Junsong Liu

Spectroscopic investigation on carbon nanotubes coated with ZnO nanoparticles

ZnO nanoparticles were successfully coated on the surface of carbon nanotubes (CNTs) during the final stage of the growth process of CNTs using radio-frequency plasma enhanced chemical vapour deposition. During the coating process, Zn or ZnO particles with oxygen vacancies can be selectively anchored to the oxygen atom of the oxygen-containing groups on the surface of CNTs and can be perfectly oxidized by active oxygen atoms in the annealing process. The appropriate amount of coated nanoparticles effectively reduces the formation of various structural defects induced by oxygen or hydrogen atoms on the surface of the CNT wall, which can be evaluated through a decrease in the intensity ratio of disorder graphitic band (D peak) over graphitic C–C stretching band (G peak) in the Raman spectrum as well as a distinct decrease in the intensity peak, corresponding to C–H stretching vibration, in the infrared spectrum.

Synthesis and field electron emission properties of hybrid carbon nanotubes and nanoparticles

Hybrid ZnO-carbon nanotubes as well as nanodiamond-carbon nanotubes were synthesized via a straightforward process of plasma enhanced chemical vapor deposition. For the former, ZnO nanoparticles were instantly coated on the tube surface in the final growing process of carbon nanotubes, while for the latter diamond nanoparticles were grown using pretreatment of a silicon substrate with Ni(NO(3))(2)·6H(2)O/Mg(NO(3))(2)·6H(2)O alcohol solution prior to deposition and a high H(2)/CH(4) gas flow ratio in the deposition process. The morphology and microstructure of the obtained hybrid materials were characterized by transmission electron microscopy. Both hybrid ZnO-carbon nanotubes and nanodiamond-carbon nanotubes exhibited excellent field emission properties.

Diamond-based electrochemical aptasensor realizing a femtomolar detection limit of bisphenol A

In this study, we designed and fabricated an electrochemical impedance aptasensor based on Au nanoparticles (Au-NPs) coated boron-doped diamond (BDD) modified with aptamers, and 6-mercapto-1-hexanol (MCH) for the detection of bisphenol A (BPA). The constructed BPA aptasensor exhibits good linearity from 1.0×10-14 to 1.0×10-9molL-1. The detection limitation of 7.2×10-15molL-1 was achieved, which can be attributed to the synergistic effect of combining BDD with Au-NPs, aptamers, and MCH. The examine results of BPA traces in Tris-HCl buffer and in milk, UV spectra of aptamer/BPA and interference test revealed that the novel aptasensors are of high sensitivity, specificity, stability and repeatability, which could be promising in practical applications.

Ultraviolet photoelectrical properties of a n-ZnO nanorods/p-diamond heterojunction

The ultraviolet (UV) photoresponse properties of a n-ZnO nanorods/p-diamond heterojunction were investigated by studying the dark and photo I–V characteristics. It shows typical rectifying behavior with a rectification ratio of 3.2 and 8.8 at 5 V for the dark current and the photocurrent, respectively. The turn on voltage under UV illumination is three times lower than that under the dark current and the ideality factor of the device is decreased. The forward current under UV illumination is more than 4 times higher than the dark one at 10 V whereas the leakage current shows a little increase at −10 V. The electrical transport behaviors are investigated both under the dark current and the photocurrent. The photogenerated charges and their transfer processes were analyzed by surface photovoltage (SPV) measurements.

Effect of nitrogen on deposition and field emission properties of boron-doped micro- and nano-crystalline diamond films

In this paper, we report the effect of nitrogen on the deposition and properties of boron doped diamond films synthesized by hot filament chemical vapor deposition. The diamond films consisting of micro-grains (nano-grains) were realized with low (high) boron source flow rate during the growth processes. The transition of micro-grains to nano-grains is speculated to be strongly (weekly) related with the boron (nitrogen) flow rate. The grain size and Raman spectral feature vary insignificantly as a function of the nitrogen introduction at a certain boron flow rate. The variation of electron field emission characteristics dependent on nitrogen is different between microcrystalline and nanocrystalline boron doped diamond samples, which are related to the combined phase composition, boron doping level and texture structure. There is an optimum nitrogen proportion to improve the field emission properties of the boron-doped films.

Influence of oxygen on the growth of carbon nanotubes

The influence of oxygen on the growth of carbon nanotubes (CNTs) using plasma-enhanced chemical vapour deposition has been studied. The cobalt catalyst film and CNTs were characterized by scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscope, x-ray photoelectron spectroscopy and Raman spectroscopy. The results showed that small cobalt oxide particles obtained by O2-etching were deoxidized back to Co catalyst particles with small size in the CH4/H2 atmosphere for the growth of CNTs. Small Co particles and the inlet of oxygen in the stage of CNT growth enhanced the yield rate and purity of aligned CNTs.

Plasmon resonance enhanced temperature-dependent photoluminescence of Si-V centers in diamond

Temperature dependent optical property of diamond has been considered as a very important factor for realizing high performance diamond-based optoelectronic devices. The photoluminescence feature of the zero phonon line of silicon-vacancy (Si-V) centers in Si-doped chemical vapor deposited single crystal diamond (SCD) with localized surface plasmon resonance (LSPR) induced by gold nanoparticles has been studied at temperatures ranging from liquid nitrogen temperature to 473 K, as compared with that of the SCD counterpart in absence of the LSPR. It is found that with LSPR the emission intensities of Si-V centers are significantly enhanced by factors of tens and the magnitudes of the redshift (width) of the emissions become smaller (narrower), in comparison with those of normal emissions without plasmon resonance. More interestingly, these strong Si-V emissions appear remarkably at temperatures up to 473 K, while the spectral feature was not reported in previous studies on the intrinsic Si-doped diamonds wh...

Tuning surface plasmon resonance by the plastic deformation of Au nanoparticles within a diamond anvil cell

In this work, surface plasmon resonance (SPR) is tuned by controlling the deformation of Au nanoparticles within a diamond anvil cell (DAC). Colloidal Au nanoparticles were loaded into a DAC and pressurized into a mixture of ice and Au nanoparticles. The Au nanoparticles were reshaped by their anisotropic compression of surrounding ice, which leads to the spectral variations of absorption peaks, broadening or red-shifting. These spectral features are well tuned by controlling the deformation process of Au nanoparticle with choosing the initial intended thickness of DAC gasket. The mechanical properties of Au nanoparticles are also revealed by the shape-dependent SPR in nanometer scale. This result provides us a way to fabricate Au nanoparticles into new shapes and tune SPR of metallic nanoparticles with pressure.

Blue light-induced apoptosis of human promyelocytic leukemia cells via the mitochondrial-mediated signaling pathway

Acute promyelocytic leukemia is frequently associated with dizziness, fever, nausea, hematochezia and anemia. Blue light, or light with wavelengths of 400–480 nm, transmits high levels of energy. The aim of the present study was to determine the pro-apoptotic effects of blue light (wavelength, 456 nm; radiation power, 0.25 mW/cm2) and the underlying mechanisms in a human promyelocytic leukemia cell line (HL60). Blue light reduced the viability and enhanced the mortality of HL60 cells in a time-dependent manner. Exposure to blue light for 24 h caused depolarization of the mitochondrial membrane potential and the overproduction of reactive oxygen species in HL60 cells. In a nude mouse model, 9-day exposure to blue light markedly suppressed the growth of HL60-xenografted tumors; however, it had no effect on hepatic and renal tissues. In addition, blue light abrogated the expression of B-cell lymphoma (Bcl)-2 and Bcl extra-long, while enhancing the levels of Bcl-2-associated X protein, cytochrome c, and cleaved caspases-3 and −9 in tumor tissues. The results suggested that the pro-apoptotic effects of blue light in human promyelocytic leukemia cells may be associated with the mitochondrial apoptosis signaling pathway.

Enhanced proliferation inhibition of HL60 cells treated by synergistic all-trans retinoic acid/blue light/nanodiamonds

To improve drug efficacy and minimize side effects for treating human promyelocytic leukemia cells, we explored a strategy using the traditional chemotherapy drug all-trans retinoic acid (ATRA) combined with nanodiamonds (NDs) and blue light (BL) irradiation on the typical HL60 cell line. The synergistic ATRA–BL–ND could significantly induce cell inhibition ∼4 times that treated by ATRA alone. The introduction of BL plays an important role in the enhancement of cells apoptosis, improves the level of reactive oxygen species (ROS), reduces the expression of B-cell leukemia/lymphoma 2 (Bcl-2) mRNA, and increases the activation of caspase-3 of HL60 cells. The biocompatible NDs are favorable for increasing ATRA concentration and improving drug delivery. The synergistically enhanced antitumor effect was further verified by in vivo examinations. The results in this paper could be helpful to establish a high efficiency and low toxicity strategy for clinical treatment of various tumors.