Zheng Xie

Organic–Inorganic Hybrid Functional Carbon Dot Gel Glasses

Silane pre-functionalized carbon dots, arbitrarily doped (0-100% scale) carbon dot nanohybrid gel glasses and macrostructures with high luminescence (quantum yields = 47% and 88%, respectively) and broadband optical limiting properties (532 and 1064 nm) are reported. These glasses are optically, thermally, and mechanically stable, as well as highly transmissive (ca. 90%) in the 400-1350 nm region.

Reduced graphene oxide–CdS nanocomposites with enhanced visible-light photoactivity synthesized using ionic-liquid precursors

A series of reduced graphene oxide and CdS nanocomposites (RGO–CdS) with different weight ratios of RGO have been synthesized by a facile microwave-assisted solvothermal method, in which the room temperature ionic-liquid 1-butyl-3-methylimidazolium thiocyanate ([BMIM]·SCN) served as sulfur source as well as stabilizing agent. RGO sheets were uniformly decorated by CdS nanospheres in the as-prepared samples. Only aggregates of CdS particles over 100 nm were obtained, when graphene oxides were not employed. The existence of RGO could effectively enhance the photocatalytic activity for the degradation of rhodamine B (RhB) under visible light irradiation and the RGO–CdS-10% sample possessed the highest activity and excellent stability. The improved photocatalytic efficiency of RGO–CdS nanocomposites could be attributed to the enhanced adsorbability of RhB molecules, a broadened light response range in the visible spectrum and improved separation efficiency of electron–hole pairs, all of which result from the introduction of RGO. It is hoped that this facile and efficient synthesis route can promote the exploration and utilization of graphene-based semiconductor nanocomposites as visible-light photocatalysts.

Polysiloxane Functionalized Carbon Dots and Their Cross-Linked Flexible Silicone Rubbers for Color Conversion and Encapsulation of White LEDs

In this work, aminopropylmethylpolysiloxane (AMS) functionalized luminescent carbon dots (AMS-CDs) were prepared via a one-step solvothermal method. AMS-CDs could be self- or co-cross-linking with AMS to form 3D flexible transparent silicone rubbers (SRs) where CDs acted as cross-linking points, so the loading fraction of AMS-CDs could be adjusted from 10 to 100 wt %, thus modulating fluorescence properties and flexibility of silicone rubbers. Because of the self-curing property and high thermal stability, AMS-CDs were also studied in white LEDs (WLEDs), serving as a color conversion and encapsulation layer of GaN based blue LEDs simultaneously that would avoid the traditional problem of poor compatibility between emitting and packaging materials. And the color coordinate of AMS-CDs based WLEDs (0.33, 0.28) was very close to the pure white light. In addition, the obtained CDs cross-linked SRs had good transparency (T > 80%) at 510-1400 nm and high refractive indexes (1.33-1.54) that could meet the need of commercial packaging materials and optical application. AMS-CDs were also promising to be used in the UV LEDs based WLEDs according to their wide wavelength emission and flexible optoelectronic device.

Three-arm star compounds composed of 1,3,5-tri(azobenzeneethynyl)benzene cores and flexible PEO arms: synthesis, optical functions, hybrid Ormosil gel glasses

A three-arm star rod-coil block conjugated compound composed of 1,3,5-tri(azobenzeneethynyl)benzene core and flexible poly(ethylene oxide) arms was synthesized. For comparison, two others with the same core but different end groups were also prepared. The compounds show thermotropic discotic liquid crystalline phase behavior and properties of optical limiting and photo-induced trans–cis isomerization. The star-shaped compound with poly(ethylene oxide) arms can be homogeneously dispersed into Ormosil gel glass monoliths up to 12 wt% without any compatibilizer. The glasses are mechanically stable and highly transparent in the visible and near IR region. The nonlinear optical and optical limiting properties of the gel glasses are comparable or superior to those of the corresponding solutions. The photochromic property of the azobenzene units can be maintained in the gel glass state.

Enhanced photoelectrochemical and photocatalytic behaviors of MFe2O4 (M = Ni, Co, Zn and Sr) modified TiO2 nanorod arrays

Modified TiO2 nanomaterials are considered to be promising in energy conversion and ferrites modification may be one of the most efficient modifications. In this research, various ferrites, incorporated with various cations (MFe2O4, M = Ni, Co, Zn, and Sr), are utilized to modify the well aligned TiO2 nanorod arrays (NRAs), which is synthesized by hydrothermal method. It is found that all MFe2O4/TiO2 NRAs show obvious red shift into the visible light region compared with the TiO2 NRAs. In particular, NiFe2O4 modification is demonstrated to be the best way to enhance the photoelectrochemical and photocatalytic activity of TiO2 NRAs. Furthermore, the separation and transfer of charge carriers after MFe2O4 modification are clarified by electrochemical impedance spectroscopy measurements. Finally, the underlying mechanism accounting for the enhanced photocatalytic activity of MFe2O4/TiO2 NRAs is proposed. Through comparison among different transition metals modified TiO2 with the same synthesis process and under the same evaluating condition, this work may provide new insight in designing modified TiO2 nanomaterials as visible light active photocatalysts.

Retraction of “Few-Layer Antimonene: Large Yield Synthesis, Exact Atomical Structure, and Outstanding Optical Limiting”

The predictions of arsenene and antimonene open a gate to new two-dimensional (2D) materials. In contrast to the severe unstability of black phosphorus in ambient atmosphere, arsenene and antimonene were recently predicted to be of high stability, as well as outstanding physical and chemical properties, such as extremely high mobility, superior thermal conductivity, high refractive index, and directionally optically transparent. Significantly, monolayer and few-layer antimonenes were recently experimentally fabricated by mechanical exfoliation, however the yield was very low and there’s lack of clear characterizations on the atomical structure and potential applications, which are critical and necessary to promote the developments of this field. Here, we report on a high-yield experimental preparation of high quality, few-layer antimonenes via liquid exfoliation, their atomic level structural elucidation, and unexpected but outstanding nonlinear optical limiting properties even better than graphene in the visible and near infrared region (532 nm-2000 nm) and high transmission (more than 80%) when dispersed in solutions or high concentration doped in Ormosil gel glasses, which might lead to many promising applications in nonlinear optical fields such as laser protection. This work demonstrates that Group 15 2D materials beyond BP could be not only a new 2D crystal family with stability in ambient condition, but also of unique properties

High color rendering index trichromatic white and red LEDs prepared from silane-functionalized carbon dots

In this work, silane-functionalized carbon dots with green and red emission (G-SiCDs and R-SiCDs) were prepared via a one-step solvothermal method. Red LEDs were fabricated using a combination of R-SiCDs and blue LED chips since there have been few reports on red LEDs that have carbon dots as a converter. Also, different ratios of G-SiCDs to R-SiCDs were adjusted so they could serve as optical converters in trichromatic WLEDs. Compared to G-SiCD-based dichromatic WLEDs, the color rendering index (CRI), which represents the true color of irradiated objects, of R-SiCD- and G-SiCD-based trichromatic WLEDs was found to be significantly improved from 58 to 88. The CIE coordinates of the G-SiCD- and R-SiCD-based trichromatic WLEDs were very close to and were even the same as pure white light (0.33, 0.33). G-SiCDs and R-SiCDs have a similar functional alkoxysilane group, thus they will show good compatibility and can co-condense with each other to form a 3D cross-linking structure. Whats more, environmental SiCDs have the potential to be luminescent and encapsulation layers simultaneously in trichromatic WLEDs. This strategy will help to avoid traditional compatibility problems between luminescent and encapsulation materials in WLEDs. The as-prepared polymerizable SiCDs could provide a new opportunity to simplify the preparation process and improve the optical performances of WLEDs.

Full-band UV shielding and highly daylight luminescent silane-functionalized graphene quantum dot nanofluids and their arbitrary polymerized hybrid gel glasses

A facile and efficient approach for the preparation of silane-functionalized graphene quantum dot (SiGQD) nanofluids is described. The functionalized SiGQDs are self- and co-polymerized with silane to easily obtain the arbitrary concentration (0–100%) of SiGQD doped organically modified silicate gel glasses with good processability. The glasses feature arbitrary concentration doping, transparency, homogeneity, various solid structures, luminescence and full-UV shielding capability and are thus suitable for the preparation of bulk hybrid nanocomposites. The SiGQDs with functional groups attached to the surface are strongly photoluminescent both in solution (quantum yield = 82%) and in the solid state (96%). The trace amounts of UV light in daylight could excite these materials and could be observed by the naked eye. The resultant SiGQDs and their gel glasses can absorb and convert UV light into blue light, which can be effectively modulated by the arbitrary concentration of the SiGQDs. These non-toxic, low cost, heavy metal-free, and eco-friendly SiGQDs and their corresponding gel glass systems are promising candidates for high performance UV filters as well as optical materials and devices.

In situ bifunctionalized carbon dots with boronic acid and amino groups for ultrasensitive dopamine detection

In this paper, in situ bifunctionalized carbon dots (B-N-CDs) with boronic acid and amino groups were prepared by a simple hydrothermal method using 3-aminophenylboronic acid as the sole precursor. The high quantum yield of B-N-CDs is as high as 67%, leading to fluorescence emission observed even under daylight excitation. The B-N-CDs exhibited obvious fluorescence enhancement to trace dopamine in the range of 1 pM to 1 μM with a detection limit of 0.1 pM (S/N = 3), which is two orders of magnitude more sensitive than that of present fluorescent sensors. The excellent sensing performance is based on the interaction of two functional groups with DA. This dopamine probe owned advantages of high sensitivity, superior selectivity, good reproducibility and simplicity. Moreover, the analytical reliability of this dopamine sensor was demonstrated in human serum samples.

Multimodal bioimaging based on gold nanorod and carbon dot nanohybrids as a novel tool for atherosclerosis detection

Advanced biocompatible and robust platforms equipped with diverse properties are highly required in biomedical imaging applications for the early detection of atherosclerotic vascular disease and cancers. Designing nanohybrids composed of noble metals and fluorescent materials is a new way to perform multimodal imaging to overcome the limitations of single-modality counterparts. Herein, we propose the novel design of a multimodal contrast agent; namely, an enhanced nanohybrid comprising gold nanorods (GNRs) and carbon dots (CDs) with silica (SiO2) as a bridge. The nanohybrid (GNR@SiO2@CD) construction is based on covalent bonding between SiO2 and the silane-functionalized CDs, which links the GNRs with the CDs to form typical core–shell units. The novel structure not only retains and even highly improves the optical properties of the GNRs and CDs, but also possesses superior imaging performance in both diffusion reflection (DR) and fluorescence lifetime imaging microscopy (FLIM) measurements compared with bare GNRs or fluorescence dyes and CDs. The superior bioimaging properties of the GNR@SiO2@CD nanohybrids were successfully exploited for in vitro DR and FLIM measurements of macrophages within tissue-like phantoms, paving the way toward a theranostic contrast agent for atherosclerosis and cancer.