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Photoluminescent carbon nanoparticles, or carbon dots, are an emerging class of materials that has recently attracted considerable attention for biomedical and energy applications. They are defined by characteristic sizes of <10 nm, a carbon-based core and the possibility to add various functional groups at their surface for targeted applications. These nanomaterials possess many interesting physicochemical and optical properties, which include tunable light emission, dispersibility and low toxicity. In this Review, we categorize how chemical tools impact the properties of carbon dots. We look for pre- and postsynthetic approaches for the preparation of carbon dots and their derivatives or composites. We then showcase examples to correlate structure, composition and function and use them to discuss the future development of this class of nanomaterials. This Review discusses synthetic strategies to functionalize photoluminescent carbon nanomaterials, or carbon dots, for targeted applications.

The design of novel carbon dots with ad hoc properties requires a comprehensive understanding of their formation mechanism, which is a complex task considering the number of variables involved, such as reaction time, structure of precursors or synthetic protocol employed. Herein, we systematically investigated the formation of carbon nanodots by tracking structural, chemical and photophysical features during the hydrothermal synthesis. We demonstrate that the formation of carbon nanodots consists of 4 consecutive steps: (i) aggregation of small organic molecules, (ii) formation of a dense core with an extended shell, (iii) collapse of the shell and (iv) aromatization of the core. In addition, we provide examples of routes towards tuning the core-shell design, synthesizing five novel carbon dots that all consist of an electron-dense core covered by an amine rich ligand shell. Studying the formation processes of carbon nanodots remains crucial for understanding their properties and chemical structure. Here, the authors investigate the steps involved in their formation process and provide examples for tuning the core-shell design.

Carbon-based dots (CDs) and their functionalized (nano)composites have recently attracted attention due to their seemingly easy preparation and numerous potential applications, ranging from those in the biomedical field (i.e., imaging and drug delivery) to those in (opto)electronics (i.e., solar cells and LEDs). This protocol details step-by-step procedures for synthesis, purification, functionalization and characterization of nitrogen-doped carbon nanodots (NCNDs), which we have been preparing for the past few years. First, we describe the bottom-up synthesis of NCNDs, starting with the use of molecular precursors (arginine (Arg) and ethylenediamine (EDA)) and making use of microwave-assisted hydrothermal heating. We also provide guidelines for the purification of these materials, through either dialysis or low-pressure size-exclusion chromatography (SEC). Second, we outline post-functionalization procedures for the surface modification of NCNDs, such as alkylation and amidation reactions. Third, we provide instructions for the preparation of NCNDs with different properties, such as color emission, electrochemistry and chirality. Given the fast evolution of preparations and applications of CDs, issues that might arise from artifacts, errors and impurities should be avoided. In this context, the present protocol aims to provide details and guidelines for the synthesis of high-quality nanomaterials with high reproducibility, for various applications. Furthermore, specific needs might require the CDs to be prepared by different synthetic procedures and/or from different molecular precursors, but such CDs can still benefit from the purification and characterization procedures outlined in this protocol. The sample preparation takes various time frames, ranging from 4 to 18 d, depending on the adopted synthesis and purification steps. This protocol describes the synthesis, purification, functionalization and characterization of nitrogen-doped carbon nanodots (NCNDs). In addition, examples of how to tailor the color emission, electrochemistry and chirality of NCNDs are provided.

The chirality of (nano)structures is paramount in many phenomena, including biological processes, self-assembly, enantioselective reactions, and light or electron spin polarization. In the quest for new chiral materials, metallo-organic hybrids have been attractive candidates for exploiting the aforementioned scientific fields. Here, we show that chiral carbon nanoparticles, called carbon nanodots, can be readily prepared using hydrothermal microwave-assisted synthesis and easily purified. These particles, with a mean particle size around 3 nm, are highly soluble in water and display mirror-image profile both in the UV–Vis and in the infrared regions, as detected by electronic and vibrational circular dichroism, respectively. Finally, the nanoparticles are used as templates for the formation of chiral supramolecular porphyrin assemblies, showing that it is possible to use and transfer the chiral information. This simple (and effective) methodology opens up exciting opportunities for developing a variety of chiral composite materials and applications. A promising and efficient route to chiral materials involves the transfer of chirality across length scales. Here, the authors use chiral molecular precursors to synthesize chiral carbon nanodots, which in turn can template the formation of chiral supramolecular assemblies.

Carbon nanodots with opposite chirality possess the same major physicochemical properties such as optical features, hydrodynamic diameter, and colloidal stability. Here, a detailed analysis about the comparison of the concentration of both carbon nanodots is carried out, putting a threshold to when differences in biological behavior may be related to chirality and may exclude effects based merely on differences in exposure concentrations due to uncertainties in concentration determination. The present study approaches this comparative analysis evaluating two basic biological phenomena, the protein adsorption and cell internalization. We find how a meticulous concentration error estimation enables the evaluation of the differences in biological effects related to chirality. Chirality is known to impact the biological activity of materials but concentration differences can often lead to errors in analysis. Here, the authors report on detailed concertation analysis of different chiral carbon nanodots to accurately investigate chiral effects on the protein absorption and cell internalisation.

The production of polymers from ethylene requires the ethylene feed to be sufficiently purified of acetylene contaminant. Accomplishing this task by thermally hydrogenating acetylene requires a high temperature, an external feed of H 2 gas and noble-metal catalysts. It is not only expensive and energy-intensive, but also prone to overhydrogenating to ethane. Here we report a photocatalytic system that reduces acetylene to ethylene with ≥99% selectivity under both non-competitive (no ethylene co-feed) and competitive (ethylene co-feed) conditions, and near 100% conversion under the latter industrially relevant conditions. Our system uses a molecular catalyst based on earth-abundant cobalt operating under ambient conditions and sensitized by either [Ru(bpy) 3 ] 2+ or an inexpensive organic semiconductor (metal-free mesoporous graphitic carbon nitride) under visible light. These features and the use of water as a proton source offer advantages over current hydrogenation technologies with respect to selectivity and sustainability. The acetylene contaminant present in ethylene feeds used to produce polymers is typically removed by thermal hydrogenation. Now, it has been shown that the conversion of acetylene to ethylene at room temperature can be achieved in a visible-light-driven process using an earth-abundant metal (cobalt) catalyst and a water proton source.

Carbon dots (CDs), defined by their size of less than 10 nm, are a class of photoluminescent (PL) and electrochemiluminescent (ECL) nanomaterials that include a variety of carbon‐based nanoparticles. However, the control of their properties, especially ECL, remains elusive and afflicted by a series of problems. Here, the authors report CDs that display ECL in water via coreactant ECL, which is the dominant mechanism in biosensing applications. They take advantage of a multicomponent bottom‐up approach for preparing and studying the luminescence properties of CDs doped with a dye acting as PL and ECL probe. The dependence of luminescence properties on the surface chemistry is further reported, by investigating the PL and ECL response of CDs with surfaces rich in primary, methylated, or propylated amino groups. While precursors that contribute to the core characterize the PL emission, the surface states influence the efficiency of the excitation‐dependent PL emission. The ECL emission is influenced by surface states from the organic shell, but states of the core strongly interact with the surface, influencing the ECL efficiency. These findings offer a framework of pre‐ and post‐synthetic design strategies to improve ECL emission properties, opening new opportunities for exploring biosensing applications of CDs. Pre‐ and post‐synthetic strategies enhance the electrochemiluminescence (ECL) of carbon dots (CDs). By using a fluorophore and ECL emitter in the bottom‐up synthesis, the major contribution of the surface emitting states to the ECL emission and the role from the states of the core are revealed. These findings have implications for advancing the ECL applications of CDs.

Enhancing the photoelectrochemical (PEC) performance of CuWO4 photoanodes has typically relied on doping or co‐catalyst strategies to improve charge carrier dynamics. In this work, an alternative approach is presented in which Fe(III) acts as a self‐assembly mediator during hydrothermal synthesis, enabling the formation of a core–shell heterostructure composed of a crystalline CuWO4 core, a partially amorphous CuO/WO3 shell, and embedded metallic Cu nanoinclusions. Rather than functioning as a dopant or co‐catalyst, Fe(III) is completely removed during post‐synthetic treatment, mediating a redox‐guided phase reorganization without being incorporated into the final material. This architecture establishes local heterojunctions that facilitate charge separation, suppress recombination, and enhance oxygen evolution reaction (OER) activity. A relative increase of ≈30‐fold in photocurrent is observed compared to pristine CuWO4, as confirmed by structural, spectroscopic, and electrochemical analyses. While absolute photocurrents remain modest, this enhancement reflects intrinsic modifications in charge transport and recombination behavior driven by Fe(III)‐mediated structural reorganization. Complementary photocatalytic dye degradation experiments reveal that Fe‐activated particles act as highly efficient ROS‐generating catalysts in suspension, demonstrating functionality beyond thin‐film devices. These findings offer a new paradigm for oxide photoanode design, leveraging Fe(III)‐induced self‐assembly to engineer multifunctional heterostructures without relying on conventional doping. Fe(III) mediates the self‐assembly of CuWO4 nanostructures into core–shell architectures with Cu inclusions and WO3‐rich shells, enabling local p–n junction formation. This nanostructural transformation enhances charge separation and enables dual activity: oxygen evolution under photoelectrochemical operation and reactive oxygen species (ROS) generation in photocatalysis. A multifunctional approach for efficient solar‐driven water oxidation and pollutant degradation.

Enhancing the photoelectrochemical (PEC) performance of CuWO 4 photoanodes has typically relied on doping or co‐catalyst strategies to improve charge carrier dynamics. In this work, an alternative approach is presented in which Fe(III) acts as a self‐assembly mediator during hydrothermal synthesis, enabling the formation of a core–shell heterostructure composed of a crystalline CuWO 4 core, a partially amorphous CuO/WO 3 shell, and embedded metallic Cu nanoinclusions. Rather than functioning as a dopant or co‐catalyst, Fe(III) is completely removed during post‐synthetic treatment, mediating a redox‐guided phase reorganization without being incorporated into the final material. This architecture establishes local heterojunctions that facilitate charge separation, suppress recombination, and enhance oxygen evolution reaction (OER) activity. A relative increase of ≈30‐fold in photocurrent is observed compared to pristine CuWO 4 , as confirmed by structural, spectroscopic, and electrochemical analyses. While absolute photocurrents remain modest, this enhancement reflects intrinsic modifications in charge transport and recombination behavior driven by Fe(III)‐mediated structural reorganization. Complementary photocatalytic dye degradation experiments reveal that Fe‐activated particles act as highly efficient ROS‐generating catalysts in suspension, demonstrating functionality beyond thin‐film devices. These findings offer a new paradigm for oxide photoanode design, leveraging Fe(III)‐induced self‐assembly to engineer multifunctional heterostructures without relying on conventional doping.

Diazotrophic cyanobacteria fix both atmospheric carbon (C) and nitrogen (N) into biomass, but the two assimilation pathways are not compatible. Species like Anabaena sp. PCC 7120 physically separates C and N assimilation in different cell types. Even if separated, they are strongly intertwined, as N assimilation relies on the C skeletons and reducing power from photosynthesis, that in turn depends on N rich molecules as pigments and proteins. Whereas the two pathways have been extensively studied individually, here we investigate their interaction by analysing photosynthetic properties upon exposure to changes in light, CO2 and N availability, including the contribution of photosynthetic electron fluxes. Growth depended on the availability of both light and CO2, while the N2 fixation activity mainly on the C supply. Upon diazotrophic conditions, the total photosynthetic electron transport activity increased, with a modified contribution of different electron pathways. A mutant strain affected in the vehiculation of fixed N between cell types showed that the modulation of photosynthesis depended on the metabolic connection between assimilation pathways. Overall, data showed that the regulation of photosynthetic electron fluxes is a major component of the synergic metabolic relationship between C and N assimilation pathways upon dynamic environmental conditions.