P-doped Nanotubes Research Articles

Theoretical study of ethanol interaction with pristine and P-doped single-walled carbon nanotubes

Feasible interactions between metallic single-walled carbon nanotubes (CNT) and ethanol gases were carried out using theory of first principles based on DFT. Also, the vdW correction and spin polarized were included in this account. The equilibrium position, adsorption energy, charge transfer and electronic band structure of ethanol rearranged inside and outside pristine also with P-doped nanotubes were calculated to estimate the responses of P-CNT. It was found that the ethanol preferred to absorb inside than outside the tube and revealed that ethanol fit suitably inside CNT at diameter of 8.19 Å. Conversely, larger size of nanotubes diameter than 13.63 Å, the ethanol equivalently forms both inside and outside carbon nanotubes. The investigations on electronic properties have been shown that ethanol performed as electron-withdrawing group because of hydroxyl group attached with ethyl group. Then, the electron in CNT moves toward the adsorbate thereby enhancing its conductivity. Furthermore, doping an impurity, Phosphorus, on the surface improved the absorption and the characteristic of all intermolecular interactions.

Preparation of P doped TiO2 nanotubes and its photocatalytic activity

ABSTRACTUsing tetrabutyl titanate as the titanium precursor, H3PO4 as the source of phosphorus, P-doped TiO2 nanoparticles HPT were prepared by hydrothermal method. Then P-doped nanotubes ETNT and DTNT were prepared by two-step hydrothermal and calcination method by taking titanate nanotubes (TNT) TiO2 as raw materials. The resulting materials were characterized by XRD, TEM, DRS and N2 adsorption. The photocatalytic degradation of phenol experiments showed that the P-doped nanotubes, especially the DTNT photocatalyst exhibited higher degradation efficiency than the others. Hydroxyl radicals (•OH) have been confirmed to be the active species during the photo-catalytic oxidation reaction.

Biocompatible calcium and phosphorous-doped titania nanotubes influences the osteogenic differentiation of human mesenchymal stem cells

Biocompatible calcium and phosphorous-doped titania nanotubes influences the osteogenic differentiation of human mesenchymal stem cells

Phosphorus and phosphorus–nitrogen doped carbon nanotubes for ultrasensitive and selective molecular detection

A first-principles approach is used to establish that substitutional phosphorus atoms within carbon nanotubes strongly modify the chemical properties of the surface, thus creating highly localized sites with specific affinity towards acceptor molecules. Phosphorus-nitrogen co-dopants within the tubes have a similar effect for acceptor molecules, but the P-N bond can also accept charge, resulting in affinity towards donor molecules. This molecular selectivity is illustrated in CO and NH3 adsorbed on PN-doped nanotubes, O2 on P-doped nanotubes, and NO2 and SO2 on both P- and PN-doped nanotubes. The adsorption of different chemical species onto the doped nanotubes modifies the dopant-induced localized states, which subsequently alter the electronic conductance. Although SO2 and CO adsorptions cause minor shifts in electronic conductance, NH3, NO2, and O2 adsorptions induce the suppression of a conductance dip. Conversely, the adsorption of NO2 on PN-doped nanotubes is accompanied with the appearance of an additional dip in conductance, correlated with a shift of the existing ones. Overall these changes in electric conductance provide an efficient way to detect selectively the presence of specific molecules. Additionally, the high oxidation potential of the P-doped nanotubes makes them good candidates for electrode materials in hydrogen fuel cells.

Electronic Transport and Mechanical Properties of Phosphorus- and Phosphorus−Nitrogen-Doped Carbon Nanotubes

We present a density functional theory study of the electronic structure, quantum transport and mechanical properties of recently synthesized phosphorus (P) and phosphorus-nitrogen (PN) doped single-walled carbon nanotubes. The results demonstrate that substitutional P and PN doping creates localized electronic states that modify the electron transport properties by acting as scattering centers. Nonetheless, for low doping concentrations (1 doping site per ∼200 atoms), the quantum conductance for metallic nanotubes is found to be only slightly reduced. The substitutional doping also alters the mechanical strength, leading to a 50% reduction in the elongation upon fracture, while Young's modulus remains approximately unchanged. Overall, the PN- and P-doped nanotubes display promising properties for components in composite materials and, in particular, for fast response and ultra sensitive sensors operating at the molecular level.

Electrochemical Doping of Chirality-Resolved Carbon Nanotubes

Raman spectra of electrochemically charged single-wall carbon nanotubes (HiPco) were studied by five different laser photon energies between 1.56 and 1.92 eV. The bands of radial breathing modes (RBM) were assigned to defined chiralities by using the experimental Kataura plot. The particular (n,m) tubes exhibit different sensitivity to electrochemical doping, monitored as the attenuation of the RBM intensities. Tubes which are in good resonance with the exciting laser exhibit strong doping-induced drop of the RBM intensity. On the other hand, tubes whose optical transition energy is larger than the energy of an exciting photon show only small changes of their RBM intensities upon doping. This rule presents a tool for analysis of mixtures of single-walled carbon tubes of unknown chiralities. It also asks for a re-interpretation of some earlier results which were reported on the diameter-selectivity of doping. The radial breathing mode in strongly n- or p-doped nanotubes exhibited a blue-shift. A suggested interpretation follows from the charging-induced structural changes of SWCNTs bundles, which also includes a partial de-bundling of tube ropes.

Controlled creation of a carbon nanotube diode by a scanned gate

We use scanning gate microscopy to precisely locate the gating response in field-effect transistors (FETs) made from semiconducting single-wall carbon nanotubes. A dramatic increase in transport current occurs when the device is electrostatically doped with holes near the positively biased electrode. We ascribe this behavior to the turn-on of a reverse biased Schottky barrier at the interface between the p-doped nanotube and the electrode. By positioning the gate near one of the contacts, we convert the nanotube FET into a rectifying nanotube diode. These experiments both clarify a longstanding debate over the gating mechanism for nanotube FETs and indicate a strategy for diode fabrication based on controlled placement of acceptor impurities near a contact.