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A PT-SWCNTs self-assembled nanorobot is proposed to release residual H2 based on adhesion competition in a SWCNT system.

The thermal conductivity (TC) of non-periodic Si/Ge superlattice nanowire (SLNW) is investigated by non-equilibrium molecular dynamics simulation (NEMD). It is found that the TC of non-periodic Si/Ge SLNW can be significantly reduced at room temperature. Compared to the minimum TC of periodic Si/Ge SLNWand pure Si nanowire, the TC of non-periodic Si/Ge SLNW is further decreased to be around 47.4%, 4.4% of that of periodic Si/Ge SLNW and pure Si nanowire respectively. By introducing 20% Ge atom doping, the TC of non-periodic Si/Ge SLNW with 10-unit cell (UC) thickness is reduced by 38%. The reduction of TC of non-period Si/Ge SLNW is first due to the destruction of phonon coherent transport. Additionally, the change of periodic length can cause shift of density of state (DOS), which makes the interface of Si/Ge with different lengths play roles to scatter the phonon with different wavelengths. Therefore, the distribution of thickness from atomic to nano scale can decrease the TC by scattering phonon with more wavelengths. The results provide an efficient way for future thermoelectric applications.

The thermal conductivity of isotopically pure wurtzite GaN and the corresponding two-dimensional monolayer crystals are investigated based on first-principles calculations and phonon Boltzmann transport equation. It is found that the c-axis thermal conductivity of defect-free wurtzite GaN is 42–11% higher than that along the in-plane direction when temperature increases from 100 to 800 K. Our calculation also shows that the thermal conductivity of monolayer GaN with hexagonal lattice is higher than that with haeckelite lattice by a factor of four at room temperature. The phonon dispersion relation, phonon group velocity and the phonon scattering rate are extracted to uncover the underlying physical mechanism. The thermal conductivity accumulation function with respect to the phonon mean free path and the relative contribution of each phonon branch for the two kinds of monolayer GaN are further calculated as compared to that of graphene. These investigations would provide important guidance to develop GaN-based electronic and photonic device.

We describe here an Nd3+-sensitized upconversion fluorescent sensor for epirubicin (EPI) detection in aqueous solutions under 808 nm laser excitation. The upconversion fluorescence of nanoparticles is effectively quenched in the presence of EPI via a fluorescence resonance energy transfer mechanism. The dynamic quenching constant was 2.10 &times, 104 M&minus, 1. Normalized fluorescence intensity increased linearly as the EPI concentration was raised from 0.09 &mu, M to 189.66 &mu, M and the fluorometric detection limit was 0.05 &mu, M. The sensing method was simple, fast, and low-cost and was able to be applied to determine the levels of EPI in urine with spike recoveries from 97.5% to 102.6%. Another important feature of the proposed fluorescent sensor is that it holds a promising potential for in vivo imaging and detection due to its distinctive properties such as weak autofluorescence, low heating effect, and high light penetration depth.

We describe here an Nd3+-sensitized upconversion fluorescent sensor for epirubicin (EPI) detection in aqueous solutions under 808 nm laser excitation. The upconversion fluorescence of nanoparticles is effectively quenched in the presence of EPI via a fluorescence resonance energy transfer mechanism. The dynamic quenching constant was 2.10 × 104 M−1. Normalized fluorescence intensity increased linearly as the EPI concentration was raised from 0.09 μM to 189.66 μM and the fluorometric detection limit was 0.05 μM. The sensing method was simple, fast, and low-cost and was able to be applied to determine the levels of EPI in urine with spike recoveries from 97.5% to 102.6%. Another important feature of the proposed fluorescent sensor is that it holds a promising potential for in vivo imaging and detection due to its distinctive properties such as weak autofluorescence, low heating effect, and high light penetration depth.

Severe stress concentration and bad sealing performance are encountered in a non-metallic engineering part during an interference fit assembly process. Both numerical calculation and experimental test are employed to analyze the causes resulting in the assembly failure. Based on the finite element method (FEM), commercial computational software, ANSYS, is first used to simulate the whole assembly process with different boundary conditions. By comparing simulation results of the assembly process with various boundary conditions, it is found that deformation energy and friction force contribute differently to the reaction force at varying assembly depths. In virtue of these simulation results, an improved engineering part is designed and fabricated. Experimental test results show that stress concentration and sealing performance problems are basically solved compared to those in the original model. Moreover, reaction forces calculated from numerical simulation and measured from experimental tests agree reasonably with each other during the interference fit progress. This work is beneficial to the understanding of the interference fit process in engineering application and the avoiding of part failure resulting from inappropriate design.

The precise thermal expansion coefficient (TEC) of single layer graphene (SLG) is of vital importance to the preparation and application of graphene-based devices. In this work, a comprehensive Raman investigation on the TECs of SLG was conducted by reducing the effects of defects, native strains, and substrate doping. The TECs of graphene with few defects extracted from Raman spectra remained negative without the appearance of a positive transition in the temperature range of 303–503 K. After eliminating the influence of native strains and substrate doping on the TEC acquisition by excluding the first thermal cycle, a more reliable TEC, (−3.68 ± 0.49) × 10−6 /K, was obtained at room temperature, which was much closer to the theoretical predictions than those results in previous experimental reports. This investigation provides a more precise approach to measure the TECs of two-dimensional materials by Raman spectroscopy.

The electrochemical intercalation of metal ions into layered materials is an innovative approach to actively and reversely regulate the thermal transport properties of layered materials. In this work, the molecular dynamics (MD) simulation and lattice dynamics calculation are performed to investigate the thermal boundary conductance (TBC) between metal aluminum (Al) and intercalated graphite with various lithium-ion (Li-ion) concentrations. Both the thermal relaxation simulation and the non-equilibrium MD simulation show that the TBC in the intercalated graphene/Al interface is significantly high as compared to that in pristine graphite/Al interface, by a factor of 5.5. Besides, the TBC presents a slightly increasing trend with increasing Li-ion concentration. This is because increasing the Li-ion concentration increases the out-of-plane phonon group velocity of the intercalated graphite, leading to a sharp increase of phonon irradiation heat flux. By calculating the phonon interfacial transmission coefficient that includes the inelastic scattering effects, it is found that the transmission from the intercalated graphite to Al significantly decreases with increasing Li-ion concentration. The competition between the increased phonon irradiation heat flux and the decreased phonon interfacial transmission coefficient results in the slight increase of the TBC at high Li-ion concentration. This study provides important guidance to develop novel electrode materials and structures for thermal management in Li-ion batteries.

Low-dimensional materials such as graphene provide an ideal platform to probe the correlation between thermal transport and lattice defects, which could be engineered at the molecular level. In this work, we perform molecular dynamics simulations and non-contact optothermal Raman measurements to study this correlation. We find that oxygen plasma treatment could reduce the thermal conductivity of graphene significantly even at extremely low defect concentration (∼83% reduction for ∼0.1% defects), which could be attributed mainly to the creation of carbonyl pair defects. Other types of defects such as hydroxyl, epoxy groups and nano-holes demonstrate much weaker effects on the reduction where the sp2 nature of graphene is better preserved. With the capability of selectively functionalizing graphene, we propose an asymmetric junction between graphene and defective graphene with a high thermal rectification ratio of ∼46%, as demonstrated by our molecular dynamics simulation results. Our findings provide fundamental insights into the physics of thermal transport in defective graphene and two-dimensional materials in general, which could help on the future design of functional applications such as optothermal and electrothermal devices.

Monolayer transition metal dichalcogenides (TMDs) such as MoS2 and WS2 have been considered as promising candidate materials in nanophotonic applications. However, the structure stability of TMDs based optoelectronic devices is highly sensitive to the working environment. Here we present a successive photoluminescence study of the thermal stability characterization of grain boundary in chemical vapor deposition grown monolayer WS2. Results show that PL intensity enhancement in grain boundaries can be significantly weakened during the annealing process. Transformation temperature starts around 210 °C, substantially lower than the surrounding non-grain-boundary area. First-principle calculations results show that the PL quenching of grain boundaries is caused by the increased structural defects induced by annealing process, which makes the transition of electrons more difficult. Our results provide a route for characterizing the structure stability of two dimensional (2D) semiconductors, calling for extra attention to nanophotonic device working condition.

In this paper we show that the fluorescence of rhodamine 6G (R6G) can be manipulated by applying mechanical strains to gold nanoparticles (GNs) sandwiched in graphene/GNs/polydimethylsiloxane (graphene/GNs/PDMS) structure. The fluorescence intensity of R6G on the graphene/GNs/PDMS sample shows a gradual increase with the mechanical strain. However, the fluorescence intensity of R6G on the graphene/PDMS structure without the GNs buried in between is almost unchanged under the action of the external mechanical strain. Experiment results indicate that the gap distance change between the GNs is the main cause of the fluorescence intensity increase and graphene, as a passivation layer, does not block the energy transfer from R6G to GNs. Compared with that tuning the gap distance between GNs by preparing various GNs samples, applying macroscopic mechanical strain on GNs is a simple way to manipulate the fluorescence intensity of a specific material and brings a new perspective for optoelectronic applications.

Nature Nanotechnology 9, 384–390 (2014); published online 30 March 2014; corrected after print 17 June 2014. In the version of this Article originally published, in the section 'Thermal conductivity of individual fibres', the second sentence should have read “The measured thermal conductivity of theseveral nanofibre samples increases with decreasing diameter.