Jianpang Zhai

Synthesis of 4Å single-walled carbon nanotubes in catalytic Si-substituted AlPO4‐5 molecular sieves

4A single-walled carbon nanotubes (SWCNs) were fabricated using Si-substituted AlPO4‐5 (SAPO-5) molecular sieves as the template. In comparison with neutral AlPO4‐5, the SAPO-5 framework plays an important role as a catalyst in pyrolyzing the hydrocarbon molecules, owing to the Bonsted acid sites. The first-principles calculation shows the Si decoration to be very favorable to the formation of carbon nanotubes in the SAPO-5 channels. The resulting SWCNs have better quality than those fabricated without Si doping, evidenced by clearer and stronger radial breathing modes in the Raman spectra.

Passively Q-switching induced by the smallest single-walled carbon nanotubes

We report a passively Q-switched erbium-doped fiber laser (EDFL) by using the smallest single-walled carbon nanotubes (SWNTs) with a diameter of 0.3 nm as the saturable absorber. These small SWNTs are fabricated in the nanochannels of a ZnAPO-11 (AEL) single crystal. By inserting one of the AEL crystal into an EDFL cavity pumped by a 980 nm laser diode, stable passive Q-switching is achieved for a threshold pump power of 206.2 mW, and 4.73 μs pulses with a repetition rate of 41.78 kHz and an average output power of 3.75 mW are obtained for a pump power of 406 mW.

Visible cathodoluminescence of 4 Å single-walled carbon nanotubes

We report on cathodoluminescence (CL) of monosized and well-aligned 4 A single-walled carbon nanotubes in a zeolite template (AlPO4-5 single crystal). The CL exhibits three emission bands centered at 1.87, 2.22, and 2.98 eV, which are assigned to three possible 4 A tube structures (4,2), (5,0), and (3,3), respectively. The assignation is based on first-principles calculations, Raman scattering measurement, and CL behavior of various samples. The emission peak shift of the (5, 0) tube is explained by the transition mechanism being different from photoluminescence due to the excitation of electrons with high energy.

Passively mode-locking erbium-doped fiber lasers with 0.3 nm single-walled carbon nanotubes.

We demonstrate a passively mode-locked erbium-doped fiber laser (EDFL) by using the smallest single-walled carbon nanotubes (SWNTs) with a diameter of 0.3 nm as the saturable absorber. These ultrasmall SWNTs are fabricated in the elliptical nanochannels of a ZnAPO4-11 (AEL) single crystal. By placing an AEL crystal into an EDFL cavity pumped by a 980 nm laser diode, stable passive mode-locking is achieved for a threshold pump power of 280 mW, and 73 ps pulses at 1563.2 nm with a repetition rate of 26.79 MHz.

Synthesis of large MgAPO-11 single crystals in a F− free system

The synthesis process of large magnesium substituted AlPO4-11 single crystals (MgAPO-11) under hydrothermal conditions has been reported. The crystal size and morphology sensitively depend on crystallization conditions and gel compositions. The addition of HF acid in the gel undermines rather than favours the growth of MgAPO-11 single crystals. Using the optimal gel composition with magnesium oxide as the magnesium source, large MgAPO-11 single crystals with good quality have been synthesized in a F− free system. The typical crystal dimensions are 25 × 157 ×254 μm3, the synthesis temperature is 180 °C, and the crystallization period is 60 hours.

Facile synthesis of graphene nanoribbons from zeolite-templated ultra-small carbon nanotubes for lithium ion storage

One-dimensional graphene nanoribbons are attracting considerable attention due to their extraordinary electronic, magnetic, and optical properties, and have a wide range of applications, but have not attained full success owing to the lack of simple and efficient synthetic strategies. Here, we present a facile strategy for the synthesis of graphene nanoribbons by unraveling ultra-small carbon nanotubes. The armchair (2,2) carbon nanotubes with a theoretical diameter of 0.28 nm fabricated in the nanochannels of zeolite ZnAPO4-11 (AEL) can be transformed into graphene nanoribbons by removing the AEL template through chemical treatment. The as-synthesized graphene nanoribbons are N-doped with a thickness of two- to seven-layers, have a width of 10–30 nm and length of >1 μm, and show high performance as an anode material for lithium ion batteries. Moreover, this strategy can be readily scaled up for practical applications requiring bulk quantities of graphene nanoribbons.

Host-guest interaction between Acridine orange molecules and AFI or CHA zeolite crystals

Acridine orange (AO) molecules were incorporated in AlPO4-5, SAPO-5 and SAPO-47 single crystals by vapor-phase diffusion method. Polarized absorption spectra show that AO molecules are well aligned by the one-dimensional channel systems of AlPO4-5 and SAPO-5 matrices. While the orientation of AO molecules in SAPO-47 crystals is diverse owing to the three-dimensional cage structure of chabazite (structure code CHA). The absorption peak and emission peak of AO/SAPO-5 blue shift compared with that of AO/AlPO4-5 because the channel environment changes from non-polar medium to polar medium when Si substituted in the framework of AlPO4-5. The greater blue shift in absorption band and emission band of AO/SAPO-47 are expected to originate from the polar channel medium and smaller channel size of SAPO-47.

Synthesis of high density 4 A single-walled carbon nanotubes in AlPO/sub 4/-5 zeolites

The effect of carbon precursors on the formation of 0.4 nm single-walled carbon nanotubes (SWNTs) in one-dimensional channels of AlPO4-5 single crystals was studied by means of Raman spectroscopy. Among more than ten carbon precursors which can be used in the fabrication of 0.4 nm SWNTs in the channels, the precursor of tetrapropylammonium-hydroxide (TPAOH) molecule not only contains rich carbon atoms, but also well fits to the unit cell of the AlPO4-5 framework. Thus, the loading density of TPAOH carbon precursor inside the channels of AlPO4-5 crystals is much more than other ones. The resulting SWNTs have higher filling density in the channels and have a better quality than those fabricated using other carbon precursors, as evidenced by the intensive Raman signals in the radial-breathing modes