CdS Quantum Dots Research Articles

Lattice-matched controllable construction of nanometer scale CdS/TiO2 hollow nanoboxes Z-scheme heterojunctions based on micrometer and sub-nanometer CdS for comparison of visible photocatalytic activity

Size effect exerts a significant influence on the photocatalytic properties of materials. Nanometer CdS/TiO2 hollow nanoboxes (TiO2-HNBs) (tetragonal phase) Z-scheme heterojunctions were lattice-matched controllably fabricated by using cubic TiOF2 as a template and loading with micrometer CdS micron rods (hexagonal phase) or sub-nanometer CdS quantum dots (cubic phase) through one-pot template ultrasonic hydrothermal method. The morphology, constitution, physical property, as well as photocatalytic properties of as-prepared samples were investigated comprehensively. Under visible light irradiation (λ ≥ 420 nm), the hydrogen production rates of CdS micron rods, CdS nanorods/TiO2-HNBs (CT-7), CdS quantum dots/TiO2-HNBs (CTQ-7) and CdS quantum dots was 1642.61, 455.35, 148.92 and 1025.53 μmol/g/h, which was 26.39, 7.32, 2.39 and 16.48 times that of TiO2-HNBs, respectively. Meanwhile, the photodegradation rate of Rhodamine B by CdS micron rods, CT-7, CTQ-7 and CdS quantum dots within 60 min was 69.59%, 99.90%, 89.96% and 40.70%, which were 4.77, 6.85, 6.17 and 2.79 times that of P25, respectively. CdS micron rods had the largest size but the strongest photo-hydrogen production properties. Due to its Z-scheme heterojunction structure and Ti-S bond, CT-7 exhibited enhanced electron-hole separation rate and electron transfer rate, resulting in superior RhB degradation performance. Although CdS quantum dots had the smallest size, it did not boast the best performance, indicating that smaller size does not necessarily correlate with better photocatalytic performance. This study provides a reference for comparing the performance of photocatalytic materials with different sizes.

Electrochemiluminescent CdS Quantum Dots Biosensor for Cancer Mutation Detection at Different Positions on Linear DNA Analytes.

PCR-based techniques routinely employed for the detection of mutated linear DNA molecules, including circulating tumor DNA (ctDNA), require large nucleotide sections on both sides of the mutation for primer annealing. This means that DNA fragments with a mutation positioned closer to the extremities are unlikely to be detected. Thus, sensors capable of recognizing linear DNA with characteristic mutations closer to the ends would be advantageous over the state-of-the-art approaches. Here, an electrochemiluminescence-resonance energy transfer (ECL-RET) biosensor comprising capped CdS quantum dots and hairpin DNA probes labeled with Au nanoparticles was developed for the detection of epidermal growth factor receptor (EGFR) ctDNA carrying the critical T790M lung cancer mutation. The ECL-RET system detected different DNA molecules including single-stranded 18-nucleotides (nt) and 40-nt as well as double-stranded 100-nt with the single nucleotide polymorphism (SNP) coding for T790M located either in the middle or only 7 nt from one end. For all target DNA, the sensor's limits of detection (LODs) were in the aM range, with excellent selectivity. It was the case of 100-nt target linear ctDNA fragments with LODs of 8.1 and 3.4 aM when the EGFR T790M SNP was either in the middle or at the end, respectively. These results show that ECL-RET systems can sense mutations in DNA fragments that would remain undetected by standard techniques.

Building of a three-dimensional apta-nano interface using silver nanoflower for photoelectrochemical detection of carcinoembryonic antigen

Enhancing the sensitivity of photoelectrochemical (PEC) assays poses a challenging task. This study proposes a method to improve the sensitivity of PEC assays by creating a three-dimensional (3D) apta-nano interface using silver nanoflowers (AgNFs) with a 3D flower-like structure as a substrate. The aptamer (Apt) was immobilized on the surface of the AgNF-loaded gold nanoparticles (AuNPs) through the dual action of polyA blocking and Au-S bonding. Despite using cadmium sulfide quantum dots (CdS QDs) as the sole photoactive material, the as-prepared photoelectrode still showed excellent sensitivity. Using carcinoembryonic antigen (CEA) as a model target, the variation value of photocurrent (ΔI) exhibited good linear correlation (R2 = 0.9974) with the logarithm of CEA concentration in a wide detection range from 0.001 to 100 ng mL−1, and the detection limit was as low as 0.64 pg mL−1. In the assay of CEA in 1% serum, the recoveries reached 98.70 ∼ 99.63% with a low relative standard derivation (RSD) ranging from 1.11% to 2.05%. This study introduces novel concepts for the development of PEC sensors, potentially enhancing their utility in the clinical detection of disease markers.

Balancing Near-Field Enhancement and Hot Carrier Injection: Plasmonic Photocatalysis in Energy-Transfer Cascade Assemblies.

Photocatalysis stands as a very promising alternative to photovoltaics in exploiting solar energy and storing it in chemical products through a single-step process. A central obstacle to its broad implementation is its low conversion efficiency, motivating research in different fields to bring about a breakthrough in this technology. Using plasmonic materials to photosensitize traditional semiconductor photocatalysts is a popular strategy whose full potential is yet to be fully exploited. In this work, we use CdS quantum dots as a bridge system, reaping energy from Au nanostructures and delivering it to TiO2 nanoparticles serving as catalytic centers. The quantum dots can do this by becoming an intermediate step in a charge-transfer cascade initiated in the plasmonic system or by creating an electron-hole pair at an improved rate due to their interaction with the enhanced near-field created by the plasmonic nanoparticles. Our results show a significant acceleration in the reaction upon combining these elements in hybrid colloidal photocatalysts that promote the role of the near-field enhancement effect, and we show how to engineer complexes exploiting this approach. In doing so, we also explore the complex interplay between the different mechanisms involved in the photocatalytic process, highlighting the importance of the Au nanoparticles' morphology in their photosensitizing capabilities.

Rhenium(I) Complex-Containing Amphiphilic Metallopolymer Stabilizing CdS Quantum Dots for Synergistically Boosting Photoreduction of CO2

Rhenium(I) Complex-Containing Amphiphilic Metallopolymer Stabilizing CdS Quantum Dots for Synergistically Boosting Photoreduction of CO₂

Mechanistic Study of Amphiphilic-Assisted Self-Assembled Cadmium Sulfide Quantum Dots into 3D Superstructures.

Self-assembling of nanoparticles into complex superstructures is very challenging, which usually depends on postorganizing techniques or pre-existing templates such as polypeptide chains or DNA or external stimulus. Such self-assembled processes typically lead to close-packed structures. Here, it has been demonstrated that under carefully template-free reaction conditions CdS quantum dots (QDs) could be synthesized and simultaneously self-assembled into complex superstructures without compromising individual QD properties. The superstructures of CdS QDs attained by the chemical-based method demonstrate Stokes-shifted photoluminescence (PL) from trap states. Remarkably, the PL decay of superstructures exhibits a single-exponential feature. This behavior is unusual for the synthesized superstructures, indicating that the trap states are restricted to a narrow range. The growth mechanism of these superstructures is explained through the formation of liquid crystal phases (LCPs) with the help of a small-angle X-ray scattering (SAXS) analysis.

Efficient and Direct Functionalization of Allylic sp3 C−H Bonds with Concomitant CO2 Reduction

AbstractSolar‐driven CO2 reduction integrated with C−C/C−X bond‐forming organic synthesis represents a substantially untapped opportunity to simultaneously tackle carbon neutrality and create an atom‐/redox‐economical chemical synthesis. Herein, we demonstrate the first cooperative photoredox catalysis of efficient and tunable CO2 reduction to syngas, paired with direct alkylation/arylation of unactivated allylic sp3 C−H bonds for accessing allylic C−C products, over SiO2‐supported single Ni atoms‐decorated CdS quantum dots (QDs). Our protocol not only bypasses additional oxidant/reductant and pre‐functionalization of organic substrates, affording a broad of allylic C−C products with moderate to excellent yields, but also produces syngas with tunable CO/H2 ratios (1 : 2–5 : 1). Such win‐win coupling catalysis highlights the high atom‐, step‐ and redox‐economy, and good durability, illuminating the tantalizing possibility of a renewable sunlight‐driven chemical feedstocks manufacturing industry.

Efficient and Direct Functionalization of Allylic sp3 C-H Bonds with Concomitant CO2 Reduction.

Solar-driven CO2 reduction integrated with C-C/C-X bond-forming organic synthesis represents a substantially untapped opportunity to simultaneously tackle carbon neutrality and create an atom-/redox-economical chemical synthesis. Herein, we demonstrate the first cooperative photoredox catalysis of efficient and tunable CO2 reduction to syngas, paired with direct alkylation/arylation of unactivated allylic sp3 C-H bonds for accessing allylic C-C products, over SiO2 -supported single Ni atoms-decorated CdS quantum dots (QDs). Our protocol not only bypasses additional oxidant/reductant and pre-functionalization of organic substrates, affording a broad of allylic C-C products with moderate to excellent yields, but also produces syngas with tunable CO/H2 ratios (1 : 2-5 : 1). Such win-win coupling catalysis highlights the high atom-, step- and redox-economy, and good durability, illuminating the tantalizing possibility of a renewable sunlight-driven chemical feedstocks manufacturing industry.

Study on photoinduced charge transfer between Citrus Limon capped CdS quantum dots with natural dyes

The development of highly efficient Quantum dots-based Dye Sensitized Solar Cells (DSSCs) capable of absorbing a broader spectrum of solar light has garnered significant interest. In these systems, the proper selection of sensitizers plays a crucial role. Consequently, the exploration of highly efficient, cost effective and non-toxic sensitizer options has led to a growing focus on natural dyes. In this study, we investigated the credibility of natural dyes Beta Vulgaris, Ixora coccinea and Butea monosperma were explored as potential sensitizer in a Cadmium Sulphide (CdS) quantum dots-based system. Moreover, the effect of Citrus Limon Extract (CLE) as a capping agent through X-ray Photoelectron Spectroscopy (XPS) and Electron Paramagnetic Resonance (EPR) analyses. A Density Functional Theory (DFT) model was also presented to explore the charge accumulation on CdS surface due capping action. Quenching mechanism of CLE-CdS with different dyes under various irradiation conditions was studied and their mechanism were defined. Lastly, our finding demonstrates the effect of H-aggerated dye on CLE-CdS, indicating its potential in increasing solar light absorption.

Synthesis, characterization, and pharmacological evaluation of dextrin capped cadmium sulfide quantum dots conjugated with temozolomide for drug delivery and imaging application

Quantum dots (QDs) of cadmium sulfide semiconductor capped with dextrin and bioconjugated with temozolomide (CdS/Dx+TMZ) were used to target and provide imaging of glioma cells. CdS/Dx+TMZ QDs were in the range of 6.5 nm in size and exhibited an intense fluorescence emission in the green spectrum, which allowed us to monitor fluorescence imaging in a rat glioma cell line. The results showed that glioma cells efficiently took up the CdS/Dx+TMZ QDs, which had a large accumulation time in cells and were distributed in both the cytoplasm and nucleus, where the pharmacological drug effects were enhanced. CdS/Dx+TMZ QDs were more cytotoxic than TMZ and CdS/Dx alone. Glioma cells treated with 100 µM CdS/Dx+TMZ QDs showed both an increase in size (cytoplasm and nucleus) and in the number of cell deaths by apoptosis. The morphological analysis showed the presence of binucleated cells and membrane blebbing, as well as apoptotic bodies. This study confirmed the effective cellular uptake of CdS/Dx QDs bioconjugated with TMZ and their pharmacological effects in a glioma cell line. Our conclusion is that CdS/Dx+ TMZ QDs could be simultaneously used as drug delivery and cell monitoring system for the treatment of GBM and other brain tumors.

Engineering of Solar Energy Harvesting Tb3+-Ion-Doped CdS Quantum Dot Glasses for Photodissociation of Hydrogen Sulfide.

The photocatalytic properties of CdS quantum dots (Q-dots) and Tb3+-doped CdS Q-dots dispersed in a borosilicate glass matrix were investigated for the photodissociation of hydrogen sulfide (H2S) into hydrogen (H2) gas and elemental sulfur (S). The Q-dot-containing glass samples were fabricated using the conventional melt-quench method and isothermal annealing between 550 and 600 °C for 6 h for controlling the growth of CdS and Tb3+-ion-doped CdS Q-dots. The structure, electronic band gap, and spectroscopic properties of the Q-dots formed in the glass matrix after annealing were analyzed using Raman and UV-visible spectroscopies, X-ray powder diffraction, and transmission electron microscopy. With increasing annealing temperature, the average size range of the Q-dots increased, corresponding to the decrease of electronic band gap from 3.32 to 2.24 eV. For developing the model for photocatalytic energy exchange, the excited state lifetime and photoluminescence emission were investigated by exciting the CdS and Tb3+-doped CdS quantum states with a 450 nm source. The results from the photoluminescence and lifetime demonstrated that the Tb3+-CdS photodissociation energy exchange is more efficient from the excited Q-dot states compared to the CdS Q-dot glasses. Under natural sunlight, the hydrogen production experiment was conducted, and an increase of 26.2% in hydrogen evolution rate was observed from 0.02 wt % Tb3+-doped CdS (3867 μmol/h/0.5 g) heat-treated at 550 °C when compared to CdS Q-dot glass with a similar heat treatment temperature (3064 μmol/h/0.5 g). Furthermore, the photodegradation stability of 0.02 wt % Tb3+-CdS was analyzed by reusing the catalyst glass powders four times with little evidence of degradation.

Ultrafast electron transfer from CdS quantum dots to atomically-dispersed Pt for enhanced H2 evolution and value-added chemical synthesis

Photocatalytic hydrogen production is enchanting in solar energy utilization. And mechanism elucidation in interfacial electron transfer rate is a prerequisite for performance improvement. Herein, atomically dispersed Pt-modified CdS quantum dots (Pt-CdS QDs), prepared by a facile one-step in-situ deposited method, are used as a prototype. Benefiting from the maximized utilization of Pt cocatalyst as well as the strong electronic metal-support interaction, ultrafast electron transfer from CdS to Pt (∼1.7 ps) is achieved, as revealed by femtosecond transient absorption spectra. The optimal sample simultaneously realizes photocatalytic hydrogen evolution coupled with selective oxidation of 2-thiophene methanol (TM) into 2-thiophenecarboxaldehyde (TD). Specifically, it exhibits an enhanced H2-evolution rate, which is 70-fold higher than pristine CdS QDs. Moreover, a TM conversion rate of 95.3 % with a TD selectivity of 87.2 % is reached after 4 h. This work will provide some guidance for the design of photocatalytic systems with efficient interfacial electron transfer.

Ultrafast Hole Migration at the p-n Heterojunction of One-Dimensional SnS Nanorods and Zero-Dimensional CdS Quantum Dots.

The p-n heterojunctions fabricated from one-dimensional (1D) p-type tin sulfide nanorods (SnS NRs) decorated with n-type zero-dimensional (0D) cadmium sulfide quantum dots (CdS QDs) have gained significant research attention in energy storage devices. Herein, we have successfully synthesized a 1D/0D SnS@CdS heterostructure (HS) using a hot injection method. Structural and morphological studies clearly suggest that CdS QDs are uniformly anchored on the surface of SnS NRs, resulting in intimate contact between two components. The photoluminescence (PL) study revealed the transfer of photoexcited holes from CdS QDs to SnS NRs, which was further confirmed by transient absorption (TA) studies. TA measurements demonstrate the hole transfer from the valence band of CdS QDs to SnS NRs and delocalization of electrons between the conduction band of SnS NRs and CdS QDs in SnS@CdS HS, resulting in efficient charge separation across the p-n heterojunction. These findings will open up a new paradigm for improving the efficiency of optoelectronic devices.

Constructing a CdS QDs/silica gel composite with high photosensitivity and prolonged recyclable operability for enhanced visible-light-driven NADH regeneration

Visible-light-driven nicotinamide adenine dinucleotide (NADH) regeneration is one of the most effective measures, and cadmium sulfide (CdS) materials are typically used as low-cost photocatalysts. The CdS photocatalysts, however, still suffer from low regeneration efficiency and poor cycle stability. In this work, the CdS quantum dots (QDs) less than 10 nm embedded onto silica gel (CdS QDs/Silica gel) were constructed for visible-light-driven NADH regeneration by a successive ionic layer adsorption reaction and ball milling method. Results demonstrate that the photosensitivity of the CdS QDs/Silica gel composite was 31 times higher than that of the bulk CdS. Moreover, the conduction band (CB) edge of the CdS QDs/Silica gel composite is −1.34 eV, which is more negative 0.5 eV than that of the bulk CdS. The obtained CdS QDs/Silica gel composites showed the highest NADH regeneration yields of 68.8% under visible-light (LED, 420 nm) illumination and can be reused for over 40 cycles. Finally, the bioactivity of NADH toward enzyme catalysis is further confirmed by the hydrogenation of benzaldehyde to benzyl alcohol catalyzed with an alcohol dehydrogenase as enzyme catalysis.

Dual-potential electrochemiluminescence cytosensor based on a metal-organic framework and ABEI-PEI-Au@AgNPs for the simultaneous determination of phosphatidylserine and epidermal growth factor receptors on an apoptotic cell surface.

A new electrochemiluminescence (ECL) cytosensor is proposed for the simultaneous determination of phosphatidylserine (PS) and epidermal growth factor receptor (EGFR) based on the ECL signals of metal-organic framework-5 (MOF-5) loaded CdS quantum dots and N-(aminobutyl)-N-(ethylisoluminol)-polyethylenimine capped Au and Ag nanoparticles. Apoptosis promotes the exposure of PS and reduces the expression of EGFR in cell membranes. Two spatially resolved areas on dual-disk glassy carbon electrodes were designed to eliminate the interference from different ECL probes. Using HepG2 cells treated with resveratrol to induce apoptosis, thecytosensor exhibited high sensitivity, simplicity, and high reproducibility, demonstrating its potential in drug screening and rapid apoptotic cell detection. The strategy reported provides a promising platform for the highly sensitive cytosensing and convenient screening of clinically relevant anticancer drugs.

A “battery” like Z-scheme heterojunction photocatalyst fabricated from aminated CdS and Ni3-polyoxometalate for promoted hydrogen production and electron transfer mechanism studies

In recent years, composite photocatalysts prepared from semiconductor quantum dots have received great attentions, however, the cases on functionalizing the surface of semiconductor quantum dots and combining them with polyoxometalate are not common. Based on this, a photocatalytic material was assembled from the aminated CdS quantum dots and Ni3-containing polyoxometalate by electrostatic adsorption. Interestingly, it has been found that the light source, electron sacrificial agent and polyoxoanions could form a high-speed electron transfer channel in the photocatlytic process, in which these three components behave like a “switch”, “power source” and “battery” in the system, respectively. Due to the Z-scheme driven effect, the hydrogen production activity of the composite catalyst is 25 times higher than that of the substrate material. This work may provide an insight for studying the electron transfer mechanism of polyoxometalate-based photocatalytic systems.

Linker-Assisted Assembly of Ligand-Bridged CdS/MoS2 Heterostructures: Tunable Light-Harvesting Properties and Ligand-Dependent Control of Charge-Transfer Dynamics and Photocatalytic Hydrogen Evolution.

We used linker-assisted assembly (LAA) to tether CdS quantum dots (QDs) to MoS2 nanosheets via L-cysteine (cys) or mercaptoalkanoic acids (MAAs) of varying lengths, yielding ligand-bridged CdS/MoS2 heterostructures for redox photocatalysis. LAA afforded precise control over the light-harvesting properties of QDs within heterostructures. Photoexcited CdS QDs transferred electrons to molecularly linked MoS2 nanosheets from both band-edge and trap states; the electron-transfer dynamics was tunable with the properties of bridging ligands. Rate constants of electron transfer, estimated from time-correlated single photon counting (TCSPC) measurements, ranged from (9.8 ± 3.8) × 106 s-1 for the extraction of electrons from trap states within heterostructures incorporating the longest MAAs to >5 × 109 s-1 for the extraction of electrons from band-edge or trap states in heterostructures with cys or 3-mercaptopropionic acid (3MPA) linkers. Ultrafast transient absorption measurements revealed that electrons were transferred within 0.5-2 ps or less for CdS-cys-MoS2 and CdS-3MPA-MoS2 heterostructures, corresponding to rate constants ≥5 × 109 s-1. Photoinduced CdS-to-MoS2 electron transfer could be exploited in photocatalytic hydrogen evolution reaction (HER) via the reduction of H+ to H2 in concert with the oxidation of lactic acid. CdS-L-MoS2-functionalized FTO electrodes promoted HER under oxidative conditions wherein H2 was evolved at a Pt counter electrode with Faradaic efficiencies of 90% or higher and under reductive conditions wherein H2 was evolved at the CdS-L-MoS2-heterostructure-functionalized working electrode with Faradaic efficiencies of 25-40%. Dispersed CdS-L-MoS2 heterostructures promoted photocatalytic HER (15.1 μmol h-1) under white-light illumination, whereas free cys-capped CdS QDs produced threefold less H2 and unfunctionalized MoS2 nanosheets produced no measurable H2. Charge separation across the CdS/MoS2 interface is thus pivotal for redox photocatalysis. Our results reveal that LAA affords tunability of the properties of constituent CdS QDs and MoS2 nanosheets and precise, programmable, ligand-dependent control over the assembly, interfacial structure, charge-transfer dynamics, and photocatalytic reactivity of CdS-L-MoS2 heterostructures.

Bi-functional aqueous starch capped CdS quantum dots synthesis and their application as sensor of heavy metal-ions as well as photocatalytic dye degradation

CdS quantum dots (QDs) have emerged as the promising nanomaterial for various applications. This study reported bi-functional usage of aqueous starch capped CdS QDs as heavy metal-ion sensor for selective detection of Hg2+ and Cu2+ in aqueous medium as well as sunlight driven photocatalyst for degradation of organic dyes. CdS QDs exhibited colorimetric, spectroscopic, and compositional change with Hg2+ and Cu2+ via cation exchange reaction (CER). The CER of yellow color CdS QDs solution with Hg2+ showed rapid colour change to orange, red and white with composition Cd1-xSHgxS, HgS/CdS, and mixture of HgS and Hg sol, respectively whereas, CER of CdS QDs with Cu2+ resulted in pale brown, brown and greenish brown with composition Cd1-xCuxS, CuxS/CdS and Cu2-xS, respectively. Further, CdS QDs displayed excellent sunlight driven photocatalytic degradation of cationic, anionic and hair dye with good efficiency, reusability, and stability.

In Situ Characterizations Revealing Ruthenium‐Atom‐Induced Raise of Photocatalytic Performance

AbstractRational design/fabrication of high‐activity photocatalysts is of central importance to realize solar‐to‐chemical conversion for tackling worldwide energy/environmental issues. Hence, it is desirable to disclose the element/space/time‐resolved charge kinetics and surface species evolution of photocatalysts under realistic conditions using various in situ characterizations. Furthermore, the correlation of the above‐disclosed mechanisms with atomic‐scale compositions/structures of photocatalysts can further direct the atomic‐level design/synthesis of high‐performance photocatalysts. Herein, Ru atoms incorporated CdS quantum dots (QDs) are synthesized using an in situ hot‐injection route. The optimized Ru incorporated CdS QDs (Ru0.1) exhibit excellent photocatalytic evolution rates of H2O2 (8.78 mmol g−1 h−1) and benzaldehyde (11.70 mmol g−1 h−1), respectively. Four different in situ characterizations demonstrate that in realistic conditions, the incorporated Ru atoms with high oxidation state (+3) effectively attract photo‐generated electrons from bulk to the overall surface of Ru0.1; these directed electron flows also greatly facilitate the transfer of photo‐generated holes from bulk to surface of Ru0.1 via efficiently reducing electron‐hole recombination. in situ diffuse reflectance infrared Fourier transform spectroscopy, electron spin spectroscopy, and species‐trapping experiments further reveal three possible reaction pathways for H2O2 evolution. This work underscores the use of in situ characterizations to reveal the element/space/time‐resolved electrons/holes kinetics and surface‐species generation for photocatalysts in realistic conditions.

Proximity hybridization regulated dual-mode ratiometric biosensor for estriol detection in pregnancy serum

Sensitive and accurate determination of estriol level is vastly significant for the fetal growth and development. Herein, we constructed a dual-mode ratiometric biosensor for estriol assay combining the competitive immunoreaction, proximity hybridization with a two-step resonance energy transfer (RET) strategy. Estriol antibody and goat anti-rabbit antibody labeled DNA probes (Ab1-DNA1-Pt NPs and Ab2-DNA2) both hybridized with silver nanoclusters labeled DNA strands (H1-Ag NCs). Thus, the formed proximity hybridization enabled the occurrence of fluorescence RET (FL-RET, as the primary RET) between Ag NCs (donor) and Pt NPs (acceptor), quenching FL intensity of Ag NCs (FL off). When target estriol existed, the competitive reaction of Ab1-DNA1-Pt NPs with estriol and Ab2-DNA2 avoided the proximity hybridization. Then, the estriol-dependent H1-Ag NCs quenched electrochemiluminescence (ECL) emission of CdS quantum dots (CdS QDs, ECL off), generating ECL-RET (as the second RET). Consequently, according to the reverse changes of FL and ECL responses, this sensor realized the quantification of estriol from 1 to 100 ng/mL. Moreover, satisfactory results were achieved while testing estriol in pregnancy serum specimens, suggesting that the system is promising for potential application in samples analysis.