Zhixing Gan

Mn2+-Bonded Reduced Graphene Oxide with Strong Radiative Recombination in Broad Visible Range Caused by Resonant Energy Transfer

The photoluminescence (PL) characteristics of Mn(2+)-bonded reduced graphene oxide (rGO) are studied in details. The Mn(2+)-bonded rGO is synthesized using MnO(2)-decorated GO as the intermediate products and ideal tunable PL is obtained by enhancing the long-wavelength (450-550 nm) emission. The PL spectra excited by different wavelengths are analyzed to elucidate the mechanism, and the resonant energy transfer between Mn(2+) and sp(2) clusters of the rGO appears to be responsible for the enhanced long-wavelength emission. To examine the effect of Mn(2+) on the long-wavelength emission from the Mn(2+)-bonded rGO, the PL characteristics of Mn(2+)-bonded rGO with smaller Mn concentrations are studied and weaker emission is observed. Our theoretical calculation corroborates the experimental results.

Photothermal contribution to enhanced photocatalytic performance of graphene-based nanocomposites.

Photocatalysts possessing high efficiency in degrading aquatic organic pollutants are highly desirable. Although graphene-based nanocomposites exhibit excellent photocatalytic properties, the role of graphene has been largely underestimated. Herein, the photothermal effect of graphene-based nanocomposites is demonstrated to play an important role in the enhanced photocatalytic performance, which has not been considered previously. In our study on degradation of organic pollutants (methylene blue), the contribution of the photothermal effect caused by a nanocomposite consisting of P25 and reduced graphene oxide can be as high as ∼38% in addition to trapping and shuttling photogenerated electrons and increasing both light absorption and pollutant adsorptivity. The result reveals that the photothermal characteristic of graphene-based nanocomposite is vital to photocatalysis. It implies that designing graphene-based nanocomposites with the improved photothermal performance is a promising strategy to acquire highly efficient photocatalytic activity.

Light‐Induced Ferroelectricity in Bioinspired Self‐Assembled Diphenylalanine Nanotubes/Microtubes

The switchable SP together withthe unique properties of ferroelectric materials can lead toPNTs/PMTs that have a wide range of applications butexperimental verification of the predicted FE is imperative.In FF PNTs/PMTs, direct experimental demonstration ofthe hysteresis loop is rather difficult because of the highcoercive field of the PMTs. A change of the SP under anapplied external field is an important experimental indicatortoidentifythepossiblepresenceofFE.Inthiswork,theoriginof the SP based on the structure of the PNTs is studied. Byobserving the photoluminescence (PL) spectral shift and itssplitting with increasing intensity of the excitation light, wedisclose the photoinduced reduction of the PNT intrinsicpolarization field which implies that SP occurs at the nano-scale.Thesaturatedpolarization–electricfield(P-E)loopsareobtained by the action of light during the hysteresis loopmeasurements.Figure 1a depicts the optical microscopy image ofa cleaved PMT prepared by immersing the as-made FFPMTs in ethanol for several hours. The optical microscopicimage of some PNTs stripped from the PMTs is shown inFigure 1b. The remarkable stepwise surface of the cleavedPMT confirms that the PMTs are composed of multi-NTsproduced by a self-assembly process (inset),

Cubic In2O3 Microparticles for Efficient Photoelectrochemical Oxygen Evolution

Cubic In2O3 microparticles with exposed {001} facets as well as single morphology and size are produced on a large scale on silicon with a high yield. The morphological evolution during chemical vapor deposition is investigated and the new knowledge enables precise facet cutting. The synthesized Cubic In2O3 microparticles possess superior photoelectrocatalytic activity and excellent chemical and structural stability in oxygen evolution reaction on account of the unique surface structure and electronic band structure of the {001} facets. Our results reveal that it is feasible to promote the photolectrochemical water splitting efficiency of photoanode materials by controlling the growth on specific crystal facets. The technique and concept can be extended to other facet-specific materials in applications such as sensors, solar cells, and lithium batteries.

The mechanism of blue photoluminescence from carbon nanodots

The blue photoluminescence from carbon nanodots (CNDs) weakens gradually and the most intense peak red-shifts slightly as the hydrothermal reaction time increases. The 890 cm−1 infrared vibration band, which is associated with carbon defects, decreases with the reaction time being consistent with the blue emission tendency. Based on the growth model of CNDs and understanding of photoluminescence from other carbon nanomaterials, carbon defects are believed to be responsible for the blue emission.

In Situ Thermal Imaging and Absolute Temperature Monitoring by Luminescent Diphenylalanine Nanotubes

The temperature sensing capability of diphenylalanine nanotubes is investigated. The materials can detect local rapid temperature changes and measure the absolute temperature in situ with a precision of 1 °C by monitoring the temperature-dependent photoluminescence (PL) intensity and lifetime, respectively. The PL lifetime is independent of ion concentrations in the medium as well as pH in the physiological range. This biocompatible thermal sensing platform has immense potential in the in situ mapping of microenvironmental temperature fluctuations in biological systems for disease diagnosis and therapeutics.

Unidirectionally aligned diphenylalanine nanotube/ microtube arrays with excellent supercapacitive performance

High-temperature (150–220 °C) growth leads to the formation of some peptide nanotube/microtube (NT/MT) arrays but the NTs/MTs exhibit closed ends, irreversible phase modification and eliminations of piezoelectric and hydrophilic properties. Here we demonstrate the fabrication of unidirectionally aligned and stable diphenylalanine NT/MT arrays with centimeter scale area at room temperature by utilizing an external electric field. The interactions between the applied electric field and dipolar electric field on the NTs and surface positive charges are responsible for the formation. The unidirectionally aligned MT array exhibits a supercapacitance of 1,000 μF·cm−2 at a scanning rate of 50 mV·s−1; this is much larger than the values reported previously in peptide NT/MT arrays.

The origins of the broadband photoluminescence from carbon nitrides and applications to white light emitting

Carbon nitrides synthesized by thermal polycondensation of melamine at 700 °C exhibit photoluminescence (PL) ranging from 400 to 650 nm. This broad PL is attributed to band to band transitions and bandtail transitions of lone pair (LP) states of intra-tri-s-triazine and inter-tri-s-triazine nitrogens. The proposed PL mechanism is further confirmed by diffusion reflectance spectroscopy, as well as time-resolved and temperature-dependent PL. This intense fluorescence is stable at different pH and resistant to UV exposure, suggesting that this inexpensive broadband luminescent material could be significant for whitelight-emitting (WLE) applications. Thus, quasi-WLE films and membranes with designed patterns are fabricated by embedding the carbon nitrides into polymethyl methacrylate. Moreover, even broader PL (400 to 740 nm) is acquired in composite films composed of carbon nitrides, further suggesting that the carbon nitrides are robust candidates for WLE.

Electron transition pathways of photoluminescence from 3C-SiC nanocrystals unraveled by steady-state, blinking and time-resolved photoluminescence measurements

The cubic phase SiC nanocrystals (3C-SiC NCs) have been extensively studied for electronics and photonics applications. In this work we study the electron transition pathways of photoluminescence ( ...

Modulating the fluorescent color of carbon nanodots via photon reabsorption and carbonization degree

A strategy is developed to modulate the fluorescent color of carbon nanodots (CNDs) through regulating photon reabsorption and carbonization degree. On the one hand, the emission color is tuned through enhancing the photon reabsorption via the concentration increase. Essentially, the emitted photon of short wavelengths is supposed to be reabsorbed by a neighboring CND, subsequently resulting in a photon emission of long wavelengths. On the other hand, by reaction time control, a higher carbonization degree of CNDs is obtained, which renders larger sizes and less oxygen related groups of CNDs, giving rise to narrower bandgaps, e.g., emissions of longer wavelengths. Through cooperatively managing the carbonization degree and photon reabsorption, a single ultraviolet light can be converted into multi-color luminescence across the entire visible range by using our one-pot-pyrolysis CNDs.