Carbon Nanodots Research Articles

Comprehensive review on fluorescent carbon dots and their applications in nucleic acid detection, nucleolus targeted imaging and gene delivery.

Carbon dots (CDs), including carbon quantum dots, graphene quantum dots, carbon nanodots, and polymer dots, have gained significant attention due to their unique structural and fluorescence characteristics. This review provides a comprehensive overview of the classification, structural characteristics, and fluorescence properties of CDs, followed by an exploration of various fluorescence sensing mechanisms and their applications in gene detection, nucleolus imaging, and gene delivery. Furthermore, the functionalization of CDs with diverse surface ligand molecules, including dye molecules, nucleic acid probes, and metal derivatives, for sensitive nucleic acid detection is systematically examined. Fluorescence imaging of the cell nucleolus plays a vital role in examining intracellular processes and the dynamics of subcellular structures. By analyzing the mechanism of fluorescence and structure-function relationships inherent in CDs, the nucleolus targeting abilities of CDs in various cell lines have been discussed. Additionally, challenges such as the insufficient organelle specificity of CDs and the inconsistent mechanisms underlying nucleolus targeting have also been highlighted. The unique physical and chemical properties of CDs, particularly their strong affinity toward deoxyribonucleic acid (DNA), have spurred interest in gene delivery applications. The use of nuclear-targeting peptides, polymers, and ligands in conjunction with CDs for improved gene delivery applications have been systematically reviewed. Through a comprehensive analysis, the review aims to contribute to a deeper understanding of the potential and challenges associated with CDs in biomedical applications.

Carbon nanodots from orange peel waste as fluorescent probes for detecting nitrobenzene

An integrated approach combining thermal and electrochemical technologies for the valorization of agro-industrial waste. The resulting carbon dots (CDs) show fascinating optical properties, enabling their application as fluorescent chemical probes.

Waste-derived carbon nanodots for fluorimetric and simultaneous electrochemical detection of heavy metals in water

Sustainable synthesis of carbon nanodots (CNDs) through a green route – converting beer bagasse, a by-product of the beer industry, into hydrochar via eco-friendly hydrothermal carbonization, and their application for the selective detection of harmful heavy metal ions.

A portable fluorescence detection device based on a smartphone employing carbon nanodots for Mn2+ sensing.

The measurement of fluorescence emission for quantitative analysis is typically based on a traditional spectrofluorometer, which limits an onsite detection approach. Thus, an alternative device should be developed for fulfilling this analysis outside of the laboratory. Therefore, a low-cost, portable, and low-energy consumption fluorescence reader-based smartphone device was developed. An ultraviolet light-emitting diodes (UV-LED) was used to construct the fluorescence device-based smartphone as a low-power excitation light source. The smartphone camera was used as a detector for detecting photons from the fluorescence emission process of the fluorescence probe and was connected to a digital image platform. Transparent acrylic with orange and yellow colors was employed as a filter for reducing the interference from light source intensity. The obtained digital image was converted to red, green and blue (RGB) intensity using a custom-designed smartphone application. N,S-doped carbon nanodots (N,S-CDs) were demonstrated to be a good fluorescence indicator for determining trace quantities of Mn2+ in cosmetics. The approach exhibited high selectivity and sensitivity, detecting and quantifying analytes at 1-5 μM concentrations. Furthermore, the method's detection limit of 0.5 μM reflects its capacity to detect trace amounts of a target analyte. Mn2+ in cosmetic products was successfully analyzed using this device with high accuracy comparable with the results from inductively coupled plasma-optical emission spectroscopy (ICP-OES).

Optimization of extraction conditions to synthesize green carbon nanodots using the Maillard reaction

Developed method to optimize green CNDs synthesis & measure concentration in baked goods. Extracted CNDs characterized using TEM, Raman, UV-Vis & fluorescence.

Tartaric acid-derived chiral carbon nanodots for catalytic enantioselective ring-opening reactions of styrene oxide.

Chiral carbon nanodots (CNDs) were fabricated through the hydrothermal processing of sulfanilic acid and chiral tartaric acid, exhibiting outstanding catalytic performance for the chiral catalysis of the ring-opening reaction. Furthermore, the catalytic mechanism was proposed to understand the link between the chiral structure and the performance of the catalyst.

A low-cost assay for hydrogen peroxide using sewage sludge-based carbon nanodots

In this work, sewage sludge is considered for the first time as a colorimetric detection probe for H2O2. This work is beneficial to the management and resource utilization of sewage sludge and the visual detection of H2O2.

Revealing two chemical strategies to tune bright one- and two-photon excited fluorescence of carbon nanodots

The internal structure (oxygenous groups and conjugated aromatic domains) and the hydrogen-bonding network with solvent molecules are two ways to tune the fluorescence of carbon nanodots upon one- and two-photon excitation.

A simple route to functionalized porous carbon foams from carbon nanodots for metal-free pseudocapacitors.

The development of potent pseudocapacitive charge storage materials has emerged as an effective solution for closing the gap between high-energy density batteries and high-power density and long-lasting electrical double-layer capacitors. Sulfonyl compounds are ideal candidates owing to their rapid and reversible redox reactions. However, structural instability and low electrical conductivity hinder their practical application as electrode materials. This work addresses these challenges using a fast and clean laser process to interconnect sulfonated carbon nanodots into functionalized porous carbon frameworks. In this bottom-up approach, the resulting laser-converted three-dimensional (3D) turbostratic carbon foams serve as high-surface-area, conductive scaffolds for redox-active sulfonyl groups. This design enables efficient faradaic processes using pendant sulfonyl groups, leading to a high specific capacitance of 157.6 F g-1 due to the fast reversible redox reactions of sulfonyl moieties. Even at 20 A g-1, the capacitance remained at 78.4% due to the uniform distribution of redox-active sites on the graphitic domains. Additionally, the 3D-tsSC300 electrode showed remarkable cycling stability of >15 000 cycles. The dominant capacitive processes and kinetics were analysed using extensive electrochemical characterizations. Furthermore, we successfully used 3D-tsSC300 in flexible solid-state supercapacitors, achieving a high specific capacitance of up to 17.4 mF cm-2 and retaining 91.6% of the initial capacitance after 20 000 cycles of charge and discharge coupled with 90° bending tests. Additionally, an as-assembled flexible all-solid-state symmetric supercapacitor exhibits a high energy density of 12.6 mW h cm-3 at a high power density of 766.2 W cm-3, both normalized by the volumes of the full device, which is comparable or better than state-of-the-art commercial pseudocapacitors and hybrid capacitors. The integrated supercapacitor provides a wide potential window of 2.0 V using a serial circuit, showing great promise for metal-free energy storage devices.

Rapid targeting and imaging of mitochondria via carbon dots using an amino acid-based amphiphile as a carrier.

Green-fluorescent biocompatible carbon dots with a quantum yield of 40% were successfully synthesized through a solvothermal process and then they are comprehensively characterized. The carbon dots showed a negatively charged surface owing to the presence of carboxylic groups. This negative surface charge hinders the effective targeting and imaging of mitochondria. To address this limitation, a new approach is developed in this study. An amphiphile containing phenylalanine, with a positively charged polar head consisting of triphenylphosphine and a hydrophobic aliphatic tail, was designed, synthesized, purified, and characterized. This amphiphile formed spherical micelle-type nanostructures in an aqueous medium in the aggregated state. Although these nanoprobes lack inherent fluorescence, they exhibited the capability to image mitochondria when their spherical micelle-type nanostructures were decorated with negatively charged fluorescent nanocarbon dots in both cancerous (KB cells) and non-cancerous (CHO cells) cell lines. Notably, carbon dots without the amphiphile failed to penetrate the cell membrane as they exhibited significantly low emission inside the cell. This study extensively explored the cell entry mechanism of the hybrid nanoprobes. The photophysical changes and the interaction between the negatively charged carbon dots and the positively charged nanospheres of the amphiphile were also analyzed in this study.

Utilization of Tuna Fish Skin Waste: Synthesis and Application of Nanocarbon Dots for Corrosion Resistance in Epoxy Polymers

Utilization of Tuna Fish Skin Waste: Synthesis and Application of Nanocarbon Dots for Corrosion Resistance in Epoxy Polymers

Photoluminescence of Argan-Waste-Derived Carbon Nanodots Embedded in Polymer Matrices.

In this work, photoluminescent (PL) carbon nano dots (CNDs) prepared from argan waste were embedded in highly optical transparent poly(styrene-co-acrylonitrile) (PSA) and cyclo-olefin copolymer (COC) matrices, which were further processed into thin films. In the first step, the luminescent CNDs were prepared through thermal processing of fine-groundargan waste, followed, in the second step, by direct dispersion in the polymer solutions, obtained by solving PSA and COC in selected solvents. These two polymer matrices were selected due to their high optical transparency, resilience to various environmental factors, and ability to be processed as quality thin films. The structural configuration of the CNDs was investigated through EDX, XPS, and FTIR, while DLS, HR-SEM, and STEM were used for their morphology investigation. The luminescence of the prepared CNDs and resulted polymer nanocomposites was thoroughly investigated through steady-state, absolute PLQY, and lifetime fluorescence. The quality of the resulted CND-polymer nanocomposite thin films was evaluated through AFM. The prepared highly luminescent thin films with a PL conversion efficiency of 30% are intended to be applied as outer photonic conversion layers on solar PV cells for increasing their conversion efficiency through valorization of the UV component of the solar radiation.

Synthetic Strategies for the Selective Functionalization of Carbon Nanodots Allow Optically Communicating Suprastructures.

The surface of Carbon Nanodots (CNDs) stands as a rich chemical platform, able to regulate the interactions between particles and external species. Performing selective functionalization of these nanoscale entities is of practical importance, however, it still represents a considerable challenge. In this work, we exploited the organic chemistry toolbox to install target functionalities on the CND surface, while monitoring the chemical changes on the material's outer shell through nuclear magnetic resonance spectroscopy. Following this, we investigated the use of click chemistry to covalently connect CNDs of different nature en-route towards covalent suprastructures with unprecedent molecular control. The different photophysical properties of the connected particles allowed their optical communication in the excited state. This work paves the way for the development of selective and addressable CND building blocks which can act as modular nanoscale synthons that mirror the long-established reactivity of molecular organic synthesis.

Synthetic Strategies for the Selective Functionalization of Carbon Nanodots Allow Optically Communicating Suprastructures

AbstractThe surface of Carbon Nanodots (CNDs) stands as a rich chemical platform, able to regulate the interactions between particles and external species. Performing selective functionalization of these nanoscale entities is of practical importance, however, it still represents a considerable challenge. In this work, we exploited the organic chemistry toolbox to install target functionalities on the CND surface, while monitoring the chemical changes on the material's outer shell through nuclear magnetic resonance spectroscopy. Following this, we investigated the use of click chemistry to covalently connect CNDs of different nature en‐route towards covalent suprastructures with unprecedent molecular control. The different photophysical properties of the connected particles allowed their optical communication in the excited state. This work paves the way for the development of selective and addressable CND building blocks which can act as modular nanoscale synthons that mirror the long‐established reactivity of molecular organic synthesis.

The mechanical and heat aging properties of natural rubber latex modified by carbon nanodots

AbstractDue to their unique structure and tuneable physical, optical, and electronic properties, carbon nanodots (CDs) become one of the perfect nano‐materials in many fields such as biomarkers, optical sensing, and catalysis. The application of CDs in modifying polymers has also attracted much interest. In this work, a simple process was employed for introducing CDs to modify natural rubber (NR) latex. Glucose was applied as the precursor to prepare CDs by hydrothermal method, subsequently, the crude CDs were directly added to NR latex at a very lower concentration to prepare NR/CDs films. The results of mechanical properties demonstrate that the 500% modulus, tensile and tear strength of NR composites are significantly improved by the introduction of CDs. When the theoretical loading of CDs is 2 phr, the tensile strength and tear strength of NR/CDs film reach to 33.1 MPa and 56.4 N/mm, and improve 17.8% and 29.4% than NR without CDs respectively. It is particularly noteworthy that when the amount of CDs is higher than 1.5 phr, the heat‐aging resistance of NR has been enhanced. It has been confirmed by crosslink density, dynamic mechanical analysis, and Fourier Transform Infrared Spectrometer analysis that CDs have a certain confinement effect on the mobility of rubber molecular segments through physical adsorption and chemical crosslinking. The Tube model theory was employed to calculate parameters of the network structure of NR/CDs films (based on the stress–strain curves), the results indicate that CDs give NR film more chemical crosslinking points and less entanglement network.Highlights The crude carbon nanodots are used to modify NR latex at a lower concentration The mechanical properties of NR films are obliviously improved The heat‐aging resistance of NR has been enhanced by adding carbon nanodots higher than 1.5 phr The Tube model theory are employed to analysis the crosslink network CDs give NR film more chemical crosslinking points and less entanglement network

In vitro cytotoxic potential of cow dung and expired tomato sauces-derived carbon nanodots against A-375 human melanoma cell line

Converting biowaste into a functional product is put to the test by the growing amount of biowaste in the world and the environmental problems it causes. In this research study, we synthesized, characterized, and evaluated bluish-green luminescent carbon nanodots (CNDs) from cow dung and expired tomato sauces via a hydrothermal synthesis method at 160 °C for 8 h. The carbon nanodots were fabricated without additional passivating agents and exhibited good physicochemical and optical properties. The intrinsic properties of carbon nanodots were characterized using various spectral techniques. First, we evaluated the cytotoxic potential of carbon nanodots against A-375 human melanoma cell lines. This study revealed that carbon nanodots exhibited potent cytotoxicity and significantly inhibited the proliferation of A-375 cells in a dose-dependent manner. Next, we demonstrated these carbon nanodot's free radical scavenging potential by employing 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The bluish-green fluorescent carbon nanodots fabricated using a green synthesis approach have broad potential for biological applications.

Metal–Organic Framework‐Assisted Rational Design of Multicolor Solid‐State Fluorescent Carbon Nanodots and Its Application for LEDs

AbstractCarbon nanodots (CDs) are a new type of carbon‐based fluorescent nanomaterials, but they are limited in many applications due to the inherent fluorescence weakening and quenching problems suffered in solid state. Herein, ZIF‐8, a class of metal–organic framework (MOF) is employed as a matrix to immobilize fluorescent CDs, resulting in the strong luminescence of CDs achieved in solid state. The as‐synthesized CDs@ZIF‐8 fluorescent powders possess blue, green, and red emissions with the main emission at ≈495, 528, and 600 nm, and the corresponding photoluminescence quantum yields (PLQYs) are as high as 25.89%, 52.24%, and 15.42%, respectively. It is found that the encapsulation of ZIF‐8 with CDs will increase the excitation dependence of the product fluorescence, which may be attributed to the carrier effect of ZIF‐8 as a carrier of CDs and some surface defects or surface functional groups change of the CDs introduced by ZIF‐8. In addition, the encapsulation of CDs with ZIF‐8 may result in the charge transfer. Importantly, the prepared CDs@ZIF‐8 phosphors present a promising application in the fabrication of monochromatic light‐emitting diodes (LEDs). The synthesis design is expected to provide technical support for future solid‐state fluorescent CDs preparation and applications.

Physicochemical and Inflammatory Analysis of Unconjugated and Conjugated Bone-Binding Carbon Dots.

Carbon nanodots (CDs) have drawn significant attention for their potential uses in diagnostic and therapeutic applications due to their small size, tissue biocompatibility, stable photoluminescence, and modifiable surface groups. However, the effect of cargo molecules on CD photoluminescence and their ability to interact with tissues are not fully understood. Our previous work has shown that CDs produced from the acidic oxidation of carbon nanopowder can bind to mineralized bone with high affinity and specificity in a zebrafish animal model system. Using this model, we investigated the impact of loading Cy5 and biotin cargo on CDs' photoluminescence and bone-binding properties. We report that CD cargo loading alters CD photoluminescence in a pH- and cargo-dependent manner without interfering with the CDs' bone binding properties. In a reciprocal analysis, we show that cargo loading of CDs does not affect the cargo's fluorescence. Significantly, CDs do not trigger nitric oxide production in a mouse macrophage assay, suggesting that they are noninflammatory. Together, these results further support the development of carbon nanopowder-derived CDs for the precise delivery of therapeutic agents to bone tissue.

Functional Groups Accessibility and the Origin of Photoluminescence in N/O‐containing Bottom‐up Carbon Nanodots

AbstractChemical surface functionalization of carbon nanodots (CNDs) offers a valuable opportunity to tailor multifunctionality in these nanocarbons, by engineering the composition of their molecular surface. Therefore, it is important to elucidate the type and amount of CNDs surface functionalization to be able to design their properties accurately. CNDs are often functionalized through amide coupling without validating the degree of surface functionalization. As a measure of surface functionalization, the amounts of primary amines via Kaiser test (KT) or imine reactions of the bare CNDs is often considered. However, this may lead to overestimating the degree of surface functionalization obtained by the pure amide coupling due to different reaction mechanisms and involved intermediates. Herein, four different CNDs prepared by microwave‐assisted synthesis from arginine or citric acid with varying amounts of ethylenediamine are presented. We resorted to combining physicochemical methods to provide elemental, structural, and optical information. By that, we developed a method to quantify the degree of surface functionalization by amide coupling and show that the surface functionalization is lower than anticipated. Comparing experimental optical features of the CNDs with different computed model systems enables us to provide a more advanced vision of structure‐property relationships in these still elusive nanocarbons.

Fluorometric Sensing of Metal Ions by Carbon Nano Dots - A Review

abstract: Contamination from heavy metal ions is a rising problem. It has direct and indirect impacts on human health, the environment, and aquatic life. Thus, detecting trace amounts of these elements presents significant challenges. It is important to develop effective, affordable, accurate, fast sensing monitoring systems. A new field of sensing techniques has emerged with the discovery of bio-compatible fluorescent carbon nanodots. Although the study of heavy metal ion detection using carbon nanodots and fluorometric sensing techniques is relatively new and developing, it holds great potential for aiding scientists in the development of environmentally friendly sensing systems. This article focuses on the utilization of carbon nanodots in fluorescencebased detection of metal ions in various media. The ability to emit fluorescence across the entire visible spectrum under UV and visible light excitation offers fluorescent quenching or fluorescent enhancement phenomena in the presence of trace amount of metal ions. The present work discusses different fluorometric sensing phenomena, its mechanism and applications of carbon dots on it. It covers the recent progress in carbon-nano dots for bio-based synthesis, physical properties, and application in heavy metal sensing.