Influence of Electron Acceptor and Electron Donor on the Photophysical Properties of Carbon Dots: A Comparative Investigation at the Bulk‐State and Single‐Particle Level

Carbon dots (CDs) are extensively studied to investigate their unique optical properties such as undergoing electron transfer in different scenarios. This work presents an in‐depth investigation to study the ensemble‐averaged state/bulk state and single‐particle level photophysical properties of CDs that are passivated with electron‐accepting (CD‐A) and electron‐donating molecules (CD‐D) on their surface. The bulk‐state experiments reveal that in a mixture of these CDs, CD‐A dominates the overall photophyiscal properties and eventually leads to formation of at least two associated geometries, which is dependent on time, concentration, intramolecular electron/charge transfer, and hydrogen bonding. Single‐particle studies, however, do not reveal an “acceptor‐dominating” scenario based on analysis of instantaneous intensity, bleaching kinetics, and photoblinking, indicating that the direct interaction of these CDs may affect their photophysical properties in the bulk state due to formation of hierarchical structural assemblies. Here it is anticipated that these fundamental results will further provide insights toward the understanding of the complex mechanism associated with CD emission, which is one of the key contributors to their successful application. As an immediate application of these functional CDs, it is shown that they can be used as a sensing array for metal ions and serve as a powerful toolbox for their technological applications.     

Biocompatible PEG‐Chitosan@Carbon Dots Hybrid Nanogels for Two‐Photon Fluorescence Imaging,Near‐Infrared Light/pH Dual‐Responsive Drug Carrier,and Synergistic Therapy

This work designs a class of biocompatible PEG‐chitosan@CDs hybrid nanogels by integrating nonlinear poly(ethylene glycol) (PEG), chitosan, and graphitic carbon dots (CDs) into a single nanoparticle for two‐photon fluorescence (TPF) bioimaging, pH and near‐infrared (NIR) light dual‐responsive drug release, and synergistic therapy. Such hybrid nanogels can be simply prepared from a one‐pot surfactant‐free precipitation polymerization of the PEG macromonomers complexed with chitosan and CDs in water, resulting in a semi‐interpenetration of chitosan chains and an immobilization of CDs in the nonlinear PEG networks. The embedded CDs in hybrid nanogels not only serve as an excellent confocal and TPF imaging contrast agent and fluorescent pH‐sensing probe, but also enhance the loading capacity of the hybrid nanogels for hydrophobic anticancer drug. The chitosan can induce a pH‐sensitive swelling/deswelling of the hybrid nanogels for pH‐regulated drug release over the physiologically important range of 5.0–7.4 and surface modulation of embedded CDs to realize fluorescent pH sensing. The thermosensitive nonlinear PEG network can promote the drug release through the local heat produced by the embedded CDs under NIR irradiation. The in vitro results indicate that the hybrid nanogels demonstrated high therapeutic efficacy through the synergistic effect of combined chemo–photothermal treatments.     

Highly Biocompatible Carbon Nanodots for Simultaneous Bioimaging and Targeted Photodynamic Therapy In Vitro and In Vivo

Photosensitizers (PSs) are light‐sensitive molecules that are highly hydrophobic, which poses a challenge to their use for targeted photodynamic therapy. Hence, considerable efforts have been made to develop carriers for the delivery of PSs. Herein, a novel design is described of highly biocompatible, fluorescent, folic acid (FA)‐functionalized carbon nanodots (CDs) as carriers for the PS zinc phthalocyanine (ZnPc) to achieve simultaneous biological imaging and targeted photodynamic therapy. FA is modified on PEG‐­passivated CDs (CD‐PEG) for targeted delivery to FA‐positive cancer cells, and ZnPc is loaded onto CD‐PEG‐FA via π–π stacking interactions. CD‐PEG‐FA/ZnPc exhibits excellent targeted delivery of the PS, leading to simultaneous imaging and significant targeted photodynamic therapy after irradiation in vitro and in vivo. The present CD‐based targeted delivery of PSs is anticipated to offer a convenient and effective platform for enhanced photodynamic therapy to treat cancers in the near future.     

High-Throughput One-Photon Excitation Pathway in 0D/3D Heterojunctions for Visible-Light Driven Hydrogen Evolution

The development of an effective one-photon excitation pathway to improve the charge-carrier separation and mobility of semiconductors, which have been proven to be favorable for heterogeneous catalysis, is highly desirable but remains a great challenge. Herein, a high-throughput one-photon excitation pathway is reported by constructing 0D carbon dots/3D porous carbon nitride nanovesicles (denoted as CDs/PCN NVs) heterostructures for photocatalytic hydrogen evolution. In particular, the optimum CDs/PCN NVs heterostructures exhibit an impressive performance of 14.022 mmol h⁻¹ g⁻¹, which is 56.54 times higher than that of pristine CN. Detailed characterization reveals that the improved performance is primarily attributed to the high-throughput and one-photon excitation pathway. The former could be attributed to a great deal of CDs with high charge-carrier mobility coupled to PCN NVs, which enable more electrons to be photoexcited via the broad absorption response, and the multiple reflection of incident light owing to the porous nanovesicle structure with shortened route of carriers migrating toward the surface; the latter would lead to the photoinduced holes and electrons accumulated at the valence band of PCN NVs and surface of CDs, respectively, achieving an effective spatial separation. The high-throughput one-photon excitation pathway demonstrated here may provide insights into the development of nanocomposites for various related applications.     

Mimicking Neuroplasticity in a Hybrid Biopolymer Transistor by Dual Modes Modulation

Neuromorphic computing systems that are capable of parallel information storage and processing with high area and energy efficiencies, offer important opportunities for future storage systems and in‐memory computing. Here, it is shown that a carbon dots/silk protein (CDs/silk) blend can be used as a light‐tunable charge trapping medium to fabricate an electro‐photoactive transistor synapse. The synaptic device can be optically operated in volatile or nonvolatile modes, ensuring concomitant short‐term and long‐term neuroplasticity. The synaptic‐like behaviors are attributed to the photogating effect induced by trapped photogenerated electrons in the hybrid CDs/silk film which is confirmed with atomic force microscopy based electrical techniques. In addition, system‐level pattern recognition capability of the synaptic device is evaluated by a single‐layer perceptron model. The remote optical operation of neuromorphic architecture provides promising building blocks to complete bioinspired photonic computing paradigms.     

Synthesis and Optoelectronic Properties of Nonpolar Polyrotaxane Insulated Molecular Wires with High Solubility in Organic Solvents

Hydrophilic polyanionic conjugated polyrotaxanes are readily synthesized in water by Suzuki coupling, but their high polarity and ionic nature limit the potential applications of these materials. Here, we demonstrate three methods for transforming these polar polyelectrolytes into nonpolar lipophilic insulated molecular wires. A water‐soluble polyfluorene‐alt‐biphenylene β‐cyclodextrin (CD) polyrotaxane was converted into nonpolar derivatives by methylation of the carboxylic acid groups with diazomethane and conversion of the hydroxyl groups of the CDs to benzyl ethers, trihexylsilyl ethers, benzoyl esters, and butanoate esters to yield polyrotaxanes that are soluble in organic solvents such as chloroform and cyclohexane. Elemental analysis, NMR spectroscopy, and gel permeation chromatography (GPC) data support the proposed structures of the organic‐soluble polyrotaxanes. The extents of reaction of the polyrotaxane CD hydroxyl groups were 55% for trihexylsilyl chloride/imidazole; 81% for benzyl chloride/sodium hydride; 72% for benzoyl chloride/pyridine/4‐dimethylaminopyridine; and 98% butanoic anhydride/pyridine/4‐dimethylaminopyridine. Alkylation, silylation, and esterification increase the bulk of the encapsulating sheath, preventing interstrand aggregation, increasing the photoluminescence efficiency in the solid state and simplifying the time‐resolved fluorescence decay. The organic‐soluble polyrotaxanes were processed into polymer light‐emitting diodes (PLEDs) from solution in nonpolar organic solvents, thereby excluding ionic impurities from the active layer.     

Controlled Synthesis of Multicolor Carbon Dots Assisted by Machine Learning

Carbon dots (CDs) have received extensive attention and applications in recent years due to their remarkable characteristics of tunable emission wavelength, high stability, and a variety of synthetic raw materials. Since the formation process and photoluminescence properties of CDs are affected by multiple factors, the luminescence regulation of CDs has always been a troublesome problem. Furthermore, it is still a lack of appropriate approaches to reveal the hidden rules between the synthesis conditions and the luminescence properties of CDs. Inspired by machine learning (ML) applications in molecular and materials science, herein, a data-driven ML strategy is proposed to multi-dimensionally investigate the correlation between reaction parameters and the photoluminescence properties of CDs. Meanwhile, it is demonstrated that reaction parameters and solvent properties have different influences on the fluorescence properties of CDs, and the intelligently optimizing synthesis route of CDs is achieved using ML algorithms. CDs with excellent luminescent properties screened by ML are further applied to high-capacity colorful information encryption. This study provides an efficient ML-assisted strategy to guide the synthesis of multicolor CDs, helping researchers to quickly and easily obtain CDs according to experimental requirements.     

FPGA as Process Monitor-an effective method to characterize poly gate CD variation and its impact on product performance and yield

This paper illustrates how field programmable gate array (FPGA) is used as a process monitor for yield and performance improvements. Poly gate critical dimension (CD) variation has been increasingly affecting product performance and yield in advanced process technology. Here, a built-in-self-test (BIST) pattern-based poly gate CD measurement (Tilo) methodology is introduced in FPGA product. The FPGA circuit is programmed into a small, local BIST pattern (Tilo) and its delay is accurately reflecting local poly gate CDs and variation. This methodology can conveniently capture poly gate CD statistical variation at both the intrafield and interfield level. This paper shows that the Tilo measurement is very useful in poly process debugging and yield improvement.     

Carbon and Graphene Quantum Dots for Optoelectronic and Energy Devices: A Review

As new members of carbon material family, carbon and graphene quantum dots (CDs, GQDs) have attracted tremendous attentions for their potentials for biological, optoelectronic, and energy related applications. Among these applications, bio‐imaging has been intensively studied, but optoelectronic and energy devices are rapidly rising. In this Feature Article, recent exciting progresses on CD‐ and GQD‐based optoelectronic and energy devices, such as light emitting diodes (LEDs), solar cells (SCs), photodetctors (PDs), photocatalysis, batteries, and supercapacitors are highlighted. The recent understanding on their microstructure and optical properties are briefly introduced in the first part. Some important progresses on optoelectronic and energy devices are then addressed as the main part of this Feature Article. Finally, a brief outlook is given, pointing out that CDs and GQDs could play more important roles in communication‐ and energy‐functional devices in the near future.     

DVD-Video: multimedia for the masses

DVD (digital video disc, or digital versatile disc) is the next generation of optical disc storage technology. It's essentially a bigger, faster compact disc (CD) that can hold video as well as audio and computer data. DVD aims to encompass home entertainment, computers and business information with a single digital format, eventually replacing audio CD, videotape, laser disc, CD-ROM, and perhaps even video game cartridges. DVD has widespread-and unprecedented-support from all major electronics companies, all major computer hardware companies and most major movie and music studios, which says much for its chances of success. DVD-ROM holds computer data read by a DVD-ROM drive hooked up to a computer. DVD-Video is an application built on top of DVD-ROM. DVD-Video holds video programs played in a DVD player hooked up to a TV. The difference between DVD-ROM and DVD-Video resembles that between CD-ROM and audio CDs, including the important point that DVD-Video discs can be played in computers     

One‐Step Ionic‐Liquid‐Assisted Electrochemical Synthesis of Ionic‐Liquid‐Functionalized Graphene Sheets Directly from Graphite

Graphite, inexpensive and available in large quantities, unfortunately does not readily exfoliate to yield individual graphene sheets. Here a mild, one‐step electrochemical approach for the preparation of ionic‐liquid‐functionalized graphite sheets with the assistance of an ionic liquid and water is presented. These ionic‐liquid‐treated graphite sheets can be exfoliated into functionalized graphene nanosheets that can not only be individuated and homogeneously distributed into polar aprotic solvents, but also need not be further deoxidized. Different types of ionic liquids and different ratios of the ionic liquid to water can influence the properties of the graphene nanosheets. Graphene nanosheet/polystyrene composites synthesized by a liquid‐phase blend route exhibit a percolation threshold of 0.1 vol % for room temperature electrical conductivity, and, at only 4.19 vol %, this composite has a conductivity of 13.84 S m⁻¹, which is 3–15 times that of polystyrene composites filled with single‐walled carbon nanotubes.     

Polyvinylpyrrolidone‐Directed Crystallization of ZnO with Tunable Morphology and Bandgap

A novel polyvinylpyrrolidone (PVP)‐directed crystallization route is successfully developed for the shape‐selective synthesis of ZnO particles with distinctive shapes, including monolayer, bilayer, and multilayer structures, gears, capped pots, hemispheres, and bowls, at temperatures as low as 32 °C. This route is based on exploiting a new water/PVP/n‐pentanol system. In the system, PVP can greatly promote ZnO nucleation by binding water and direct ZnO growth by selectively capping the specific ZnO facets, which is confirmed by IR absorption spectra. The bandgap of the ZnO particles is readily tuned by modifying the product morphology by adjusting the PVP chain length, PVP amount, water volume, and reaction temperature. The remarkable ZnO structures and the biomimetic method demonstrated here not only expand the structures and applications of ZnO but also provide a new approach to explore the unusual structures for novel physicochemical properties and technological applications. Furthermore, the novel ZnO/Au/ZnO sandwich structure is successfully fabricated by inserting a Au plate into the bilayer ZnO structure.     

Innovations in the Solid-State Fluorescence of Carbon Dots: Strategies,Optical Manipulations,and Applications

Carbon dots (CDs)—carbon nanoparticles smaller than 10 nm—have attracted widespread attention owing to their excellent optical properties. However, high-performing CDs often suffer from severe aggregation-induced quenching in the solid state, which limits their commercial applicability. Therefore, CD materials with efficient solid-state luminescence are sought. As research on the structure and photoluminescence mechanisms of CDs has intensified in recent years, strategies to construct fluorescent solid-state CD materials and tune their emissions have broadened. This article reviews recent advances in the strategies and mechanisms for attaining solid-state fluorescence in CDs, describes specific ways to tune the optical properties of this fluorescence, introduces the latest applications of the resulting CDs to optoelectronics, biology, and sensing, and finally considers the prospects for future application and current challenges facing the development of solid-state fluorescence in CDs.     

A new method for fiber chromatic dispersion measurement with microwave interference effect

The chromatic dispersion (CD) is a key parameter for optical fibers. Based on the microwave interference effect, a new method for CD measurement of optical fibers is proposed. The radio frequency (RF) signals carried by two light-waves with different wavelengths transmit through the dispersive optical fiber under test. After photo-detector they interfere with each other due to the different phase shifts induced by the CD of fiber. The CD can be obtained by monitoring the changing interference RF power with scanning the wavelength of tunable laser source. The CD values of single mode fiber and dispersion compensating fiber are measured within the wavelength range from 1525 to 1605 nm. The common phase shift method is used to measure the CDs of the two types of fiber, which demonstrates the feasibility and veracity of the proposed method.     

Emancipating Target‐Functionalized Carbon Dots from Autophagy Vesicles for a Novel Visualized Tumor Therapy

Killing the tumor cells by a visualized targeting system is a promising strategy with which to achieve high efficiency, low side effects, and a high survival rate for tumor therapy. Here, an autophagy regulation strategy is reported by emancipating target‐functionalized carbon dots from autophagy vesicles for the efficient visualized tumor therapy. The folic acid modified N‐doped carbon dots (FN‐CDs) are selectively endocytosed (specific cellular uptake rate >93.40%) and stably existed in autophagic vacuoles in tumor cells. Next, the autophagic vacuoles are “opened” by the autophagy inhibitors. Released FN‐CDs activate both the intrinsic and extrinsic apoptotic signaling pathway and kill tumor cells efficiently. This method achieves therapeutic effects with high performance in 26 types of tumor cell lines. Animal experiments show that the 30 d survival rate of this therapeutic strategy is much higher than that with traditional drug treatment. Real‐time imaging/monitoring and its effects on the intelligent tumor therapy are also demonstrated based on the stable, strong, green emission from FN‐CDs.     

Macroscopic and Mechanically Robust Hollow Carbon Spheres with Superior Oil Adsorption and Light‐to‐Heat Evaporation Properties

Hollow carbon spheres (HCSs) represent a special class of functional materials, to which intense interest has been paid in the fields of materials science and chemistry. A major problem with these materials is the lack of sufficient particle engineering and mechanical strength for practical applications and the difficulty of up‐scaling. Herein, we report a general, template‐free, phase‐separation approach, in which the liquid–liquid phase‐inversion process and a gas‐foaming process are coupled for the first time, for fast and continuous processing of uniform HCSs. The obtained HCSs have particle sizes on the millimeter scale, and a hierarchical structure with an interpenetrating, open‐porous, carbon shell and huge external voids, therefore permitting rapid transport of molecules into, throughout, and out of the hollow structure. By evenly dispersing the CNTs in the precursor solution, CNT‐reinforced HCSs can be achieved with significantly enhanced mechanical strength, hydrophobicity, and electronic and thermal properties. The resulting CNT‐reinforced HCSs offer a viable route to remove the engine oil from water in a fixed‐bed system. Moreover, these floatable HCSs can receive and convert sunlight to heat at the water–air interface, resulting in a great enhancement in solar evaporation rate compared to conventional bulk heating schemes.     

Energy Level Modification with Carbon Dot Interlayers Enables Efficient Perovskite Solar Cells and Quantum Dot Based Light‐Emitting Diodes

Controlling the transport and minimizing charge carrier trapping at interfaces is crucial for the performance of various optoelectronic devices. Here, how electronic properties of stable, abundant, and easy‐to‐synthesized carbon dots (CDs) are controlled via the surface chemistry through a chosen ratio of their precursors citric acid and ethylenediamine are demonstrated. This allows to adjust the work function of indium tin oxide (ITO) films over the broad range of 1.57 eV, through deposition of thin CD layers. CD modifiers with abundant amine groups reduce the ITO work function from 4.64 to 3.42 eV, while those with abundant carboxyl groups increase it to 4.99 eV. Using CDs to modify interfaces between metal oxide (SnO₂ and ZnO) films and active layers of solar cells and light‐emitting diodes (LEDs) allows to significantly improve their performance. Power conversion efficiency of CH₃NH₃PbI₃ perovskite solar cells increases from 17.3% to 19.5%; the external quantum efficiency of CsPbI₃ perovskite quantum dot LEDs increases from 4.8% to 10.3%; and that of CdSe/ZnS quantum dot LEDs increases from 8.1% to 21.9%. As CD films are easily fabricated in air by solution processing, the approach paves the way to a simplified manufacturing of large‐area and low‐cost optoelectronic devices.     

Bandwidth‐satisfied routing in multi‐rate MANETs by cross‐layer approach

Previous quality‐of‐service (QoS) routing protocols in mobile ad hoc networks (MANETs) determined bandwidth‐satisfied routes for QoS applications. Since the multi‐rate enhancements have been implemented in MANETs, QoS routing protocols should be adapted to exploit them fully. However, existing works suffer from one bandwidth‐violation problem, named the hidden route problem (HRP), which may arise when a new flow is permitted and only the bandwidth consumption of the hosts in the neighborhood of the route is computed. Without considering the bandwidth consumption to ongoing flows is the reason the problem is introduced. This work proposes a routing protocol that can avoid HRP for data rate selection and bandwidth‐satisfied route determination with an efficient cross‐layer design based on the integration of PHY and MAC layers into the network layer. To use bandwidth efficiently, we aim to select the combination of data rates and a route with minimal bandwidth consumption to the network, instead of the strategy adopted in the most previous works by selecting the combination with the shortest total transmission time. Using bandwidth efficiently can increase the number of flows supported by a network. Copyright 2010 John Wiley & Sons, Ltd.     

Amide (n, π*) Transitions Enabled Clusteroluminescence in Solid-State Carbon Dots

Carbon dots (CDs) demonstrate great superiority in optoelectronic devices due to their tunable emission and photobleaching resistance properties. Although the fluorescence of CDs in solution has been extensively studied, their solid-state fluorescence (SSF) mechanism still remains largely unexplored experimentally. Herein, solid-state fluorescent CDs with unique clusteroluminescence (CL) generated from clusterization-triggered emission are designed based on condensation between precursors with carboxyl and amino groups. The CDs demonstrate obvious concentration-dependent fluorescence and quench-resistant SSF, which is attributed to the activation of amide (n, π*) transition by the clusterization process. This sub-luminophore is non-luminescent at long wavelengths in isolated state, while it induces photoluminescence redshift via through-space interaction in aggregated state. Besides, the SSF of CDs can be tuned from quenched to quenching-resistant emission through amide formation, and the dominant fluorescent center of CDs solids is switchable from surface to edge state through amide passivation. Based on their long-wavelength CL feature, high-purity red light-emitting diode devices exhibiting 656-nm warm light are fabricated with the Commission Internationale de l´Eclairage (CIE) coordinates of (0.66, 0.34) and unchanged wavelength under different driving currents. These findings provide novel insights into the SSF mechanism of CDs and a universal strategy to construct fluorescent materials with tailored properties.     

Antipiracy software opens door to electronic intruders

This paper discusses how Sony BMG made a big mistake in the production of hundreds of music CDs equipped with a copy protection software known as XCP. The concept of XCP was to block consumers from converting audio files to mp3's, as well as third-party sharing. The CD can be normally played in several audio players, but in the case of using it in a computer, XCP automatically prompts a specific music player to be installed together with a rootkit. The rootkit is designed to hide the existence of any file or folder whose name begins with "$sys$". Through this concept, hackers can hide anything they want. Overall, Sony's aim of stopping piracy was a complete failure. However, Sony came up with a complex multistep process to uninstall the rootkit and unfortunately stopped the production of XCP-protected CDs.