Carbon-based photocatalysis in organic transformation

Carbon‐based‐materials, owing to their wide availability and low cost, have been utilized for a variety of applications including heterogeneous catalysis. Various carbonaceous materials have been used as supports for transition metals or other materials. These support materials have shown their potential for development of green and sustainable approaches to heterogeneous catalysis. In this review, we discuss the utilization of carbon‐based materials as supports for heterogeneous catalysts, especially in organic transformations. We have focused our discussions predominantly on four categories of carbonaceous supports, namely graphene (including, graphene oxide (GO) and reduced graphene oxide (RGO)), graphitic carbon nitride (GCN), carbon nanotubes (CNT) and activated carbon (AC) for various organic transformation reactions. Several approaches for the synthesis of these materials along with their application as heterogeneous catalysts for organic transformation reactions have been elaborated in detail. In addition, different aspects of organic synthesis, including hydrogenation, oxidation, reduction, condensation, and multi‐component reactions, catalyzed by these materials have been discussed. Furthermore, organic transformations leading to the sustainable synthesis of valuable products from biomass have also been discussed. Finally, after a brief summary, the future perspectives of this very interesting class of materials are provided.

The use of carbon materials in persulfate-based advanced oxidation processes: A review

Carbon quantum dots (CQDs) have emerged as a promising class of nanomaterials, distinguished by their unique optical and electronic properties, making them ideal candidates for catalyzing various organic synthesis reactions. This review provides a comprehensive overview of recent advancements in the application of CQDs as catalysts in organic transformations, with a focus on their synthesis, functionalization, and mechanisms of action. CQDs, also referred to as carbon dots (CQDs), are innovative zero-dimensional fluorescent carbon-based nanomaterials that have garnered significant global interest. The advantages of CQDs over traditional catalysts are noteworthy. They possess a high surface area, which facilitates increased interaction with reactants, and their surface chemistry can be easily tuned to optimize catalytic performance. Additionally, CQDs exhibit excellent stability under a wide range of reaction conditions, ensuring consistent catalytic activity. Their biocompatibility and low toxicity further enhance their appeal, positioning them as environmentally friendly and sustainable alternatives in chemistry. Due to their catalytic applications, CQDs are recognized for their remarkable optical properties, including strong fluorescence and water solubility, which allow them to be utilized in diverse fields, such as bioimaging, biosensing, and chemical sensing. Their eco-friendliness and simple synthesis methods make CQDs attractive for applications in nanomedicine, solar cells, drug delivery systems, and light-emitting diodes. The combination of these favorable characteristics positions CQDs as promising candidates for advancing technology across multiple domains, especially in medical and environmental applications. As research continues to uncover new functionalities and applications of CQDs, their role in catalysis and other fields is expected to expand, paving the way for innovative solutions to pressing challenges in organic synthesis and beyond.

In this work, carbon quantum dots (CDs) was successfully synthesized by hydrothermal treatment using dried leaves as green precursor. Graphitic carbon nitride (g-C3N4) was combined with CDs to prepare CDs/g-C3N4 composites with three different weight percentage at 0.6, 0.8 and 1.0 wt%, respectively. The morphological structure, optical properties and chemical compositions of CDs and composites were characterized using various spectroscopic techniques. CDs solution portrayed a significant fluorescence property that bright blue-green fluorescence can be observed by naked eye under ultraviolet (UV) light irradiation. The highest fluorescence emission was recorded at 320 nm with the optimal excitation wavelength of 423 nm. Ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS) results displayed red-shifted adsorption spectra of CDs/g-C3N4 composites from 500 nm to 800 nm. No upconversion photoluminescence (UCPL) was detected in CDs based on the photoluminescence (PL) study. The loading of CDs on g-C3N4 reduced the band gap from 2.7 eV to 2.59 eV.

Surface chemistry-dependent activity and comparative investigation on the enhanced photocatalytic performance of graphitic carbon nitride modified with various nanocarbons

Carbon, having 6 electrons, shows sp1 , sp2 and sp3 hybridization to produce novel allotropes. Since the recent discoveries of fullerenes in 1985, carbon nanotubes in 1991 and graphene in 2004, there is immense regard for the amazing physical and chemical properties of carbon nanomaterials, promoting the growth of techniques for large-scale manufacturing. Carbon nanomaterials have been the subject of extensive scientific study all around the world due to their important structural dimensions and excellent chemical, mechanical, electrical, optical, magnetic, catalytic and thermal properties different from bulk counterparts. The carbon nanomaterials with 0, 1, 2 and 3 dimensions (carbon black, nanodiamonds, fullerenes, carbon quantum dots, carbon nano-horns, carbon nanofibers, carbon nanotubes and graphene) have shown such built-in properties that are easily exploitable in cutting edge technology for a numerous application. Applications in technology, medicine, environment and agriculture are all part of the ever-expanding commercial use of carbon nanomaterials. In this chapter, brief history and recent advancements in carbon nanomaterials specifically fullerenes, carbon nanotubes, graphene, carbon quantum dots, and nanodiamonds have been thoroughly reviewed. Along with their methods of synthesis, future prospects and opportunities in a variety of industries have also been discussed. Significant applications of different carbon materials in important areas have been highlighted. A summary of toxic effects of carbon nanomaterials on biological systems has also been given to support wise usage and careful handling.

Carbon nanotubes, nanochains and quantum dots synthesized through the chemical treatment of charcoal powder

At present, the energy shortage and environmental pollution are the burning global issues. For centuries, fossil fuels have been used to meet worldwide energy demand. However, thousands of tons of greenhouse gases are released into the atmosphere when fossil fuels are burned, contributing to global warming. Therefore, green energy must replace fossil fuels, and hydrogen is a prime choice. Photocatalytic water splitting (PWS) under solar irradiation could address energy and environmental problems. In the past decade, solar photocatalysts have been used to manufacture sustainable fuels. Scientists are working to synthesize a reliable, affordable, and light-efficient photocatalyst. Developing efficient photocatalysts for water redox reactions in suspension is a key to solar energy conversion. Semiconductor nanoparticles can be used as photocatalysts to accelerate redox reactions to generate chemical fuel or electricity. Carbon materials are substantial photocatalysts for total WS under solar irradiation due to their high activity, high stability, low cost, easy production, and structural diversity. Carbon-based materials such as graphene, graphene oxide, graphitic carbon nitride, fullerenes, carbon nanotubes, and carbon quantum dots can be used as semiconductors, photosensitizers, cocatalysts, and support materials. This review comprehensively explains how carbon-based composite materials function as photocatalytic semiconductors for hydrogen production, the water-splitting mechanism, and the chemistry of redox reactions. Also, how heteroatom doping, defects and surface functionalities, etc., can influence the efficiency of carbon photocatalysts in H2 production. The challenges faced in the PWS process and future prospects are briefly discussed.

Developing gas sensors using carbon materials can be cost-effective and ecofriendly in comparison with metal oxides and chalcogenides. The carbon materials are found to have high response, recovery rates, as well as good reproducibility. The incorporation of conductive carbon materials into polymers results in high-performing gas sensors at room temperature. The combined contributions of carbon matrix and polymer are described by means of several examples highlighting the most significant achievements in the field of sensing. The combination of polymers with carbon nanomaterials is opening up exciting areas of research for gas sensors owing to their biocompatibility, excellent selectivity, and sensitivity. Among carbon materials, graphene, carbon nanotubes, carbon quantum dots, etc., are usually explored for their inherent properties like mechanical strength, high surface area, and electronic conductivity. There will be emphasis on specific synthesis of polymer composite with carbon, followed by stability, and selectivity of gas molecules by various composites materials in sensing platform. Sensing characteristics of gas sensors could be improved by the integration of smart nanomaterials or dopants, defects or structural changes, or functionalization in polymers chains. In this book chapter, the recent advances of carbon composites with polymer, their gas sensing properties and factors governing the gas sensing applications will be discussed extensively. Insights will be given for future perspectives of carbon composites with polymers materials applied in gas sensors.

Cancer poses a significant threat to global health due to its continuously rising incidence rate, high mortality rate, and recurrence rate. Nowadays, traditional cancer treatment methods have limitations, while new therapies such as phototherapy are emerging continuously. With the continuous development of science and technology, an increasing number of nanomaterials are being applied in photothermal therapy and photodynamic therapy within phototherapy, bringing new opportunities for cancer treatment. Among them, carbon-based nanomaterials, including carbon quantum dots, graphene and its derivatives, carbon nanotubes, fullerenes, etc., exhibit great potential in the field of cancer phototherapy because of their unique structures and properties, such as a high specific surface area and strong light absorption ability. For example, carbon quantum dots can be used to construct drug carrier systems and trigger immunogenic cell death. Graphene derivatives can enhance the efficacy of photodynamic therapy. Carbon nanotubes can achieve photothermal ablation and reduce the drug resistance of tumor cells. Functionalized fullerenes can be used for photothermal treatment. However, challenges still remain, including the poor biocompatibility of nanomaterials and the limitations of phototherapy itself. In the future, developing biodegradable nanomaterials, designing multifunctional treatment platforms, and combining photothermal therapy/photodynamic therapy with other treatment methods will continue to be key research directions in the field of biomedicine.

Cancer poses a significant threat to global health due to its continuously rising incidence rate, high mortality rate, and recurrence rate. Nowadays, traditional cancer treatment methods have limitations, while new therapies such as phototherapy are emerging continuously. With the continuous development of science and technology, an increasing number of nanomaterials are being applied in photothermal therapy and photodynamic therapy within phototherapy, bringing new opportunities for cancer treatment. Among them, carbon-based nanomaterials, including carbon quantum dots, graphene and its derivatives, carbon nanotubes, fullerenes, etc., exhibit great potential in the field of cancer phototherapy because of their unique structures and properties, such as a high specific surface area and strong light absorption ability. For example, carbon quantum dots can be used to construct drug carrier systems and trigger immunogenic cell death. Graphene derivatives can enhance the efficacy of photodynamic therapy. Carbon nanotubes can achieve photothermal ablation and reduce the drug resistance of tumor cells. Functionalized fullerenes can be used for photothermal treatment. However, challenges still remain, including the poor biocompatibility of nanomaterials and the limitations of phototherapy itself. In the future, developing biodegradable nanomaterials, designing multifunctional treatment platforms, and combining photothermal therapy/photodynamic therapy with other treatment methods will continue to be key research directions in the field of biomedicine.

Taurine‐functionalized Carbon Quantum Dots (Tau‐CQDs) were synthesized and evaluated for their catalytic potential under metal‐, acid‐, and base‐free sustainable conditions, using water as a solvent for various organic transformations, including Knoevenagel condensation, the Biginelli reaction, and the Knoevenagel–Michael cascade. These bioinspired N, S‐doped CQDs exhibit bifunctionality, acting as hydrogen bond donors and acceptors for C−C, C−N, and C−O bond formation. Comprehensive characterization of the catalyst was performed using HRTEM, PXRD, XPS, FTIR, AFM, Zeta potential, UV–Vis, and photoluminescence spectrometry. The Tau‐CQDs demonstrated excellent reusability, maintaining catalytic performance over 10 cycles. Green chemistry metrics, including a low E‐factor, high atom economy, and favorable PMI, CE, and RME values, highlight this approach's environmental and economic advantages. Key properties, such as high reaction yields, short reaction times, water solubility, enhanced surface functionality, non‐toxicity, and mild operating conditions, underscore the broader significance of Tau‐CQDs as an efficient, sustainable catalytic platform. Additionally, the simple recovery of the catalyst via filtration, without the need for further purification, enhances its practical applicability.

Solid-state synthesis of self-functional carbon quantum dots for detection of bacteria and tumor cells

Metal-free graphitic carbon nitride (g-C3N4) and carbon quantum dots (CQDs) have a promising attention as to their superior photocatalytic activities and physicochemical properties. In the article, g-C3N4 and CQDs were connected effectively through porous modification of g-C3N4 by directly heating melamine hydrochlorid, which benefits to the enhancement of the composites’ photocatalytic activity. The structures and morphologies of the photocatalysts were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, N2 adsorption–desorption, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance spectrum and photoluminescence spectroscopy. Meanwhile, the porous g-C3N4 and CQDs composite (pg-C3N4/CQDs) exhibited the improved photocatalytic activity for the degradation of RhB under visible light irradiation, which may be contributed three reasons: (1) pg-C3N4 has much higher surface area (~ 20 times) and more stronger photocatalytic oxidation capacity than that of g-C3N4; (2) as the electron-sinks, CQDs can improve the photogenerated electron–hole pair’s separation; (3) CQDs can upconvert the light with wavelengths longer than 650 nm into the shorter wavelengths to increase light harvesting, while pg-C3N4 utilizes the light to degrade pollutants. In addition, the possible photocatalytic degraded mechanism was investigated in detail. This work will be useful for designing other CQDs-based photocatalysts and providing a promising approach to environmental purification.

The conversion of CO2 into value-added chemicals and fuels is one of the potential approaches to deal with the environmental issues caused by the increasing carbon dioxide concentration in the atmosphere. CO2 can be transformed into a variety of valuable products, including but not limited to carbon monoxide, cyclic carbonates, formic acid, methanol, methane, ethanol, acetic acid, propanol, light olefins, aromatics, and gasoline through thermal catalysis, electrocatalysis, and photo(electro)catalysis. In the ongoing search for new CO2 catalytic conversions, the utilization of carbon-based materials as catalyst supports demonstrates improvement in catalytic performance. This is because of the unique features of carbonaceous supports, such as tunable porous structure, high specific surface area, good thermal and chemical stability, and excellent thermal conductivity. Though there are other strategies for CO2 conversion into value-added chemicals, including cycloaddition, methanation, hydrogenation, electrocatalysis, and photocatalysis, the thermal catalytic conversion of CO2 into five-membered cyclic carbonates has garnered significant attention for its potential to address environmental concerns and reduce reliance on fossil fuels; however, it faces considerable challenges due to the high thermodynamic stability of CO2. To address these issues, this review particularly presents the recent advancements in chemical fixation of CO2 into five-membered cyclic carbonate using carbonaceous-supported catalytic systems viz. graphitic carbon nitride, graphene, carbon nanotubes, carbon nanofiber, porous activated carbon, and carbon sphere, that provide advantages such as tunable porous structures, high specific surface areas, and excellent thermal and chemical stability. Furthermore, carbon materials can be easily modified by introducing defects or heteroatoms to enhance their catalytic performance. This review provides information on current research, development trends, and the necessary path to expedite the current technological CO2 conversion technologies in terms of catalytic materials, and the various experimental conditions employed in these reactions. The important role of molecular and process modeling in implementing these technologies at a commercial scale is also highlighted. The review aims to provide the current advancements in CO2 conversion and demonstrate the potential of carbonaceous-supported catalysts to improve the efficiency of cyclic carbonate production, thereby contributing to more sustainable chemical processes.Graphical