Fluorescence bioimaging affords a vital tool for both researchers and surgeons to molecularly target a variety of biological tissues and processes. This review focuses on summarizing organic dyes ...emitting at a biological transparency window termed the near‐infrared‐II (NIR‐II) window, where minimal light interaction with the surrounding tissues allows photons to travel nearly unperturbed throughout the body. NIR‐II fluorescence imaging overcomes the penetration/contrast bottleneck of imaging in the visible region, making it a remarkable modality for early diagnosis of cancer and highly sensitive tumor surgery. Due to their convenient bioconjugation with peptides/antibodies, NIR‐II molecular dyes are desirable candidates for targeted cancer imaging, significantly overcoming the autofluorescence/scattering issues for deep tissue molecular imaging. To promote the clinical translation of NIR‐II bioimaging, advancements in the high‐performance small molecule–derived probes are critically important. Here, molecules with clinical potential for NIR‐II imaging are discussed, summarizing the synthesis and chemical structures of NIR‐II dyes, chemical and optical properties of NIR‐II dyes, bioconjugation and biological behavior of NIR‐II dyes, whole body imaging with NIR‐II dyes for cancer detection and surgery, as well as NIR‐II fluorescence microscopy imaging. A key perspective on the direction of NIR‐II molecular dyes for cancer imaging and surgery is also discussed.
Among all existing near‐infrared (NIR)‐II fluorophores, the NIR‐II molecular dyes are the most remarkable in translating this imaging window into the clinical setting. Advanced NIR‐II dye‐derived bioconjugates will give doctors an unparalleled view into tissues for tumor detection at greater depths and contrast, allowing early detection during cancer screenings and solid tumor resection by delineation of the boundaries between healthy and cancerous tissues.
The crosslink‐enhanced emission effect was first proposed to explore the strong luminescence of nonconjugated polymer dots possessing only either non‐emissive or weakly emissive sub‐luminophores. ...Interesting phenomena in recent research indicate such enhancement caused by extensive crosslinking appears in diverse luminescent polymers with sub‐luminophores (electron‐rich heteroatomic moieties) or luminophores (conjugated π domains). This enhancement can promote the emission from nonluminous to luminous, from weakly luminous to strongly luminous, and even convert the pathway of radiative transitions. The concept of the crosslink‐enhanced emission effect should be updated and extended to an in‐depth spatial effect, such as electron overlap and energy splitting in confined domains by effective crosslinking, more than initial immobilization. This Minireview outlines the development of the crosslink‐enhanced emission effect from the perspective of the detailed classification, inherent mechanism and applicable systems. An outlook on the further exploration and application of this theory are also proposed.
Strong links: Polymers containing luminophores or sub‐luminophores may display enhanced emission upon crosslinking by covalent, supramolecular, and ionic bonding, and by through‐space interactions in confined domains. In this Minireview the theoretical background is discussed and numerous examples are provided, which may guide researchers in crosslinkage techniques to improve luminescent systems.
Abstract
Carbon dots (CDs) have received immense attention in the last decade because they are easy-to-prepare, nontoxic, and tailorable carbon-based fluorescent nanomaterials. CDs can be categorized ...into three subgroups based on their morphology and chemical structure: graphene quantum dots (GQDs), carbon quantum dots (CQDs), and carbonized polymer dots (CPDs). The detailed structures of the materials can vary significantly, even within the same category. This property is particularly predominant in chemically synthesized CPDs, as their formation proceeds via the polymerization–carbonization of molecules or polymer precursors. Abundant precursors endow CPDs with versatile structures and properties. A wide variety of carbon nanomaterials can be grouped under the category of CPDs because of their observed diversity. It is important to understand the precursor-dependent structural diversity observed in CPDs. Appropriate nomenclature for all classes and types of CPDs is proposed for the better utilization of these emerging materials.
Despite the various synthesis methods to obtain carbon dots (CDs), the bottom‐up methods are still the most widely administrated route to afford large‐scale and low‐cost synthesis. However, as CDs ...are developed with increasing reports involved in producing many CDs, the structure and property features have changed enormously compared with the first generation of CDs, raising classification concerns. To this end, a new classification of CDs, named carbonized polymer dots (CPDs), is summarized according to the analysis of structure and property features. Here, CPDs are revealed as an emerging class of CDs with distinctive polymer/carbon hybrid structures and properties. Furthermore, deep insights into the effects of synthesis on the structure/property features of CDs are provided. Herein, the synthesis methods of CDs are also summarized in detail, and the effects of synthesis conditions of the bottom‐up methods in terms of the structures and properties of CPDs are discussed and analyzed comprehensively. Insights into formation process and nucleation mechanism of CPDs are also offered. Finally, a perspective of the future development of CDs is proposed with critical insights into facilitating their potential in various application fields.
The classification of carbon dots (CDs) is improved and carbonized polymer dots (CPDs) are revealed with distinctive polymer/carbon hybrid structures and properties, as a new classification of CDs. The synthesis methods of CDs and effects of synthesis on the structures and properties of CPDs are discussed. Furthermore, insights are offered into the nucleation mechanism and the future development of CPDs.
At present, the actual mechanism of the photoluminescence (PL) of fluorescent carbon dots (CDs) is still an open debate among researchers. Because of the variety of CDs, it is highly important to ...summarize the PL mechanism for these kinds of carbon materials; doing so can guide the development of effective synthesis routes and novel applications. This review will focus on the PL mechanism of CDs. Three types of fluorescent CDs were involved: graphene quantum dots (GQDs), carbon nanodots (CNDs), and polymer dots (PDs). Four reasonable PL mechanisms have been confirmed: the quantum confinement effect or conjugated π-domains, which are determined by the carbon core; the surface state, which is determined by hybridization of the carbon backbone and the connected chemical groups; the molecule state, which is determined solely by the fluorescent molecules connected on the surface or interior of the CDs; and the crosslink-enhanced emission (CEE) effect. To give a thorough summary, the category and synthesis routes, as well as the chemical/physical properties for the CDs, are briefly introduced in advance.
Bioelectricity generation, by Shewanella oneidensis (S. oneidensis) MR-1, has become particularly alluring, thanks to its extraordinary prospects for energy production, pollution treatment, and ...biosynthesis. Attempts to improve its technological output by modification of S. oneidensis MR-1 remains complicated, expensive and inefficient. Herein, we report on the augmentation of S. oneidensis MR-1 with carbon dots (CDs). The CDs-fed cells show accelerated extracellular electron transfer and metabolic rate, with increased intracellular charge, higher adenosine triphosphate level, quicker substrate consumption and more abundant extracellular secretion. Meanwhile, the CDs promote cellular adhesion, electronegativity, and biofilm formation. In bioelectrical systems the CDs-fed cells increase the maximum current value, 7.34 fold, and power output, 6.46 fold. The enhancement efficacy is found to be strongly dependent on the surface charge of the CDs. This work demonstrates a simple, cost-effective and efficient route to improve bioelectricity generation of S. oneidensis MR-1, holding promise in all relevant technologies.
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•This article summarizes the significant advances achieved in the past few years on synthesis, classification, mechanism and applications of CDs and CDs-based photocatalysts to give a ...thorough summary.•CDs-derived photocatalysts are devided into pure CDs and CDs composite photocatalysts and the photocatalytic efficiencies are compared.•Various kinds of mechanism during photocatalytic process in typical systems are concluded.•Applications in the fields of degradation of organics, water splitting for H2 and O2 evolution, CO2 conversion and photocatalytic chemical reactions are also reviewed to confirm the great potential of CDs-derived photocatalysts for environmental and energy issues.
With the rapid development of science and technology, environmental pollution and energy shortage become more and more prominent. To solve these problems, photocatalytic technology is regarded as one of the most efficient methods, allowing for both pollutant degradation and energy conversion. Compared with traditional group IIVI, IIIV quantum dots (QDs), carbon dots (CDs), as a newly emerging kind of fluorescent carbon-based material, possess many excellent properties, such as high aqueous solubility, low cost, low toxicity, abundant surface functional groups and good biocompatibility. In particular, the unique up-converted photoluminescence (PL) behavior and photo-induced electron transfer ability of CDs provide the new route to achieve efficient metal-free photocatalysts. This article reviews recent progress on CDs utilized for photocatalysis from different perspectives, including the following three parts: classification and synthesis, mechanism of CDs-derived photocatalysts as well as the applications for environmental issues (up-converted PL process) and energy conversion (photo-induced electron transfer process).
Shine on you crazy dots: A rapid and high‐output strategy allows the fabrication of polymer‐like carbon dots (CDs) with quantum yields as high as ca. 80 %. This value is the highest reported to date ...for fluorescent carbon‐based materials, and gives promise for their application in multicolor‐patterning and biosensors.
Polymer carbon dots (PCDs) are proposed as a new class of room‐temperature phosphorescence (RTP) materials. The abundant energy levels in PCDs increase the probability of intersystem crossing (ISC) ...and their covalently crosslinked framework structures greatly suppress the nonradiative transitions. The efficient methods allow the manufacture of PCDs with unique RTP properties in air without additional metal complexation or complicated matrix composition. They thus provide a route towards the rational design of metal‐free RTP materials that may be synthesized easily. Furthermore, we find that RTP is associated with a crosslink‐enhanced emission (CEE) effect, which provides further routes to design improved PCDs with diverse RTP performance. Our results show the potential of PCDs as a universal route to achieve effective metal‐free RTP.
Room‐temperature phosphorescence: Polymer carbon dots (PCDs) showing metal‐free room‐temperature phosphorescence (RTP) have been constructed by using a facile method. The contribution of the cross‐link‐enhanced emission effect to the generation of RTP is verified and proposed as a guideline to forecast and synthesize a series of PCDs with diverse RTP performance (ISC=intersystem crossing).
Abstract
The outcome of radiotherapy is significantly restricted by tumor hypoxia. To overcome this obstacle, one prevalent solution is to increase intratumoral oxygen supply. However, its ...effectiveness is often limited by the high metabolic demand for O
2
by cancer cells. Herein, we develop a hybrid semiconducting organosilica-based O
2
nanoeconomizer pHPFON-NO/O
2
to combat tumor hypoxia. Our solution is twofold: first, the pHPFON-NO/O
2
interacts with the acidic tumor microenvironment to release NO for endogenous O
2
conservation; second, it releases O
2
in response to mild photothermal effect to enable exogenous O
2
infusion. Additionally, the photothermal effect can be increased to eradicate tumor residues with radioresistant properties due to other factors. This “reducing expenditure of O
2
and broadening sources” strategy significantly alleviates tumor hypoxia in multiple ways, greatly enhances the efficacy of radiotherapy both in vitro and in vivo, and demonstrates the synergy between on-demand temperature-controlled photothermal and oxygen-elevated radiotherapy for complete tumor response.
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