Efficient Cascade Resonance Energy Transfer in Dynamic Nanoassembly for Intensive and Long-Lasting Multicolor Chemiluminescence

Finely-Tuning Chemiluminescent Color of CdTe Nanocrystals and Its Application for Near-Infrared Semi-Automatic Immunoassay

Chemiluminescence (CL), especially commercialized CL immunoassay (CLIA), is normally performed within the eye-visible region of the spectrum by exploiting the electronic-transition-related emission of the molecule luminophore. Herein, dual-stabilizers-capped CdTe nanocrystals (NCs) is employed as a model of nanoparticulated luminophore to finely tune the CL color with superior color purity. Initialized by oxidizing the CdTe NCs with potassium periodate (KIO4), intermediates of the reactive oxygen species (ROS) tend to charge CdTe NCs in both series-connection and parallel-connection routes and dominate the charge-transfer CL of CdTe NCs. The CdTe NCs/KIO4 system can exhibit color-tunable CL with the maximum emission wavelength shifted from 694 nm to 801 nm, and the red-shift span is over 100 nm. Both PL and CL of each of the CdTe NCs are bandgap-engineered; the change in the NCs surface state via CL reaction enables CL of each of the CdTe NCs to be red-shifted for ∼20 nm to PL, while the change in the NCs surface state via labeling CdTe NCs to secondary-antibody (Ab2) enables CL of the CdTe NCs-Ab2 conjugates to be red-shifted for another ∼20 nm to bare CdTe NCs. The CL of CdTe753-Ab2/KIO4 is ∼791 nm, which can perform near-infrared CL immunoassay and semi-automatically determined procalcitonin (PCT) on commercialized in vitro diagnosis (IVD) instruments.

Catalytic NIR chemiluminescence sensor with enhanced persistence and intensity for in vivo imaging

Chemiluminescence (CL) is a self-illumination phenomenon that involves the emission of light from chemical reactions, and it provides favorable spatial and temporal information on biological processes. However, it is still a great challenge to construct effective CL sensors that equip strong CL intensity, long emission wavelength, and persistent luminescence for deep tissue imaging. Here, we report a liposome encapsulated polymer dots (Pdots)-based system using catalytic CL substrates (L-012) as energy donor and fluorescent polymers and dyes (NIR 695) as energy acceptors for efficient Near-infrared (NIR) CL in vivo imaging. Thanks to the modulation of paired donor and acceptor distance and the slow diffusion of biomarker by liposome, the Pdots show a NIR emission wavelength (λ em, max = 720 nm), long CL duration (>24 h), and a high chemiluminescence resonance energy transfer efficiency (46.5 %). Furthermore, the liposome encapsulated Pdots possess excellent biocompatibility, sensitive response to H2O2, and persistent whole-body NIR CL imaging in the drug-induced inflammation and the peritoneal metastatic tumor mouse model. In a word, this NIR-II CL nanoplatform with long-lasting emission and high spatial-temporal resolution will be a concise strategy in deep tissue imaging and clinical diagnostics.

Multi-step FRET systems based on discrete supramolecular assemblies

Fluorescence resonance energy transfer (FRET) from the excited state of the donor to the ground state of the acceptor is one of the most important fluorescence mechanisms and has wide applications in light-harvesting systems, light-mediated therapy, bioimaging, optoelectronic devices, and information security fields. The phenomenon of sequential energy transfer in natural photosynthetic systems provides great inspiration for scientists to make full use of light energy. In recent years, discrete supramolecular assemblies (DSAs) have been successively constructed to incorporate donor and multiple acceptors, and to achieve multi-step FRET between them. This perspective describes recent advances in the fabrication and application of DSAs with multi-step FRET. These DSAs are categorized based on the non-covalent scaffolds, such as amphiphilic nanoparticles, host-guest assemblies, metal-coordination scaffolds, and biomolecular scaffolds. This perspective will also outline opportunities and future challenges in this research area.

Machine learning assisted discrimination and detection of antibiotics by using multicolor microfluidic chemiluminescence detection chip

The fabrication of multicolor chemiluminescence (CL) sensing chip for the discrimination and detection of multianalytes remains a great challenge. Herein, machine learning assisted multicolor microfluidic CL detection chip for the identification and concentration prediction of antibiotics was presented. Firstly, a three-channel microfluidic CL detection chip was fabricated. The three detection zones of the microfluidic detection chip were modified with CL catalyst Co(II) and different CL reagents including luminol, luminol mixed with fluorescein, and luminol mixed with phloxine B, respectively. Strong blue, green and pink-purple colored light emissions can be generated from the three detection zones in the presence of H2O2 solution. The three multicolor CL emissions show different degrees of reduce in intensity and change in color in the presence of different antibiotics, including diethylstilbestro (DES), metronidazole (MNZ), kanamycin (KAN), isoniazide (INH), and ceftiofur sodium (CS), resulting in distinct fingerprint-like response patterns. The red (R), green (G), blue (B) and gray scale values of the three multicolor light emissions were extracted and ten characteristic sensing parameters were chosen to obtain multicolor CL response database. Then, machine learning assisted data analysis were carried out. The five antibiotics can be facilely classified by using principal component analysis (PCA) and hierarchical clustering analysis (HCA), and further quantified by using deep neural networks (DNN) algorithm. Good results were obtained for identification of binary antibiotic mixtures, spiked antibiotics in water samples, and unknown antibiotic samples. Satisfied results were obtained for concentration prediction of antibiotics. This work provides a simple machine learning assisted and multicolor microfluidic CL detection chip based CL sensing strategy for discrimination and quantitative detection of multiple analytes.

Chemiluminescence sensing for Hg2+ in environment water using carbon materials from PVC dechlorination as signal initiator

Chemiluminescence (CL) sensing with good performance remains a challenge. The utilization of secondary residues from polyvinyl chloride (PVC) treatment is the key to improve PVC recycling rate. Herein, dechlorinated carbon materials from PVC/iron scrap co-treatment in subcritical water were used as CL sensing element. It was found that tiny changes in the spatial structure of aptamer could cause huge changes in CL signal of the residue-luminol system. A CL biosensor was constructed for mercury in environment water for the first time. The detection limit was estimated to be 0.37 pM. High sensitivity was mainly due to strong CL triggering and signal amplification from residues and effective regulating residue activity by aptamer space dimension. For real water samples, the results by residue CL analysis were consistent with that by cold vapor atom adsorption spectroscopy (CVAAS). Most strikingly, the used material was secondary residues from the treatment of PVC waste, which reduced the time and energy consumption of CL sensing. This research proposed the approach for routine monitoring mercury in environment but also provided the reference for developing other environmentally beneficial analysis platforms.

Escherichia coli-Based In Situ Triggerable Probe as an Amplifier for Sensitive Diagnosis and Penetrated Therapy of Cancer

Escherichia coli (E. coli) was used for cancer therapy due to the tumor-targeting, catalytic, and surface-reducing properties. Effective diagnosis combined with treatment of cancer based on E. coli, however, was rarely demonstrated. In this study, E. coli was used to surface reduce HAuCl4 and as a carrier to modify riboflavin (Rf) and luminol (E-Au@Rf@Lum). After targeted delivery to tumor, the E-Au@Rf@Lum probe could actively emit 425 nm blue-violet chemiluminescence (CL) to achieve cell imaging for cancer diagnosis. Furthermore, this light could in situ trigger the photosensitizer (Rf) through CL resonance energy transfer, which produces reactive oxygen species (ROS) for accurate photodynamic therapy. In return, the excessive ROS enhanced the blue-violet light which was further absorbed by Rf, and ROS production was cyclically amplified. Abundant ROS broke down the dense extracellular matrix network and penetrated deep into tumors. Besides, E. coli with excellent catalytic property could decompose H2O2 to O2 to relieve tumor hypoxia for a long time and enhance the photosensitized process of Rf. By self-illumination, effective penetration, and tumor hypoxia relief, this work opens a self-amplified therapy modality to tumor.

AIE Nanozyme-Based Long Persistent Chemiluminescence and Fluorescence for POCT of Pathogenic Bacteria

Pathogenic bacteria are widely distributed in diverse environments and significantly threaten human health. Point-of-care testing (POCT) is a valuable way for early warnings of bacteria threat. Herein, a chemiluminescence (CL)-based ratiometric sensing platform was constructed for sensitive POCT of bacteria according to a newly designed aggregation-induced emission (AIE) molecule. The new AIE molecule presents oxidase-like properties (named as AIEzyme) and can trigger long persistent CL of luminol (LUM) with strong intensity in the absence of H2O2. The CL emission can be monitored with the naked eye for over 2 h. The emission mechanism is explored and may be attributed to the persistent reactive oxygen species generation of the AIEzyme according to the cyclic energy transfer between the AIEzyme and luminol, which catalyzes CL of luminol. Based on the CL resonance energy transfer mechanism, an afterglow luminescence system is further developed, which is used to construct a ratiometric biosensor for detection of pathogenic bacteria. With a homemade holder as a detection room and a smartphone as an analyzer, the portable biosensing platform is used for quantitative POCT of bacteria in real samples with good recovery. The detection is free of H2O2 and an external excitation source, which not only simplifies the operation but reduces interference. Specifically, the long persistent luminescence and the ratiometric strategy can significantly improve accuracy, providing an instructive way for point-of-need analysis, for example, SARS-CoV-2 detection and bioimaging analysis.

Vanillin-Catalyzed highly sensitive luminol chemiluminescence and its application in food detection

Among various chemiluminescence (CL) systems, luminol-H₂O₂ system is used extensively due to its cheapness and sensitivity. Herein, 4-hydroxy-3-methoxybenzaldehyde, known as vanillin, was firstly found to be able to catalyze H₂O₂ very efficiently to produce ^•OH and O₂^•-, which can be used to enhance the CL of luminol-H₂O₂ as Co⁺. In alkaline aqueous solution, vanillin catalyzed the dissociation of H₂O₂ into active ^•OH and O₂^•- radicals and accelerated luminol-H₂O₂ reaction to emit strong CL signal. Combining the stabilizing function of β-CD, CL intensity of luminol-H₂O₂ was enhanced further. Thus, dual-signal amplification of luminol-H₂O₂ chemiluminescence based on the catalyzing function of vanillin and the stabilizing function of β-CD was proposed and its mechanism was explored deeply in the manuscript. Interestingly, vanillin is a highly prized flavor compound broadly used as food additive, however, the excessive intake of vanillin is harmful to human and thus the determination of vanillin is very important. On the basis of the luminol-β-CD-H₂O₂/vanillin reaction, a low-cost, rapid and simple CL sensor has been established to detect vanillin. The sensor was able to detect vanillin in the range of 1.0 μM ∼ 75 μM with a detection limit of 0.89 μM (S/N = 3). It can also be used for CL imaging detection with satisfactory results.

Enhanced Chemiluminescence under the Nanoconfinement of Covalent-Organic Frameworks and Its Application in Sensitive Detection of Cancer Biomarkers

Chemiluminescence (CL) with intensive emission has been pursued for decades. It is still challenging to find a new mechanism to enhance CL. In this work, confinement-enhanced CL was developed for the first time by the coembedding of N-(aminobutyl)-N-(ethylisoluminol) (ABEI) and Co²⁺ into gold nanoparticle-modified covalent-organic frameworks (COFs). For the consideration of improving the hydrophilicity of COFs and facilitating subsequent biological modification, gold nanoparticles were first reduced on the COF surface (Au-COF) in situ without other reducing reagents. By virtue of the abundant imine bond and π backbones, ABEI and Co²⁺ were embedded in Au-COF synergistically through π-π stacking and coordination. The confinement of ABEI and Co²⁺ into Au-COF brought an over 20-fold enhancement of CL intensity compared to that of adding them to a liquid phase, which benefitted from the three aspects of the confinement effect, including the molecular enrichment effect, the physical constraint effect, and the molecular preorganization effect. As proof of concept, a lipid-protein dual-recognition sandwich strategy based on this CL-functionalized COF was developed for the detection of breast cancer cell line-derived extracellular vesicles (EVs) with four orders of magnitude improvement in the detection limit compared to ELISA. The successful distinction of human epidermal growth factor receptor 2 (HER2)-positive patients from HER2-negative patients indicated the great application potential of the proposed bioassay in HER2-positive breast cancer diagnosis. This work proposed a novel enhancement mechanism for CL based on crystalline porous materials, which provides a new perspective for the development of CL-functionalized materials for biosensors and bioassays.

Chemiluminescent carbon nanodots for dynamic and guided antibacteria

Advanced antibacterial technologies are needed to counter the rapid emergence of drug-resistant bacteria. Image-guided therapy is one of the most promising strategies for efficiently and accurately curing bacterial infections. Herein, a chemiluminescence (CL)-dynamic/guided antibacteria (CDGA) with multiple reactive oxygen species (ROS) generation capacity and chemiexcited near-infrared emission has been designed for the precise theranostics of bacterial infection by employing near-infrared emissive carbon nanodots (CDs) and peroxalate as CL fuels. Mechanistically, hydrogen peroxide generated in the bacterial microenvironment can trigger the chemically initiated electron exchange between CDs and energy-riched intermediate originated from the oxidized peroxalate, enabling bacterial induced inflammation imaging. Meanwhile, type I/II photochemical ROS production and type III ultrafast charge transfer from CDs under the self-illumination can inhibit the bacteria proliferation efficiently. The potential clinical utility of CDGA is further demonstrated in bacteria infected mice trauma model. The self-illuminating CDGA exhibits an excellent in vivo imaging quality in early detecting wound infections and internal inflammation caused by bacteria, and further are proven as efficient broad-spectrum antibacterial nanomedicines without drug-resistance, whose sterilizing rate is up to 99.99%.

Direct and Specific Detection of Glyphosate Using a Phosphatase-like Nanozyme-Mediated Chemiluminescence Strategy

Most organophosphorus pesticide (OP) sensors reported in the literature rely on the inhibition effect of OPs on the activity of acetylcholinesterase (AChE), which suffer from the drawbacks of lack of selective recognition of OPs, high cost, and poor stability. Herein, we proposed a novel chemiluminescence (CL) strategy for the direct detection of glyphosate (an organophosphorus herbicide) with high sensitivity and specificity, which is based on the porous hydroxy zirconium oxide nanozyme (ZrO_X-OH) obtained via a facile alkali solution treatment of UIO-66. ZrO_X-OH displayed excellent phosphatase-like activity, which could catalyze the dephosphorylation of 3-(2'-spiroadamantyl)-4-methoxy-4-(3'-phosphoryloxyphenyl)-1,2-dioxetane (AMPPD) to generate strong CL. The experimental results showed that the phosphatase-like activity of ZrO_X-OH is closely related to the content of hydroxyl groups on their surface. Interestingly, ZrO_X-OH with phosphatase-like properties exhibited a unique response to glyphosate because of the consumption of the surface hydroxyl group by the unique carboxyl group of glyphosates and was thus employed to develop a CL sensor for direct and selective detection of glyphosate without using bio-enzymes. The recovery for glyphosate detection of cabbage juice ranged from 96.8 to 103.0%. We believe that the as-proposed CL sensor based on ZrO_X-OH with phosphatase-like properties supplies a simpler and more highly selective approach for OP assay and provides a new method for the development of CL sensors for the direct analysis of OPs in real samples.

A novel enzyme-free long-lasting chemiluminescence system based on a luminol functionalized β-cyclodextrin hydrogel for sensitive detection of H2O2 in urine and cells

A novel long-lasting chemiluminescent (CL) hydrogel (β-CD@luminol-Co²⁺) was synthesized by embedding luminol and cobalt ions (Co²⁺) into β-cyclodextrin (β-CD) through non-covalent interactions. Due to its porous structure and viscosity, the synthesized β-CD@luminol-Co²⁺ hydrogel exhibited long-lasting CL properties and can emit light for 12 h under both alkaline and neutral conditions. In addition, the CL intensities of β-CD@luminol-Co²⁺ were linear with the logarithm of the hydrogen peroxide (H₂O₂) concentration in the range of 1.0 × 10^-11-1.0 × 10^-7 M, and the limit of detection (LOD) was 0.63 × 10^-11 M and 0.85 × 10^-11 M under alkaline and neutral conditions, respectively. On this basis, an enzyme-free CL sensor based on β-CD@luminol-Co²⁺ was fabricated for the sensitive detection of H₂O₂ in human urine samples under alkaline conditions, and showed good accuracy and recovery. Since β-CD@luminol-Co²⁺ showed good CL properties under neutral conditions, it can be applied to detect H₂O₂ in cells. In order to prolong the emission wavelength of β-CD@luminol-Co²⁺ for better cell imaging, β-CD@luminol-FL-Co²⁺ was prepared by adding fluorescein (FL) to β-CD@luminol-Co²⁺. The as-prepared β-CD@luminol-FL-Co²⁺ also displayed long-lasting CL properties and showed a linear relationship with H₂O₂ concentrations. In addition, the maximum emission wavelength of β-CD@luminol-FL-Co²⁺ was 520 nm, which was red-shifted by 95 nm compared with β-CD@luminol-Co²⁺. The methyl thiazolyl tetrazolium (MTT) assay results and confocal microscopy images illustrated that β-CD@luminol-FL-Co²⁺ had low toxicity and can be taken up by A549 cells. Finally, β-CD@luminol-FL-Co²⁺ was successfully applied for CL imaging and detection of intracellular H₂O₂ in A549 cells under neutral conditions. This enzyme-free long-lasting CL system with high sensitivity can also be extended to real-time monitoring of H₂O₂in vivo.

Hydrogen-bond-driven self-assembly of chemiluminophore affording long-lasting in vivo imaging

Developing chemiluminescence probe with a slow kinetic profile, even a constant emission within analytical time, would improve the analytical sensitivity, but still remains challenging. This work reports a novel strategy to afford long-lasting in vivo imaging by developing a self-assembled chemiluminophore HPQCL-Cl via the introduction of the hydrogen-bond-driven self-assembled dye HPQ to Schaap's dioxetane. Compared with classical chemiluminophore HCL, self-assembled HPQCL-Cl was isolated from the physiological environment, thereby lowering its deprotonation and prolonging its half-life. Based on HPQCL-Cl, the long-lasting in vivo imaging of 9L-lacz tumor was achieved by developing a β-gal-responsive probe. Its signals remained constant (<5% change) for about 20 min, which may provide a wide time window for the determination of β-gal. This probe also showed high tumor-to-normal tissue ratio throughout tumor resection, highlighting its potential in image-guided clinical surgery.

Chemiluminescent Nanogels as Intensive and Stable Signal Probes for Fast Immunoassay of SARS-CoV-2 Nucleocapsid Protein

It is highly desired to exploit good nanomaterials as nanocarriers for immobilizing chemiluminescence (CL) reagents, catalysts and antibodies to develop signal probes with intensive and stable CL properties for immunoassays. In this work, N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and Co2+ bifunctionalized polymethylacrylic acid nanogels (PMAANGs-ABEI/Co2+) were synthesized via a facile strategy by utilizing carboxyl group-rich PMAANGs as nanocarriers to immobilize ABEI and Co2+. The obtained PMAANGs-ABEI/Co2+ showed extraordinary CL performance. The CL intensity is 2 orders of magnitude higher than that of previously reported ABEI and Cu2+-cysteine complex bifunctionalized gold nanoparticles with high CL efficiency. This was attributed to the excellent catalytic ability of Co2+ and polymethylacrylic acid nanogels, as well as the improved CL catalytic efficiency from a decreased spatial distance between ABEI and the catalyst. The as-prepared nanogels also possess abundant surface reaction sites and good CL stability. On this basis, a sandwich immunoassay for the nucleocapsid protein of SARS-CoV-2 (N protein) was developed by using magnetic bead connected primary antibody as a capture probe and PMAANGs-ABEI/Co2+ connected secondary antibody as a signal probe. The linear range of the proposed method for N protein detection was 3.16-316 ng/mL, and its detection limit was 2.19 ng/mL (S/N = 3). Moreover, the developed immunoassay was performed with a short incubation time of 5 min, which greatly reduced the detection time for N protein. By using corresponding antibodies, the developed strategy might be applied to detect other biomarkers.

A chemical timer approach to delayed chemiluminescence

Although the onset time of chemical reactions can be manipulated by mechanical, electrical, and optical methods, its chemical control remains highly challenging. Herein, we report a chemical timer approach for manipulating the emission onset time of chemiluminescence (CL) reactions. A mixture of Mn²⁺, NaHCO₃, and a luminol analog with H₂O₂ produced reactive oxygen species (ROS) radicals and other superoxo species (superoxide containing complex) with high efficiency, accompanied by strong and immediate CL emission. Surprisingly, the addition of thiourea postponed CL emission in a concentration-dependent manner. The delay was attributed to a slow-generation-scavenging mechanism, which was found to be generally applicable not only to various types of CL reagents and ROS radical scavengers but also to popular chromogenic reactions. The precise regulation of CL kinetics was further utilized in dynamic chemical coding with improved coding density and security. This approach provides a powerful platform for engineering chemical reaction kinetics using chemical timers, which is of application potential in bioassays, biosensors, CL microscopic imaging, microchips, array chips, and informatics.

Meter-scale chemiluminescent carbon nanodot films for temperature imaging

Chemiluminescence (CL), as one class of luminescence driven by chemical reaction, exhibits obvious temperature-dependence in its light emission process. Herein, temperature-dependent CL emission of carbon nanodots (CDs) in the chemical reaction of peroxalate and hydrogen peroxide is demonstrated and temperature imaging based on the temperature-dependent CL has been established for the first time. In detail, the temperature-dependent CL emission of CDs in the chemical reaction of peroxalate and hydrogen peroxide is observed, and the linear relationship between the CL intensity and temperature is demonstrated in both the CL solution and film, enabling their applications in temperature sensing and imaging capabilities. The increase of the CL emission with temperature can be attributed to the accelerated electron exchange between the CDs and intermediate generated in the peroxalate system. Meter-scale chemiluminescent CD films have been constructed. The CL sensor based on the films presents a high spatial resolution of 0.4 mm and an outstanding sensitivity of 0.08 °C^-1, which is amongst the best values for the thermographic luminophores. With the unique temperature response and flexible properties, non-planar, meter-scale and sensitive palm temperature imaging has been achieved. These findings present new opportunities for designing CL-based temperature probes and thermography.

A General Route for Chemiluminescence of n-Type Au Nanocrystals

The photoluminescence, electroluminescence, and electrochemiluminescence from nanocrystals (NCs) have been extensively exploited for both fundamental and applied investigation over two decades, while the understanding of chemiluminescence (CL) from NCs is still far from clear by now. Herein, a general route for triggering CL from NC luminophore is proposed by extensively exploiting the charge transfer between n-type NCs and oxidants. Oxidants, such as K₂S₂O₈, H₂O₂, KMnO₄, and NaClO, can chemically inject the hole onto the valence band (VB) of methionine-capped n-type AuNCs (Met@AuNCs) and enable the occurrence of efficient radiative-charge-recombination between the chemically injected exogenous VB hole and the pre-existed endogenous conduction band (CB) electron, which eventually results in single-color and defect-involved CL with the maximum emission wavelength around 824 nm. The CL of Met@AuNCs/oxidant is qualified for ultrasensitive CL immunoassay in a similar procedure to the biotin-avidin and magnetic separation involved commercial CL immunoassay and exhibits acceptable performance for linearly determining carcinoembryonic antigen from 50 pg/mL to 100 ng/mL with a limit of detection of 10 pg/mL (S/N = 3). This strategy provides a general route to develop nanoparticulate CL luminophores and might eventually enable CL multiplexing assay via extensively exploiting the CL of different wavebands.

Multicharged cyclodextrin supramolecular assemblies

Multicharged cyclodextrin (CD) supramolecular assemblies, including those based on positively/negatively charged modified mono-6-deoxy-CDs, per-6-deoxy-CDs, and random 2,3,6-deoxy-CDs, as well as parent CDs binding positively/negatively charged guests, have been extensively applied in chemistry, materials science, medicine, biological science, catalysis, and other fields. In this review, we primarily focus on summarizing the recent advances in positively/negatively charged CDs and parent CDs encapsulating positively/negatively charged guests, especially the construction process of supramolecular assemblies and their applications. Compared with uncharged CDs, multicharged CDs display remarkably high antiviral and antibacterial activity as well as efficient protein fibrosis inhibition. Meanwhile, charged CDs can interact with oppositely charged dyes, drugs, polymers, and biomacromolecules to achieve effective encapsulation and aggregation. Consequently, multicharged CD supramolecular assemblies show great advantages in improving drug-delivery efficiency, the luminescence properties of materials, molecular recognition and imaging, and the toughness of supramolecular hydrogels, in addition to enabling the construction of multistimuli-responsive assemblies. These features are anticipated to not only promote the development of CD-based supramolecular chemistry but also contribute to the rapid exploitation of these assemblies in diverse interdisciplinary applications.

Removed heavy metal ions from wastewater reuse for chemiluminescence: Successive application of lignin-based composite hydrogels

The novel sulfomethylated lignin-grafted-polyacrylic acid (SL-g-PAA) hydrogel was fabricated in this work via a facile and green synthetic strategy for the efficient removal of heavy metal ions from wastewater, and then successively reused for chemiluminescence (CL). The sulfomethylation of lignin was first performed to improve its water solubility and introduce numerous active sites for adsorption of heavy metal ions. The as-synthesized SL-g-PAA hydrogel with high content of lignin exhibited the highly efficient and rapid removal of various metal ions from simulated wastewater. More importantly, the spent hydrogel (M²⁺@SL-g-PAA) after adsorption was reused for the first time to develop a new CL system by an ingenious strategy, in which these metal ions adsorbed on M²⁺@SL-g-PAA act as heterogeneous catalytic sites to catalyze the CL reaction between N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and H₂O₂. The resultant CL system displayed high CL intensity and long duration time, which could be observed by naked eye in the dark and lasted for > 24 h. The combination of facile fabrication process, renewable raw materials, and ingenious strategy for successive application in adsorption and CL endows this lignin-based composite hydrogel with a great potential for application in wastewater treatment, biological imaging and cold light sources.

Direct and Indirect Chemiluminescence: Reactions, Mechanisms and Challenges

Emission of light by matter can occur through a variety of mechanisms. When it results from an electronically excited state of a species produced by a chemical reaction, it is called chemiluminescence (CL). The phenomenon can take place both in natural and artificial chemical systems and it has been utilized in a variety of applications. In this review, we aim to revisit some of the latest CL applications based on direct and indirect production modes. The characteristics of the chemical reactions and the underpinning CL mechanisms are thoroughly discussed in view of studies from the very recent bibliography. Different methodologies aiming at higher CL efficiencies are summarized and presented in detail, including CL type and scaffolds used in each study. The CL role in the development of efficient therapeutic platforms is also discussed in relation to the Reactive Oxygen Species (ROS) and singlet oxygen (1O2) produced, as final products. Moreover, recent research results from our team are included regarding the behavior of commonly used photosensitizers upon chemical activation under CL conditions. The CL prospects in imaging, biomimetic organic and radical chemistry, and therapeutics are critically presented in respect to the persisting challenges and limitations of the existing strategies to date.

Multifunctional MgO/HKUST-1 Composite for Capture, Catalysis, and Cyclic Cataluminescence Detection of Esters All-In-One to Rapidly Identify Scented Products

The integration of metallic oxide and metal-organic frameworks has attracted considerable attention as obtained composite materials because they show synergistic effects in applications of catalysis and sensing. Herein, we developed the hybrid MgO and HKUST-1 for efficient capture, catalysis, and cyclic cataluminescence (CCTL) detection of esters all-in-one to rapidly identify scented products. The multifunctional MgO/HKUST-1 composite with high CCTL activity was synthesized and characterized. The multifunctional MgO/HKUST-1 composite acts as an enrichment material for ester capture and serves as a catalyst, assisting the analyte to trigger multistage signals. The multistage signals of ester-containing scented products also satisfy the exponential decay equation with a certain τ-value. The τ-values obtained by the CCTL system were applied to identify the brands of essential oils. The working temperature served as the sensor element to obtain various τ-values. The τ-values constituted a digital code to label the different brands of cigarettes with the same aroma type. The multistage signals could be used to distinguish the origin regions of essential oils and tobacco. This work combines the CCTL strategy with the sample pretreatment, opening up a new direction to develop CCL and providing a new platform to rapidly identify ester-containing scented products.

Encoding Fluorescence Anisotropic Barcodes with DNA Fameworks

Fluorescence anisotropy (FA) holds great potential for multiplexed analysis and imaging of biomolecules since it can effectively discriminate fluorophores with overlapping emission spectra. Nevertheless, its susceptibility to environmental variation hampers its widespread applications in biology and biotechnology. In this study, we design FA DNA frameworks (FAFs) by scaffolding fluorophores in a fluorescent protein-like microenvironment. We find that the FA stability of the fluorophores is remarkably improved due to the sequestration effects of FAFs. The FA level of the fluorophores can be finely tuned when placed at different locations on an FAF, analogous to spectral shifts of protein-bound fluorophores. The high programmability of FAFs further enables the design of a spectrum of encoded FA barcodes for multiplexed sensing of nucleic acids and multiplexed labeling of live cells. This FAF system thus establishes a new paradigm for designing multiplexing FA probes for cellular imaging and other biological applications.

Multicolor Chemiluminescent Resonance Energy-Transfer System for In Vivo High-Contrast and Targeted Imaging

Chemiluminescence (CL) resonance energy transfer (CRET) has received great attention due to its fascinating applications in in vivo imaging and photodynamic therapy. Here, we report a highly efficient CRET polymer dot (CRET-Pdots)-based system using catalytic CL reagents as energy donors and fluorescent polymers and dyes as energy acceptors. CRET-Pdots consist of Fe(III) deuteroporphyrin IX (CL catalyst), fluorescent polymers, and dyes. The CL intensity and duration are markedly enhanced by using ultrasensitive catalytic CL reaction of luminol analogue-H₂O₂, and the CL emission wavelength can be adjusted by one-step/two-step energy-transfer strategies. CRET-Pdots show intensive multicolor CL (about 3000× enhanced), an adjustable emission wavelength (470-720 nm), long CL duration (over 8 h), and a high CRET efficiency (50%). CRET-Pdots possess excellent biocompatibility, sensitive response to reactive oxygen species (ROS), and ultrahigh catalytic activity. They are successfully used for high-contrast real-time ROS imaging and in vivo tumor-targeted imaging with an excellent signal-to-noise ratio (over 90).

Energy transduction through FRET in self-assembled soft nanostructures based on surfactants/polymers: current scenario and prospects

The self-assembled systems of surfactants/polymers, which are capable of supporting energy funneling between fluorophores, have recently gained significant attraction. Surfactant and polymeric micelles form nanoscale structures spanning a radius of 2-10 nm are generally suitable for the transduction of energy among fluorophores. These systems have shown great potential in Förster resonance energy transfer (FRET) due to their unique characteristics of being aqueous based, tendency to remain self-assembled, spontaneous formation, tunable nature, and responsiveness to different external stimuli. This review presents current developments in the field of energy transfer, particularly the multi-step FRET processes in the self-assembled nanostructures of surfactants/polymers. The part one of this review presents a background and brief overview of soft systems and discusses certain aspects of the self-assemblies of surfactants/polymers and their co-solubilization property to bring fluorophores to close proximity to transduce energy. The second part of this review deals with single-step and multi-step FRET in the self-assemblies of surfactants/polymers and links FRET systems with advanced smart technologies including multicolor formation, data encryption, and artificial antenna systems. This review also discusses the diverse examples in the literature to present the emerging applications of FRET. Finally, the prospects regarding further improvement of FRET in self-assembled soft systems are outlined.

Quantitative Supramolecular Heterodimerization for Efficient Energy Transfer

The challenge of quantitatively forming self-assembled heterodimers without other equilibrium by-products is overcome through self-sorting favored by the introduction of designed shape-complementary moieties. Such a supramolecular strategy based on cucurbit[8]uril-directed dimerization is further applied to generate hetero-chromophore dimers quantitatively, leading to efficient energy transfer (>85 %) upon photoexcitation.