Colloidal Carbon Research Articles

Photoluminescent carbon colloids prepared by laser fragmentation of carbon from waste coffee grounds

Colloidal suspensions of carbon nanostructures (CNSs) were prepared by laser fragmentation in various liquid media using heat-treated coffee grounds as carbon precursor. A study by calorimetry was done in powder of waste coffee grounds to determine the temperature of obtaining carbon. The experiments were carried out in two stages, the first one consisted in obtaining the carbon source, for which powder of waste coffee grounds was thermally treated in air. The as-obtained carbon was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy and infrared spectroscopy. In the second step the as-obtained carbon was separately dispersed in four liquid media (acetone, toluene, methanol and isopropyl alcohol) to be fragmented by using a ns-pulsed Nd:YAG laser at its 1064 nm fundamental emission. The morphological features of the carbon nanostructures were obtained by transmission electron microscopy, while the optical properties of the colloidal suspensions were characterized by UV-Vis and photoluminescence spectroscopies. Results indicate that carbon nanostructures are successfully obtained in the four liquid media after the fragmentation process. The four colloidal suspensions show photoluminescent properties, which are seen to depend on the liquid medium nature. We found that the liquid medium also influences the efficiency of the laser fragmentation.

Impact of chemical aging on pyrogenic carbon colloid facilitated transport and transformation of Cr (VI) in anoxic environments

Frequent wildfires have accumulated the pyrogenic carbon (PyC) colloids in the environment, where they undergo environmental aging processes. The altered properties of aged PyC colloids may affect their ability to facilitate transformation and transport of contaminants in post-fire environments, posing unknown threats to ecological security. This study investigated the effect of chemical aging on the PyC colloid-facilitated transformation and transport of chromium (Cr) using batch experiments, column experiments, and transport model simulations. Results showed that aged PyC colloids exhibited weaker electron-donating capacity, and the reduction of Cr (VI) to Cr (III) decreased from 37.6 % to 13.5 % with the increasing aging time. Although PyC colloid transport increased with aging time, the PyC colloid-facilitated Cr (III) transport decreased because of the weakened reduction of Cr (VI). The transport of PyC colloid-facilitated Cr (III) was weaker at low pH. The reactive solute transport model well simulated the aged PyC colloid-facilitated transformation and transport of Cr (VI). Our findings highlight the significance of aging processes and environmentally relevant conditions in influencing the PyC colloid-facilitated transformation and transport of Cr, which is crucial for assessing risks of wildfire-driven Cr pollution and the potential of PyC for in-situ pollution control.

A comparative study of optical and size properties of dissolved organic matter in the lower Mississippi River and Pearl River

Monthly water samples were collected from the lower Mississippi and Pearl Rivers between January 2009 and August 2011 to investigate the heterogeneity in the dynamic variations of dissolved organic carbon (DOC), colloidal organic carbon, chromophoric and fluorescence dissolved organic matter (CDOM and FDOM), PARAFAC-derived fluorescent components, and other optical properties including spectral slope, specific UV absorbance (SUVA), and fluorescence indices between the two contrasting river systems. The lower Mississippi River exhibits relatively lower concentrations of DOC (306 ± 41 μM C) and CDOM (27.9 ± 5.7 m−1 at 254 nm), featuring lower aromaticity (indicated by SUVA254) and apparent molecular weight (or higher spectral slope) with weak seasonal variability. The Pearl River, in contrast, has elevated levels of DOC (537 ± 212 μM C) and CDOM (66.4 ± 31.4 m−1), characterized by higher aromaticity, higher molecular weight, and significant seasonality, primarily originating from soil-derived allochthonous sources. The abundance of the >1 kDa colloidal DOC was, on average, 58 ± 3 % of the bulk DOC in the lower Mississippi River and 68 ± 6 % in the lower Pearl River. The >1 kDa high-molecular weight DOM (HMW-DOM) consistently had lower spectral slope and biological index (BIX) values, but higher humification index (HIX) values compared to both bulk DOM and low-molecular-weight DOM (LMW-DOM) counterparts. These trends could be representative of other similar large and small rivers. Four PARAFAC-derived fluorescent components (three humic-like and one protein-like) were identified for both rivers. A positive correlation between discharge and terrestrial humic-like fluorescent components indicated their dominant allochthonous sources, while the protein-like component decreased with increasing discharge, consistent with its autochthonic source and a dilution effect during high flow seasons. The occurrence of large flood events during the sampling period contributed to large DOC pulses, with DOM of higher aromaticity and HMW-DOM. This has important implications for coastal ocean ecosystems, which are increasingly impacted by river flooding events under changing climate conditions. Our results also provide an improved understanding of DOM dynamics in two representative rivers and establish a baseline dataset for future studies to assess changes in sources and composition of DOM and their impacts on the coastal ocean in response to climate, hydrological, and anthropogenic influences.

Fractional-order memristive dynamics in colloidal graphitic carbon nitride systems.

We report on the synthesis and characterization of a colloidal graphitic carbon nitride (g-C_{3}N_{4}) system exhibiting complex memfractance behavior. The g-C_{3}N_{4} colloid was prepared through thermal polymerization of urea, followed by dispersion in deionized water. X-ray diffraction and scanning electron microscopy confirmed the successful synthesis of g-C_{3}N_{4}. Electrical characterization revealed nonpinched hysteresis loops in current-voltage curves, indicative of memristive behavior with additional capacitive components. The device demonstrated stable resistive switching between high (∼50kΩ) and low (∼22kΩ) impedance states over 500 cycles, as well as synaptic plasticity-like conductance modulation. To capture these complex dynamics, we employed a generalized memfractance model that interpolates between memristive, memcapacitive, and second-order memristive elements. This model, employing fractional-order derivatives, accurately fitted the experimental data, revealing the device's memory effects. The emergence of memfractance in this colloidal system opens new avenues for neuromorphic computing and unconventional information processing architectures, leveraging the unique properties of liquid-state memory devices.

Improved purification efficiency and stability of photocatalytic cement-based pavement coated with colloidal graphitic carbon nitride

Photocatalytic coatings applied onto cement-based pavement materials have been intensely developed to purify runoff pollution and vehicle exhaust. However, the masking effect of the adhesive incorporation often results in an unsatisfactory purification efficiency. Thus, developing an adhesive-free photocatalytic coating with high stability and purification efficiency on cement-based pavements is still urgently needed. Herein, a colloidal graphitic carbon nitride (g-C3N4) modified with hydroxyl groups was sprayed onto cement pastes to prepare a photocatalytic coating on the cement-based materials. The results of photocatalytic degradation of Rhodamine B (RhB) indicated that the RhB degradation efficiency and stability of the colloidal g-C3N4-coated cement paste were significantly improved compared to pristine g-C3N4-coated cement paste. After a runoff-washing trial, photocatalytic RhB degradation by colloidal g-C3N4-coated cement paste was 13.8-fold higher than that of pristine g-C3N4-coated cement paste. Mechanistic studies suggested that the well-distributed membrane microstructure of colloidal g-C3N4 and coordinate bonds between colloidal g-C3N4 and calcium-silicate-hydrates were mainly responsible for the improved stability and purification efficiency of colloidal g-C3N4-coated cement pastes. These results support the use of colloidal g-C3N4 as a promising strategy to prepare photocatalytic cement-based pavements with good stability and purification efficiency.

Singlet oxygen species induced by colloidal crystalline carbon nitride induced for efficient H2O2 synthesis with in situ antibacterial effect

Solar-driven hydrogen (H2) and hydrogen peroxide (H2O2) generation over visible-light responsive carbon nitride (CN) photocatalysts for in situ efficient sterilization is a promising and eco-friendly strategy. Herein, a colloidal potassium-ion (K+) intercalated crystalline CN nanosheets (KCCN) photocatalyst was constructed for boosting synergetic H2O2 synthesis with isopropanol (IPA) oxidation and in situ antibacterial effect. The surface hydroxyl (−OH) and cyano (−CN) groups induced by molten salt (KCl)-assisted thermal treatments contributed to the colloidal nature of CN, facilitating for high wettability of KCCN in aqueous solution to gain active hydrogen (H+) from water sustainably. Meaningfully, the enhanced high-energy singlet oxygen species (1O2) produced by KCNN-2 were verified by electron paramagnetic resonance (EPR) and 9,10-anthracenediyl-bis(methylene)-dimalonic acid (ABDA)-fluorescent probe, significantly contributing to H2O2 production and antibacterial effect. Consequently, the optimal KCCN-2 exhibited a much enhanced H2 generation of 4.11 mmol g−1 h−1, and H2O2 production activity of 1.82 mmol L−1 h−1 with acetone yield rate of 47.3 mmol g−1 h−1 under visible-light (λ > 420 nm) irradiation in 10 vol% IPA solution. The in-situ generated H2O2 can be activated to produce reactive oxygen species (ROS), especially 1O2, to effectively kill the Escherichia coli, reaching an improved an antibacterial rate of 89.7% under stimulated sunlight irradiation in 1 h. This work could offer a new insight into the photoinduced ROS for aqueous H2O2 photosynthesis and antibacterial application.

Rare-Earth-Metal-Free Solid-State Fluorescent Carbonized-Polymer Microspheres for Unclonable Anti-Counterfeit Whispering-Gallery Emissions from Red to Near-Infrared Wavelengths.

Colloidal carbon dots (CDs) have garnered much attention as metal-free photoluminescent nanomaterials, yet creation of solid-state fluorescent (SSF) materials emitting in the deep red (DR) to near-infrared (NIR) range poses a significant challenge with practical implications. To address this challenge and to engineer photonic functionalities, a micro-resonator architecture is developed using carbonized polymer microspheres (CPMs), evolved from conventional colloidal nanodots. Gram-scale production of CPMs utilizes controlled microscopic phase separation facilitated by natural peptide cross-linking during hydrothermal processing. The resulting microstructure effectively suppresses aggregation-induced quenching (AIQ), enabling strong solid-state light emission. Both experimental and theoretical analysis support a role for extended π-conjugated polycyclic aromatic hydrocarbons (PAHs) trapped within these microstructures, which exhibit a progressive red shift in light absorption/emission toward the NIR range. Moreover, the highly spherical shape of CPMs endows them with innate photonic functionalities in combination with their intrinsic CD-based attributes. Harnessing their excitation wavelength-dependent photoluminescent (PL) property, a single CPM exhibits whispering-gallery modes (WGMs) that are emission-tunable from the DR to the NIR. This type of newly developed microresonator can serve as, for example, unclonable anti-counterfeiting labels. This innovative cross-cutting approach, combining photonics and chemistry, offers robust, bottom-up, built-in photonic functionality with diverse NIR applications.

Colloidal carbon soot templated TiO2/Ag surface functionalized 3D printed metal brushes as new generation surface enhanced Raman scattering substrates

This present work demonstrated the functional transformation of 3D printed metal substrates into a new family of Surface-enhanced Raman Scattering substrates, a promising approach in developing SERS-based Point-of-care (PoC) analytical platforms. l-Powder Bed Fusion (l-PBF, Additive manufacturing or 3D printing technique) printed metal substrates have rough surfaces, and exhibit high thermal stability and intrinsic chemical inertness, necessitating a suitable surface functionalization approach. This present work demonstrated a unique multi-stage approach to transform l-PBF printed metal structures as recyclable SERS substrates by colloidal carbon templating, chemical vapor deposition, and electroless plating methods sequentially. The surface of the printed metal structures was functionalized using the colloidal carbon soot particles, that were formed by the eucalyptus oil flame deposition method. These carbon particles were shown to interact with the metals present in the printed structures by forming metal carbides and function as an adlayer on the surface. Subsequent deposition of TiO2 onto these templates led to strong grafting of TiO2 and retaining the fractal structure of the soot template onto the metal surface. Electroless deposition of silver nanoparticles resulted in the formation of fractally structured TiO2/Ag nanostructures and these functionalized printed metal structures were shown as excellent SERS substrates in enhancing the vibrational spectral features of Rhodamine B (RhB). The presence of TiO2 photocatalyst on the surface was shown to remove the RhB analyte from the surface under photochemical conditions, which enables the regeneration of SERS activity, and the substrate can be recycled. The migration of metals from the printed metal structures into the fractally ordered TiO2/Ag nanostructures was found to enhance the photocatalytic activity and increase the recyclability of these substrates. This study demonstrates the potential of 3D-printed Inconel metal substrates as next-generation recyclable SERS platforms, offering a substantial advancement over traditional colloidal, thin-film, flexible, and hard SERS substrates.

Synergetic Exterior and Interfacial Approaches by Colloidal Carbon Quantum Dots for More Stable Perovskite Solar Cells Against UV.

The achievement of both efficiency and stability in perovskite solar cells (PSCs) remains a challenging and actively researched topic. In particular, among different environmental factors, ultraviolet (UV) photons play a pivotal role in contributing to device degradation. In this work, by harvesting simultaneously both the optical and the structural properties of bottom-up-synthesized colloidal carbon quantum dots (CQDs), a cost-effective means is provided to circumvent the UV-induced degradation in PSCs without scarification on their power conversion efficiencies (PCEs). By exploring and optimizing the number of CQDs and the different locations/interfaces of the solar cells where CQDs are applied, a synergetic configuration is achieved where the photovoltaic performance drop due to optical loss is completely compensated by the increased perovskite crystallinity due to interfacial modification. As a result, on the optimized configurations where CQDs are applied both on the exterior front side as an optical layer and at the interface between the electron transport layer and the perovskite absorber, unencapsulated PSCs with PCEs >20% are fabricated which can maintain up to ≈94% of their initial PCE after 100h of degradation in ambient air under continuous UV illumination (5mWcm-2).

Elucidating the intrinsic core-shell structure of carbon nanospheres from glucose hydrothermal carbonization

This study explores the core-shell structure formation mechanisms of primary carbon nanospheres (PCNs) through hydrothermal carbonization (HTC) of glucose at 200 °C, focusing on key phase-change polymerization reactions. Colloidal carbon nanoparticles in the aqueous phase filtrate self-assembled into secondary carbon nanospheres (SCNs) with intrinsic hollow structures during room temperature storage. FTIR results revealed similar functional groups on the surfaces of PCNs and SCNs due to esterification reactions during HTC cooling. XPS and 13 C NMR analyses identified HMF aldol condensation and etherification as dominant reactions for PCNs, while esterification and aldol condensation with levulinic acid were dominant for SCNs. The hypothesis suggests that PCNs initially formed hollow microframeworks but collapsed due to consumption of encapsulated organics, resulting in hydrophobic cores. These cores grew through aggregation (linear) and surface reactions (exponential), internalizing hydrophilic surfaces into hydrophobic cores, forming the final core-shell structure of PCNs.

Impact of length and radius of carbon nanotubes on flow and heat transfer in converging and diverging channels with entropy generation

This research examines the complex interplay between the carbon nanotubes' length and radius and how that affects flow patterns, heat transfer properties, and entropy creation in both convergent and divergent channels. Our research elucidates the mechanisms at play by revealing a crucial link between carbon nanotube dimensions and the efficacy of heat transfer processes. In particular, carbon nanotubes with a longer length have better heat transmission properties, while carbon nanotubes with a smaller radius generate less entropy. From microfluidics to energy-efficient materials, these results show significant promise for optimizing thermal systems and improving performance. This research looks on the differences between the thermal transports of single- and multi-walled carbon nanotubes in water. Thermo physical characteristics of carbon nanoparticles are one of a kind and essential for this purpose. The fluid is assumed to be incompressible and to flow steadily a two-dimensional plane. The effects of thermal radiation on the heat transfer of a water-based fluid in convergent and divergent channels with decreasing and expanding walls have been studied. In order to quickly sketch the equations, the RK-4 method with shooting approach is used, and similarity transformation is employed to reduce their dimensionality. The key factors influencing hydrothermal performance have been visualized through the use of graphs. The production numbers of entropy are also shown and explained at length. The obtained data supports the reliability of the approach used. Surface heat transport was found to be negatively impacted by elongation. Colloidal single-walled carbon nanotube (SWCNT) suspensions in water had higher thermal conductivity than water itself.

Colloidal Filterable Bacteria Enhance Ammonia Nitrogen Enrichment in River Colloids under Different Turbidity Conditions: Bacterial Diversity, Assembly Mechanism, and Nitrogen Transformation

Turbidity has been one of the most typical problems in urban rivers, accompanied by eutrophication. Though the colloid is a nonnegligible factor associated with turbidity and nutrient enrichment in urban rivers, the characteristics of nitrogen enrichment and bacterial communities of colloids under different turbidity conditions of urban rivers have not been well understood. In this study, colloids of low and high molecular weights (LMW, 30 kDa–0.2 μm, and HMW, 0.2–1 μm) were separately collected from the bulk water (<1 μm) of several typical urban rivers in China. Since the colloidal concentration presented the significantly highest correlation with turbidity, colloidal characteristics were further explored under three turbidity gradients with two cutoffs of 10 and 30 NTU. Results showed that colloidal organic matter in medium and high turbidity rivers was mainly sourced from the release of endogenous plankton and the proportion of colloidal organic carbon in dissolved organic carbon increased from 33% to 38% with increased turbidity. Colloidal ammonia nitrogen in medium turbidity accounted for the highest proportion (an average of 60%) in bulk water, which could be explained by the significantly positive correlation of colloidal ester groups and ammonia nitrogen (R2 = 0.47). Bulk water, HMW, and LMW colloids presented different dominant bacterial genera and LMW colloids also contained three unique dominant filterable genera: Flavobacterium, Acinetobacter, and Limnohabitans. LMW colloidal filterable bacteria under medium and high turbidities presented the greatest potential for dissimilatory nitrate reduction to ammonium, which might further enhance the enrichment of ammonia nitrogen in colloids. This study provides a primary understanding of the characteristics of colloids and colloidal bacterial communities in urban rivers from the perspective of turbidity and puts a new insight on the remediation of rivers under medium turbidity.

Composition analysis of Magnolia flower and their use for highly bright carbon dots

Colloidal carbon dots (C-dots) have excellent optical properties and they have been widely used for various types of applications. Compared to the C-dots prepared using chemicals, the Biomass-derived C-dots have attracted a great of attention because of their environmental friendliness and biocompatibility. However, currently obtained C-dots using biomass have low quantum yield. In this work, we demonstrated an efficient precursor of Magnolia flower for synthesizing high-quantum yield C-dots via hydrothermal approach. High performance liquid chromatography and Bradford assay were used to analyze the compositions of the Magnolia flower, which determine the quality of the C-dots. The typical emission bands of the as-prepared C-dots cover from 400 to 550 nm at different excitation wavelengths. The C-dots synthesized using violet Magnolia flower have the QY as high as 11.9%, which is higher than that of 10.4% (white Magnolia flower), because the violet color gives the higher content of the N. The as-obtained C-dots have excitation-dependent color and high quantum yield, showing a great potential for the use of the anti-counterfeiting system.

Controlling the rheo-electric properties of graphite/carbon black suspensions by ‘flow switching’

The ability to manipulate rheological and electrical properties of colloidal carbon black gels makes them attractive in composites for energy applications such as batteries and fuel cells, where they conduct electricity and prevent sedimentation of ‘granular’ active components. While it is commonly assumed that granular fillers have a simple additive effect on the composite properties, new phenomena can emerge unexpectedly, with some composites exhibiting a unique rheological bi-stability between high-yield-stress and low-yield-stress states. Here we report such bi-stability in suspensions of non-Brownian graphite and colloidal carbon black in oil, a model system to mimic composite suspensions for energy applications. Steady shear below a critical stress elicits a transition to a persistent mechanically weak and poorly conducting state, which must be ‘rejuvenated’ using high-stress shear to recover a stronger, high-conductivity state. Our findings highlight the highly tunable nature of binary granular/gel composite suspensions and present new possibilities for optimising mixing and processing conditions for Li-ion battery slurries.Graphical abstract

Green chemistry routed sugar press mud for (2D) ZnO nanostructure fabrication, mineral fortification, and climate-resilient wheat crop productivity

Nanotechnology appears to be a promising tool to redefine crop nutrition in the coming decades. However, the crucial interactions of nanomaterials with abiotic components of the environment like soil organic matter (SOM) and carbon‒sequestration may hold the key to sustainable crop nutrition, fortification, and climate change. Here, we investigated the use of sugar press mud (PM) mediated ZnO nanosynthesis for soil amendment and nutrient mobilisation under moderately alkaline conditions. The positively charged (+ 7.61 mv) ZnO sheet-like nanoparticles (~ 17 nm) from zinc sulphate at the optimum dose of (75 mg/kg blended with PM (1.4% w/w) were used in reinforcing the soil matrix for wheat growth. The results demonstrated improved agronomic parameters with (~ 24%) and (~ 19%) relative increases in yield and plant Zn content. Also, the soil solution phase interactions of the ZnO nanoparticles with the PM-induced soil colloidal carbon (− 27.9 mv and diameter 0.4864 μm) along with its other components have influenced the soil nutrient dynamics and mineral ecology at large. Interestingly, one such interaction seems to have reversed the known Zn-P interaction from negative to positive. Thus, the study offers a fresh insight into the possible correlations between nutrient interactions and soil carbon sequestration for climate-resilient crop productivity.

Effect of coupled physical and chemical heterogeneity on the transport of pristine and aged pyrogenic carbon colloids in unsaturated porous media

Due to extensive application and recurrent wildfires, an increasing number of pyrogenic carbon (PyC) colloids are present in the environment, experiencing processes of environmental aging. Subsurface environments are typically heterogeneous in unsaturated conditions, which may affect the transport of PyC colloids. This study focused on the transport of both pristine and aged PyC colloids in physically (clean coarse and fine sand) and physicochemically (iron oxides-coated coarse and clean fine sand) heterogeneous porous media at three different water saturations (100 %, 70 %, and 40 %). In physically heterogeneous porous media, the decrease in water saturation from 100 % to 40 % led to a shift in the main water flow from the clean coarse sand to the clean fine sand domain, resulting in a continuous decrease in the transport of PyC colloids. In physicochemically heterogeneous porous media, the primary water flow shifted from the iron oxides-coated coarse sand to the clean fine sand domain, resulting in an initial increase and subsequent decrease in PyC colloid transport. Aging enhanced the transport of PyC colloids, attributed to the increasingly negative and hydrophilic surface. Retention profiles revealed substantial PyC colloid retention at the interface between coarse and fine sand domains. The release of retained PyC colloids exhibited two peaks at 100 % and 70 % water saturations, along with a single peak at 40 % water saturation. Additionally, the increased irreversible retention was observed at lower water saturation. This study underscores the significance of water content, environmental aging, and heterogeneity in PyC colloid transport. It provides essential insights into the environmental fate of PyC colloids in natural field conditions.

The effect of natural ingredients extracts on the phagocytosis index of the carbon clearance animal models

The immune system has a very important role to fight foreign substances in the body. Immunostimulants are needed to stimulate the activity of the immune system and immunosuppressants are needed to suppress the immune system. The aims of this study is to evaluate phagocitytosis index of several natural ingredient extract using carbon clearance method. The natural ingredients are the ethanol extract of Ageratum conyzoides leaves 160 mg/kgBW, ethanol extract of Artocarpus heterophyllus leaves 500 mg/kgBW, ethanol extract of Nephelium lappaceum peel 650 mg/kgBW, ethanol extract of Cucurbita moschata seed 342 mg/kgBW and ethanol extract of Citrullus lanatus rind 55 mg/kgBW. Tests were carried out on male mice Balb/C strains using the carbon clearance method, where colloidal carbon ink acts as an antigen. The phagocytic activity of macrophages in eliminating carbon ink was measured based on the stimulation index value and then the immunomodulatory effect was classified according to Wagner's criteria. The stimulation index of A.heterophyllus was 1.423; A. conyzoides was 1.201; N. lappaceum was 1.236; C.lanatus was 0.909 and C. moschata was 1.299. The potential extract as immunostimulant was A.heterophyllus, as immunosupressant was C. lanatus. A.conyzoides and probably had no effect (act as imunorestorant) and C. moschata 342 mg/kgBW had slight immunostimulant effect.

Colloidal Chiral Carbon Dots: An Emerging System for Chiroptical Applications.

Chiral CDots (c-CDots) not only inherit those merits from CDots but also exhibit chiral effects in optical, electric, and bio-properties. Therefore, c-CDots have received significant interest from a wide range of research communities including chemistry, physics, biology, and device engineers. They have already made decent progress in terms of synthesis, together with the exploration of their optical properties and applications. In this review, the chiroptical properties and chirality origin in extinction circular dichroism (ECD) and circularly polarized luminescence (CPL) of c-CDots is briefly discussed. Then, the synthetic strategies of c-CDots is summarized, including one-pot synthesis, post-functionalization of CDots with chiral ligands, and assembly of CDots into chiral architectures with soft chiral templates. Afterward, the chiral effects on the applications of c-CDots are elaborated. Research domains such as drug delivery, bio- or chemical sensing, regulation of enzyme-like catalysis, and others are covered. Finally, the perspective on the challenges associated with the synthetic strategies, understanding the origin of chirality, and potential applications is provided. This review not only discusses the latest developments of c-CDots but also helps toward a better understanding of the structure-property relationship along with their respective applications.

Highly efficient and high color rendering index multilayer luminescent solar concentrators based on colloidal carbon quantum dots

Compared to the silicon-based photovoltaics, large-area luminescent solar concentrators (LSCs) can be used as smart PV window for building-integrated photovoltaics (BIPVs). However, because of the low quantum yield of the fluorophores, and reabsorption energy loss, the current obtained large-area LSCs have low optical efficiency. Herein, we demonstrated highly efficient and semitransparent multilayer LSCs based on three types of carbon quantum dots (C-dots). The blue and green C-dots were synthesized using vacuum heating approach and the orange C-dots were synthesized using solvothermal approach. The as-prepared B-, G- and O-C-dots have the QYs of 90 %, 73 % and 72 %, respectively, with large Stokes shift (0.37–0.73 eV). By optimizing the concentration of the C-dots in each layer, the best LSC (100 cm2) with multilayer structure exhibited an external optical efficiency of 9.1 %, and a power conversion efficiency (PCE) of 6.0 %, which are higher than that of most of reported LSCs. The simulations indicate that optimized multilayer LSCs could have a theoretical external optical efficiency over 12 % for 1 m2 devices. Besides high optical efficiency, the multilayer LSCs also have high Color Rendering Index (above 80) and high average visible transmission (above 70 %), which make the as-prepared LSCs suitable for potential commercial BIPVs.

High-Yield Synthesis of Colloidal Carbon Rings and Their Applications in Self-Standing Electrodes of Li-O2 Batteries.

The use of carbon materials in porous electrodes has impressive advantages. However, precisely tailoring the multilevel pore structure of carbon electrodes remains an unsolved challenge. Here, we report a highly efficient site-selective growth strategy to synthesize colloidal carbon rings by templating patchy droplets. Carbon rings are used for the direct fabrication of self-standing porous electrodes with hierarchical pores for lithium-oxygen batteries (LOBs). In situ atomic force microscopy reveals that during discharge the discharge products densely nucleate and grow on carbon rings, demonstrating that such rings are a very potential electrode material in LOBs. The hollow carbon ring electrode (HCRE) possesses micrometer-scale channels formed by random packing of rings and nanochannels consisting of ring-shaped hollow cavities connected by nanosized pores in the wall. Both channels contribute to ion transportation and gas diffusion, but the storage of the discharge products mainly lies in micrometer-scale channels, leading to a high discharge capacity of LOBs (20 658 mAh/g). Our work paves a new way to construct hierarchically porous electrodes for application in electrocatalysis and electrochemical energy storage.