Electronic interaction-enhanced NO photorelease and photothermal conversion in N-doped carbon dot nanoconjugates

A nitric oxide (NO) photodonor (1) capable of releasing two NO molecules through a stepwise mechanism has been covalently grafted to blue-emitting N-doped carbon dots (NCDs). The resulting water-soluble nanoconjugate (NCDs-1), ca. 10 nm in diameter, exhibits a new absorption band not present in the simple physical mixture of the two components and is attributable to strong electronic interactions between them in the ground state. Blue light excitation of NCDs-1 leads to NO photogeneration with an efficiency almost one order of magnitude higher than that observed for 1 alone, probably due to a photoinduced electron transfer between the NCDs and the grafted 1. Photoexcitation of the nanoconjugate also results in effective photothermal conversion, which is negligible in the naked NCDs. Furthermore, in contrast to 1, the nanoconjugate liberates NO also under excitation with green light. Finally, the typical blue fluorescence of the NCDs is quenched in NCDs-1 but restored upon the photouncaging of the second NO molecule, providing readable and real-time information about the amount of NO photogenerated.

Green synthesis of highly fluorescent carbon quantum dots from almond resin for advanced theranostics in biomedical applications

Fluorescent Carbon Quantum Dots (CQDs) are being used in medical applications, particularly in theranostics. These Carbon Quantum Dots have been gaining more attention lately due to their potential as an effective replacement for hazardous synthetic organic dyes in a variety of biomedical applications, including live cell imaging and diagnostics. In this study, highly fluorescent Carbon Quantum Dots by one pot microwave based green route with a size of less than 10 nm, was prepared from commercially available almond resin, Prunus dulcis and conjugated with honey as additional reagent for surface functionalization. They exhibit a deep blue emission on excitation at 350 nm with an elevated quantum yield at 61%. They possess atomic nature and basic features such as high photo-stability, varying fluorescence, greater biocompatibility, and better water solubility. These fluorescent labels exhibit faster cellular invagination without disturbing the cell stability. The CQDs present cell imaging capacity with multi-coloration for visualizing the fine architecture of the nucleus naming, the nuclear membrane and nucleolus, which is linked with their varied, surface structures such as amphiphilic property and higher positive charges. These characteristics with minimal invasion have made carbon quantum dots to become the spotlight in theranostics. They can be used as alternatives to synthetic dyes for fluorescence- related cell-imaging. The intriguing fact about this approach is that it opens the possibility of combining therapy and diagnostics into one unit, which can alter how some diseases are handled and, in turn, transform the field of healthcare.

Recent Advances of Graphene Quantum Dots in Chemiresistive Gas Sensors

Graphene quantum dots (GQDs), as 0D graphene nanomaterials, have aroused increasing interest in chemiresistive gas sensors owing to their remarkable physicochemical properties and tunable electronic structures. Research on GQDs has been booming over the past decades, and a number of excellent review articles have been provided on various other sensing principles of GQDs, such as fluorescence-based ion-sensing, bio-sensing, bio-imaging, and electrochemical, photoelectrochemical, and electrochemiluminescence sensing, and therapeutic, energy and catalysis applications. However, so far, there is no single review article on the application of GQDs in the field of chemiresistive gas sensing. This is our primary inspiration for writing this review, with a focus on the chemiresistive gas sensors reported using GQD-based composites. In this review, the various synthesized strategies of GQDs and its composites, gas sensing enhancement mechanisms, and the resulting sensing characteristics are presented. Finally, the current challenges and future prospects of GQDs in the abovementioned application filed have been discussed for the more rational design of advanced GQDs-based gas-sensing materials and innovative gas sensors with novel functionalities.

A dual-recognition-controlled electrochemical biosensor for selective and ultrasensitive detection of acrylamide in heat-treated carbohydrate-rich food

A synergistic hybrid was fabricated for the electrochemical aptasensing of acrylamide (AAM) via molecularly imprinted technology. The aptasensor depends on the modification of glassy carbon electrode with AuNPs and reduced graphene oxide (rGO)/multiwalled carbon nanotubes (MWCNTs) {Au@rGO-MWCNTs/GCE}. The aptamer (Apt-SH) and AAM (template) were incubated with the electrode. After that, the monomer was electro-polymerized to fabricate molecular imprinted polymeric film (MIP) over the surface of Apt-SH/Au@rGO/MWCNTs/GCE. The modified electrodes were characterized using different morphological and electrochemical techniques. Under optimum conditions, the aptasensor exhibited a linear relationship between AAM concentration and anodic peak current difference (ΔIpa) in the range of 1-600 nM with a limit of quantitation (LOQ, S/N = 10) and a limit of detection (LOD, S/N = 3) of 0.346 and 0.104 nM, respectively. The aptasensor was successfully applied for the determination of AAM in potato fries samples with recoveries % in the range of 98.7-103.4 % and RSDs did not exceed 3.2 %. The advantages of MIP/Apt-SH/Au@rGO/MWCNTs/GCE are low detection limit, high selectivity, and satisfactory stability towards AAM detection.

Ultrafast Electron Transfer Dynamics of Organic Polymer Nanoparticles with Graphene Oxide

We prepared organic polymer poly-3-hexylthiophene (p3ht) nanoparticles (NPs) and graphene oxide (GO)/reduced graphene oxide (RGO) composites p3ht NPs-GO/RGO by using the reprecipitation method. We demonstrated that GO/RGO could improve the ordering and planarity of p3ht chains as well as the formation of p3ht NPs, and confirmed the effects of GO/RGO on the fluorescence and carrier transport dynamics of p3ht NPs by using femtosecond fluorescence upconversion and transient absorption (TA) techniques. Ultrafast electron transfer (∼1 ps) between GO/RGO and p3ht NPs quenched the fluorescence of p3ht NPs, indicating excellent properties of p3ht NPs-GO/RGO as the charge transfer complexes. Efficient electron transfer may promote the applications of p3ht NPs-GO/RGO composites in organic polymer solar cells and photocatalysis. Moreover, RGO had stronger interfacial interactions and more matched conduction band energy levels with p3ht NPs than GO did, which implied that p3ht NPs-RGO might have greater application values than p3ht NPs-GO.

Tunable 0D/2D/2D Nanocomposite Based on Green Zn-Doped CuInS2 Quantum Dots and MoS2/rGO as Photoelectrodes for Solar Hydrogen Production

Charge separation, transmission, and light absorption properties are critical to determining the performance of photoelectrochemical (PEC) devices. An important strategy to control such properties is based on using heterostructured materials. Herein, a tunable zero-dimensional (0D)/two-dimensional (2D) heterostructure is designed based on quantum dots (QDs) and 2D nanosheets (NSs). Specifically, eco-friendly Zn-doped CuInS₂ QDs prepared by hot injection were anchored on hierarchical (2D/2D) MoS₂/rGO (MG) NSs through a facile sonication-assisted method to develop a 0D/2D/2D heterojunction-based photoelectrode for solar hydrogen production. The interfacial structure and band alignment between the proposed 0D QDs and 2D/2D MG NSs were engineered by modulating the Zn molar ratio during the QD synthesis. As proof of concept, the optimized 0D/2D/2D photoanode exhibits almost five times higher PEC activity than MG/CuInS₂ and MoS₂/Zn-CuInS₂ NSs due to the enhanced light absorption, efficient charge separation, and transmission. Zn doping and the presence of graphene are essential in enhancing performance in the proposed heterostructure, reducing recombination of charge carriers, and improving sunlight absorption. This work shows how optimal band alignment control and carbon addition can facilitate charge transfer, enabling the development of highly efficient PEC devices based on 0D/2D/2D heterostructure nanocomposites.

Synthesis and Structure of a Two-Dimensional Palladium Oxide Network on Reduced Graphene Oxide

New nanostructures often reflect new and exciting properties. Here, we present an two-dimensional, hitherto unreported PdO square network with lateral dimensions up to hundreds of nanometers growing on reduced graphene oxide (rGO), forming a hybrid nanofilm. An intermediate state of dissolved Pd(0) in the bacterium S. oneidensis MR-1 is pivotal in the biosynthesis and inspires an abiotic synthesis. The PdO network shows a lattice spacing of 0.5 nm and a thickness of 1.8 nm on both sides of an rGO layer and is proposed to be cubic or tetragonal crystal, as confirmed by structural simulations. A 2D silver oxide analog with a similar structure is also obtained using an analogous abiotic synthesis. Our study thus opens a simple route to a whole new class of 2D metal oxides on rGO as promising candidates for graphene superlattices with unexplored properties and potential applications for example in electronics, sensing, and energy conversion.

Challenges and prospects about the graphene role in the design of photoelectrodes for sunlight-driven water splitting

Graphene and its derivatives have emerged as potential materials for several technological applications including sunlight-driven water splitting reactions. This review critically addresses the latest achievements concerning the use of graphene as a player in the design of hybrid-photoelectrodes for photoelectrochemical cells. Insights about the charge carrier dynamics of graphene-based photocatalysts which include metal oxides and non-metal oxide semiconductors are also discussed. The concepts underpinning the continued progress in the field of graphene/photoelectrodes, including different graphene structures, architecture as well as the possible mechanisms for hydrogen and oxygen reactions are also presented. Despite several reports having demonstrated the potential of graphene-based photocatalysts, the achieved performance remains far from the targeted benchmark efficiency for commercial application. This review also highlights the challenges and opportunities related to graphene application in photoelectrochemical cells for future directions in the field.

Solution processed nanostructured hybrid materials based on PbS quantum dots and reduced graphene oxide with tunable optoelectronic properties

Nanostructured hybrid materials (NHMs) are promising candidates to improve the performance of several materials in different applications. In the case of optoelectronic technologies, the ability to tune the optical absorption of such NHMs is an appealing feature. Along with the capacity to transform the absorbed light into charge carriers (CC), and their consequently efficient transport to the different electrodes. In this regard, NHM based on graphene-like structures and semiconductor QDs are appealing candidates, assuming the NHMs retain the light absorption and CC photogeneration properties of semiconductor QDs, and the excellent CC transport properties displayed by graphene-like materials. In the current work a solution-processed NHM using PbS quantum dots (QDs) and graphene oxide (GO) was fabricated in a layer-by-layer configuration by dip-coating. Afterwards, these NHMs were reduced by thermal or chemical methods. Reduction process had a direct impact on the final optoelectronic properties displayed by the NHMs. All reduced samples displayed a decrement in their resistivity, particularly the sample chemically reduced, displaying a 10⁷ fold decrease; mainly attributed to N-doping in the reduced graphene oxide (rGO). The optical absorption coefficients also showed a dependence on the rGO's reduction degree, with reduced samples displaying higher values, and sample thermally reduced at 300 °C showing the highest absorption coefficient, due to the combined absorption of unaltered PbS QDs and the appearance of sp² regions within rGO. The photogenerated current increased in most reduced samples, displaying the highest photocurrent the sample reduced at 400 °C, presenting a 2500-fold increment compared to the NHM before reduction, attributed to an enhanced CC transfer from PbS QDs to rGO, as a consequence of an improved band alignment between them. These results show clear evidence on how the optoelectronic properties of NHMs based on semiconductor nanoparticles and rGO, can be tuned based on their configuration and the reduction process parameters.

Production of novel carbon nanostructures by electrochemical reduction of polychlorinated organic rings under mild conditions for supercapacitors

Here, new carbon-based nanostructures were prepared via a one-step electrochemical method using hexagonal and pentagonal polychlorinated organic rings as the carbon source.

Engineering silicon-carbide quantum dots for third generation photovoltaic cells

Interested in the recent development of the building up of photovoltaic devices using graphene-like quantum dots as a novel electron acceptor; we study in this work the optoelectronic properties of edge-functionalized SiC quantum dots using the first principles density functional. For an accurate quantitative estimation of key parameters, a many-body perturbation theory within GW approximation is also performmed. We examine the ability to tailor the electronic gap and optical absorption of the new class of QDs through hydroxylation and carboxylation of seam atoms, in order to improve their photovoltaic efficiency. The HOMO-LUMO energy gap was significantly altered in terms of the type, the concentration and the position of functional groups. The spatial charge separation and charge transfer characterizing our systems seem very prominent to use as dye-sensitized solar cells. Furthermore, the optical band gap of all our compounds is in the NIR-visible energy window, and exhibits a magnitude smaller than that calculated in the pristine case, which enhances the photovoltaic efficiency. Likewise, absorption curves, exciton binding energy and singlet-triplet energy splitting have been broadly modified by functionalization confirming the great luminescent yield of SiCQDs. Depending on the size, SiC quantum dots absorb light from the visible to the near-infrared region of the solar spectrum, making them suitable for third generation solar cells.

Supramolecular Vesicles Based on Amphiphilic Pillar[n]arenes for Smart Nano-Drug Delivery

Supramolecular vesicles are the most popular smart nano-drug delivery systems (SDDs) because of their unique cavities, which have high loading carrying capacity and controlled-release action in response to specific stimuli. These vesicles are constructed from amphiphilic molecules via host-guest complexation, typically with targeted stimuli-responsive units, which are particularly important in biotechnology and biomedicine applications. Amphiphilic pillar[n]arenes, which are novel and functional macrocyclic host molecules, have been widely used to construct supramolecular vesicles because of their intrinsic rigid and symmetrical structure, electron-rich cavities and excellent properties. In this review, we first explain the synthesis of three types of amphiphilic pillar[n]arenes: neutral, anionic and cationic pillar[n]arenes. Second, we examine supramolecular vesicles composed of amphiphilic pillar[n]arenes recently used for the construction of SDDs. In addition, we describe the prospects for multifunctional amphiphilic pillar[n]arenes, particularly their potential in novel applications.

Strategies for development of nanoporous materials with 2D building units

It has already been realized that two-dimensional (2D) materials carry a great potential in energy conversion and storage, gas storage, chemical sensing, and many other applications closely related to human life. These applications benefit from a key feature of 2D materials, namely the large specific surface area, which however can be diminished significantly due to the tendency of these materials to restack. In this review, we revisit the strategies - including soft and hard templating - that have been developed for generating nanoporosity in 3D materials and demonstrate their adaptation for 2D materials using carbon nitride and graphene materials as examples. Owing to the 2D nature of the building units, a new type of nanopore can be generated by perforating the basal planes. These in-plane nanopores are essential in many emerging applications of 2D materials such as semipermeable membranes; hence, their creation methods, including post-synthesis activation, ion bombardment, electron beam drilling, and nanolithography, are worthy of a critical review. Lastly, techniques for preventing the restacking by fabricating 2D-0D, 2D-1D, and 2D-2D layer-by-layer composite structures are discussed. The goal is to promote the use of these methods for creating nanoporosity in more 2D materials.

Highly Selective Detection of Metronidazole by Self-Assembly via 0D/2D N-C QDs/g-C3N4 Nanocomposites Through FRET Mechanism

A 0D/2D (0-dimensional/2-dimensional) nanostructure was designed by self-assembly of N-C QDs and carboxylated g-C3N4 nanosheets and used as a fluorescence resonance energy transfer (FRET) fluorescent sensor. The N-C QDs/g-C3N4 nanosheets were synthesized via the amino group on the N-C QD surface and the -COOH of the carboxylated g-C3N4 nanosheets. The mechanism of detection of metronidazole (MNZ) by N-C QDs/g-C3N4 nanocomposites is based on FRET between negatively charged N-QDs and positively charged carboxylated g-C3N4 nanoparticles. N-C QDs/g-C3N4 nanostructures displayed good responses for the detection of MNZ at normal temperature and pressure. The decrease in the fluorescence intensity showed a good linear relationship to MNZ concentration within 0-2.6 × 10-5 mol/L, and the detection limit was 0.66 μM. The novel FRET sensor will have a great potential in clinical analysis and biological studies.

Application of Zero-Dimensional Nanomaterials in Biosensing

Zero-dimensional (0D) nanomaterials, including graphene quantum dots (GQDs), carbon quantum dots (CQDs), fullerenes, inorganic quantum dots (QDs), magnetic nanoparticles (MNPs), noble metal nanoparticles, upconversion nanoparticles (UCNPs) and polymer dots (Pdots), have attracted extensive research interest in the field of biosensing in recent years. Benefiting from the ultra-small size, quantum confinement effect, excellent physical and chemical properties and good biocompatibility, 0D nanomaterials have shown great potential in ion detection, biomolecular recognition, disease diagnosis and pathogen detection. Here we first introduce the structures and properties of different 0D nanomaterials. On this basis, recent progress and application examples of 0D nanomaterials in the field of biosensing are discussed. In the last part, we summarize the research status of 0D nanomaterials in the field of biosensing and anticipate the development prospects and future challenges in this field.

A highly responsive methanol sensor based on graphene oxide/polyindole composites

Graphene-based materials, namely commercial graphene (cm-G), commercial graphene oxide (cm-GO), reduced graphene oxide (rGO), and synthesized graphene oxide (OIHM-GO), and their composites with polyindole (PIn) were used as sensing materials for methanol vapor. The synthesized graphene oxide was prepared by the optimized improved Hummers' method. rGO was prepared from cm-GO by two different methods: thermally mild reduction at 120 °C to yield T-rGO and chemical reduction by ascorbic acid to yield C-rGO. Graphene-based material/polyindole composites were prepared by in situ polymerization. In this report, the sensing responses were evaluated from the responsive electrical currents at room temperature. cm-GO showed the highest methanol response because it possessed the highest number of oxygen species, which act as the active sites. The relative electrical conductivity response of the in situ cm-GO/dPIn composite to methanol was the highest amongst the composites. The in situ OIHM-GO/dPIn composite possessed the high relative conductivity response of 81.89 ± 2.12 at 11.36 ppm, a sensitivity of 7.37 ppm-1 with R 2 of 0.9967 in the methanol concentration range of 1.14-11.36 ppm, a theoretical LOD of 0.015 ppm, and repeatability of at least 4 cycles with good selectivity. This work represents the first report of the preparation and testing of graphene-based materials/polyindole composites as methanol sensors.

A universal growth strategy for DNA-programmed quantum dots on graphene oxide surfaces

The emerging materials of semiconductor quantum dots/graphene oxide (QDs/GO) hybrid composites have recently attracted intensive attention in materials science and technology due to their potential applications in electronic and photonic devices. Here, a simple and universal strategy to produce DNA-programmed semiconductor quantum dots/graphene oxide (QDs/GO) hybrid composites with controllable sizes, shapes, compositions, and surface properties is reported. This proof-of-concept work successfully demonstrates the use of sulfhydryl modified single-stranded DNA (S-ssDNA) as a 'universal glue' which can adsorb onto GO easily and provide the growth sites to synthesize CdS QDs, CdSe QDs, CdTe QDs and CdTeSe QDs with distinctive sizes, shapes and properties. Also, adapting this method, other graphene oxide-based hybrid materials which are easily synthesized in aqueous solution, including oxides, core-shell structure QDs and metal nanocrystals, would be possible. This method provided a universal strategy for the synthesis and functional realization of graphene -based nanomaterials.

Photoinduced charge carrier dynamics in a ZnSe quantum dot-attached CdTe system

A new nanohybrid material is prepared by attaching CdTe nanoneedles (NNs) to surface-modified ZnSe quantum dots (QDs). The NNs and QDs are prepared by a colloidal synthesis method in an aqueous alkaline medium. The surface modification and the attachment of nanostructures are achieved by a bifunctional ligand 3-mercaptopropionic acid (3-MPA). The band gap of the ZnSe QDs is varied by controlling the size of the QDs in order to get the maximum overlap between the absorption band of the CdTe NNs and the emission band of the ZnSe QDs, which is a prerequisite for effective charge/energy transfer. The possibility of photoinduced charge transfer (PCT) and Förster resonance energy transfer (FRET) from the donor (QDs) to the acceptor (NNs) has been assessed. Very fast (less than 800 ps) PCT and FRET from QDs to NNs occur because the emission band of QDs overlaps with the absorption band of NNs. The calculated large value of the overlapping integral, J(λ) ∼4.5 × 10¹⁹M^-1cm^-1nm⁴, of the donor and the acceptor bands proves the feasibility of energy transfer. These findings suggest that the ZnSe QDs can exchange photoinduced energy with the CdTe NNs effectively over a wide distance in a CdTe-ZnSe nanohybrid.

Growth and photocatalytic behavior of transparent reduced GO-ZnO nanocomposite sheets

Reduced graphene oxide-zinc oxide (rGO-ZnO) nanocomposites were grown on solid substrates by rapid thermal treatment of Langmuir-Blodgett transferred GO-Zn composite sheets in oxygen ambient. The changes induced by uptake of Zn²⁺ ions and subsequent thermal treatment on surface morphology, micro-structure, composition and optical properties of composite sheets were investigated by atomic force microscopy, high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared (FT-IR) and Raman measurements. The morphological features of composites are practically independent of subphase Zn concentration and are largely determined by the temperature of rapid thermal treatment. FT-IR results indicate the presence of zinc carboxylate in composites and HR-TEM results confirm the formation of ZnO nanoparticles upon subsequent oxidation. XPS and Raman measurements show that rapid thermal treatment in oxygen ambient results in decrease of carbon-oxygen functional groups and increase in graphitic carbon content leading to the reduction of GO in the composites. The average optical transmittance of rGO-ZnO composites in the visible region is found to be ∼87%. Photocatalytic studies carried out on methylene blue (MB) overlayer coated rGO-ZnO composites show reduction in concentration of MB with increasing duration of UV irradiation. The transparent two-dimensional rGO-ZnO composite solid state structures thus facilitate efficient adsorption and degradation of MB molecules, without any composite aggregation.

Potential of a sensitive uric acid biosensor fabricated using hydroxyapatite nanowire/reduced graphene oxide/gold nanoparticle

In this study, a ternary nanocomposite consisting of gold nanoparticles (AuNPs), hydroxyapatite (HAP) nanowires, and reduced graphene oxide (rGO) is synthesized by a simple one-step hydrothermal method, which is used to modify glassy carbon electrode (GCE) for detecting uric acid. The nanocomposite is characterized through various methods such as scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Electrochemical measurements of the modified GCE are performed in a conventional three-electrode system. Experimental results show that the obtained HAP nanowire and rGO are mixed homogeneously, and the AuNPs are deposited into this matrix. The GCE modified by the nanocomposites have superior electrocatalytic activities for uric acid. The peak current intensities of UAO (uricase)/HAP-rGO/AuNPs sensing system linearly increase as the uric acid concentration increases substantially in a range of 1.95 × 10^-5 to 6.0 × 10^-3  M (R² = .9943), with a detection limit of 3.9 × 10^-6  M (S/N = 3) and analytical sensitivity of 13.86 mA/M. The biosensor performs well in determining uric acid concentration in human urine samples.

A DFT study for silicene quantum dots embedded in silicane: controllable magnetism and tuneable band gap by hydrogen

This paper presents a design for silicene quantum dots (SiQDs) embedded in silicane. The shape and size of an embedded SiQD are managed by hydrogen atoms. A first-principles method was used to evaluate the magnetism as well as the electronic and structural properties of embedded SiQDs of various shapes and sizes. The shape of the embedded SiQD determined its electronic structure as well as the dot size. Moreover, the magnetic properties of SiQDs in silicane were highly shape dependent. The triangular SiQDs were all magnetic, some small parallelogram SiQDs were nonmagnetic, and all others were antiferromagnetic; almost all hexagonal SiQDs were nonmagnetic. An unequal number of bare Si atoms at the A and B sites was identified as a critical factor for establishing magnetism in embedded SiQDs. The tip of a triangular SiQD enhanced the magnetic moment of the dot. The parallelogram SiQD with two tip atoms appeared as a magnetic needle and has potential for use in spintronic applications. SiQDs embedded in silicane can be used in the design of silicon-based nanoelectronic devices and binary logic based on nanoscale magnetism.

Carbon-Intercalated 0D/2D Hybrid of Hematite Quantum Dots/Graphitic Carbon Nitride Nanosheets as Superior Catalyst for Advanced Oxidation

Efficient charge separation and sufficiently exposed active sites are important for light-driving Fenton catalysts. 0D/2D hybrids, especially quantum dots (QDs)/nanosheets (NSs), offer a better opportunity for improving photo-Fenton activity due to their high charge mobility and more catalytic sites, which is highly desirable but remains a great challenge. Herein, a 0D hematite quantum dots/2D ultrathin g-C₃ N₄ nanosheets hybrid (Fe₂ O₃ QDs/g-C₃ N₄ NS) is developed via a facile chemical reaction and subsequent low-temperature calcination. As expected, the specially designed 0D/2D structure shows remarkable catalytic performance toward the removal of p-nitrophenol. By virtue of large surface area, adequate active sites, and strong interfacial coupling, the 0D Fe₂ O₃ QDs/2D g-C₃ N₄ nanosheets establish efficient charge transport paths by local in-plane carbon species, expediting the separation and transfer of electron/hole pairs. Simultaneously, highly efficient charge mobility can lead to continuous and fast Fe(III)/Fe(II) conversion, promoting a cooperative effect between the photocatalysis and chemical activation of H₂ O₂ . The developed carbon-intercalated 0D/2D hybrid provides a new insight in developing heterogeneous catalysis for a large variety of photoelectronic applications, not limited in photo-Fenton catalysis.

Dual Role of Graphene Quantum Dots in Active Layer of Inverted Bulk Heterojunction Organic Photovoltaic Devices

Graphene quantum dots (GQDs) have shown broad application prospects in the field of photovoltaic devices due to their unique quantum confinement and edge effects. Here, we prepared GQDs by a photon-Fenton reaction as reported in our previous work, which has great advantage in the preparation scale. The photoelectric properties of the inverted hybrid solar cells based on poly(3-hexylthiophene) (P3HT):(6,6)-phenyl-C₆₁ butyric acid methylester (PCBM):GQDs and P3HT:GQDs with different contents of GQDs as the active layers are demonstrated, as well as their morphology and structure by atomic force microscopy images. Then, the different roles of GQDs played in the ternary (P3HT:PCBM:GQDs) and binary (P3HT:GQDs) hybrid solar cells are studied systematically. The results indicate that the GQDs provide an efficient excition separation interface and charge transport channel for the improvement of hybrid solar cells. The preliminary exploration and elaboration of the role of GQDs in hybrid solar cells will be beneficial to understand the interfacial procedure and improve device performance in the future.

sp2-sp3-Hybridized Atomic Domains Determine Optical Features of Carbon Dots

Carbon dots (CDots) are a promising biocompatible nanoscale source of light, yet the origin of their emission remains under debate. Here, we show that all the distinctive optical properties of CDots, including the giant Stokes shift of photoluminescence and the strong dependence of emission color on excitation wavelength, can be explained by the linear optical response of the partially sp²-hybridized carbon domains located on the surface of the CDots' sp³-hybridized amorphous cores. Using a simple quantum chemical approach, we show that the domain hybridization factor determines the localization of electrons and the electronic bandgap inside the domains and analyze how the distribution of this factor affects the emission properties of CDots. Our calculation data fully agree with the experimental optical properties of CDots, confirming the overall theoretical picture underlying the model. It is also demonstrated that fabrication of CDots with large hybridization factors of carbon domains shifts their emission to the red side of the visible spectrum, without a need to modify the size or shape of the CDots. Our theoretical model provides a useful tool for experimentalists and may lead to extending the applications of CDots in biophysics, optoelectronics, and photovoltaics.

Emission-Color Control in Polymer Films by Memorized Fluorescence Solvatochromism in a New Class of Totally Organic Fluorescent Nanogel Particles

In this work, a new class of totally organic fluorescent nanogel particles and their exceptionally specific behaviors based on their unique structures are introduced, which draws a sharp line from conventional fluorophore-doped and fluorophore-branched-type particles. The nanogel particles, the diameter of which could be controlled by adjusting reaction conditions, such as the solvent system, were spontaneously fabricated with a spherical shape by direct polymerization of non-heterocyclic aromatic compounds, such as 2,6-dihydroxyanthracene, 2,6-dihydroxynaphthalene, and 9,9-bis(4-hydroxyphenyl)fluorene with triazinane as the cross-linker. A fluorophoric moiety formed from a polymer main chain was realized in the particle, and consequently, the resultant content of the fluorophoric moiety was around 70-80 wt % per particle. The uniqueness and versatility of the particles can be emphasized by their good compatibility with various solvents due to their amphiphilic and ampholytic swelling properties, but also by their remarkable fluorescent solvatochromism in the dispersion state. Furthermore, these behaviors were preserved even in their polymer composite system. This study also demonstrates that various fluorescent polymer films can be fabricated with emission color control due to memorization of the solvatochromism phenomenon of the dispersed fluorescent nanoparticles.

Improved photo- and chemical-responses of graphene via porphyrin-functionalization for flexible, transparent, and sensitive sensors

The functionalization of graphene with organic molecules is beneficial for the realization of high-performance graphene sensors because functionalization can provide enhanced functionalities beyond the properties of pristine graphene. Although various types of sensors based on organic-graphene hybrids have been developed, the functionalization processes have poor thickness-controllability/reliability or require post-processing, and sensor applications rely on conventional, rigid substrates such as SiO₂/Si. Here, a flexible and transparent metalloporphyrin (MPP)-graphene hybrid for sensitive UV detection and chemical sensing is demonstrated. MPP, which provides strong light absorption, redox chemistry, and catalytic activity, is simply deposited onto graphene via one-step evaporation. Optical and electronic characterizations confirm that the graphene is successfully functionalized by MPP while maintaining its outstanding electronic properties. The MPP-functionalization greatly improves the photo- and chemical-sensing performances of the graphene, resulting in over 200% enhanced sensitivities for both UV light (365 nm) and toluene. Simultaneously, the MPP-graphene sensor exhibits no considerable change in electrical resistance under bending conditions, and remarkable optical transmittance in the visible range. On the basis of the excellent performances of the MPP-graphene hybrid, including high sensitivities, flexibility, transparency, and the ease and cost-effectiveness of the MPP-functionalization, it will be a promising candidate for flexible and transparent sensor applications.

Electrochemiluminescent aptasensor based on resonance energy transfer system between CdTe quantum dots and cyanine dyes for the sensitive detection of Ochratoxin A

In this work, an innovative aptasensor based on electrochemiluminescence resonance energy transfer (ECL-RET) from CdTe quantum dots (QDs) to a cyanine dye (Cy5) fluorophore for the determination of Ochratoxin A (OTA) was fabricated. A strong cathodic ECL emission was obtained by the CdTe QDs modified glassy carbon electrode (GCE). After the immobilization with the capture DNA (cDNA) and the sequential hybridization with the probe DNA-modified Cy5 (pDNA, the aptamer of OTA), the ECL signal enhanced obviously through the ECL-RET. Meanwhile, the spectrum- and distance-related ECL enhancement effect was investigated. When the target OTA was in the presence, the pDNA-Cy5 molecules were released from the electrode surface owing to the specific interaction between OTA and aptamer, resulting in an evident decrease of ECL signal. Under optimal conditions, the developed aptasensor displayed the linear response toward OTA in the wide range of 0.0005-50 ng/mL with a low detection limit of 0.17 pg/mL. With the excellent selectivity, stability and repeatability, the strategy provided an efficient and universal method for the sensitive detection of target in practical application.