Van De Waals Research Articles

Effect of N-doping on tribological properties of graphene by molecular dynamics simulation

Graphene has attracted a lot of attention due to its excellent electrical properties, however, the gapless nature of graphene limits its further applications. Doping is an effective way to open the bandgap, in which nitrogen-doped (N-doped) graphene has potential applications, but the study of its tribological properties is still lacking. In this work, the effects of nitrogen doping on the tribological properties of graphene under different interfacial structures are investigated by molecular dynamics simulation. The simulation models include a hexagonal graphene sheet, graphene or N-doped graphene substrate. The results show that the nitrogen doping has different effects on friction when interface structure is in a commensurate state and an incommensurate state. In a commensurate state, N-doping reduces the friction between interfaces in all cases, but the friction first goes up and then decreases with the increase of doping ratio of nitrogen. The local maximum value of friction occurs at a doping ratio of 7.5%. This phenomenon results from the interface structure and the change of van de Waals force between interfaces. The introduction of nitrogen atoms causes the lattice of graphene to distort, which results in the formation of local incommensurate state, thus reducing the interfacial potential barrier and friction. However, the van der Waals force between nitrogen atom and carbon atom between layers is stronger than that between carbon atoms and carbon atoms, which causes the friction to increase. When the doping ratio is low or high, lattice distortion plays more important role. The friction of N-doped graphene shows much smaller increase with load than that of ideal graphene, which indicates that the N-doped graphene possesses a better performance under high load. When the interface structure is in an incommensurate state, the introduction of nitrogen atoms shows slight influence on lattice mismatch, therefore, the change of atomic type plays a dominant role in determining the friction between interfaces, which goes up with the increase of N-doping ratio. When the substrate is graphene with vacancy defects, the value of friction between interfaces is larger than the ideal graphene substrate or N-doped graphene substrate, which indicates that the doping of nitrogen atoms has positive effect on reducing the friction of graphene with defects.

CoO modified porous boron nitride fibers for the adsorption and removal of chlortetracycline from aqueous solution

Antibiotic pollution in the aquatic environment seriously threatens human health and ecological balance, which violates the trend of sustainable and green development in today's world. Therefore, how to effectively solve the current problem of antibiotic residues in water is highly imminent. Here, we developed CoO modified porous boron nitride fibers (CoO/P-BNFs) by relying on the strong adsorption of polar B–N bonds for cobalt(Ⅱ) to enhance the absorption and removal capacity for chlortetracycline (CTC). The prepared adsorbent was characterized via XRD, FT-IR, XPS, SEM, TEM and BET methods and then the adsorption behavior was explored by batches of experiments. The results indicated that CoO/P-BNFs achieved excellent removal percentage (97.69%) to CTC at 100 mg/L, which far exceeds the P-BNFs (46.08%) and other conventional adsorbents. The kinetics and isotherms could be well described by the pseudo-second-order model and Freundlich model, and the adsorption was a spontaneous exothermic process. In addition, the possible adsorption mechanisms of CTC onto CoO/P-BNFs were mainly π-π and cation-bridge interaction, while other forces such as hydrogen bond, Van de Waals force, electrostatic interaction and pore-filling effect also played an important role. Finally, our research results indicated that CoO/P-BNFs is a promising adsorbent for removing antibiotic contaminants from aquatic environment.

Photoemission oscillation in epitaxially grown van der Waals β-In2Se3WS2 heterobilayer bubbles* *Project supported by the National Natural Science Foundation of China (Grant Nos. 51732010 and 51972280), the Natural Science Foundation of Hebei Province, China (Grant No. E2019203233), the Research Program of the College Science & Technology of Hebei Province, China (Grant No. ZD2020121).

Thin films of millimeter-scale continuous monolayer WS2 have been grown on SiO2/Si substrate, followed by the deposition of β-In2Se3 crystals on monolayer WS2 to prepare In2Se3/WS2 van de Waals heterostructures by a two-step chemical vapor deposition (CVD) method. After the growth of In2Se3 at elevated temperatures, high densities of In2Se3/WS2 heterostructure bubbles with monolayer to multilayer β-In2Se3 crystals atop are observed. Fluorescence of the resultant β-In2Se3/WS2 heterostructure is greatly enhanced in intensity upon the formation of bubbles, which are evidenced by the Newton’s rings in optical image owing to constructive and destructive interference. In photoluminescence (PL) mapping images of monolayer β-In2Se3/monolayer WS2 heterobilayer bubble, significant oscillatory behavior of emission intensity is demonstrated due to constructive and destructive interference. However, oscillatory behaviors of peak position are also observed and come from a local heating effect induced by an excitation laser beam. The oscillatory mechanism of PL is further verified by changing the exterior pressure of bubbles placed in a home-made vacuum chamber. In addition, redshifted in peak position and broadening in peak width are observed due to strain effect during decreasing the exterior pressure of bubbles.

Ionic-Liquid-Catalyzed Approaches under Metal-Free Conditions.

ConspectusMetal-free catalysis is a promising protocol to access chemicals without metal contamination. Ionic liquids (ILs) that are entirely composed of organic cations and inorganic/organic anions have emerged as promising alternatives to molecular solvents and metal catalysts due to their unique properties such as structural tunability, the coexistence of multiple interactions among ions (e.g., electrostatic interaction, hydrogen bonding, van de Waals forces, acid/base interactions, hydrophilic/hydrophobic interactions, etc.), unique affinity for a wide range of chemicals, good chemical and thermal stability, and quite low volatility. ILs have shown potential applications in various chemical processes.In this Account, we systematically described our most recent work on IL-catalyzed approaches under metal-free conditions. The first section presents the IL-catalyzed strategies toward the transformation of CO2 to value-added chemicals, focusing on the CO2-reactive IL-catalyzed CO2 transformation to various heterocycles and the IL-catalyzed reductive transformation of CO2 to chemicals. In these approaches, we designed task-specific ILs that are able to chemically capture and activate CO2 via forming anion-based carbonate/carbamate or cation-based carboxylate/carbamate intermediates, thus further accomplishing its transformation to a series of heterocycles including quinazoline-2,4(1H,3H)-diones, cyclic carbonates, 2-oxazolidinones, oxazolones, and benzimidazolones under metal-free conditions. For the IL-catalyzed approaches to reducing CO2 with hydrosilanes to chemicals, we employed ILs capable of activating the Si-H bond in hydrosilanes and the N-H bond in amine substrates via H-bonding, thus achieving the reductive transformation of CO2 to formamides, benzimidazoles, and benzothiazoles via cooperative catalysis. The second section describes our finding on the IL-catalyzed hydration of the C≡C bond in propargylic alcohols. Azolate anion-based ILs that can chemically capture CO2 via the formation of carbamates could serve as robust nucleophiles to attack the C≡C bond in propargylic alcohols and then efficiently catalyze the hydration of propargylic alcohols to produce α-hydroxy ketones with the assistance of atmospheric CO2 gas under metal-free conditions. The third section unveils the cooperative catalysis strategy of hydrogen bond donors and acceptors of ILs for chemical reactions. In the hydrogen-bonding catalysis protocols, cations of the ILs act as H-bond donors and anions, as acceptors, forming H-bonds with the reactant molecules, respectively, in opposite ways, which can cooperatively catalyze the ring-closing C-O/C-O bond metathesis reactions of aliphatic diethers to O-heterocycles, the dehydrative etherification of alcohols to ethers, and direct oxidative esterification of alcohols to esters. We believe that these IL-catalyzed metal-free processes and strategies display promising practical applications, and their commercialization would bring great benefits to the production of the as-afforded value-added chemicals.

Understanding the rheological properties of alkali-activated slag pastes from the cohesion and friction interactions

The workability and pumping performance of alkali-activated slag (AAS) concrete are affected by its rheological properties, which are related to the interactions between slag particles in the pastes. The rheological properties of AAS paste with different equivalent sodium oxide (Na2Oeq) dosage activated by sodium hydroxide (NaOH) and sodium silicate (waterglass) with different SiO2/Na2O molar ratios were investigated in this study. The rheological mechanism was studied from the cohesion and friction interactions by calculations from parameters such as the Zeta potential of particles in the pastes, surface energy, hydrogen bond, and friction coefficient of the alkaline activators. The results indicated that the yield stress of AAS pastes was lower than that of the paste made with slag and water, whereas the plastic viscosity was higher. The yield stress of AAS pastes was mainly determined by the friction interactions between particles. The plastic viscosity was mainly affected by attractive interactions, including van de Waals interactions and Lewis acid-base interactions. The electrostatic repulsion interactions were felt at a very short distance because the AAS pastes were systems with the high ionic strength, which means that the electric double layer were severely compressed, therefore, the attractive interactions were predominant. Taken together, these results suggest that the improvement of plastic viscosity of AAS pastes should be achieved by changing the attractive interactions.

In-situ desorption of acetaminophen from the surface of graphene oxide driven by an electric field: A study by molecular dynamics simulation

• Electric field weakens interaction energy between GO and ACT in alkaline conditions. • Electric field destroys the hydrogen bond between GO and ACT. • Electric field reduces hydration energy barrier during the escape of ACT from GO. • Electric field makes ACT can desorb from GO surface more easily. • Electric field can change the hydrophobicity on both sides of GO. In the present study, molecular dynamics (MD) simulation was performed to study the effect of electric field on the adsorption characteristics of acetaminophen (APAP) on graphene oxide (GO) under alkaline conditions by calculating and analyzing the structural and energy parameters of a ternary system containing GO, APAP and water molecules. Our simulations result shows that when there is no electric field, the adsorption of APAP on the GO surface is mainly due to the Van de Waals interaction. When the external electric field exists, it can significantly weaken the interaction energy between GO and APAP, destroy the hydrogen bond, and reduce the hydration energy barrier during the escape of APAP from the GO surface, thereby making APAP can desorb from the GO surface more easily. In addition, the applied electric field can change the hydrophobicity on both sides of GO, which means the hydrophobicity and hydrophilicity of both sides of the GO can be switched by changing the direction and strength of the electric field. Our research results are expected to propose a novel GO regeneration method and provide a new perspective to explore the mechanism.

Observation of a Liquid–Gas Phase Transition upon Antiproton Annihilation in a Nuclear Emulsion

Five hundred events of antiproton stopping and annihilation in nuclear emulsion were observed. A description of the equation of state for nuclear matter in terms of the van de Waals equation made it possible to determine the temperature dependence of the pressure and density and to obtain an estimate for the boundary of the spinodal region in which a uniform state undergoes an instantaneous transition from to a uniform state to a mixture of two phases—fragments and a nuclear gas of nucleons observed experimentally.

Chain conformation and dynamics in ultrahigh molecular weight polyethylene melts undergoing extensional–shear coupled flow: insight from dissipative particle dynamics simulation

AbstractA first attempt is made to present a detailed mesoscopic‐level description of the conformation and equilibrium dynamic properties of macromolecular chains in ultrahigh molecular weight polyethylene/polypropylene blends driven by extension‐dominated coupled flow, in comparison with shear‐dominated coupled flow. Extension‐dominated coupled flow can be defined as = 0.005, ≥ 0.1 and shear‐dominated coupled flow as = 0.1, ≥ 1, as verified by the time‐dependent evolution tendency of cell parameters and velocity profiles along the x, y, z directions. In the case of extension‐dominated coupled flow, the chains are greatly elongated and prefer to align along the flow direction, where the polypropylene chains appear to form a somewhat uniform layer. By comparison, the macromolecular chains assume a highly collapsed conformation and have a greater preference to align themselves perpendicular to the flow direction under shear‐dominated coupled flow, which can be ascribed to the rapid diffusion of polymer chains and a minor role of the weak van de Waals interaction in structural transitions. Analyses of conformational behavior derived from dissipative particle dynamics trajectories can, in general, serve as a useful guideline for experimental investigations of ultrahigh molecular weight polyethylene based materials prepared by eccentric rotor extrusion. © 2020 Society of Chemical Industry

High‐Performance Broadband Photodetectors of Heterogeneous 2D Inorganic Molecular Sb2O3/Monolayer MoS2 Crystals Grown via Chemical Vapor Deposition

AbstractThe newly emerged 2D materials heterostructures, including layered and nonlayered structures, are regarded as the building blocks for future high performance optoelectronic devices. However, it still remains a great challenge to directly synthesize 2D heterostructures for realizing broadband detection in photodetectors. In this work, the growth of vertically stacked inorganic molecular Sb2O3/monolayer MoS2 heterostructures through a two‐step chemical vapor deposition method is demonstrated, and high performance ultraviolet/near‐infrared photodetectors based on the achieved heterostructures are further developed. Excellent responsivity of 5.3 × 104 A W−1 and detectivity of 2.0 × 1015 Jones are obtained under 457 nm illumination. Additionally, the photodetection range can be extended to near‐infrared region. Maximum responsivity of 7.8 A W−1, detectivity of 3.4 × 1011 Jones, and fast response speed (<60 ms) are obtained under 1064 nm laser illumination at room temperature, which is far superior to those of the previously reported ultra‐thin 2D van de Waals heterostructures. The inorganic molecular Sb2O3/monolayer MoS2 heterostructures enrich the family of 2D materials heterostructures, showing potential applications in high performance functional electronics and optoelectronics.

Tunable excitonic properties in two-dimensional heterostructures based on solution-processed PbI2 flakes

We investigate the manifestations of band structure engineering in few-layer PbI2-based heterostructures by probing their tunable optical properties. First, we have successfully prepared atomically thin flakes from PbI2 solution by two distinct approaches. A drop-casting of PbI2 solution onto various substrates followed by a simple heating process yields abundant flakes with different thickness and regular shape. Mechanical exfoliation of PbI2 bulk crystals, obtained from a low-temperature recrystallization process of PbI2 solution, also gives ultrathin PbI2 flakes of high quality. Moreover, these PbI2 flakes are employed to construct various van de Waals heterostructures. A significant enhancement of photoluminescence in MoSe2 interfaced with PbI2 was observed at different laser excitation intensity, due to the forming of type-I band alignment. Type-I band alignment can also be investigated in MoS2/PbI2 heterostructure, while type-II band alignment is built-in WSe2/PbI2 heterostructure. These results demonstrate that the strong interfacial coupling between PbI2 and other two-dimensional semiconductors can modulate their band alignment, and as a result, the exciton properties noticeably, which provides new insights of building a designer heterostructure device at the atomic level.

Nickel (II) modified porous boron nitride: An effective adsorbent for tetracycline removal from aqueous solution

Contamination of aqueous environment caused by various antibiotics has attracted wide attention. It is important to find effective adsorbents for the removal of toxic compounds. Herein, Ni (II) was anchored at the surface of porous boron nitride (BN) by a facile way to enhance the adsorption performance for tetracycline (TC). The interaction between porous BN and Ni (II) was proved to be B-O-Ni bond. It is noteworthy that Ni (II) modified porous BN shows excellent removal percentage up to 99.769% for TC which far exceeds the pristine porous BN (70.853%) and most other reported adsorption materials. The maximum adsorption capacity calculated from the Langmuir model is 429.582 mg g−1, confirming that Ni (II) modified porous BN has a remarkable performance for removing TC. In addition, the adsorption of TC onto Ni (II) modified porous BN followed pseudo-second-order kinetics and the equilibrium data fitted well with the Freundlich isotherm, revealing that chemisorption and multilayer adsorption was dominated. Finally, the results of DFT calculations further demonstrated that the effective adsorption of TC on Ni (II) modified porous BN could be ascribed to cation bridge interaction, π-π interaction, Van de Waals force and electrostatic interaction.

Adsorption of 2-Butanone on Pristine Graphene: A First-principles Study

The adsorption mechanism of 2-butanone (ethyl methyl ketone) on the surface of graphene is investigated by using Density Functionals Theory (DFT). A 2-butanone molecule is chosen as a selected example of main volatile organic compounds (VOCs) in exhaled breath. To describe the absorption of 2-butanone and graphene substrate, we have performed DFT simulations including van de Waals (vdW) interactions implemented in the Vienna Ab-initio Simulation Package (VASP). The global minimum energy configurations and binding energies for a 2-butanone molecule adsorbed on graphene are determined by using Computational DFT-based Nanoscope tool for imaging the binding possibility of the adsorbed molecules on the graphene surface. The adsorption energy profiles are calculated by three functionals of van der Waals interactions: revPBE-vdW, optPBE-vdW, and vdW-DF2. It is shown that the adsorption energy is highly sensitive to the vdW functionals. The fundamental insights of the interactions between 2-butanone and graphene through molecular doping, i.e., charge transfer are discussed in detail.

Magnetic two‐dimensional layered crystals meet with ferromagnetic semiconductors

AbstractThe existence of intrinsic ferromagnetic semiconductors (FMSs) in two‐dimensional (2D) materials has been a long‐term concern and pursuit. Recent breakthroughs in the 2D FMSs, such as CrGeTe3 and CrX3 (X = Cl, Br, I) from bulk down to monolayer, have stimulated intensive researches on new physical phenomena and creative concepts. This minireview mainly summarizes recent progress of 2D intrinsic FMSs in theoretical side, and focuses on the ongoing strategies proposed to enhance ferromagnetism, involving the mechanisms of magnetic exchange interaction and the significance of magnetic anisotropy. Meanwhile, spin‐related multifunctionality with ultrathin FMSs and their van de Waals heterostructures in magnetoelectric, valleytronic, and nondissipative electronic technology are introduced, as well as the current challenges and the prospects in this field are discussed.image

Understanding the inconsistency between mechanism and rate constants of acetylene ozonolysis

The reaction mechanism of acetylene with ozone was studied by using the complete active space self-consistent-field (CASSCF) and the CASPT2 methods. It was confirmed that the reaction follows the Criegee mechanism, yet a van de Waals complex was introduced in the mechanism. We found the master equation method is the key factor to accurately calculate the rate constants and Arrhenius parameters of this reaction, comparing to the results calculated by the traditional transition state method with steady-state assumption by Cremer which are about an order of magnitude smaller than the experimental data.

Mechanism and kinetics of the reaction of the 2‐propargyl radical with ammonia

AbstractGas‐phase mechanism and kinetics of the reactions of the 2‐propargyl radical (H2CCCH), an important intermediate in combustion processes, with ammonia were investigated using ab initio molecular orbital theory at the coupled‐cluster CCSD(T)//B3LYP/6‐311++G(3df,2p) method in conjunction with transition state theory (TST), variational transition state theory (VTST), and Rice–Ramsperger–Kassel–Macus (RRKM) calculations for rate constants. The potential energy surface (PES) constructed shows that the C3H3 + NH3 reaction has four main entrances, including two H‐abstraction and two addition channels in which the former are energetically more favorable. The H‐abstraction channels occur via energy barriers of 24 (T0/P2) and 26 kcal/mol (T0/P3) forming loose van de Waals complexes, COM_1 (12 kcal/mol) and COM_2 (14 kcal/mol), respectively. These complexes can easily be decomposed via barrier‐less processes resulting HCCCH3 + NH2 (P2, 14 kcal/mol) and HCCCH3 + NH2 (P3, 15 kcal/mol), respectively. The additional channels occur initially by formation of two intermediate states, H2CCCHNH3 (35 kcal/mol) and H2CC(NH3)CH (37 kcal/mol) via energy barriers of 37 and 40 kcal/mol at T0/1 and T0/5, respectively, followed by isomerization and decomposition yielding 21 different products. These processes are fully depicted in an as‐complete‐as‐possible PES. The rate constants and product branching ratios for the low‐energy channels calculated show that the C3H3 + NH3 reaction is almost pressure‐independent. For the temperature range of 300–2000 K, the HCCCH3 + NH2 is the major product, whereas the minor one, HCCCH3 + NH2, has more contribution when temperature increases. Theoretical results on the mechanism and kinetics of the reaction considered may be helpful for future experiments as well as for understanding the role of the propargyl radical in combustion chemistry.

Thickness dependence of domain size in 2D ferroelectric CuInP2S6 nanoflakes

Two-dimensional (2D) ferroelectrics refer to those ferroelectrics with layered structure and weak interlayer interactions (e.g., van de Waals interlayer coupling). A number of basic physical issues in the framework of ferroelectricity deserve clarifications, and one of them is the size effect regarding the dependence of ferroelectricity on material thickness. In this work, we investigate the ferroelectric domain structures of 2D ferroelectric CuInP2S6 nanoflakes attached on heavily doped Si wafers and polarization switching using the piezoresponse force microscopy. While the domain structure shows highly irregular morphology and 180° domain walls, the statistics on domain size (diameter) W and nanoflake thickness d demonstrates the remarkable thickness dependence of domain size, illustrated by the shrinking domain size from 630 nm to 75 nm with decreasing thickness d from ∼130 nm to ∼11 nm. This dependence fits the Landau-Lifshitz-Kittel (LLK) scaling law with the scaling exponent of ∼0.65, slightly larger than 0.5 for 3D ferroelectrics. It is suggested that the size effect in terms of the LLK scaling law does not show an essential difference between the 2D and 3D ferroelectric systems.

High-Frequency Elastic Coupling at the Interface of van der Waals Nanolayers Imaged by Picosecond Ultrasonics.

Although the topography of van de Waals (vdW) layers and heterostructures can be imaged by scanning probe microscopy, high-frequency interface elastic properties are more difficult to assess. These can influence the stability, reliability, and performance of electronic devices that require uniform layers and interfaces. Here, we use picosecond ultrasonics to image these properties in vdW layers and heterostructures based on well-known exfoliable materials, i.e., InSe, hBN, and graphene. We reveal a strong, uniform elastic coupling between vdW layers over a wide range of frequencies of up to tens of gigahertz (GHz) and in-plane areas of 100 μm2. In contrast, the vdW layers can be weakly coupled to their supporting substrate, behaving effectively as free-standing membranes. Our data and analysis demonstrate that picosecond ultrasonics offers opportunities to probe the high-frequency elastic coupling of vdW nanolayers and image both "perfect" and "broken" interfaces between different materials over a wide frequency range, as required for future scientific and technological developments.

In silico studies of the interaction of the colon cancer receptor and RNA aptamer adsorbed on (1 0 1) facet of TiO2 nanoparticle investigated by molecular dynamics simulation

The epidermal growth factor receptor (EGFR) is a trans-membrane protein which belongs to the ErbB family of receptor tyrosine kinases (RTK). The peptide growth factors of the EGF-family of proteins activated these trans-membrane proteins by binding to them. In order to blocking these receptors and prevent over-expression in human carcinomas, we used a potential anticancer RNA aptamer. The RNA aptamer was delivered to the target receptor with the TiO2 nanosheet using the molecular dynamics simulation. The structural and energetic parameters were measure and analyzed in detail. The root mean square deviation and fluctuation and center of mass of components were calculated. Besides, the hydrogen bonds were considered to investigate the effect of water molecules. The van de Waals and electrostatics contributions depict the attractive force between RNA aptamer and the receptor. Our results suggest that for better interaction of RNA aptamer and receptor, first the RNA aptamer should release from the Nano carrier surface.

Hetero-layered MoS2/C composites enabling ultrafast and durable Na storage

Transition metal dichalcogenides have been considered as promising conversion-type electrode materials in sodium ion batteries, which allow multi-electron redox processes providing high capacities. However, the conversion reaction often leads to dramatic structural degradation of the electrodes during de-/sodiation, which strongly limits their cycle lifetime, achievable capacities and rate performances. To circumvent these obstacles, in this study, we applied an interfacial engineering strategy by constructing a MoS2/C composite with an inter-overlapped hierarchical structure (MoS2-C@C) through a bottom-up synthesis method. With the alternative stacking of MoS2 and carbon layers, MoS2-C@C provides an ideal environment to maintain the MoS2 structure through the van de Waals interaction within the multilayers. At the same time, the heterointerfaces in MoS2-C@C offer abundant electron transfer pathways. Consequently, the MoS2-C@C electrode exhibits prominently improved electrochemical performance including a high reversible capacity of 590 mA h g−1, a superior cycling stability up to 1000 cycles and an excellent rate capability (164 mA h g−1 at 20 A g−1 and 51 mA h g−1 at 50 A g−1). The fast kinetics and high reversibility of the hetero-layered MoS2/C composite for Na storage demonstrate the feasibility of this synthetic strategy to prevent the structural degradation of the conversion-type battery materials.

(Invited) Controlling Energy Transport in Tailored Carbon Nanotubes Networks for Energy Harvesting Applications

The ability to selectively extract semiconducting single-walled carbon nanotube (s-SWCNT) species from the raw material with high fidelity is leading to their incorporation as elements in a variety of optical and electronic applications. We have recently employed conjugated polymers based on the fluorene chemical moiety to produce tailored s-SWCNT samples that can be incorporated into photovoltaic, thermoelectric, and transistor architectures.By controlling both the extent of carbon nanotube bundling and/or removing the insulating polymer that wraps the individual carbon nanotubes, we explore the complex effects of these morphological modifications on the transport of energy by excitonic species and charge carriers in enriched s-SWCNT networks. We show that removal of the insulating polymer, which is often strongly bound to the carbon nanotubes through van de Waals forces between the π-electron systems of the two components, results in a significant improvement in charge carrier transport. In contrast, exciton transport is subtly dependent on the specific nanotube-nanotube interactions in the network. For instance, exciton energy transfer to minority low-bandgap species within a bundle is extremely efficient, but this often traps the exciton in an individual bundle, thereby inhibiting long-range transport within the network.As alluded to above, the performance of carbon nanotubes in these applications is sometimes strongly dependent on the interplay between the optical and electronic properties of the s-SWCNT networks, which can be controlled by tuning the charge carrier density. We have developed a number of processes that allow us to exert fine control over the charge carrier density injected by redox-active chemical dopants, including the ability to controllably dope the s-SWCNT network p-type and n-type. We will discuss how these strategies can be exploited to exert fine control over charge-carrier transport in the doped s-SWCNT networks, allowing us to target the optimum doping level for the desired application.Finally, we will discuss the implications of our findings within the context of the incorporation of enriched s-SWCNT networks in energy harvesting applications.