Nanoparticles (NPs) are alternative chemiluminescence (CL) luminophores to molecular luminophores and are strongly anticipated to extend molecular luminophore-tagged commercial CL immunoassays (CLIA) with wavebands beyond the eye-visible region and sensitivity beyond the pg/mL level. Herein, a surficial bond-involved repetitive excitation strategy for near-infrared CL with enhanced photons per luminophore is proposed by exploiting l-methionine (l-Met)-capped gold NPs (AuNPs) as luminophores. The surficial Au-S bonds of l-Met@AuNPs can be involved in the procedure of NP core excitation via oxidation, and bring out defect-involved CL around 830 nm. Because there are plenty of Au-S bonds on every AuNP core, l-Met@AuNPs can be repetitively excited over a hundred times and give off greatly enhanced CL photons per luminophore than all molecular CL luminophores. CL of l-Met@AuNPs/(NH4)2S2O8 can directly enable automatic near-infrared CLIA for myoglobin (MYO) determination on in vitro diagnostic instruments, with a limit of detection of 10 fg/mL (S/N = 3), which significantly surpasses the threshold of molecular luminophores. This Au-S bond-triggered AuNP CL strategy not only offers an alternative to molecular CL strategies with improved sensitivity and to II-VI NP CL strategies with fewer toxic concerns, but also indicates that exploiting the surficial bond energy of NPs could be an alternative to designing NPs with unique morphology, structure, and composition in the CL domain.

Near-infrared (NIR) electrogenerated chemiluminescence (ECL) offers superior tissue penetration and reduced background for bioimaging, yet stable, efficient NIR luminophores remain rare. This study investigates the photophysical dynamics and ECL mechanisms of two donor-acceptor-donor platinum-acetylide oligomers, Pt2DTB and Pt2BTDEDOT. Using femtosecond transient absorption spectroscopy, we identify an ultrafast intersystem crossing process (τISC ≈ 0.5-1.2 ps) driven by strong spin-orbit coupling, which establishes a robust triplet reservoir. Temperature-dependent TRPL and oxygen-quenching measurements support a triplet-mediated delayed-emission channel, while density functional theory calculations reveal large singlet-triplet energy gaps, ΔEST > 0.6 eV, that disfavor efficient TADF. These observations are consistent with a Singlet-Initiated ISC-Triplet pathway involving Triplet-Triplet Annihilation (SIT-TTA). While electrochemical analysis shows that the radical anions of these oligomers are unstable, leading to weak annihilation ECL, the use of tripropylamine (TPrA) as a coreactant bypasses this instability, enhancing ECL intensity by 2-3 orders of magnitude. The resulting emission is significantly red-shifted, indicating a stabilized lower-energy emissive manifold. These findings provide critical design principles for organometallic NIR emitters, demonstrating that coreactant strategies are essential for leveraging triplet reservoirs in high-sensitivity optoelectronics.

Quantum dots (QDs) are attractive electrochemiluminescence (ECL) luminophores because of their quantum confinement and tunable band structures; however, QD-based ECL is often limited by low efficiency and inadequate operational stability. Here, low-toxic CuInS2 QDs (CIS) are assembled into an aerogel through a facile in situ gelation strategy to enhance ECL emission. The aerogel architecture strengthens interparticle electronic coupling, lowers the interparticle charge-transfer barrier, and facilitates charge separation and transport. As a result, the CIS aerogel delivers a 76-fold enhancement in ECL intensity compared with individual CIS QDs. Notably, the in situ gelation strategy is scalable, producing 0.54 g of CIS aerogel per batch, which supports practical use in ECL sensing. As a proof-of-concept, the CIS aerogel is integrated into an ECL immunosensor for carcinoembryonic antigen (CEA), affording a satisfactory linear range of 1 pg mL-1 to 100 ng mL-1 and a detection limit of 0.34 pg mL-1 (S/N = 3). The immunosensor also exhibits excellent selectivity and reproducibility. This work highlights interparticle charge transport as an effective lever for boosting QD-based ECL and underscores the potential of QD aerogels for advanced ECL biosensing.

Amide bonds are most frequently utilized to form the bioconjugates of nanoclusters (NCs) and biomolecules; however, the amide bonds involved in the bioconjugation process tend to dramatically alter the functional group of NCs, decrease storage stability, and eventually block their practical bioapplication. With N-acetyl-l-cysteine (NAC)-capped AuNCs (NAC-AuNCs) as a model, we propose a biocompatible electrochemiluminescence (ECL) luminophore with thiol as a stabilizer and bioconjugate anchor. The NAC-AuNCs can exhibit a solely oxidative-reduction ECL process around +0.94 V with a maximum emission wavelength of around 824 nm. By immobilizing SH-modified probe hepatitis B virus (HBV) DNA (p-DNA) onto NAC-AuNCs via Au-S bonds, NAC-AuNCs can be used as ECL tags for gene assays with thiol as the anchor of bioconjugates, which provides an alternative to conventional bioconjugates and proves that ECL reagent kits can be developed in a 1-ethyl-3-(3-(dimethylamino)propyl) carbodiimide hydrochloride (EDC)-free way. The NIR ECL of NAC-AuNCs can be utilized to linearly determine HBV from 10 pM to 5 nM with a limit of detection (LOD) of 5 pM (S/N = 3). Notably, NAC-AuNCs can be safely stored for over four months without signal attenuation and can link the SH-modified gene without permanent precipitation.

The commercialized immunoassay of glow-type chemiluminescence (CL) is always performed in an enzyme-assisted and indirect CL way, with molecular luminophores as tags. Herein, dual-stabilizer-capped Au nanoclusters (NCs) are proposed as nanoparticulate glow-CL luminophores and perform automatic immunoassays on commercialized in vitro diagnosis (IVD) instruments in a direct and enzyme-free CL way. The thiosalicylic acid (TSA) and bovine serum albumin (BSA) stabilized AuNCs (TSA/BSA-AuNCs) are water-soluble, biocompatible, and n-type CL luminophores, which can give off dark-red and glow-type CL with the coexistence of both hydrazine hydrate (N2H4·H2O) and hydrogen peroxide (H2O2). The glow-CL of TSA/BSA-AuNCs is generated in a combined route of bandgap-engineered CL (∼711 nm) and surface-defect-engineered CL (∼860 nm), and its total emission is strong enough to linearly determine procalcitonin (PCT) from 0.1 to 5000 pg/mL with a limit of detection of 0.05 pg/mL (S/N = 3), which is superior to the limit of detection for all of the commercialized CL immunoassays. Promisingly, TSA/BSA-AuNCs can be safely stored over 5 months and safely labeled to proteins without permanent precipitation and damage, which are strongly anticipated for the design of CL reagent kits with nanoparticles as tags and might initiate the commercialized application of NCs CL.

Herein, a zinc ion (Zn2+)-induced aggregation strategy is proposed for 1690-fold enhanced electrochemiluminescence (ECL) from d-penicillamine (DPA)-capped gold nanoclusters (AuNCs), and the aggregation-induced ECL (AIECL) is a multiplicative effect of two enhancing factors. One is the improved ligand rigidification of Zn2+-induced aggregation of AuNCs, i.e. Zn2+-AuNCs. The Zn2+ of Zn2+-AuNCs can reduce the vibration and rotation of DPA, suppress non-radiative decay, and result in ∼17-fold enhanced emission with photoluminescence (PL) as control. The other is the promoted electron transfer by Zn2+-DPA bonds, which can enhance charge annihilation with the assistance of energy level alignment between AuNCs and the Zn2+-DPA bond, further amplifying ECL by another ∼100-fold. The dual-enhanced AIECL strategy can be utilized to design even brighter ECL luminophores.

Organic-inorganic halide perovskites have emerged as a novel category of optoelectronic materials owing to their exceptional physical and chemical properties. Notably, zero-dimensional (0-D) dimethylammonium bismuth iodide (DMA2BiI6) perovskite is an...

The unary nanocrystals (NCs) of copper are frequently employed as a catalyst, sensitizer, and energy transfer mediator of chemiluminescence (CL). Herein, the direct and defect-involved CL of copper NCs (CuNCs) for the semiautomatic immunoassay is proposed with bovine serum albumin (BSA)-stabilized CuNCs (BSA-CuNCs) as luminophores. The biocompatible BSA-CuNCs are a kind of n-type NC that can directly give off flash CL via charge annihilation between its endogenous electrons and exogenously injected holes by the coexisting oxidative activators. Potassium hexacyanoferrate(III) (K3[Fe(CN)6]) can trigger BSA-CuNCs with efficient CL around ∼701 nm, a waveband longer than all commercial-available CL reagent kits. The coexisting citric ion can also directly reduce the hole-injected BSA-CuNCs to further enhance CL emission. The CL of BSA-CuNCs/K3[Fe(CN)6] in citrate buffer is consequently utilized to detect myoglobin on the commercialized and semiautomatic IVD device, which exhibits improved determination performance compared to the commercially available CL reagent kits, with a wide linear response range from 0.25 to 1000 pg/mL and a limit of detection of 0.10 pg/mL (S/N = 3). BSA-CuNCs can be safely stored in pure water and label protein without unintended precipitation, which might provide an alternative to the molecule tagged CL reagent kits.

Ru(bpy)32+/tripropylamine (TPrA) is the sole electrochemiluminescence (ECL) system, which is being extensively employed in commercialized In Vitro Diagnosis. The coreactant ECL of Ru(bpy)32+/TPrA is of a multiple-channel emission and wide electrochemical potential window nature. Herein, a coreactant-free and single-potential-channel ECL strategy is proposed with a biocompatible nano-electrochemiluminophore, i.e., dihydrolipoic acid-capped Au nanoclusters (DHLA-AuNCs) as model, in which the metal-sulfur bonds between two sulfhydryls of DHLA and the Au element enable AuNCs with a S vacancies involved electron-rich and n-type nature for DHLA-AuNCs. The DHLA-AuNCs can be electrochemically oxidized, the annihilation reaction between exogenous holes and endogenous free-electrons can emit a kind of coreactant-free single-potential-channel ECL between +0.70 and + 1.20 V (vs Ag/AgCl) with the maximum emission potential of +0.91 V (vs Ag/AgCl) and the maximum emission wavelength of 778 nm. The ECL can be conveniently achieved, and selectively determine human carcinoembryonic antigen with the linear response range from 20 to 5000 pg/mL and the limit of detection of 5 pg/mL. The coreactant-free and single-potential-channel ECL of DHLA-AuNCs provides an alternative to the coreactant ECL of Ru(bpy)32+/TPrA for less electrochemical-interference and signal-crosstalk.

This work presents the synthesis, electrochemical behavior, and photophysical properties of a novel platinum acetylide metallopolymer (p-PtBTD), designed for enhanced electrogenerated chemiluminescence (ECL) performance. The metallopolymer features alternating pi-conjugated segments of 2,1,3-benzothiadiazole (BTD) and trans-Pt(PBu3)2 units. The inclusion of platinum centers facilitates efficient intersystem crossing (ISC), allowing the radiative decay of triplet excitons, which is typically challenging in conventional ECL systems dominated by singlet emission. Photoluminescence (PL) studies reveal dual emission, with a prominent fluorescence peak at 584 nm and a weak phosphorescence peak near 800 nm. Electrochemical investigations demonstrate quasi-reversible oxidation and irreversible reduction waves for p-PtBTD, while transient ECL studies reveal instability in the radical cation, which has been successfully addressed using tripropylamine (TPrA) as a co-reactant. The ECL spectrum shows dual emission arising from both singlet and triplet states, facilitated by triplet-triplet annihilation (TTA) and reverse intersystem crossing (RISC) due to a small energy gap (similar to 0.5 eV) between these states. This dual emission mechanism, involving both fluorescence and phosphorescence, highlights the potential of p-PtBTD for advanced ECL applications, particularly in sensing and optoelectronics. These findings underscore the utility of metallopolymers in overcoming the limitations of traditional ECL systems, paving the way for more efficient and versatile luminescent materials.

All of the commercialized electrochemiluminescence (ECL) immunoassays are automatically conducted at +1.40 V (vs Ag/AgCl) in the coreactant route. To alleviate the exogenous effect of coreactants and simplify the operation procedures, herein, a sulfur-vacancy-involved and free electron strategy is proposed to exploit Au nanoclusters (NCs) as anodic electrochemiluminophores and perform a coreactant-free immunoassay. The deficient coordination between the sulfhydryl of Met and the Au core might induce the departure of partial S atoms and enable Met-capped AuNCs (Met-AuNCs) with a sulfur-vacancy-involved electron-rich nature. The electron-rich nature tends to endow Met-AuNCs with unpaired endogenous free electrons, which can directly combine exogenous holes for light emitting. Coreactant-free ECL at around +0.86 V is consequently and conveniently achieved by merely oxidizing Met-AuNCs at the anode. The coreactant-free ECL is qualified to determine human carcinoembryonic antigen from 10 to 5000 pg/mL with a limit of detection of 5 pg/mL. Electron paramagnetic resonance provides clear evidence that endogenous free electrons within Met-AuNCs play an important role in the generation of coreactant-free ECL. This sulfur-vacancy-involved and free electron strategy is promising for designing nanoelectrochemiluminophores with improved immunoassay performance.

The copper(Ⅱ)-ammonia coordination ion represents a quintessential model for understanding the coordination equilibrium and distribution characteristics of coordination compounds in the teaching of analytical chemistry. Current textbooks, however, often limit their scope to providing stability constants for select copper-ammonia coordination ions, without delving into the correlation between their coordination numbers and stability. This study leverages density functional theory to firstly establish a connection between the stability of copper-ammonia coordination ions and their coordination numbers, achieved through structural optimization. Subsequently, it offers a qualitative interpretation by examining the molecule spatial configuration, shedding light on the fundamental nature of these structures. This research not only enhances the effectiveness of pedagogical approaches, but also cultivates students' interest in the application of the theoretical calculations within the realm of analytical chemistry.

A low-triggering potential and a narrow-potential window are anticipated to decrease the electrochemical interference and cross talk of electrochemiluminescence (ECL). Herein, by exploiting the low oxidative potential (0.82 V vs Ag/AgCl) of dihydrolipoic acid-capped sliver nanoclusters (DHLA-AgNCs), a coreactant ECL system of DHLA-AgNCs/hydrazine (N2H4) is proposed to achieve efficient and oxidative-reduction ECL with a low-triggering potential of 0.82 V (vs Ag/AgCl) and a narrow-potential window of 0.22 V. The low-triggering-potential and narrow-potential-window nature of ECL can be primarily preserved upon labeling DHLA-AgNCs to probe DNA and immobilizing DHLA-AgNCs onto the Au surface via sandwiched hybridization, which eventually enables a selective ECL strategy for the gene assay at +0.82 V. This gene assay strategy can sensitively determine the gene of human papillomavirus from 10 to 1000 pM with a low limit of detection of 5 pM (S/N = 3) and would open a way to improve the applied ECL bioassay.

The oxidative-reduction electrochemiluminescence (ECL) potential of a luminophore is one of the most significant parameters during light generation processes when considering the growing demand for anti-interference analysis techniques, electrode compatibility and the reduction of damage to biological molecules due to excessive excitation potential. Nanoparticle luminophores, including quantum dots (QDs) and metal nanoclusters (NCs), possess tremendous potential for forming various ECL sensors due to their adjustable surface states. However, few reviews focused on nanoparticle luminophore-based ECL systems for low-triggering-potential (LTP) oxidative-reduction ECL to avoid the possible interference and oxidative damage of biological molecules. This review summarizes the recent advances in the LTP oxidative-reduction ECL potential strategy with nanoparticle luminophores as ECL emitters, including matching efficient coreactants and nanoparticle luminophores, doping nanoparticle luminophores, constructing donor-acceptor systems, choosing suitable working electrodes, combining multiplex nanoparticle luminophores, and employing surface-engineering strategies. In the context of the different LTP ECL systems, potential-lowering strategies and bio-related applications are discussed in detail. Additionally, the future trends and challenges of low ECL-triggering-potential strategies are discussed.

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.

The low-triggering-potential and potential-selective electrochemiluminescence for a highly selective immunoassay by exploiting AgInS 2 /ZnS nanocrystals as a tag and N 2 H 4 as a coreactant.

The commercialized electrochemiluminescence (ECL) immunoassay is carried out by holding luminophore Ru(bpy)32+ at a given potential. Designing an electrochemiluminophore with a narrow triggering potential window is strongly anticipated to decrease the electrochemical cross-talk and improve the flux of the commercialized ECL immunoassay in a potential-resolved way. Herein, L-penicillamine-capped silver nanoclusters (LPA-AgNCs) are facilely synthesized and utilized as tags to perform the ECL immunoassay with a sole and narrow triggering potential window of 0.24 V by employing hydrazine (N2H4) as a coreactant. The maximum ECL emission of the LPA-AgNCs/N2H4 system is located ca. +1.27 V. Upon immobilizing LPA-AgNCs onto the electrode surface via forming a sandwich immunocomplex, the ECL of LPA-AgNCs/N2H4 can be utilized to sensitively and selectively determine human carcinoembryonic antigen from 0.5 to 1000 pg/mL with a low limit of detection of 0.1 pg/mL (S/N = 3). This work might open a way to screen electrochemiluminophores for the multiple ECL immunoassay in a potential-resolved way.

Optical single molecule detection is normally achieved via amplifying the total emission of photons of luminophores and is strongly anticipated to extend the commercialized application of chemiluminescence (CL). To overcome the limited CL photons of molecule luminophores, herein, a nanocrystal (NC) luminophore self-amplified strategy is proposed to repetitively excite CL luminophores for amplifying the total CL photons per luminophore, which can be exploited to perform CL immunoassays (CLIAs) toward single molecule detection via employing KMnO4 as the CL triggering agent and the dual-stabilizer-capped CdTe NCs as the CL luminophore. KMnO4 can oxidize the S element from each stabilizer of mercaptopropionic acid (MPA) and release enough energy to excite the CdTe core for flash CL. The substantial MPA around each CdTe core enables every CdTe luminophore to be repetitively excited and give off amplified total CL photons in a self-enhanced way. The CL of CdTe NCs/KMnO4 can release all photons rapidly, and the collection of all these photons can be utilized to determine the model analyte of thyroid-stimulating hormone antigen (TSH) with a limit of detection of 5 ag/mL (S/N = 3), which is corresponding to about 2-4 TSH molecules in a 20 μL sample. The whole immunologic operating process can be terminated within 6 min. This strategy of repetitively breaking the CL reaction involving chemical bonds within one luminophore is promising for semi-automatic as well as fully automatic single molecule detection and extends the commercialized application of CL immunodiagnosis.

In accurately balancing membrane permeability and separation coefficient, effectively preventing membrane collapse in separation process is the core to improve the efficiency of membrane separation for two-dimensional materials. Here, we used L-cysteine (L-Cys) functionalized gold nanoparticles as scaffolds and spacers and fabricated a multi-effect separation membrane with GO nanosheets. The as-prepared membrane performed the following as a separation membrane: (1) As a robust spacer, the gold nanoparticles, prevented the collapse of the GO sheet and thus the membrane showed stability; (2) The existence of amphiphilic L-cysteine enabled the possibility of regulating the GO sheets layer spacing between 16.9 and 17.8 angstrom by pH, which achieves controllable ultrahigh permeance for size sieving. The maximum permeation rate of the membrane can reach 216.6 L m- 2 h-1 bar-1, which is much greater than that of pure GO membrane; (3) Further, we demonstrate the following properties of the as-prepared membranes embedded with amphiphilic chiral gold nanoparticles for the enantiomer separation. The membrane has high enantioselectivity for Pen racemates, and its chiral separation factor and permeation rate can reach 1.83 and 21.7 L m- 2 h-1 bar- 1, respectively.