Jiangling He

Solid‐State Carbon Dots with Red Fluorescence and Efficient Construction of Dual‐Fluorescence Morphologies

Stable solid-state red fluorescence from organosilane-functionalized carbon dots (CDs) with sizes around 3 nm is reported for the first time. Meanwhile, a novel method is also first reported for the efficient construction of dual-fluorescence morphologies. The quantum yield of these solid-state CDs and their aqueous solution is 9.60 and 50.7%, respectively. The fluorescence lifetime is 4.82 ns for solid-state CDs, and 15.57 ns for their aqueous solution. These CDs are detailedly studied how they can exhibit obvious photoluminescence overcoming the self-quenching in solid state. Luminescent materials are constructed with dual fluorescence based on as-prepared single emissive CDs (red emission) and nonfluorescence media (starch, Al2 O3 , and RnOCH3 COONa), with the characteristic peaks located at nearly 440 and 600 nm. Tunable photoluminescence can be successfully achieved by tuning the mass ratio of CDs to solid matrix (such as starch). These constructed dual-fluorescence CDs/starch composites can also be applied in white light-emitting diodes with UV chips (395 nm), and oxygen sensing.

Room temperature phosphorescence from moisture-resistant and oxygen-barred carbon dot aggregates

Phosphorescence is difficult to be observed from carbon dot powder due to the deliquescence and self-quenching in the aggregation state. In this study, aggregation-induced room temperature phosphorescence (RTP) is first reported in self-quenching-resistant nitrogen-doped carbon dot powder, which is suggested to take advantage of the moisture-resistance, rigidization and oxygen-barrier induced by PVA-chains. Furthermore, the optical mechanism of RTP as well as fluorescence is investigated through the abnormal excitation-responsive phenomena, and the potential application in temperature sensing is also preliminarily evaluated. This study may benefit in developing phosphorescence from undesirable aggregation through structure design and exploiting emerging applications for carbon dots.

Luminescent properties and energy transfer of luminescent carbon dots assembled mesoporous Al2O3: Eu3+ co-doped materials for temperature sensing

Owning to the hydrogen-band interactions, blue-light-emitting luminescent carbon dots (CDs) synthesized by one-pot hydrothermal treatment were successfully assembled into Eu3+ doped mesoporous aluminas (MAs). Interesting, dual-emissive CDs/MAs co-doped materials with higher quantum yield (QY), long-term stability, mesoporous structure, high thermal stability, and large surface areas were obtained. Furthermore, the obtained CDs/MAs co-doped materials possessed tunable color, and excellent temperature sensitivity due to the existing of energy transfer between CDs and Eu3+ ion. The energy transfer efficiency (η) and energy transfer probability (P) for CDs/Eu3+ co-doped materials possessed a monotonous tendency with the change of Eu3+ content. More importantly, the dual-emissive colors can be regularly adjusted through regulating their excitation wavelength or relative mass ratio. In addition, the emission intensity of the CDs/MAs co-doped materials gradually decreased with increasing temperature showing the clear temperature dependence, this dual-emissive thermometer was with high sensitivity, owning a great fitted curve in the range from 100 to 360K under a single wavelength excitation.

Double carbon dot assembled mesoporous aluminas: solid-state dual-emission photoluminescence and multifunctional applications

Carbon dot (CD)-based solid-state fluorescent materials have attracted a lot of attention in recent years owing to their superior optical and environmentally friendly properties, demonstrating a potential use in many applications. However, previously reported CD-based solid-state fluorescent materials mostly assemble a type of CD in the matrix which has only a single characteristic peak, and those of assembled double CDs with two characteristic peaks are very rare. Such a drawback restricts their further application, particularly in the field of white light emitting diodes (WLEDs). Herein, a rare type of double CD-based fluorescent material has been synthesized with dual characteristic peaks at 420 nm and 635 nm via the one-step assembly of blue- and red-emissive carbon dots (bCDs, rCDs) into mesoporous aluminas (MAs). The MA non-fluorescent matrix neither competes for absorbing excitation light nor absorbs the emission from the CDs, leading to excellent PL emitting properties and color and thermal stabilities. The emissive colors are tunable in the white-light region simply through adjusting excitation wavelengths, showing their great potential for phosphor-based WLEDs. In the field of agricultural planting, transparent sunlight conversion films based on co-assembled phosphors have been obtained, revealing inherent optical properties and an efficient process for converting sunlight into blue and red lights, which are essential for plant photosynthesis.

Luminescent carbon dots assembled into mesoporous aluminas for oxygen sensing

As a result of hydrogen-band interactions, blue-light-emitting luminescent carbon dots (CDs) synthesized by one-pot hydrothermal treatment were successfully assembled into mesoporous aluminas (MAs). Blue-light-emitting CDs/MAs compounds with mesoporous structures, narrow pore size distribution, high thermal stability, and large surface areas were obtained. Furthermore, the obtained CDs/MAs compounds possessed high sensitivity and selectivity for oxygen, and excellent photochemical stability. The assembled compounds can potentially be applied to oxygen sensing.

Using hydrogen peroxide to mediate through a one-step hydrothermal method for the fast and green synthesis of N-CDs

A facile and green approach for preparation of photoluminescent nitrogen-doped carbon dots (N-CDs) is reported, using cheap and extensively available cocoon silk as raw material. The use of H2O2 leads to the enhanced formation of N-CDs. The N-CDs have been synthesized in a short time (50 minutes), and have a high fluorescence quantum yield (24.0%). A small amount of H2O2 solution plays a vital role in shortening the reaction time, which is a brand new way to synthesize N-CDs with the help of H2O2, with both reactants and products being environmentally friendly. The prepared N-CDs are collected by removing the insoluble materials through simple filtration rather than dialysis. As far as we know, this is the first report of N-CDs being synthesized simply with the help of H2O2 solution. The prepared N-CDs solution is sensitive to pH changes, which means they have promise for application in the pH detection area.