“…There have been many types of red emissive CDs synthesized, but most of them were formed using solvothermal methods [44][45][46][47][48][49]. Red emissive CDs prepared by hydrothermal methods have been rarely reported [50]. Liu et al [51] prepared red emissive CDs by the hydrothermal treatment of 2,5-diaminobenzenesulfonic acid and 4-aminophenylboronic acid hydrochloride.…”
“…There have been many types of red emissive CDs synthesized, but most of them were formed using solvothermal methods [44][45][46][47][48][49]. Red emissive CDs prepared by hydrothermal methods have been rarely reported [50]. Liu et al [51] prepared red emissive CDs by the hydrothermal treatment of 2,5-diaminobenzenesulfonic acid and 4-aminophenylboronic acid hydrochloride.…”
“…The choice of GQDs as a representative of the graphene-family materials is justified by the fact that GQD-related systems are multifunctional platforms, which can be used for production of micron-sized solid sheets (a promising working electrode material for electrochemical detection of heavy metals), 68 catalysts accelerating the reaction with HMs, 69 modified working electrodes, 70,71 aqueous solution electrolytes for optical and colorimetric detection of heavy metals [72][73][74][75][76][77][78][79][80][81][82] and adsorbent agents for removal of heavy metals. [83][84][85]…”
High-performance optical detection of toxic heavy metals by using graphene quantum dots (GQDs) requires a strong interaction between the metals and GQDs, which can be reached through a functionalization/immobilization procedure or doping effect. However, commonly used surface activation approaches induce toxicity into the analysis system and, therefore, are ineligible from the environmental point of view. Here, we show that artificial creation of vacancy-type defects in GQDs can be a helpful means of intentional control of the active sites available for reaction with cadmium (Cd), mercury (Hg) and lead (Pb). Using restricted density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, we predict the effect of vacancy complexes not previously studied to describe the binding ability of GQDs towards metal adsorbates. We also show that the interband absorption in closed-shell GQDs complexed with Cd, Hg and Pb is strongly dependent on the vacancy type and can be efficiently tuned to attain the desired coloration of the analysis system. The results suggest that the vacancy defects play an important role in governing the hybridization between locally-excited (LE) and charge-transfer (CT) states of the GQDs. Based on the molecular orbital analysis and in-depth knowledge of excited states, the mechanisms underlying the interband absorption are discussed.
“…Among their several applications, numerous CDs derived from plant parts have been used to sense metal ions in water ( Figure 4 ), such as Lotus root for Hg(II) ( Gu et al., 2016 ), Strawberry for Hg(II) ( Huang et al., 2013 ), Bamboo leaves for Pb(II) and Hg(II) ( Liu et al., 2014 ), Bergamot for Hg(II) ( Yu et al., 2015 ), Papaya for Cr(III), Cr(VI) ( Pooja et al., 2019 ), Tulsi leaves for Cr(VI) ( Bhatt et al., 2018 ), Ginkgo biloba leaves for Pb(II) ( Xu et al., 2018 ), Coriander leaves for Fe(III) ( Sachdev and Gopinath, 2015 ), and Mangosteen for Fe(III) ( Yang et al., 2017 ). Figure 4 Some examples of CDs derived from different parts of the plant ( Bhatt et al., 2018 ; Gu et al., 2016 ; Huang et al., 2013 ; Lim et al., 2015 ; Liu et al., 2019d ; Sachdev and Gopinath, 2015 ; Singh et al., 2019 ; Xu et al., 2018 ; Yang et al., 2017 ; Yu et al., 2015 ; Zulfajri et al., 2019 ). …”
Section: Biomassmentioning
confidence: 99%
“… ( Bhatt et al., 2018 ; Gu et al., 2016 ; Huang et al., 2013 ; Lim et al., 2015 ; Liu et al., 2019d ; Sachdev and Gopinath, 2015 ; Singh et al., 2019 ; Xu et al., 2018 ; Yang et al., 2017 ; Yu et al., 2015 ; Zulfajri et al., 2019 ). …”
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