不同pH值条件下多壁碳纳米管悬浮液光限幅特性的研究

采用强酸超声剪切技术对多壁碳纳米管(MWNTs)进行纯化和表面修饰,制备了功能化的多壁碳纳米管悬浮液.用波长为532nm、脉宽为6～7ns的Nd:YAG调Q脉冲激光测量了不同pH值时样品的光限幅特性.结果表明,样品的光限幅特性主要来自于非线性散射,且pH值在2.6～12.3范围内样品的光限幅特性优于强酸强碱样品的光限幅特性.     

碳纳米管/高分子复合材料的制备及应用研究进展EI北大核心

将碳纳米管掺杂到聚合物母体中形成的碳纳米管/高分子复合材料具有良好的力学、导电和非线性光学性质。在聚合物中添加少量碳纳米管可以明显改变聚合物的结晶和形貌。大量研究表明,这些复合材料在诸如太阳能电池、有机发光器件、光限幅、光学开关、防护涂料以及人造肌肉等方面具有潜在的实际应用价值。文中介绍了碳纳米管/高分子复合材料的制备方法及其在高科技领域中的应用潜能。     

碳纳米管/高分子复合材料的制备及应用研究进展

将碳纳米管掺杂到聚合物母体中形成的碳纳米管/高分子复合材料具有良好的力学、导电和非线性光学性质。在聚合物中添加少量碳纳米管可以明显改变聚合物的结晶和形貌。大量研究表明,这些复合材料在诸如太阳能电池、有机发光器件、光限幅、光学开关、防护涂料以及人造肌肉等方面具有潜在的实际应用价值。文中介绍了碳纳米管/高分子复合材料的制备方法及其在高科技领域中的应用潜能。     

尿烷取代聚二炔反饱和吸收光限幅特性的研究

聚合炔（ＰＤＡｓ）材料有较大的非线性光学效应，在全光设备中有较大的在应用本文分别研究了尿烷取聚二乙炔的增强吸收和粗糙界面的光限幅特性，并分析了共限幅机理，发现粗糙界面光限幅比增强吸收光限幅有更好的光限幅特征。     

C60溶液的无规界面光限幅实验

研究了具有无规界面的Ｃ６０甲苯溶液的光限幅效应，实验结果表明，光限幅起源于激发态吸收和无规界面散射，限幅箝位值低于Ｃ６０溶液的激发态吸收限幅箝位值。     

聚合物光限幅材料的研究

随着现代激光技术和武器的快速发展,急需激光防护材料(光限幅材料)和设备来防护人眼和光学传感设备免受激光的破坏.由于高分子光限幅材料具有大的非线性光学性能、快速的光学响应、高的损伤阈值和好的加工性能引起人们的广泛兴趣. 在这篇论文中,从分子结构以及分子结构对光限幅性能和光限幅机制的影响,对高分子光限幅材料进行了详细的综述,并提出高分子光限幅材料未来的发展方向.     

氮杂并五苯4Cl1NTP分子溶液和薄膜状态的光限幅性能研究

通过Z-扫描技术研究了氮杂并五苯衍生物分子4Cl1NTP溶液和薄膜状态的光限幅性能。结果表明,相比于参考样品富勒烯C_(60),分子4Cl1NTP表现了高稳定性、高性能的光限幅效应,相比于分子TP,通过化学修饰N原子和Cl原子的分子4Cl1NTP具有较高的光限幅性能,化学修饰能够实现非线性光学性能的调控。     

碳纳米管光学各向异性的解释

碳纳米管对光的吸收与光的偏振方向有关，光偏振方向与碳纳米管管轴方向平行时光吸收最强，光偏振方向与碳纳米管管轴方向垂直时光吸收最弱。采用半经典理论处理光和碳纳米管的相互作用，计算了碳纳米管的光吸收与光偏振方向的关系，计算结果表明碳纳米管光吸收速率与COS^2θ成正比，其中θ是光偏振方向和碳纳米管轴向夹角。     

碳纳米管光限制效应的研究现状

碳纳米管是一种优良的光限制材料,具有光限制阈值低、限制光谱范围宽、响应时间短等特点.概述了碳纳米管光限制性质的发现和研究现况,讨论了碳纳米管的光限制机理,详细介绍了碳纳米管的化学修饰在改善其光限制性能和提高其实用性方面的作用.最后对一些影响碳纳米管光限制效果的因素和原因进行了分析和说明.     

新型含非线性生色团的聚炔共聚物的制备和光限幅

制备了一个新型可溶的含非线性生色团的聚炔共聚物,在8ns脉宽532nm下研究了不同浓度溶液的光限幅性能.采用Z-扫描技术测试了聚合物的激发态吸收,基于非线性理论对光限幅机理进行了讨论.结果表明聚合物的激发态吸收截面大于其基态吸收截面,其光限幅性能主要来源于分子的反饱和吸收(RSA).     

Carbon nanotube-based functional materials for optical limiting

Optical limiting is an important application of nonlinear optics, useful for the protection of human eyes, optical elements, and optical sensors from intense laser pulses. An optical limiter is such a device that strongly attenuates high intensity light and potentially damaging light such as focused laser beams, whilst allowing for the high transmission of ambient light. Optical limiting properties of carbon nanotube suspensions, solubilized carbon nanotubes, small molecules doped carbon nanotubes and polymer/carbon nanotube composites have been reviewed. The optical limiting responses of carbon nanotube suspensions are shown to be dominated by nonlinear scattering as a result of thermally induced solvent-bubble formation and sublimation of the nanotubes, while the solubilized carbon nanotubes optically limit through nonlinear absorption mechanism and exhibit significant solution-concentration-dependent optical limiting responses. In the former case the optical limiting results are independent of nanotube concentrations at the same linear transmittance as that of the solubilized systems. Many efforts have been invested into the research of polymer/carbon nanotube composites in an attempt to allow for the fabrication of films required for the use of nanotubes in a real optical limiting application. The higher carbon nanotube content samples block the incident light more effectively at higher incident energy densities or intensities. The optical limiting mechanism of these composite materials is quite complicated. Besides nonlinear scattering contribution to the optical limiting, there may also be other contributions e.g., nonlinear absorption, nonlinear refraction, electronic absorption and others to the optical limiting. Further improvements in the optical limiting efficiency of the composites and in the dispersion and alignment properties of carbon nanotubes in the polymer matrix could be realized by variation of both nanostructured guest and polymer host, and by ex situ alignment and other methods. It would be very desirable, from the practical application point of view, if one can design broadband optical limiting chromophores that would function in a multimechanistic fashion.     

Shapes of laser radiation pulses modified by nonlinear scattering in aqueous suspension of carbon nanotubes

An improved scheme of z-scanning was used to study the parameters of nanosecond 1064-nm laser radiation pulses scattered at right angle under the conditions of optical limiting in an aqueous suspension of purified carbon nanotubes (CNTs). CNTs were synthesized by the electric-arc evaporation of graphite. It is established that the amplitude, shape, duration, and temporal position of the peak of scattered light pulses significantly depend on the laser radiation power density. The results agree with the mechanism of thermoinduced nonlinear scattering that is operative during the optical limiting of laser pulses in CNT suspensions.     

Recent research progress on optical limiting property of materials based on phthalocyanine, its derivatives, and carbon nanotubes

Carbon nanotubes and organic compounds with extensive delocalized π-electron system such as phthalocyanine and its derivatives are attracted much attention as potential optical limiting materials. In this article, the optical limiting properties of carbon nanotubes, phthalocyanine as well as its derivatives and modifying approaches to improve their optical limiting performance are reviewed. In addition, the optical limiting properties exhibited by the nanohybrids obtained from the combination between carbon nanotubes and phthalocyanine or its derivatives are also introduced.     

Investigation of an optical limiting mechanism in multiwalled carbon nanotubes

We report our investigation of the mechanism that is responsible for the optical limiting behavior in multiwalled carbon nanotubes. We conducted energy-dependent transmission measurements, picosecond time-resolved pump-probe experiment, and nonlinear scattering experiments at 532-nm wavelength on multiwalled carbon nanotube suspension. For comparison, C(60)-toluene solutions and carbon black suspensions were also studied in the same experiments. The similarities that we observed between the multiwalled carbon nanotubes and carbon black suspension suggest that nonlinear scattering, which is known to be responsible for the limiting action in carbon black suspension, should play an important role in the limiting effect in multiwalled carbon nanotubes.     

Synthesis and Superior Optical‐Limiting Properties of Fluorene‐Thiophene‐Benzothiadazole Polymer‐Functionalized Graphene Sheets

A polymer based on fluorene, thiophene, and benzothiadazole as the donor–spacer–acceptor triad is covalently coupled to reduced graphene oxide (rGO) sheets via diazonium coupling with phenyl bromide, followed by Suzuki coupling. These polymer–graphene hybrids show good solubility in organic solvents, such as chloroform, tetrahydrofuran (THF), toluene, dichlorobenzene, and N,N‐dimethylformamide (DMF), and exhibit an excellent optical‐limiting effect with a 532‐nm laser beam. The optical‐limiting threshold energy values (0.93 J cm^?2 for G–polymer 1 and 1.12 J cm^?2 for G–polymer 2) of these G–polymer hybrids are better than that of carbon nanotubes (3.6 J cm^?2).     

Preparation and optical limiting properties of carbon nanotubes coated with Au nanoparticle composites embedded in silica gel-glass

Au nanoparticle (NP) coated carbon nanotubes (CNTs) (CNTs@AuNPs) embedded in silica gel-glass (CNTs@AuNPs/silica gel-glass) were prepared by the sol-gel technique. Subsequent analysis confirmed the successful introduction of the CNTs@AuNPs to the silica gel-glass. Coating with AuNPs dramatically improved the mechanical properties of the silica gel-glass matrix, despite the higher Brunauer-Emmett-Teller (BET) specific surface area and pore volume of the CNTs@AuNPs/silica gel-glass compared with CNT/silica gel-glass. The optical limiting (OL) properties of the CNTs@AuNPs measured at a laser wavelength of 532 nm were slightly weaker after introduction into the solid-state matrix. This reduction is probably attributed to the synergistic nonlinear optical effects of reverse saturable absorption arising from the CNTs and saturable absorption from the AuNPs embedded in the silica gel-glass.     

Laser-induced processes in the IR range in nanocomposites with fullerenes and carbon nanotubes

Laser-induced processes in the IR spectral range, which are related to manifestations of the optical limiting in composite systems containing fullerenes and carbon nanotubes (CNTs), have been studied. Organic materials based on polyimides (PIs), 2-cyclooctylamine-5-nitropyridine (COANP), polyanilines, and dispersed liquid crystal (LC) structures were used as nanoparticle-sensitized matrices. Manifestations of optical limiting in the IR range at 1047, 1080, 1315, and 2940 nm are demonstrated and the position of composites studied among other systems used for optical limiting in the IR range is determined. The optical limiting at 1080 nm in CNT-containing solutions and LC cells was studied and the levels of limiting in thin-film PI-based nanocomposites with CNTs are established. A microscopic examination of thin PI films with CNTs revealed the structure of quasi-photonic crystals formed in these systems.     

Mechano-optical modulation and optical limiting by multiwall carbon nanotubes

An optical limiting effect in multiwall carbon nanotubes was modulated by using a two-wave mixing experiment assisted with a mechanical actuator. We employed a 532 nm wavelength and 1 ns pulse duration for exciting the nonlinear optical absorption. The nanotubes were prepared by an aerosol pyrolysis method. The resulting samples were deposited on a pure silica substrate as an inhomogeneous thin film. The mechano-optical modulation was obtained by the orthogonal rotation of the sample with respect to the probe beam. In addition, low-irradiance patterns provided by a Michelson optical interferometer allowed us to comparatively corroborate the mechano-optical effect induced by the rotation of the film.     

Optical limiting behavior correlated with the surface and etching time of irradiated nuclear track detector

The effects of different laser incident intensity on the optical characteristics of PM-355 nuclear track detector have been studied by using photoluminescence (PL) and UV–visible spectroscopic techniques. The polymers were irradiated with alpha particles with close contact to ²⁴¹Am (in contact with a mean energy 5.49 MeV) and then exposed to continues waveguide (cw) laser with different incident intensity. A noticeable decrease in the photoluminescence spectral intensity was observed with increasing laser incident intensity. From the UV–visible spectra, it is found that a shift in the absorption edge towards a longer wavelength with increasing laser incident intensity can be readily observed. The absorption peak with increasing incident intensity is seen to change into a broad one. The optical band gaps determined from the UV–visible spectra were found to decrease with the increase of cw laser doses. The calculations were made of the number of carbon atoms per conjugation length, N and number of carbon atoms per clusters, M embedded in the network of polymers. The effective of etching time on optical power limiting behavior of sample was also investigated. The optical power limiting behavior was found to vary with the etching time. It also shows a very good optical limiting behavior with a limiting threshold varying from 16.6 to 19.9 mW. These results indicate that the PM-355 nuclear track detector is a promising candidate for applications in the nonlinear optic field.     

Room-temperature deposition of carbon nanomaterials by excimer laser ablation

Numerous investigators have reported on pulsed laser deposition of carbon nanotubes, mostly using the Nd:YAG laser for ablation. In all cases the depositions have been conducted at high-temperatures and high pressures. Here we report on the deposition of carbon nanostructures at room temperature using a 248 nm excimer laser nm to ablate mixed graphite-nickel/cobalt targets. We find that the formation of the carbon nanomaterials is dependent on the particular ambient gas employed. In O₂ gas, carbon nanotubes and nano-onions are produced. The nanotubes have notably large channel diameters of 100-200 nm and the nano-onion structures are 100-200 nm in diameter, also much larger than previously observed. High-resolution, in-situ, time-resolved emission spectroscopy has been used to follow the production of molecular carbon species such as C₂ and C₃, as well as metals such as Ni or Co in the different ambients employed. Spectral modeling reveals significant differences in the vibrational-rotational temperatures of C₂ spectra in O₂ versus Ar. Mechanistic details of the formation of carbon nanotubes and nano-onions, and in-situ optical emission spectroscopy are described.