Adsorption Of Small Molecules Research Articles

Effect of oxygen-containing groups in functionalized graphene on its gas sensing properties

The creation of active material for chemiresistive gas sensors with high selectivity and sensitivity will allow a step towards miniaturization and reduction of power consumption of portable gas sensors. Graphene is a promising platform for the synthesis of two-dimensional active materials with high sensitivity. In this work, applying density functional theory (DFT) calculations, the effect of oxygen-containing functional groups (O, OH, O, COOH) on the adsorption of small gas molecules (NH3, CO2, CO, H2S, NO2, SO2) was rigorously studied. Based on the adsorption energies and partial charges from DFT calculations, the sensitivity and selectivity of graphene with different functionalizations were predicted. It was found that hydroxyl and carboxyl groups demonstrate increased selectivity and sensitivity of gas sensors, and the edge of graphene with hydroxyl groups shows the highest enhancement. Graphene with a carbonyl group was found to undergo irreversible chemisorption of NO2, which can potentially cause active material degradation, limiting the recyclability of gas sensors. Most of the molecules show both donor and acceptor behavior, which highlights the importance of a thorough selection of specific functional group types. The obtained results are useful for the rational design of graphene-based active material with oxygen-containing functional groups for chemiresistive gas sensors.

Insights into the hexamine-assisted ZnO based-MOFs formation on PET fabric for improved self-cleaning, flame retardant, and hydrophilic properties

Organo-metallic frameworks (MOFs) have attracted much attention in the last decade due to their large pore size, large surface area, selective adsorption of small molecules, and optical or magnetic responses in the presence of guest molecules. Particularly, the use of MOFs on textile products through in situ synthesis leads to special properties in a simple method. Here, the polyester fabric was first activated by alkali hydrolysis and then the ZnO-based MOFs were synthesized to obtain a fabric with multifunctional features. FESEM images and EDX elemental analysis showed the presence of MOF particles and zinc, nitrogen, and hydrogen on the polyester surface. The weight of the treated samples increased however the water spreading time decreased due to the polar groups of the MOFs creating higher hydrophilic properties. The presence of hydroxyl and amine groups on the surface of the MOFs-treated polyester was confirmed by FTIR spectroscopy. The final fabric showed photocatalytic self-cleaning, and UV protection properties. In addition, TGA, ash percentage, and burnt length results demonstrated the flame-retardant properties. The tensile strength, thickness, and stiffness of the MOFs-treated fabrics also increased. Finally, the hexamine-assisted ZnO-based MOFs on the polyester surface improve its properties and usability.

Transition Metal (Co, V, W, Zr) Single-Atom Decorated Biphenylene for Enhancing the Sensing Performance of SF6 Decomposition Molecules.

The highly sensitive gas sensors used to monitor the decomposition of toxic gases in the dielectric materials of electrical equipment are vital in preventing safety problems arising from corrosion of the equipment. Recently, biphenylene (BPN) has been prepared through surface interpolymer hydrofluorination (HF zipper) reaction, whereas potential gas-sensitive devices based on the BPN monolayer have lacked in-depth investigation. The stable geometries, adsorption energies, interlayer distances, and charge transfers of small molecules of toxic gases (H2S, SO2, SOF2, SO2F2) produced by SF6 chalcogenide molecules of decomposition adsorbed on the original BPN monolayer are systematically researched by using nonequilibrium Green's function methods and density functional theory. The results indicated that all small molecules adsorbed on the BPN monolayer are physisorbed, while the type of adsorption turned from physisorption to chemisorption when BPN carried out adsorption with adsorbing a transition metal atom (TMA). In addition, the characteristics of current-voltage (I-V) curves of H2S and SO2 based on the TMA-BPN gas sensors revealed that the currents in BPN-based gas sensors displayed an obvious anisotropy, and the currents in the zigzag direction are larger than that in the armchair orientation regardless of the molecular adsorption cases. Moreover, the difference of currents for TMA-decorated BPN sensors changed more remarkably before and after the adsorption of H2S and SO2 in the zigzag direction. This work offers insights into the design of gas-sensitive devices through the adsorption of small molecules on the TMA-decorated BPN monolayer.

Adsorption of small gas molecules onto boron nitride nanotubes and their Al-, Ga-, Cr- and Fe-doping derivatives for gas sensing, storage, and catalytic properties: Periodic DFT study

Based on the toxic gases and their conversion to non-toxic gases on the high potentials doping derivatives of boron nitride nanotubes (BNNTs), adsorption abilities of (5,5) and (10,0) BNNTs doped by selected dopants (Al, Ga, Cr and Fe) on small gas molecules was explored. Adsorption of small gas molecules, H2O, H2S, SO2, CO2, CO, NH3, N2O, and NO onto the pristine (5,5) and (10,0) BNNTs, their doping derivatives (Al-, Ga-, Cr- and Fe-doped (5,5) and (10,0) BNNTs) were investigated using periodic DFT method. Strong adsorptions of N2O (-4.26 eV) and SO2 (-2.56 eV) on the Cr-(5,5) and Cr-(10,0) BNNTs were found. Furthermore, the Cr-(5,5) and Cr-(10,0) BNNTs as the catalysts for N2O conversion to N2 and O2 were found. The Al- and Ga-(5,5) BNNTs, Al- and Ga-(10,0) BNNTs are suggested as the NO sensing materials and NH3 storage materials. All the suggested materials such Cr-(5,5), Cr-(10,0), Al-(5,5), Ga-(5,5), Al-(10,0) and Ga-(10,0) BNNTs could be experimentally tested for conversion, sensitivity, and storage of mentioned toxic gases in the future.

Open-Top Patterned Hydrogel-Laden 3D Glioma Cell Cultures for Creation of Dynamic Chemotactic Gradients to Direct Cell Migration.

The laminar flow profiles in microfluidic systems coupled to rapid diffusion at flow streamlines have been widely utilized to create well-controlled chemical gradients in cell cultures for spatially directing cell migration. However, within hydrogel-based closed microfluidic systems of limited depth (≤0.1 mm), the biomechanical cues for the cell culture are dominated by cell interactions with channel surfaces rather than with the hydrogel microenvironment. Also, leaching of poly(dimethylsiloxane) (PDMS) constituents in closed systems and the adsorption of small molecules to PDMS alter chemotactic profiles. To address these limitations, we present the patterning and integration of a PDMS-free open fluidic system, wherein the cell-laden hydrogel directly adjoins longitudinal channels that are designed to create chemotactic gradients across the 3D culture width, while maintaining uniformity across its ∼1 mm depth to enhance cell-biomaterial interactions. This hydrogel-based open fluidic system is assessed for its ability to direct migration of U87 glioma cells using a hybrid hydrogel that includes hyaluronic acid (HA) to mimic the brain tumor microenvironment and gelatin methacrylate (GelMA) to offer the adhesion motifs for promoting cell migration. Chemotactic gradients to induce cell migration across the hydrogel width are assessed using the chemokine CXCL12, and its inhibition by AMD3100 is validated. This open-top hydrogel-based fluidic system to deliver chemoattractant cues over square-centimeter-scale areas and millimeter-scale depths can potentially serve as a robust screening platform to assess emerging glioma models and chemotherapeutic agents to eradicate them.

On the Statistical Mechanics of Mass Accommodation at Liquid-Vapor Interfaces.

We propose a framework for describing the dynamics associated with the adsorption of small molecules to liquid-vapor interfaces using an intermediate resolution between traditional continuum theories that are bereft of molecular detail and molecular dynamics simulations that are replete with them. In particular, we develop an effective single particle equation of motion capable of describing the physical processes that determine thermal and mass accommodation probabilities. The effective equation is parametrized with quantities that vary through space away from the liquid-vapor interface. Of particular importance in describing the early time dynamics is the spatially dependent friction, for which we propose a numerical scheme to evaluate from molecular simulation. Taken together with potentials of mean force computable with importance sampling methods, we illustrate how to compute the mass accommodation coefficient and residence time distribution. Throughout, we highlight the case of ozone adsorption in aqueous solutions and its dependence on electrolyte composition.

Preparation of self-standing ultra-thin three-dimensional covalent organic frameworks by interfacial polymerization for dye separation

Three-dimensional covalent organic frameworks (3D COFs) have garnered considerable attention in the adsorption of small molecules owing to their unique 3D pore structure and easily modifiable functional group sites. However, most 3D COFs exhibit lattice interpenetration, making the membrane fabrication process difficult. Most 3D COFs are prepared as powders using solvothermal methods, which severely limits their application in material separation. Therefore, self-supporting 3D COFs membranes were fabricated using room-temperature interfacial polymerization, a low-energy method. Traditional alkane/water interfacial polymerization methods have disadvantages such as poor water solubility of the monomer, volatile solvents, and low crystallinity. Herein, an imine-linked, self-standing, 3D COFs membrane with an ultrathin layer was engineered at the alkane/ionic liquid interface. Owing to the improved crystalline structure, which exposed a large number of imine-linked sites within a 3D pore channel, the constructed 3D COFs membrane exhibited a high Brunauer–Emmett–Teller surface area of 1061.4 m2·g−1 and high water flux of approximately 76 L·m−2 h−1 bar−1 and demonstrated excellent rejection rates of 97.76% and 95.36% for two cationic dyes, rhodamine B and methylene blue, respectively. The membrane exhibited high rejection rates after seven testing cycles. This study reveals the great potential of self-standing 3D COFs membranes as dye separation.

Enhancing low-temperature CO removal in complex flue gases: A study on La and Cu doped Co3O4 catalysts under real-world combustion environment

Designing CO oxidation catalysts for complex flue gases conditions is particularly challenging in fire scenarios. Traditional flue gas simulations use a few representative gases but often fail to adequately evaluate catalyst performance in real-world combustion conditions. In this study, we developed doping strategies using La and Cu to enhance the water resistance of Co3O4 catalysts. Catalyst 0.1La-Co3O4-CuO/CeO2 exhibits exceptional low-temperature catalytic activity, achieving 100% conversion at 130 °C. This enhancement is largely due to the introduction of La, which increases the active Co3+/Co2+ ratio and suppresses hydroxyl group formation on the Co3O4 surface. Cu doping also changes the Co3O4 lattice structure, forming Cu+ as active sites and enhancing the activity at low temperatures. For the first time, steady-state tube furnace and fixed bed were employed to evaluate the catalytic performance of CO in actual combustion atmosphere. Catalyst 0.1La-Co3O4-CuO/CeO2 maintains excellent catalytic efficiency (T100 = 120 °C) under well-ventilated conditions. However, its activity significantly decreases in poorly ventilated environments, due to the competitive adsorption of small molecules at active sites, such as acetone, commonly found in smoke. This study provides valuable insights for designing water-resistant, low-temperature, non-noble metal catalysts and offers a methodology for evaluating CO catalytic activity in real-world environments.

SERS-Based Hydrogen Bonding Induction Strategy for Gaseous Acetic Acid Capture and Detection.

Surface-enhanced Raman scattering (SERS) can overcome the existing technological limitations, such as complex processes and harsh conditions in gaseous small-molecule detection, and advance the development of real-time gas sensing at room temperature. In this study, a SERS-based hydrogen bonding induction strategy for capturing and sensing gaseous acetic acid is proposed for the detection demands of gaseous acetic acid. This addresses the challenges of low adsorption of gaseous small molecules on SERS substrates and small Raman scattering cross sections and enables the first SERS-based detection of gaseous acetic acid by a portable Raman spectrometer. To provide abundant hydrogen bond donors and acceptors, 4-mercaptobenzoic acid (4-MBA) was used as a ligand molecule modified on the SERS substrate. Furthermore, a sensing chip with a low relative standard deviation (RSD) of 4.15% was constructed, ensuring highly sensitive and reliable detection. The hydrogen bond-induced acetic acid trapping was confirmed by experimental spectroscopy and density functional theory (DFT). In addition, to achieve superior accuracy compared to conventional methods, an innovative analytical method based on direct response hydrogen bond formation (IO-H/Iref) was proposed, enabling the detection of gaseous acetic acid at concentrations as low as 60 ppb. The strategy demonstrated a superior anti-interference capability in simulated breath and wine detection systems. Moreover, the high reusability of the chip highlights the significant potential for real-time sensing of gaseous acetic acid.

Effect analysis on hydrocarbon adsorption enhancement of different zeolites in cold start of gasoline engine based on Monte Carlo method

50%–80% of the hydrocarbons in gasoline engine emissions come from during cold starts. Zeolites are often used to adsorb HCs during gasoline engine cold-starting. In order to investigate the effect of adsorption enhancement of different molecular sieves on HCs during gasoline engine cold-starting. In this paper, the adsorption properties of Beta, MOR and FER zeolites at different temperatures were simulated based on Monte Carlo method using propylene and toluene as probe molecules. The results show that all three molecular sieves exhibit good adsorption properties at low temperatures. The adsorption capacity decreased with increasing temperature. The molecular sieves tend to adsorb molecules with diameters similar to the pore size of zeolite. In addition, the three-dimensional zeolites Beta and FER showed better adsorption properties than the one-dimensional zeolites. Based on Monte Carlo method, the adsorption properties of Beta, MOR and FER molecular sieves were investigated at different temperatures under multi-components using toluene, isopentane, propylene, ethylene, methane and water as adsorbents. The results showed that there was a competitive adsorption among the components due to the limited adsorption sites in the molecular sieve channels. Large molecules such as toluene and isopentane occupied most of the adsorption sites and hindered the adsorption of small molecules.

Spectra-Based Machine Learning for Predicting the Statistical Interaction Properties of CO Adsorbates on Surface.

Theoretical analyses of small-molecule adsorption on heterogeneous catalyst surfaces often rely on simplified models of molecular adsorption with the most favorable configuration. Given that real-world experimental tests frequently entail multiple molecules interacting with the surface, there is a pressing need for a comprehensive multimolecule adsorption model to bridge the gap between theory and experiment. Using machine learning, we predict the average values of important adsorption properties from conformationally averaged, calculated infrared and Raman spectra and compare these values to those theoretically derived from the conformationally averaged ensemble. Remarkably, our approach yields excellent predictions even when faced with large and indeterminate numbers of surface molecules. These quantitative spectra-averaged property relationships provide a theoretical framework for extracting key interaction properties from the spectra of real chemical environments.

Interaction of N2, O2 and H2 Molecules with Superalkalis.

Superalkalis (SAs) are exotic clusters having lower ionization energy than alkali atoms, which makes them strong reducing agents. In the quest for the reduction of diatomic molecules (X2) such as N2, O2, and H2 using Møller-Plesset perturbation theory (MP2), we have studied their interaction with typical superalkalis such as FLi2, OLi3, and NLi4 and calculated various parameters of the resulting SA-X2 complexes. We noticed that the SA-O2 complex and its isomers possess strong ionic interaction, which leads to the reduction of O2 to O2 - anion. On the contrary, there are both ionic and covalent interactions in SA-N2 complexes such that the lowest energy isomers are covalently bonded with no charge transfer from SA. Further, the interaction between SA and H2 leads to weakly bound complexes, which results in the adsorption of H2 molecules. The nature of interaction is found to be closely related to the electron affinity of diatomic molecules. These findings might be useful in the study of the activation, reduction, and adsorption of small molecules, which can be further explored for their possible applications.

Surface-segregating zwitterionic copolymers to control poly(dimethylsiloxane) surface chemistry.

The use of microfluidic devices in biomedicine is growing rapidly in applications such as organs-on-chip and separations. Polydimethylsiloxane (PDMS) is the most popular material for microfluidics due to its ability to replicate features down to the nanoscale, flexibility, gas permeability, and low cost. However, the inherent hydrophobicity of PDMS leads to the adsorption of macromolecules and small molecules on device surfaces. This curtails its use in "organs-on-chip" and other applications. Current technologies to improve PDMS surface hydrophilicity and fouling resistance involve added processing steps or do not create surfaces that remain hydrophilic for long periods. This work describes a novel, simple, fast, and scalable method for improving surface hydrophilicity and preventing the nonspecific adsorption of proteins and small molecules on PDMS through the use of a surface-segregating zwitterionic copolymer as an additive that is blended in during manufacture. These highly branched copolymers spontaneously segregate to surfaces and rearrange in contact with aqueous solutions to resist nonspecific adsorption. We report that mixing a minute amount (0.025 wt%) of the zwitterionic copolymer in PDMS considerably reduces hydrophobicity and nonspecific adsorption of proteins (albumin and lysozyme) and small molecules (vitamin B12 and reactive red). PDMS blended with these zwitterionic copolymers retains its mechanical and physical properties for at least six months. Moreover, this approach is fully compatible with existing PDMS device manufacture protocols without additional processing steps and thus provides a low-cost and user-friendly approach to fabricating reliable biomicrofluidics.

Adsorption and activation of small molecules on boron nitride catalysts.

Hexagonal boron nitride possesses a unique layered structure, high specific surface area and similar electronic properties as graphene, which makes it not only a promising catalyst support, but also a highly effective metal-free catalyst in the booming field of green chemistry. Reactions involving small molecules (e.g., oxygen, low carbon alkanes, nitrogen and carbon dioxide) have always been a hot topic in catalytic research, especially associated with the adsorption and activation regime of different forms of small molecules on catalysts. In this review, we have investigated the adsorption of different small molecules and the relevant activation mechanisms of four typical chemical bonds (OO, C-H, NN, CO) on hexagonal boron nitride. Recent progress on approaches adopted to enhance the activation capacity such as doping, defect engineering and heterostructuring are summarized, highlighting the potential applications of nonmetallic hexagonal boron nitride catalysts in various reactions. This comprehensive investigation offers a reference point for the enhanced mechanistic understanding and future design of effective and sustainable catalytic systems based on boron nitride.

Probing the role of surface termination in the adsorption of azupyrene on copper.

The role of the inorganic substrate termination, within the organic-inorganic interface, has been well studied for systems that contain strong localised bonding. However, how varying the substrate termination affects coordination to delocalised electronic states, like that found in aromatic molecules, is an open question. Azupyrene, a non-alternant polycyclic aromatic hydrocarbon, is known to bind strongly to metal surfaces through its delocalised π orbitals, thus yielding an ideal probe into delocalised surface-adsorbate interactions. Normal incidence X-ray standing wave (NIXSW) measurements and density functional theory calculations are reported for the adsorption of azupyrene on the (111), (110) and (100) surface facets of copper to investigate the dependence of the adsorption structure on the substrate termination. Structural models based on hybrid density functional theory calculations with non-local many-body dispersion yield excellent agreement with the experimental NIXSW results. No statistically significant difference in the azupyrene adsorption height was observed between the (111) and (100) surfaces. On the Cu(110) surface, the molecule was found to adsorb 0.06 ± 0.04 Å closer to the substrate than on the other surface facets. The most energetically favoured adsorption site on each surface, as determined by DFT, is subtly different, but in each case involved a configuration where the aromatic rings were centred above a hollow site, consistent with previous reports for the adsorption of small aromatic molecules on metal surfaces.

Two-dimensional Janus X2STe (X = B, Al) monolayers: the effect of surface selectivity and adsorption of small gas molecules on electronic and optical properties.

This investigation delves into the adsorption characteristics of CO, NO, NO2, NH3, and O2 on two-dimensional (2D) Janus group-III materials, specifically Al2XY and B2XY. The examination covers adsorption energies and heights, diverse adsorption sites, and molecular orientations. Employing first-principles analysis, a comprehensive assessment of structural, electronic, and optical properties is conducted. The findings highlight NO2 as a prominent adsorbate, emphasizing the Te surface of 2D Al2STe and B2STe materials as particularly adept for NO2 detection, based on considerations of adsorption energy, height, and charge transfer. Additionally, the study underscores the heightened sensitivity of work function changes in the B2STe material. The adsorption properties of all gas molecules, except for NO2, on both materials were determined to be physical. Upon adsorption of the NO2 gas molecule onto the B2STe Janus material, it was observed that the material exhibited weak chemical adsorption behavior, which was confirmed by the adsorption energy, larger band gap change, electron localization function, work function changes and charge transfer from the material. This research provides valuable insights into the gas-sensing potential of 2D Janus materials.

Cooperativity between coordinative unsaturated Fe(iii) and aryl-π electrons in MIL-100(Fe) for adsorption of small molecules

Coordinatively unsaturated sites and aryl-π electrons coorperatively affect the adsorption of aromatics with polar groups.

Capturing Acidic CO2 Using Surface-Active Difunctional Core-Shell Composite Polymer Particles via an Aqueous Medium.

Multifunctional surface-active polymeric composites are attractive materials for the adsorption of various small molecules. Herein, dual-functionalized micron-sized surface-active composite polymer particles were prepared by a three-step process for CO2 adsorption. First, polystyrene (PS) seed particles were prepared via the dispersion polymerization of styrene. PS/P(MMA-AAm-EGDMA) composite polymer particles were then synthesized by aqueous seeded copolymerization of methyl methacrylate (MMA) and acrylamide (AAm) in the presence of an ethylene glycol dimethacrylate (EGDMA) cross-linker. Finally, the amide moieties of PS/P(MMA-AAm-EGDMA) composite particles were converted into an amine-functionalized composite by using the Hofmann degradation reaction. The presence of primary amine groups on the surface of aminated composite particles was confirmed by some conventional chemical routes, such as diazotization and Schiff's base formation reactions. The formation and functionality of the PS seed, PS/P(MMA-AAm-EGDMA), and aminated PS/P(MMA-AAm-EGDMA) composite polymer particles were confirmed by Fourier transform infrared (FTIR) spectra analyses. Scanning electron microscopy (SEM) analysis revealed spherical shape, size, and surface morphologies of the PS seed, reference composite, and aminated composites. The elemental surface compositions, surface porosity, pore volume, pore diameter, and surface area of both composite particles were evaluated by energy-dispersive X-ray (EDX) mapping, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) analyses. Dynamic light scattering (DLS) and ζ-potential measurements confirmed the pH-dependent surface properties of the functionalized particles. The amount of the adsorbed anionic emulsifier, sodium dodecyl sulfate (SDS), on the surface of aminated PS/P(MMA-AAm-EGDMA) is higher at pH 4 than that at pH 10. A vice versa result was found in the case of cationic surfactant, hexadecyltrimethylammonium bromide (HTABr), adsorption. Synthesized aminated composite particles were used as an adsorbent for CO2 adsorption via bubbling CO2 in an aqueous medium. The changes in dispersion pH were monitored continuously during the adsorption of CO2 under various conditions. The amount of CO2 adsorption by aminated composite particles was found to be 209 mg/g, which is almost double that of reference composite particles.

Zeolitic imidazolate framework-8 nanosheet assemblies for high-efficiency small molecule adsorption

Metal-organic frameworks (MOFs) have gained tremendous attention based on the prospect of application-oriented structural tuning. In this study, the surfactant (SDS)-directed hydrothermal synthesis route was adopted for a one-pot, bottom-up synthesis of ZIF-8 spherical assemblies, stacked with externally oriented and intergrown two-dimensional (2D) nanosheets. The as-obtained nanosheet assemblies exhibited good crystallinity, a large surface area, and excellent thermal stability, as shown by XRD, BET, and TGA, respectively. More importantly, the ZIF-8 nanosheet assemblies displayed excellent small molecule adsorption characteristics, especially for the negatively charged dyes, including rose bengal (RB), uni-blue A (UA), and methyl orange (MO). Furthermore, samples showed a pseudo-second-order adsorption mechanism for dye molecules and presented a good fit for Langmuir's and Temkin's adsorption isotherms with an R2 value of 0.98 and 0.94, respectively. Adsorbent–adsorbate electrostatic interaction, nanosheet structures, molecular size and structural aromaticity of the dye, and the presence of SDS functionalities were found as the essential components for the high-capacity dye adsorption as compared with previous studies.

DFT study on adsorption of small gas molecules on Pt-capped armchair and zigzag single-walled carbon nanotubes

The adsorption of small gas molecules (CO, O2 and N2) on Pt-capped armchair and zigzag single-walled carbon nanotubes (SWCNT) has been investigated by density functional theory (DFT) method to determine the potential for gas sensor detection. Results indicated that O2 and N2 molecules with lower adsorption energies (1.66 eV and 1.00 eV) exhibited weak chemical adsorption on SWCNT(4,4)-Pt. However, CO demonstrates strong chemical adsorption with a high adsorption energy of 2.23 eV on SWCNT(4,4)-Pt. The adsorption energy of CO on SWCNT(7,0)-Pt shows the chemical adsorption between CO and SWCNT(7,0)-Pt. In addition, these findings also implied Pt-capped SWCNT could act as small gas molecule sensors to detect CO toxic gas at room temperature. In this system, CO is the electron donor and SWCNT-Pt is the electron receptor. The interaction of Pt and carbon nanotube backbone delocalized π electrons could not only increases the conductivity of SWCNT-Pt, but also enhances the conductivity of SWCNT-Pt-CO. The HOMO-LUMO gap (Δε) of Pt-capped SWCNT(7,0) reduced from 0.43 eV to 0.39 eV after CO adsorption, and the Δε value of Pt-capped SWCNT(4,4) decreased by 0.08 eV. The electrical conductivity of Pt-capped armchair and zigzag SWCNT has increased after the adsorption of CO molecule. The results may be helpful for designing a promising Pt-capped SWCNT-based CO sensors.