Carbon dots (CDs) possess unique optical properties such as tunable photoluminescence (PL) and excitation dependent multicolor emission. The quenching and recovery of the fluorescence of CDs can be utilized for detecting analytes. The PL mechanisms of CDs have been discussed in previous articles, but the quenching mechanisms of CDs have not been summarized so far. Quenching mechanisms include static quenching, dynamic quenching, Förster resonance energy transfer (FRET), photoinduced electron transfer (PET), surface energy transfer (SET), Dexter energy transfer (DET) and inner filter effect (IFE). Following an introduction, the review (with 88 refs.) first summarizes the various kinds of quenching mechanisms of CDs (including static quenching, dynamic quenching, FRET, PET and IFE), the principles of these quenching mechanisms, and the methods of distinguishing these quenching mechanisms. This is followed by an overview on applications of the various quenching mechanisms in detection and imaging.

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In recent years, taking advantages of high light absorption coefficients, long charge carrier diffusion lengths and intense photoluminescence, halide perovskites have attracted a great deal of interest in developing high-performance optoelectronic devices including solar cells, light-emitting diodes, photodetectors, transistors, lasers, and so on. Especially, the excellent combination of effective light absorption with tailorable absorption spectrum and high charge carrier mobility in a broadband range makes perovskite-based photodetectors different from traditional photodetectors made of inorganic semiconductors such as GaN, Si, and InGaAs. According to the recent reports, perovskites are promising to greatly improve responsivity, detectivity, noise equivalent power, linear dynamic range, and response speed of photodetectors. Here, we summarize the recent advancements in organic-inorganic hybrid perovskite-based photodetectors in terms of the progress in various low-dimension perovskites, and the recent effective approaches to enhance the performance of perovskite photodetector based on the interfacial engineering in perovskite heterostructures. Besides, two kinds of perovskite photodetectors, namely vertical structure and lateral structure, are analyzed, and the challenges to achieve practical applications in photodetectors are also discussed.

High efficiency blue fluorescent organic light-emitting diodes (OLEDs), based on 1,3-bis(carbazol-9-yl)benzene (mCP) doped with 4,4’-bis(9-ethyl-3-carbazovinylene)-1,1’-biphenyl (BCzVBi), were fabricated using four different hole transport layers (HTLs) and two different electron transport layers (ETLs). Fixing the electron transport material TPBi, four hole transport materials, including 1,1-Bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), N,N’-Di(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4’-diamine(NPB), 4,4’-Bis(N-carbazolyl)-1,1,-biphenyl (CBP) and molybdenum trioxide (MoO3), were selected to be HTLs, and the blue OLED with TAPC HTL exhibited a maximum luminance of 2955 cd/m2 and current efficiency (CE) of 5.75 cd/A at 50 mA/cm2, which are 68% and 62% higher, respectively, than those of the minimum values found in the device with MoO3 HTL. Fixing the hole transport material TAPC, the replacement of TPBi ETL with Bphen ETL can further improve the performance of the device, in which the maximum luminance can reach 3640 cd/m2 at 50 mA/cm2, which is 23% higher than that of the TPBi device. Furthermore, the lifetime of the device is also optimized by the change of ETL. These results indicate that the carrier mobility of transport materials and energy level alignment of different functional layers play important roles in the performance of the blue OLEDs. The findings suggest that selecting well-matched electron and hole transport materials is essential and beneficial for the device engineering of high-efficiency blue OLEDs.

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Rhodamine is a convenient platform for the construction of “OFF–ON” ratiometric excitation energy transfer fluorescent probes.

Since carbon dots (CDs) were reported in 2004, they have been widely used in various fields due to their outstanding optical properties. However, most CDs are self-quenched due to the direct π−π interaction in the solid-state aggregation. This shortcoming limits the wide application of CDs, because numerous optoelectronic devices and sensors usually require photoluminescent materials in the solid state. Therefore, designing and preparing carbon dots with multicolor solid emission is necessary. Here, solid-state fluorescence (SSF) CDs were prepared via a one-step solvothermal method, using MA and APTES as raw materials. Through adjusting the ratio of raw materials, solid-state emitting CDs with green, yellow, and orange colors are obtained. The fluorescence spectrum ranges from 490−625 nm, and the QYs are 34.06%, 38.07%, and 20.37%, respectively. For prepared CDs, the main reason for the solid-state emission is that the Si−O, Si−C, and Si−N bonds generated during the formation process can prevent the π−π interaction between the graphitized cores. The red shift mechanism of solid and liquid fluorescence is attributed to the decrease in particle size and the increase in the degree of particle aggregation within the unit range. In addition, based on these excellent photoluminescence properties, we have prepared colored light-emitting diodesthe CIEs are (0.22, 0.41), (0.38, 0.47), and (0.50, 0.43) (Commission Internationale de l'Elcairage coordinate)and solid-state emitting CDs/epoxy films with high transparency and stability.