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In this research, RDE tests were carried out on a pre-China 6 TGDI vehicle in the two cases of installing or not installing GPF to explore the impacts of GPF on RDE emission behaviors. The results indicated that the GPF can effectively filter PN emissions, especially at low speed, high load engine operating conditions, where the PN emissions can be reduced to about 1/200 of the original emissions. For TGDI vehicles, the installation of GPF can reduce the RDE PN emissions by more than 30 times, which indicates that the GPF is the key post-processing device for TGDI vehicles to meet the China 6 regulation. And in the upgrade process of China 5 vehicles to China 6 vehicles, especially for TGDI vehicles, the engine, the post processor and the turbocharger all needs re-calibrating or re-matching to concur a series of problems the back pressure raise caused by the installation of GPF, which may bring deterioration of engine combustion process, decrease of catalyst temperature and similar conditions that will worsen the vehicle emissions.

Solar‐driven photoelectrochemical (PEC) reactions using colloidal quantum dots (QDs) as photoabsorbers have shown great potential for the production of clean fuels. However, the low H2 evolution rate, consistent with low values of photocurrent density, and their limited operational stability are still the main obstacles. To address these challenges, the heterostructure engineering of asymmetric capsule‐shaped CdSe/CdxZn1‐xSe QDs with broad absorption and efficient charge extraction compared to pure‐shell QDs is reported. By engineering the shell composition from pure ZnSe shells into CdxZn1‐xSe gradient shells, the electron transfer rate increased from 4.0 × 107 s−1 to 32.7 × 107 s−1. Moreover, the capsule‐shaped architecture enables more efficient spatial carrier separation, yielding a saturated current density of average of 25.4 mA cm−2 under AM 1.5 G one sun illumination. This value is the highest ever observed for QDs‐based devices and comparable to the best‐known Si‐based devices, perovskite‐based devices, and metal oxide‐based devices. Furthermore, PEC devices based on heterostructured QDs maintained 96% of the initial current density after 2 h and 82% after 10 h under continuous illumination, respectively. The results represent a breakthrough in hydrogen production using heterostructured asymmetric QDs. [ABSTRACT FROM AUTHOR]

Fluorescent carbon dots (C-dots) with high optical properties and biocompatibility have great potential for various types of optoelectronic applications. Although many approaches have been used for producing high-quality C-dots, it is still a challenge to produce high-quality C-dots with required properties via a simple and efficient approach. In this work, by controlling the addition of different types of divalent (e.g. Mn and Sr) or trivalent (e.g. Al, Ga and In) metal ions, we synthesized fluorescent C-dots with single or double emissions with quantum yield (QY) as high as 61% using a simple heating approach. Transient fluorescence spectroscopy and transient absorption spectroscopy reveal that the double emission and an excitation-dependent photoluminescence behavior of trivalent ion-capped C-dots originate from the existence of multiple energy levels. Based on these optical properties, the as-prepared C-dots can be effectively used as building blocks for fabricating various types of optoelectronic devices. A single emission Mn-C-dot based large-area luminescent solar concentrator (LSC) (225 cm2) achieved a power conversion efficiency (PCE) of 1.3% under natural sunlight (50 mA cm−2); double emission Al–C-dots showed excitation wavelength dependent fluorescent codes, showing great potential for application in developing anti-counterfeiting codes; and magnetic tests showed that Mn-capped C-dots are superparamagnetic and this may be useful for magnetically driven fluorescence imaging in biomedical applications. This study offers an eco-friendly and efficient approach for producing large-scale high-quality C-dots, demonstrating great potential for optical and electrical applications. [ABSTRACT FROM AUTHOR]

Colloidal carbon dots (C‐dots) are considered as promising heavy‐metal‐free materials to achieve room‐temperature phosphorescence (RTP) properties for promising applications, such as photoelectronic devices, information encryption, and bio‐imaging. However, most of the current obtained RTP C‐dots have a short lifetime with a relatively low quantum yield (QY). In this work, the C‐dots large‐scale synthesized via a vacuum heating approach have multiple RTP emissions (blue, green, and yellow), a long RTP lifetime of as high as 1.92 s, and a high QY of 34.4% by selecting different types of precursors, which is superior to most of reported RTP C‐dots. The multiple atoms doping and strong bonding between neighbored C‐dots promoted by vacuum heating contributes to the excellent RTP properties. As a proof‐of‐concept, the as‐obtained RTP C‐dots are used as optical ink for flexible security codes, exhibiting a bright shape with a lifetime of 1.37 s. This work offers an efficient approach for producing large‐scale high‐quality RTP C‐dots, which can be applied to anti‐counterfeiting and information encryption systems. [ABSTRACT FROM AUTHOR]

Carbon dots (C-dots) have excellent optical properties and serve as optical building blocks for various potential applications. However, the origin of the double emission in C-dots is still unclear. It is highly desirable to understand deeply the exciton dynamics in double-emission C-dots on the picosecond time scale. Herein, for the first time, double-emission boron-doped carbon dots (B–C-dots) are synthesized with a quantum yield as high as 41.1%. The B–C-dots have an excitation-dependent quantum yield and photoluminescent spectrum. Compared to one dominant energy state in undoped C-dots, B–C-dots exhibited multiple energy states, as proved by femtosecond transient absorption spectroscopy. The controllable double emissions advance the design of a high-level anticounterfeiting code. As a proof-of-concept, by the combination of single-emission and double-emission C-dots, we produced a highly bright excitation-dependent photoluminescence code, showing the great potential for anticounterfeiting systems. [ABSTRACT FROM AUTHOR]