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Benzoyl peroxide (BPO) has been added in wheat flour because of its bleaching effect. However, the abnormal used BPO has caused increasing concern due to its strong oxidization capability which may have adverse effects on living organisms. Herein, we present a carbon dot (CD)-based fluorescent and colorimetric probe for visually, sensitively and selectively sensing BPO. The addition of BPO could quench the red fluorescence of CDs peaked at 622 and 677 nm, and decrease the absorbance at 613 nm, while increase the absorbance at 450 nm, resulting in a fluorescence turn-off and colorimetric spectral response. Moreover, the CDs had short response time of 10 min and high sensitivity towards BPO with a low limit of detection of 28 nmol/L. The applicability of the CDs in detecting BPO in wheat, noodle and starch samples was further demonstrated, and good recovery results were obtained.

Carbon dots (CDs) have become popular nanomaterials in biomedical and agricultural fields. Herein we synthesized multifunctional CDs which showed anti-cancer and anti-fungal activities. The low cytotoxicity, stable fluorescence and high photothermal conversion efficiency enable the CDs with imaging-guided photothermal therapy. The CDs also exhibited intrinsic anti-fungal activity even at a low concentration, i.e., 40 mg·L−1 of CDs induced 20% mortality in cucumber downy mildew. Moreover, the large π-conjugated nanostructure and the richness of amino and hydroxyl groups make them a powerful delivery platform for flumorph (a fungicide) with a high loading efficiency of 47.18%. Meanwhile, the heat converted from the light can accelerate the release of flumorph from CDs, and thus efficiently kill fungus.

The number of cases of bacterial resistance to antibiotics has been exponentially rising over the last decade. This issue is getting worse as the research and development of new antibiotics is much slower than the speed of pathogenic bacteria acquiring resistance to antibiotic treatment. To fight against antibacterial resistance, new therapeutic strategies have to be sought as alternatives to currently administered antibiotics. Many new materials, for instance, metal organic frameworks possess desirable properties such as improved bacterial internalization, flexible structural control, high selectivity, and controlled drug release and therefore, are potentially good candidates for antibacterial therapy to overcome antibiotic resistance. This review describes the most recent development of the field of the antibacterial applications of metal organic frameworks, and their hybrids and derivatives, followed by an in-depth analysis of their advantages, disadvantages and design factors of these materials. Finally, we present our insights into the important aspects of the future development of metal organic frameworks for antibacterial applications.

Photothermal therapy (PTT) has received increasing attention due to its high selectivity, non-invasiveness, negligible drug resistance, oxygen independence, and minimal side effects. In PTT, photothermal agents (PTAs) absorb light energy and generate heat to kill cancer cells. Although various PTAs with strong near-infrared (NIR) light absorption and high photothermal conversion efficiency have been developed, their clinical uses in PTT still face with challenges. For example, maintaining a temperature of above 50°C for several minutes is needed to effectively ablate tumors, but this high temperature may destroy the surrounding normal tissues. Moreover, this rapid heating can induce an immune response that increases the cell tolerance to heat, which can weaken the therapeutic effects of PTT. In this review, we mainly focus on two approaches that have been developed to overcome the limitations of PTT, including inhibiting the expression of heat shock protein (Hsp) and regulating the metabolic processes of cells to develop low temperature PTT (LTPTT). We then discuss the existing challenges in clinical uses of LTPTT for treating tumors, and finally introduce future perspectives on the design of more effective therapeutic agents.

Photosensitizers (PSs) with aggregation-induced emission (AIE) feature show promising applications in fluorescence imaging-guided photodynamic therapy (PDT) in virtue of their enhanced fluorescence and phototoxicity in aggregate state. Seeking the ideal AIE luminogens (AIEgens) with good capability of generating reactive oxygen species is still urgent. Here we rationally synthesized an acceptor-donor-acceptor (A-D-A) structured AIEgen (BTZPP) and then prepared it into nanoparticles (NPs) through a simple re-precipitation procedure. The obtained BTZPP NPs show a deep-red emission peaked at 635 nm, a large Stokes shift of 195 nm, and a high 1O2 generation quantum yield of 72.3%. Moreover, these NPs can selectively target lysosomes in live cells and image mouse tumor with a high contrast and long-term tracking (up to 14 days) capability. The high-efficiency imaging-guided PDT against cancer cells and tumors is successfully demonstrated in vitro and in vivo.

Doping is an effective approach to regulate the physicochemical properties of carbon dots (CDs) and has received increasing attention in recent years. After CDs are doped with heteroatoms, their electronic structure, nanostructure, and chemical composition will be changed due to the overlapping atomic orbitals of the heteroatoms and carbon atoms, as well as the push/pull electron effect of heteroatoms. As compared with the non-metallic atoms, metal ions have more electron and unoccupied orbitals, and larger atomic radius, doping CDs with metal ions may induce noticeable alterations of the optical, electronic, and magnetic properties by changing the electron density distribution and energy gap of the CDs. In this review, we summarize the synthesis methods of metal ions-doped CDs (M−CDs), discuss the novel physicochemical properties originating from the doping of metal ions, and provide examples of applications in sensing, imaging, phototherapy, optoelectronics, and catalysis. Furthermore, we describe challenges in preparing M−CDs and provide an outlook for their future development.

Sonodynamic therapy (SDT), which involves a combination of low-intensity ultrasound (US) and a chemical sonosensitizer, has emerged as a promising minimally invasive and selective approach for the treatment of deep tumors. US not only increases cell membrane permeability, thereby enhancing the cellular uptake efficiency of chemical sonosensitizers, but also excites chemical sonosensitizers in deep tissues to generate reactive oxygen species (ROS), which in turn kill cancer cells. As compared with inorganic materials, organic sonosensitizers exhibit a defined chemical structure, controlled synthesis process, excellent biodegradability, and high ROS generation. However, they frequently exhibit poor water solubility, strong phototoxicity, and low tumor tissue targeting capacity. In this review, we address the currently accepted mechanisms in SDT and the recent progresses in organic sonosensitizers, discuss the strategies to improve the water solubility, tumor targeting capacity, biocompatibility, and therapeutic effects of organic sonosensitizers. The advantages of combining SDT with other cancer treatments, including phototherapy, chemodynamic therapy, chemotherapy, starvation therapy, gas therapy, and immune therapy are also demonstrated. Finally, the existing challenges and future perspectives on clinical SDT of tumor are discussed.

A family of anthracene carboxyimides with multi-color fluorescence have been successfully prepared, and their spectroscopic properties were investigated by UV–vis absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy. The photostability and solvatochromic fluorescence in organic solvents were also investigated. The parent anthracene carboxyimide 4a displays very strong green fluorescence (Φ F = 0.91 in EtOH), good pH stability and photostability, as well as a large Stokes shift. By attachment of different substituents at the 10-position of the anthracene carboxyimide, the fluorescence maxima could be effectively modulated from 500 nm to 615 nm. The 10-(picolylamine) substituted anthracene carboxyimides 5a and 5b exhibit large Stokes shifts (>80 nm) and significant positive solvatochromic fluorescence in organic solvents due to their intramolecular charge-transfer (ICT) character. Furthermore, cell staining experiments indicate that anthracene carboxyimides have excellent cell membrane permeability and good photo-bleaching resistance in living cells. Particularly, compound 5a is a specific mitochondria-targeting dye with red fluorescence. All these features enable anthracene carboxyimides to serve as promising candidates for bio-labeling/imaging applications.

Photodynamic therapy (PDT) has been a preferred clinical technology for treating superficial tumors due to its advantages of high selectivity, non-invasiveness and negligible drug resistance. However, the hypoxic tumor microenvironment weakens the efficiency of O2-dependent PDT. Moreover, the PDT process consumes a large amount of O2 and destroys the tumor blood vessels and further blocks the O2 supply to tumor sites. Therefore, developing more advanced materials and methods for PDT of the hypoxic tumor is an essential scientific significance. This tutorial review summarizes the strategies for improving the efficacy of PDT in hypoxic tumor therapy, which is categorized into three sections: (I) enhancing O2 concentration in the tumor; (II) disregarding hypoxia; and (III) exploiting hypoxia. The advantages of combining PDT with other therapeutics, such as chemotherapy, chemo-dynamic therapy, gas therapy, immunotherapy and gene therapy, are also demonstrated. Finally, the existing challenges and future perspectives on clinical PDT for hypoxic tumors are discussed.

Due to the advantages of in situ, real-time, and non-destructive detection of target molecules, fluorescent probes have become an indispensable tool in the fields of disease diagnosis and environmental and food safety monitoring. However, with the development of modern science and technology, sensing techniques have new challenges and requirements, such as increased sensitivity, better selectivity, and high-throughput visual detection in complicated practical samples. Developing effective fluorescent probes is still ongoing research. Fluorescent carbon dots (CDs) are a novel carbon-based nanomaterial that have attracted tremendous attention because of their excellent biocompatibility, tunable fluorescence properties, good photostability, and easy synthesis and surface modification, and they have shown great potential in fluorescent sensing and imaging applications. In this review, we summarize the recent advances in CD-based fluorescent probes, including the design strategies, sensing mechanisms, and their applications in sensitive and selective detection of public safety substances, organic amines, phenols, bioactive molecules, biological enzymes, and inorganic salts. A future perspective is introduced to highlight the existing challenges and possible strategies to overcome the problems in practical application of currently developed CD-based fluorescent probes, which may be instructive to the design of effective fluorescent probes in the future.

Carbon dots (CDs) are novel zero-dimensional carbonaceous nanomaterial, and they are featured with an attractive combination of physical, chemical, and biomedical properties including wide absorption spectrum, tunable fluorescence, excellent water solubility, outstanding photostability, and biocompatibility, which leads to their diverse applications as optically functional materials in various fields, e.g., fluorescence sensing, bioimaging, and drug delivery. Recently, it was revealed that CDs could be used as an effective photosensitizer to generate reactive oxygen species under light excitation, and/or a photothermal agent to convert light energy into heat, which enable them to be applied in photodynamic therapy or photothermal therapy for cancer treatment. In this review, we summarize the latest progress of research on CDs in phototherapy, including their use as nanocarriers for organic phototherapy agents, and highlight the strategies which are adopted to improve the therapeutic efficacy of CDs-based phototheranostics. Furthermore, we also discuss the challenges and prospects of the CDs-based phototheranostics towards clinical applications. We hope this review will provide critical insights to inspire new exciting discoveries on CDs from both fundamental and practical views so as to prompt their advances in the phototherapy.

A carbon dot (CD)-based fluorometric probe for oxytetracycline (OTC) detection utilizing a Forster resonance energy transfer (FRET) mechanism was firstly developed. Upon addition of OTC, the blue fluorescence of the CDs peaked at 405 nm was quickly quenched, with a new fluorescence peaked at 505 nm attributed to OTC was observed within 30 s. A visual fluorescent color change of the CDs solution from blue to green was discerned under a 365 nm UV light irradiation. The CDs displayed a high sensitivity and selectivity toward OTC with a low detection limit of 0.41 μM. Furthermore, the probe was applied to detect OTC in water, milk, and pork samples with a satisfied recovery.

S,N-doped carbon dots (S,N-CDs) were facilely prepared via a hydrothermal method by using thiourea and citric acid (CA) as precursors. The as-prepared S,N-CDs exhibited high stability in aqueous solution and were applied for fluorometric detection of tetracyclines (TCs). The approach was developed on the basic of the fluorescence of S,N-CDs at 440 nm, which was selectively quenched by TCs through the inner filter effect (IFE) mechanism. Moreover, the fluorescence of TCs with maximum at 600 nm could be used as the internal standard signal, resulting in a fluorometric spectral response. The limit of detection (LOD) was 0.25, 0.39 and 0.26 μM for tetracycline (TC), doxycycline (DC) and oxytetracycline (OTC), respectively. Furthermore, S,N-CDs were successfully utilized for the detection of residual TCs in fish and pork samples with acceptable recovery and good RSD.

Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT) holds great potential for efficient cancer therapy by inducing reactive oxygen species (ROS) or heat into tumor. Nevertheless, PDT or PTT suffers from some limitations, e.g., PTT requires long-time and high-power laser irradiation to generate enough heat, while the hypoxia microenvironment of tumor and the limit diffuse distance of ROS hamper the efficacy of oxygen-dependent PDT. Here we reported the carbon dots (CDs) which could simultaneously generate singlet oxygen (1O2), hydroxyl radical (OH ), and heat under a 635 nm laser irradiation, with a 1O2 generation quantum yield of 5.7% and photothermal conversion efficiency of 73.5% (the highest thus far for CDs). Significantly, the CDs can selectively accumulate in lysosome, which is an ideal organelle for phototherapy because of its key role in sustaining cellular activity and stability. Moreover, the CDs present one-photon excited (OPE) and two-photon excited (TPE) fluorescence, and excellent photoacoustic (PA) imaging capability. Combining the good biocompatibility, the as-prepared CDs was served as multi-functional phototheranostic agent for synergistic PA/fluorescence imaging, and PDT/PTT.

A colorimetric and fluorescent dual-responses chemosensor ( PT3 , a water-soluble polythiophene) for streptomycin was designed and synthesized. The structure of PT3 was characterized by using infrared spectroscopy, 1 H NMR and gel-permeation chromatography analyses. The conformational change of PT3 induced by streptomycin resulted in the red shift of absorption spectra and fluorescent quenching. Moreover, PT3 showed excellent selectivity for streptomycin over other antibiotics and biomolecules. PT3 could quantificationally detect streptomycin in the range of 2–70 μM with a detection limit of 0.2 μM (116 ppb), which is lower than the maximum residue limit defined by World Health Organization (200 ppb).

Carbon dots (CDs) with blue fluorescence were synthesized through hydrothermal treatment of p-dihydroxybenzene and hydrazine hydrate. The fluorescence of the investigated CDs could be selectively quenched by iron ions (Fe3+) because of the strong metal-ligand coordination and electrostatic interactions between the large amount of hydroxyl, amino, and carboxyl groups on CDs’ surface and Fe3+. Interestingly, this non-fluorescent CDs + Fe3+ complex displayed a sensitive and selective turn-on fluorescence toward ampicillin with a limit of detection of 0.70 μM. The sensing process could be observed by naked eyes under the 365 nm UV light irradiation. Importantly, CDs + Fe3+ complex had been successfully applied in the detection of ampicillin in river water.

Cyan-emitting carbon dots (CDs) with a high fluorescence quantum yield of 49% were synthesized through hydrothermal treatment of 1,3,6-trinitropyrene and Na2SO3 in alkaline solution. The as-prepared CDs could be used as a label-free fluorescent probe for sensitive and selective detection of ferric ions (Fe3+). Spectral measurements revealed that the fluorescence of the CDs was quenched significantly and the emission wavelength was red-shifted from 490 nm to 515 nm upon the addition of Fe3+, which was demonstrated to be due to the formation of Fe3+-phenol complex induced inner filter effect. Furthermore, with the addition of dopamine (DA), the strong binding interaction between the catechol groups of DA and Fe3+ can extract Fe3+ from the surface of CDs, and turn on the quenched fluorescence. The formation of polydopamine (PDA) by DA and Fe3+ generated an emission peak at ∼470 nm, making the CDs + Fe3+ system a ratiometric fluorescence sensor for DA as well and the sensing processes could be directly observed by naked eye under a 365 nm UV light. Low limits of detection of 0.86 μM and 0.18 μM were achieved for Fe3+ and DA, respectively.

We have developed a conceptually new design strategy for fluorescent probes based on a combinational use of photo-induced electron transfer (PET) and excited-state intramolecular proton transfer (ESIPT) mechanisms. This turn-on fluorescence thiol-probe shows fast responses to mercapto-biomolecules with high sensitivity and selectivity. Furthermore, it was used for imaging in living cells with excellent performance.