activated carbon cloth for catalytic wet peroxide oxidation of phenol

AbstractBACKGROUNDActivated carbons (AC) can be used as catalyst in advanced oxidation processes due to the potential activity for hydrogen peroxide decomposition to hydroxyl radicals. Chemical surface groups and textural properties can play a crucial role in its catalytic behaviour. The pH of the reaction medium can also affect the adsorption properties of AC and the chemistry of hydrogen peroxide in catalytic oxidation processes. The AC/H2O2 systems have been successfully used for the degradation of some organic pollutants in wastewaters over recent years.RESULTSThe influence of different modified‐activated carbon cloth (ACC) samples has been studied. Commercial ACC samples were treated under neutral (H2O), acid (H3PO4), basic (NaOH) and oxidizing (H2O2) solutions. Modified‐ACC samples were assessed in the adsorption (in absence of H2O2) and chemical advanced oxidation (in presence of H2O2) of phenol at different pH values. ACC samples hydrothermally treated showed the best adsorption properties. ACC samples treated with NaOH solutions evidenced the best catalytic performance for phenol oxidation under acidic conditions.CONCLUSIONSThe functionalization of ACC samples with basic surface groups yielded the best catalytic performance with total phenol removal and efficient use of the hydrogen peroxide at acidic conditions. © 2014 Society of Chemical Industry

Evaluate the heavy metal toxicity to Pseudomonas fluorescens in a low levels of metal-chelates minimal medium.

A 2-(n-morpholino)ethane sulfonic acid (MES)-buffered minimal medium with low levels of metal chelates was used to evaluate the heavy metal (Co+2, Pb+2, Zn+2, Fe+2, Fe+3, Cd+2, Cu+2, and Cr+6) toxicity to Pseudomonas fluorescens through minimizing the limitation of the existing medium. The interaction between bacteria and heavy metals was real-time monitored by microcalorimetry and reflected by thermogenic curves. Compared with the main parameters, microbial growth rate constant k and total heat evolution Q total, a general order of toxicity was found to be Fe+3<Co+2<Fe+2<Cu+2<Cr+6<Zn+2<Pb+2<Cd+2. The main metal speciation was Co+2, Zn+2, Fe+2, Cd+2, PbOH+, Fe(OH)+2, CuOH+, HCrO4-, and CrO4(-2) at pH 6.4. These metal speciations are main factors to exhibit the metal toxicity to bacteria. To validate their interaction, the surface chemical functional groups of P. fluorescens biomass identified by Fourier transform infrared (FTIR) were amino, carboxyl, hydroxyl, and phosphoryl groups, which maybe involved in the biosorption of metal ions.

Molecular dynamics simulations on scattering of single Ar, N2, and CO2 molecules on realistic surfaces

The understanding of rarefied gas flows is of great interest since microelectromechanical systems are becoming ever smaller and intensification of all gas-related tasks in process engineering takes place on the microscale. With increasing rarefaction the influence of gas-surface interactions on momentum and energy transport becomes more significant producing rarefaction effects, such as wall slip. These gas-surface interactions are commonly described by means of accommodation coefficients that are input parameters for scattering kernels in rarefied gas flow simulations. In this context the tangential momentum accommodation coefficient (TMAC) is the most important input parameter since it allows to define the boundary conditions.In this work we present an approach in molecular dynamics simulations to determine the TMAC of a three-dimensional system on the basis of a few thousand single gas-surface collisions using a comparatively small super cell instead of relying on a large(r) system with a specific flow geometry which is the typical approach in literature. We demonstrate that TMAC results obtained by this method are in good agreement with results in relevant literature. The advantage of this method is the small number of atoms in the cell reducing the computational effort. Thus, the approach allows to analyze the interactions of realistic gas molecules (Ar, N2, and CO2) with realistic surfaces (Pt-, Si-, and hydroxylated Si-surfaces). This includes gas molecules with rotational degrees of freedom as well as surfaces with moving surface groups, whereby partial charges of the different atoms are taken into account. Furthermore, the presented approach allows for systematic investigation of each influencing parameter, such as temperature, electrostatic interactions, moving surface atoms, and interactions with chemical surface groups. Additionally, this approach is used to analyze the dependencies of angular scattering distributions on temperature and the incident angle of the impinging molecule.

Electrocatalytic Activity and Electroanalytical Performance of Nanodiamond-Derived Carbon Nano-Onions

Carbon nano-onions (CNOs) are an emerging, novel class of carbon nanomaterials. A CNO is a 0-D carbon analogue of a 1-D carbon nanotube (CNT) and a 2-D graphene. It is composed of sp2-bonded, concentric carbon shells surrounding a hollow core. The curved morphology of a CNO loosens the conjugation along the graphene sheet and results in the change in electronic structure. The unique structure as well as surface chemical functional groups of CNOs will significantly influence physicochemical, electronic, and electrochemical properties.In this talk, the physicochemical and electrochemical properties of CNOs will be presented. First, morphology and microstructure of CNOs were characterized by scanning and transmission electron microscopies (SEM, TEM), X-ray diffraction (XRD), and Raman spectroscopy. Chemical composition and chemical functional groups were probed by X-ray photoelectron spectroscopy (XPS). Raman spectra of CNOs showed a large value of ID/IG ratio, indicating that carbon concentric shells of CNOs include defects, i.e., exposed edge planes. Second, heteroatomic doping of CNOs and its electrocatalytic activity toward oxygen reduction reaction will be presented, in comparison with other carbon nanomaterials. Last, redox activities and electron transfer kinetics of CNOs were studied. CNOs showed remarkable electrochemical activities for the detection of biologically important molecules (such as high sensitivity, high selectivity and fast ET kinetics). Electrochemical measurements were carried out with standard redox couples such as Ru(NH3)6 3+/2+, Fe2+/3+, IrCl6 2 - /3 - and Fe(CN)6 3-/4- as well as redox-active biomolecules such as dopamine, epinephrine, and norepinephrine. The results showed a stable and fast electrochemical response of CNOs for all of the redox analytes and often surpassed the performance of other carbon electrodes like carbon nanotubes, graphite nanoflakes, and glassy carbon.