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Graphene quantum dots (GQDs) are nanosized graphene derivatives with unique photoluminescence (PL) properties that have advantages in optoelectronic applications due to their stable blue light emission. However, aggregation-caused quenching (ACQ) of GQDs limits the practical applications on light-emitting diodes. Here, we suppress the ACQ phenomena of GQDs by reducing the size and converting GQDs into aggregation-induced emission (AIE)–active materials. As the size of GQDs is reduced from 5 to 1 nm, their solid-state PL quantum yields (PLQYs) are improved from 0.5 to 2.5%, preventing ACQ. Two different rotor molecules, benzylamine (BA) and 4,4′-(1,2-diphenylethene-1,2-diyl)diphenol (TPE-DOH), are selectively functionalized by substituting carboxylic acid and carbonyl functional groups. All functionalized GQDs show AIE behaviors with significantly enhanced solid-state PLQYs, up to 16.8%. Afterglow measurements and theoretical calculations reveal that selective functionalization hinders inter- and intramolecular charge transfer, which enhances the fluorescence rate of GQDs and corresponding PLQY.

MoO3 has potential advantages in price and weight over more widely studied WO3 for electrochromic devices, but it typically suffers from inferior electrochromic performance. Here, it is demonstrate...

As an alternative to Cd-free quantum dots (QDs), graphene quantum dots (GQDs) have potential because of their various advantages, such as color tunability, nontoxicity, cost effectiveness, and phot...

Night foggy road conditions limit visibility distance of drivers and are associated with higher accident and fatality rates than other weather conditions. Therefore, ensuring road visibility in night foggy road is critical. However, it is difficult to reproduce fog on a real road and only a few studies have researched foggy road conditions and visibility in a laboratory as a small scale. Previous studies have suggested that a color temperature of road lighting is related to visibility. However, many have only investigated the effects of relative transmittance in limited indoor experiments, and the impacts of differences in transmittance on visibility have thus far not been studied in real-scale conditions. In this study, a real-scale test involving 91 subjects was conducted to investigate how the visibility distance under night foggy conditions is affected by different lighting color temperatures. Based on the real scale experiments, the correlation between the visibility distance and lighting color temperature was derived. Road lighting with a low color temperature (i.e., yellow) was found to provide longer visibility distances than that with high color temperatures under night foggy conditions having measured visibility of approximately 102m. The impact of the differences in lighting color increased as the visibility distance decreased. In contrast, road lighting with a high color temperature (i.e., white) improved driver visibility in higher-visibility conditions. Therefore, this study confirmed the correlation between lighting color temperature and visibility distance for different visibility conditions and could serve as a foundation for the development of roadway design standards as well as future studies.

Graphene quantum dots (GQDs) are promising luminescent materials for various light-emitting, biological, and energy applications due to their low toxicity compared to cadmium-based semiconductor quantum dots. The practical application and use of GQDs is driven by their luminescent characteristics. As such, a critical need exists to control and tailor the emission properties of these materials to suit the targeted optoelectronic applications. In this review, the fundamental properties, synthesis methods, and strategies for incorporating GQDs into optoelectronic devices are discussed. We present the fundamentals on luminescence mechanism of GQDs, including reflections on the defect-related properties (i.e., oxygen functional groups and odd-numbered carbon rings in the basal plane). We then offer new guidelines for the fabrication of GQDs aimed at increasing the luminescence efficiency. Finally, we introduce strategies for integrating GQDs into optoelectronic devices based on architectural design of the fundamental properties.

Long-lived afterglow emissions, such as room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF), are beneficial in the fields of displays, bioimaging, and data security. However, it is challenging to realize a single material that simultaneously exhibits both RTP and TADF properties with their relative strengths varied in a controlled manner. Herein, a new design approach is reported to control singlet-triplet energy splitting (∆EST ) in graphene quantum dots (GQD)/graphene oxide quantum dots (GOQDs) by varying the ratio of oxygenated carbon to sp2 carbon (γOC ). It is demonstrated that ∆EST decreases from 0.365 to 0.123 eV as γOC increases from 4.63% to 59.6%, which in turn induces a dramatic transition from RTP to TADF. Matrix-assisted stabilization of triplet excited states provides ultralong lifetimes to both RTP and TADF. Embedded in boron oxynitride, the low oxidized (4.63%) GQD exhibits an RTP lifetime (τTavg ) of 783 ms, and the highly oxidized (59.6%) GOQD exhibits a TADF lifetime (τDFavg ) of 125 ms. Furthermore, the long-lived RTP and TADF materials enable the first demonstration of anticounterfeiting and multilevel information security using GQD. These results will open up a new approach to the engineering of singlet-triplet splitting in GQD for controlled realization of smart multimodal afterglow materials.

Inclement weather particularly fog is the negative factor on traffic flow. In advanced countries, they control the speed in active way using Variable Speed Limit (VSL) depending on climatic condition so as to ensure the stable traffic flow is maintained. In this study, Variable Speed Limit signs with advanced visibility in inclement weather conditions was developed, which was then tested at KICT’s SOC R&D center at Yeoncheon through the off-road test and the performance of VSL was compared with conventional ones. Consequently, average legibility distance of newly-developed VSL was improved by 21.9% from the conventional ones.

This study is intended to evaluate the system operation effect of physical and chemical battery-based energy-independent low lighting system which is optimized for solar charging system by battery type depending on seasonal and climatic condition. All of 3 types of battery systems which are solar-charged at daytime proved to be useful at nighttime. The capacitor only system was turned off at night because of insufficient charge during rainy day, but when it comes to the Capacitor and Lead system and the Capacitor and Li-ion system were able to keep lighting at nighttime using the Lead/Li-ion capacitor even after the capacitor which had not been fully charged due to rain was fully discharged.

The present study aims to develop a prototype of large-size movable barriers to protect roadside workers from incoming vehicles to the road work area with the following functions: maximization of work space in the right and left directions, convenient mobility, and minimization of impact without modification of the inside of movable barriers into traffic lanes and perform safety performance assessment on passengers through full scale crash tests. The large movable barrier was divided into folder type and telescope type and the development stage was now at the prototype phase. A full scale crash test was conducted prior to certification test at a level of 90%. The full scale crash test result showed that both types of folder type movable barrier and telescope type movable barrier satisfied the standard of the passenger safety performance evaluation at a level of 90%.

We present the standalone kiosk, named CFBOX/sup TM./ The CFBOX/sup TM/ is a kind of a personal commercial film (CF) studio that replaces the face of the person in an existing CF with that of the modeled face of the user by utilizing 3D face on-off integration technology in real-time. It also has photo manipulation function to change the texture of the modeled face to one's taste. In short, the CFBOX/sup TM/ is a space where one can create personalized digital video. The prototype of the CFBOX/sup TM/ is implemented and exhibited in SEE-KAIST' 2001.