Self-assembled nitrogen-doped graphene quantum dots (N-GQDs) over graphene sheets for superb electro-photocatalytic activity

Riaz, Rabia,Ali, Mumtaz,Sahito, Iftikhar Ali,Arbab, Alvira Ayoub,Maiyalagan, T.,Anjum, Aima Sameen,Ko, Min Jae,Jeong, Sung Hoon Elsevier BV * North-Holland 2019 Applied Surface Science Vol.480 No.-

<P><B>Abstract</B></P> <P>Nitrogen-doped graphene quantum dots (N-GQDs) are emerging electroactive and visible light active organic photocatalysts, known for their high stability, catalytic activity and biocompatibility. The edge surfaces of N-GQDs are highly active, however, when N-GQDs make the film the edges are not fully exposed for catalysis. To avoid this issue, the N-GQDs are shaped to branched leaf shape, with an extended network of voids, offering highly active surfaces (edge) exposed for electrocatalytic and photocatalytic activity. The nitrogen doping causes a decrease in the bandgap of N-GQDs, thus enabling them to be superb visible light photocatalyst, for degradation of Methylene blue dye from water. Photoluminescence results confirmed that by a synergistic combination of the highly conductive substrate; Carbon fabric coated graphene sheets (CF-rGO) the recombination of photogenerated excitons is significantly suppressed, hence enabling their efficient utilization for catalysis. Comparatively, uniformly coated N-GQDs showed 49.3% lower photocatalytic activity, owing to their hidden active sites. The degradation was further boosted by 30% by combining the electrocatalytic activity, i.e. electro-photocatalysis of the proposed electrode. The proposed electrode material was analyzed using TEM, FE-SEM, FTIR, AFM, and WA-XRD, whereas the stability of electrode was confirmed by TGA, tensile test, bending test, and in harsh chemical environments. The proposed photo-electrocatalyst electrode is binder-free, stable, flexible and highly conductive, which makes the electrode quite suitable for flexible catalytic devices like flexible solar cells and wearable supercapacitors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A flexible electrode is fabricated using self-assembled overlayer of Nitrogen doped Graphene Quantum Dots (N-GQDs). </LI> <LI> Self-assembeled highly porous leaflets structure has maximum exposed edge surfaces to accelarate the catalytic reaction. </LI> <LI> The proposed electrode is metal free and is stable at high temperature, harsh chemical environments, and mechanical stresses. </LI> <LI> The surface resistance of the all carbon electrode is only 2.5 Ω sq.<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Nitrogen doped graphene quantum dots (N-GQDs) were self-assembled (with high porosity) on reduced graphene oxide coated carbon fabric to fabricate a highly stable visible light photocatlytically and electrocatalytically active flexible electrode for water treatment.</P> <P>[DISPLAY OMISSION]</P>

N-doped Cdot/PtPd nanonetwork hybrid materials as highly efficient electrocatalysts for methanol oxidation and formic acid oxidation reactions

Nguyen, Van-Toan,Tran, Quoc Chinh,Quang, Nguyen Duc,Nguyen, Ngoc-Anh,Bui, Van-Tien,Dao, Van-Duong,Choi, Ho-Suk Elsevier 2018 Journal of alloys and compounds Vol.766 No.-

<P><B>Abstract</B></P> <P>The improvement of the catalytic performance for methanol and formic acid oxidation reactions remains a key issue for the development of a new generation of direct methanol and formic acid fuel cells. This study reports a simple approach, using selective chemical etching for the synthesis of unique nitrogen-doped carbon dot/Pt<SUB>84</SUB>Pd<SUB>16</SUB> (N-Cdot/Pt<SUB>84</SUB>Pd<SUB>16</SUB>) nano-network structure at room temperature with excellent electrocatalytic properties. The obtained nano-network hybrid material exhibits significant enhancement of the electrocatalytic activity for the electro-oxidation reaction of both methanol and formic acid with current densities of 999.0 and 1919.5 mA/mg<SUB>metal</SUB>, respectively, compared with the commercial ones of 751.32 and 806.02 mA/mg<SUB>metal</SUB>, respectively. Furthermore, the N-Cdot/Pt<SUB>84</SUB>Pd<SUB>16</SUB> nano-network hybrid materials exhibit excellent stability and hydrophilic dispersibility at room temperature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> N-Cdot/PtPd nanonetwork hybrid material is synthesized at room temperature. </LI> <LI> A simple coreduction and a selective chemical etching are applied to the synthesis. </LI> <LI> It generates a nano-network structure with excellent electrocatalytic properties. </LI> <LI> N-Cdot functions as a uniform interconnection between the nanohybrid materials. </LI> <LI> The hybrid exhibits significant enhancement of the activity for both MOR and FAOR. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Facile synthesis of nitrogen-doped carbon dots (N-CDs) and N-CDs/NiO composite as an efficient electrocatalyst for oxygen evolution reaction

Kou Xiaoli,Xin Xin,Zhang Yan,Meng Long-Yue 한국탄소학회 2021 Carbon Letters Vol.31 No.4

Nitrogen-doped carbon dots (N-CDs), derived from the biomass (anthocyanin), are the novel additive to the nanocarbon materials, which is expected to bring a wide spectrum of novel applications. Moreover, metallic oxides are emerging for their unique potential for electrocatalysis. Herein, we report the synthesis of N-CDs for the selective detection of Fe3+ with a limit of detection of 2.57 μM in the range of 5–60 μM using ethylenediamine and H2O2 by a hydrothermal method. The obtained N-CDs displayed a spherical morphology with a particle size range of 2–7 nm and emitted blue luminescence at 394 nm under excitation at 319 nm. Meanwhile, we have demonstrated the fabrication of cost-efcient electrocatalysts for oxygen evolution reaction (OER) in an alkaline medium, employing N-CDs. Owing to the successful incorporation of N-CDs into NiO nanospheres, the resulting N-CDs/NiO with large surface areas, fast charge transfer, and increased conductivity vastly improved the catalytic activity. Remarkably, the optimal of N-CDs/NiO composite requires the overpotential of only 380 mV at a current density of 10 mA cm−2 and a relatively low Tafel slope of 57.96 mV dec−1 compared with pure NiO. These results open up a facile route for the application of N-CDs and ofer prospects for CD-metal hybrids as high OER catalysts in electrochemical energy devices.

Preparation of ethanediamine-doped carbon quantum dots and their applications in white LEDs and fluorescent TLC plate

Wang Wenya,Zhou Chunru,Song Weina,Wei Liguo,Wu Peng 한국탄소학회 2022 Carbon Letters Vol.32 No.2

Herein, a facile bottom–up approach for producing nitrogen-doped carbon quantum dots (N-CQDs) was carried out by the hydrothermal treatment of microcrystalline cellulose, in the presence of different nitrogen sources (blank/urea/ammonia water/ethanediamine(EDA)/Hexamethylenetetramine). The result showed that the fluorescence intensity and quantum yields (QYs) of N-CQDs with different nitrogen sources are all higher than that without nitrogen source. Compared with the other three nitrogen sources, N-CQDs prepared by EDA not only have the highest fluorescence intensity but also the largest QYs of 51.39%. Therefore, EDA was chosen as the nitrogen source to prepare N-CQDs. The obtained N-CQDs are uniform spherical particles with a diameter of 2.76 nm. The N-CQDs also exhibit excitation-dependent and long-wave emission properties. The emission range of N-CQDs is 470–540 nm. Moreover, N-CQDs as fluorescent agents successfully acted on purple LEDs (λem = 365 nm) to achieve white LEDs light emission. At the same time, a fluorescent thin layer chromatography plate was successfully prepared using N-CQDs, silica gel G and Sodium carboxymethylcellulose as raw materials. The separation trajectory of mixed sample of Sudan red III and kerosene on the fluorescent TLC plate is obviously clearer than that of the TLC plate.

Facile green synthesis of nitrogen-doped carbon dots using <i>Chionanthus retusus</i> fruit extract and investigation of their suitability for metal ion sensing and biological applications

Atchudan, Raji,Edison, Thomas Nesakumar Jebakumar Immanuel,Chakradhar, Dasagrandhi,Perumal, Suguna,Shim, Jae-Jin,Lee, Yong Rok Elsevier 2017 Sensors and actuators. B, Chemical Vol.246 No.-

<P><B>Abstract</B></P> <P>Nitrogen-doped carbon dots (N-CDs) were synthesized from <I>Chionanthus retusus (C. retusus)</I> fruit extract using a simple hydrothermal-carbonization method. Their ability to sense metal ions, and their biological activity in terms of cell viability and bioimaging applications were evaluated. The resulting N-CDs were characterized by various physicochemical techniques such as high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. The optical properties were characterized by ultraviolet visible (UV-vis) fluorescence spectroscopy techniques. The average size of the N-CDs was approximately 5±2nm with an interlayer distance of 0.21nm, as calculated from the HRTEM images. The presence of phytoconstituent functionalities and the percentages of components in the N–CDs were confirmed by XPS studies, and a nitrogen content of 5.3% was detected. The N–CDs demonstrated highly durable fluorescence properties and low cytotoxicity with a quantum yield of 9%. The synthesized N–CDs were then used as probes for the detection of metal ions. The N–CDs exhibited high sensitivity and selectivity towards Fe<SUP>3+</SUP>, with a linear relationship between 0 and 2μM and a detection limit of 70μM. The synthesized N–CDs are anticipated to have diverse biomedical applications, particularly for bioimaging, given their high fluorescence, excellent water solubility, good cell permeability, and negligible cytotoxicity. Finally, the potential of N–CDs as biological probes was investigated using fungal (<I>Candida albicans</I> and <I>Cryptococcus neoformans</I>) strains via fluorescent microscopy. We found that N–CDs were suitable candidates for differential staining applications in yeast cells with good cell permeability, localization with negligible cytotoxicity. Hence, N–CDs may find dual utility as probes for the detection of cellular pools of metal ions (Fe<SUP>3+</SUP>) and also for early detection of opportunistic yeast infections in biological samples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Durable fluorescent N-CDs prepared using <I>C. Retusus</I> via hydrothermal-carbonization. </LI> <LI> This method of synthesis and N-CDs is an ideal for sensing of Fe<SUP>3+</SUP> and bio-imaging. </LI> <LI> N-CDs was used as a promising fluorescent probe for the direct detection of Fe<SUP>3+</SUP>. </LI> <LI> N-CDs were used as selective probes for yeast <I>C. albicans</I> and <I>C. neoformans</I>. </LI> <LI> N-CDs exhibits selective uptake, good biocompatibility and negligible cytotoxicity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

The Detection of Osthole and Application of Cell Imaging Based on Nitrogen-Doped Carbon Dots

Ning Wang,Xuefang Yang,Haojiang Wang,Liping Xie,Weihua Jia,Wei Bian,Martin M. F. Choi 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2020 NANO Vol.15 No.03

A fluorescence probe has been synthesized for the detection of osthole using the nitrogen-doped carbon dots (NCDs) as shown in Fig. 1. The NCDs were fully characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR). Under the optimal experimental conditions, the NCDs fluorescence probe was highly selective and sensitive to osthole. The linear response range for osthole was 5.0–7 5μM with a detection limit of 38 nM. The mechanism of the interaction of osthole and NCDs was discussed. The fluorescence probe has been applied to the analysis of biological samples. The as-synthesized NCDs with high fluorescence intensity, low toxicity and good biocompatibility were applied to cell imaging.

Green synthesized multiple fluorescent nitrogen-doped carbon quantum dots as an efficient label-free optical nanoprobe for <i>in vivo</i> live-cell imaging

Atchudan, Raji,Edison, Thomas Nesakumar Jebakumar Immanuel,Perumal, Suguna,Clament Sagaya Selvam, N.,Lee, Yong Rok Elsevier 2019 Journal of photochemistry and photobiology Chemist Vol.372 No.-

<P><B>Abstract</B></P> <P>In this work, nitrogen-doped carbon quantum dots (N-CQDs) have been synthesized successfully by a simple hydrothermal method and demonstrated its application for multicolor imaging in <I>Caenorhabditis elegans</I> (<I>C. elegans</I>) as an <I>in vivo</I> model. The synthesized N-CQDs were characterized by various physicochemical techniques such as XRD, Raman spectroscopy, ATR-FTIR spectroscopy, XPS, HRTEM, UV–vis spectroscopy, and fluorescence spectroscopy. The synthesized N-CQDs exhibited a strong fluorescence due to the uniform size distribution with nitrogen-containing and oxygen-containing functional groups onto the surface of N-CQDs which induce the excellent dispersibility in aqueous media. The N-CQDs has an excitation-dependent fluorescence behavior and the strongest fluorescence appeared at 411 nm (emission peak position) under the excitation of 340 nm. Also, the N-CQDs displayed a high quantum yield (QY) of 12.5. The fluorescence behaviour of the aqueous N-CQDs suspension retains for a long time up to 1 year. The prolonging fluorescent N-CQDs was utilized as a staining agent for bioimaging and toxicity of N-CQDs on <I>C. elegans</I> that was conducted by killing assay. <I>In-vivo</I> studies suggested that the N-CQDs displayed excellent biocompatibility and successfully used for high-contrast imaging of N-CQDs in living and dead <I>C. elegans</I>. Based on the strongest fluorescence along with excellent aqueous dispersibility and biocompatibility, the green synthesized N-CQDs would be an ideal candidate for many biological applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A strongest multiple fluorescent N-CQDs were synthesized from the <I>P. acidus</I> fruits. </LI> <LI> Synthesized N-CQDs showed low-toxic and were employed for <I>in vivo</I> live-cell imaging. </LI> <LI> The N-CQDs were uniformly stained within the body of the nematodes (<I>C. elegans</I>). </LI> <LI> The live-cell imaging result reveals the usage of N-CQDs in drug delivery. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Highly fluorescent nitrogen-doped carbon dots derived from <i>Phyllanthus acidus</i> utilized as a fluorescent probe for label-free selective detection of Fe³⁺ ions, live cell imaging and fluorescent ink

Atchudan, Raji,Edison, Thomas Nesakumar Jebakumar Immanuel,Aseer, Kanikkai Raja,Perumal, Suguna,Karthik, Namachivayam,Lee, Yong Rok Elsevier 2018 Biosensors & bioelectronics Vol.99 No.-

<P><B>Abstract</B></P> <P>A facile, economical and one-step hydrothermal method is used to synthesize highly durable fluorescent nitrogen-doped carbon dots (FNCDs) by utilizing <I>Phyllanthus acidus</I> (<I>P. acidus</I>) and aqueous ammonia as the carbon and nitrogen sources, respectively. The synthesized FNCDs have an average size of 4.5±1nm and showed bright blue fluorescence under the irradiation of UV-light at an excitation wavelength of 365nm. It exhibits a quantum yield (QY) of 14% at an excitation wavelength of 350nm with maximum emission at 420nm. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy characterizations clearly showed the formation of FNCDs that predominantly consists of nitrogen and hydroxyl groups which can provide more adsorption sites. In addition, the above study reveals the successful bonding of nitrogen with carbon (C–N) in the FNCDs. The synthesized FNCDs with high QY can be used as efficient fluorescent probes for the detection of Fe<SUP>3+</SUP>. Based on the linear relationship between normalized fluorescence intensity and concentration of Fe<SUP>3+</SUP> ions, the prepared FNCDs can be used for label-free sensitive and selective detection of Fe<SUP>3+</SUP> ions in a wide concentration range of 2–25μM with a detection limit of 0.9μM. The present study proves that synthesized FNCDs has durable fluorescence, soluble in water very well and thus act as a promising candidate for the diverse applications such as label-free sensitive and selective detection of Fe<SUP>3+</SUP>, fluorescent ink and cellular imaging with good biocompatibility and low cytotoxicity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> FNCDs was successfully synthesized using <I>Phyllanthus acidus</I> by hydrothermal method. </LI> <LI> First time, durable FNCDs was derived from the <I>P. acidus</I> fruit juice with QY of 14%. </LI> <LI> FNCDs were used as a fluorescent probe for lable-free selective detection of Fe<SUP>3+</SUP>. </LI> <LI> FNCDs can be used as a fluorescent ink without any chemical modification. </LI> <LI> FNCDs could offer a multi-colour cell imaging and alternative for fluorescent pens. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

One-pot dual product synthesis of hierarchical Co₃O₄@N-rGO for supercapacitors, N-GDs for label-free detection of metal ion and bio-imaging applications

Atchudan, Raji,Edison, Thomas Nesakumar Jebakumar Immanuel,Chakradhar, Dasagrandhi,Karthik, Namachivayam,Perumal, Suguna,Lee, Yong Rok Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.3

<P><B>Abstract</B></P> <P>Cobalt oxide nanoparticles@nitrogen-doped reduced graphene oxide (Co<SUB>3</SUB>O<SUB>4</SUB>@N-rGO) composite and nitrogen-doped graphene dots (N-GDs) were synthesized by a one-pot simple hydrothermal method. The average sizes of the synthesized bare cobalt oxide nanoparticles (Co<SUB>3</SUB>O<SUB>4</SUB> NPs) and Co<SUB>3</SUB>O<SUB>4</SUB> NPs in the Co<SUB>3</SUB>O<SUB>4</SUB>@N-rGO composite were around 22 and 24nm, respectively with an interlayer distance of 0.21nm, as calculated using the XRD patterns. The Co<SUB>3</SUB>O<SUB>4</SUB>@N-rGO electrode exhibits superior capacitive performance with a high capability of about 450Fg<SUP>−1</SUP> at a current density of 1Ag<SUP>−1</SUP> and has excellent cyclic stability, even after 1000 cycles of GCD at a current density of 4Ag<SUP>−1</SUP>. The obtained N-GDs exhibited high sensitivity and selectivity towards Fe<SUP>2+</SUP> and Fe<SUP>3+</SUP>, the limit of detection was as low as 1.1 and 1.0μM, respectively, representing high sensitivity to Fe<SUP>2+</SUP> and Fe<SUP>3+</SUP>. Besides, the N-GDs was applied for bio-imaging. We found that N-GDs were suitable candidates for differential staining applications in yeast cells with good cell permeability and localization with negligible cytotoxicity. Hence, N-GDs may find dual utility as probes for the detection of cellular pools of metal ions (Fe<SUP>3+</SUP>/Fe<SUP>2+</SUP>) and also for early detection of opportunistic yeast infections in biological samples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dual product of Co<SUB>3</SUB>O<SUB>4</SUB>@N-rGO and fluorescent N-GDs by one-pot hydrothermal method. </LI> <LI> The Co<SUB>3</SUB>O<SUB>4</SUB>@N-rGO delivered a high C<SUB>s</SUB> of 450 F g<SUP>−1</SUP> at current density of 1 A g<SUP>−1</SUP>. </LI> <LI> First time, the byproducted N-GDs was used for label-free detection of Fe<SUP>3+</SUP>/Fe<SUP>2+</SUP>. </LI> <LI> N-GDs were used as a fluorescent probe for bio-imaging with good biocompatibility. </LI> <LI> N-GDs would offer a great potential for clinical applications in the near future. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Inner filter effect‑based highly sensitive quantification of 4‑nitrophenol by strong fluorescent N, S co‑doped carbon dots

Kandasamy Sasikumar,Ramar Rajamanikandan,Heongkyu Ju 한국탄소학회 2024 Carbon Letters Vol.34 No.2