Based on their signal response to target analytes, ratiometric fluorescent sensors are generally categorized into two types: single-signal and dual-signal modes. Single-signal ratiometric sensors exhibit variations in only one fluorescence channel, whereas dual-signal sensors manifest concurrent or independent changes across two distinct emission signals. In an ideal dual-signal response mode, the enhancement of one signal is accompanied by the concomitant attenuation of the other, resulting in a shift in the fluorescence intensity ratio that is significantly greater than the absolute variation of either individual signal. This intrinsic signal amplification effect effectively compensates for fluctuations arising from probe concentration, instrumental instability, and environmental factors, thereby markedly improving sensitivity and the signal-to-noise ratio (SNR) for more reliable trace analyte detection. Consequently, the development of dual-signal responsive ratiometric fluorescence sensors with inversely correlated signal changes is of paramount importance. Semiconductor quantum dots (QDs) have emerged as ideal candidates for high-performance sensing platforms owing to their size-tunable emission wavelengths, broad excitation spectra, narrow emission bands, high quantum yields, and exceptional photostability. Nevertheless, conventional QDs-based ratiometric fluorescence sensors predominantly operate via a “responsive + reference” single-signal mode, which inherently restricts their dynamic range. Accordingly, precise modulation of interfacial charge interactions between QDs and organic molecules enables synchronous yet opposite dual-signal responses (i.e., an ideal ratiometric sensing mode). This mechanism not only amplifies the detection contrast and SNR for target analytes but also offers a versatile strategy for fabricating high-performance fluorescence sensing platforms.
To address this challenge, a research team led by Prof. DOU Xincun from the Xinjiang Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences (CAS) has proposed a hydrogen-bond-driven self-assembly strategy to construct a QDs/molecule sensing system, denoted as CdSe/ZnS QDs@FNAC. Their findings, published in Nano Research on August 27, 2026 ，demonstrated that precise interfacial assembly and charge transfer regulation enable a dual-signal ratiometric fluorescence response with high SNR.
Specifically, carboxyl-terminated CdSe/ZnS QDs@MPA was prepared via a ligand exchange strategy, and a naphthol-based molecular probe (FNAC) featuring a twistable acrylate moiety was designed and synthesized. The self-assembled system was then established through hydrogen bonding between the aldehyde groups of FNAC and the surface carboxyl groups of the QDs. Owing to the twisted intramolecular charge transfer (TICT) within the molecular probe and the photoinduced electron transfer (PET) between the probe and the QDs, the system exhibited exclusively red fluorescence from the QDs at 639 nm under 365 nm UV excitation. To verify the ratiometric dual-emission fluorescence response of this self-assembled system, potassium permanganate (KMnO 4 ), a typical oxidant that poses hazards to environmental protection and human health, was selected as the research analyte to systematically investigate the detection performance of CdSe/ZnS QDs@FNAC toward the target analyte. The results reveal that upon exposure of the self-assembled system to KMnO 4 , the PET between the QDs and molecular probes is suppressed, while the concurrent oxidative etching of the QDs quenches their red fluorescence emission at 639 nm. Concurrently, the acrylate moieties in FNAC undergo oxidative cleavage and subsequent hydrolysis, blocking the TICT pathway to generate green-fluorescent products emitting at 521 nm. Therefore, this self-assembled system achieves a synchronous, inversely correlated dual-signal ratiometric response characterized by the quenching of red emission and the activation of green fluorescence. Compared with conventional single-signal sensing modes, the proposed strategy remarkably amplifies variations in the fluorescence intensity ratio, thereby significantly enhancing both detection sensitivity and the SNR. Further investigations demonstrate that the CdSe/ZnS QDs@FNAC system exhibits outstanding sensing performance toward KMnO 4 , featuring a rapid response time (<1 s) and an ultralow detection limit (4.80 nM). Moreover, the developed sensor possesses excellent selectivity and anti-interference capability against various potential interferents, including common oxidants, reductants, anions, and cations. On this basis, the research team further immobilized the CdSe/ZnS QDs@FNAC into a polyacrylamide hydrogel matrix via a solvent-exchange strategy to fabricate hydrogel-based ratiometric fluorescent sensing chips. The chips were integrated into self-developed portable detectors. The integration of image acquisition and color recognition algorithms enabled the on-site visual identification of ng-level solid KMnO 4 particles, paving a practical route for the field screening of hazardous chemicals.
This work was supported by the National Natural Science Foundation of China, Key Research Project of Chinese Academy of Sciences, Natural Science Foundation of Xinjiang, Central Government Guidance Fund for Local Sci-Tech Development, Tianshan Talents Plan, Tianshan Innovation Team Plan, Youth Innovation Promotion Association of the Chinese Academy of Sciences.
DOI Link:
https://doi.org/10.26599/NR.2026.94908873
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 8,000 articles. In 2025 InCites Journal Citation Reports, its 2025 IF is 9.4 (8.3, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.
Nano Research
Research progress in exact charge transfer control in quantum dots/molecule system--induced large emission contrast for ultrasensitive and anti-interfering detection
27-Aug-2026