We report that nanoscale carbon particles (carbon dots) upon simple surface passivation are strongly photoluminescent in both solution and the solid state. The luminescence emission of the carbon dots is stable against photobleaching, and there is no blinking effect. These strongly emissive carbon dots may find applications similar to or beyond those of their widely pursued silicon counterparts.

The photoluminescence in carbon dots (surface-passivated small carbon nanoparticles) could be quenched efficiently by electron acceptor or donor molecules in solution, namely that photo-excited carbon dots are both excellent electron donors and excellent electron acceptors, thus offering new opportunities for their potential uses in light energy conversion and related applications.Quantum-sized semiconductor nanoparticles (quantum dots) have emerged as an important class of photoactive nano-materials for a variety of purposes and applications. [1][2][3][4] For the utilization of semiconductor quantum dots in light energy conversion and related areas, there have been extensive investigations on their photoresponse and photoinduced charge separation and electron transfer processes. [5][6][7][8] Alternative to the traditional semiconductors, other quantum-sized nanoparticles have been explored and developed for similar photophysical and photochemical properties. Of particular interest and significance is the recent finding that small carbon nanoparticles could be surface-passivated by organic molecules or polymers to become highly photoactive, exhibiting strong photoluminescence in the visible and near-infrared spectral regions. 9-15 These photoluminescent carbon nano-particles, dubbed "carbon dots" (Scheme 1), were found to be physico-chemically and photochemically stable and nonblinking in their luminescent emissions. 9 Here we report that the photoluminescence from carbon dots could be quenched highly efficiently by either electron acceptor or electron donor molecules in solution, namely that the photo-excited carbon dots are excellent as both electron donors and electron acceptors. These interesting photoinduced electron transfer properties may offer new opportunities in potentially using carbon dots for light energy conversion and related applications, in addition to their being valuable to the effort on mechanistic elucidation.The carbon dots in this study were prepared by using the same procedures as those reported previously. 9 In the preparation, the small carbon nanoparticles (separated from the laser ablation-produced powdery sample) were refluxed in aqueous nitric acid solution for the purpose of oxidizing surface carbons into carboxylic acids, followed by thionyl chloride treatment and then amidation with the oligomeric ethylene glycol diamine H 2 NCH 2 (C 2 H 4 O) 35 C 2 H 4 CH 2 NH 2 (PEG 1500N ) to form the carbon dots with surface-attached PEGs (Scheme 1). The transmission electron microscopy (TEM) results ( Fig. 1) suggested that these dots were well-dispersed, with sizes averaging about 4.2 nm (based on statistical analyses of more than 300 dots), as also supported by the atomic force microscopy (AFM) results (Fig. 1).Photoluminescence spectra of the carbon dots in aqueous or organic solutions were generally broad ( NIH Public Access Author ManuscriptChem Commun (Camb) 3). Obviously 2,4-dinitrotoluene was a much more effective quencher than 4-nitrotoluene, consistent with its being a s...

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Single-walled and multiple-walled carbon nanotubes were functionalized with poly(vinyl alcohol) (PVA) in esterification reactions. Similar to the parent PVA, the functionalized carbon nanotube samples are soluble in highly polar solvents such as DMSO and water. The common solubilities have allowed the intimate mixing of the functionalized nanotubes with the matrix polymer for the wet-casting of nanocomposite thin films. The PVA-carbon nanotube composite films are of high optical quality, without any observable phase separation, and the carbon nanotubes in the films are as well-dispersed as in solution.The functionalization of carbon nanotubes by the matrix polymer is apparently an effective way in the homogeneous nanotube dispersion for high-quality polymeric carbon nanocomposite materials. Results from characterizations of the solubilized carbon nanotubes and the nanocomposite thin films are presented and discussed.

A derivatized porphyrin with long alkyl chains, 5,10,15,20-tetrakis(hexadecyloxyphenyl)-21H,23H-porphine, is selective toward semiconducting single-walled carbon nanotubes (SWNTs) in presumably noncovalent interactions, resulting in significantly enriched semiconducting SWNTs in the solubilized sample and predominantly metallic SWNTs in the residual solid sample according to Raman, near-IR absorption, and bulk conductivity characterizations.

Flexible, lightweight, robust, and multifunctional characteristics are greatly desirable for next-generation wearable electromagnetic interference (EMI) shielding materials. In this work, an alternating multilayered structure with robust polymer frame layers and directly contacted conducting layers was designed to prepare high-performance EMI films. Especially, the multilayered films containing alternating cellulose nanofiber (CNF) layers and MXene layers are fabricated via a facile and efficient alternating vacuum filtration approach. Deriving from the mechanical frame effect acted by CNF layers in, which is capable of preventing the nanosized “zigzag” crack in MXene layers from growing to the whole film, the alternating multilayered film (CNF@MXene) revealed the improved mechanical strength (112.5 MPa) and toughness (2.7 MJ m–3) compared to both freestanding MXene film and homogeneous CNF/MXene film. Meanwhile, the directly contacted MXene layers resulted in the increased electrical conductivity from 2 (homogeneous CNF/MXene film) to 621–82 S m–1 (CNF@MXene films). In conjunction with the extra “reflection-absorption-zigzag reflection” mechanism among the alternating multilayers, CNF@MXene films demonstrated an exceptional EMI shielding effectiveness of ∼40 dB in the X-band and K-band and high specific shielding effectiveness up to 7029 dB cm2 g–1 at a thickness of only 0.035 mm. Besides, the excellent mechanical flexibility ensured the stable EMI shielding and electrical properties, which can withstand the folding test more than 1000 times without obvious reduction. Moreover, the excellent electrical conductivity endows the alternating multilayered film with an outstanding and steady Joule heating performance, which could reach more than 100 °C at only 6 V impressed voltage to within 10 s. As a result, our alternating multilayered film with reinforced EMI shielding and Joule heating performance is promising in the next-generation intelligent protection devices applying in cold and complex practical environments.

Highly conductive and stretchable electrospun thermoplastic polyurethane yarns with multi-walled and single-walled CNTs were prepared.

Transparent conductive film (TCF) is promising for optoelectronic instrument applications. However, designing a robust, stable, and flexible TCF that can shield electromagnetic waves and work in harsh conditions remains a challenge. Herein, a multifunctional and flexible TCF with effective electromagnetic interference shielding (EMI) performance and outstanding electro-photo-thermal effect is proposed by orderly coating Ti3C2T x MXene and a silver nanowire (AgNW) hybrid conductive network using a simple and scalable solution-processed method. Typically, the air-plasma-treated polycarbonate (PC) film was sequentially spray-coated with MXene and AgNW to construct a highly conductive network, which was transferred and partly embedded into an ultrathin poly­(vinyl alcohol) (PVA) film using spin coating coupled with hot pressing to enhance the interfacial adhesion. The peeled MXene/AgNW-PVA TCF exhibits an optimal optical and electrical performance of sheet resistance 18.3 Ω/sq and transmittance 52.3%. As a consequence, the TCF reveals an effective EMI shielding efficiency of 32 dB in X-band with strong interfacial adhesion and satisfactory flexibility. Moreover, the high electrical conductivity and localized surface plasmon resonance (LSPR) effect of hybrid conductive network endow the TCF with low-voltage-driven Joule heating performance and excellent photothermal effect, respectively, which can ensure the normal functioning under extreme cold condition. In view of the comprehensive performance, this work offers new solutions for next-generation transparent EMI shielding challenges.