Maximum Emission Peak Research Articles

N-doped carbon dots for highly sensitive and selective sensing of copper ion and sulfide anion in lake water

Water contamination by copper ions (Cu2+) and sulfide anions (S2-) has been a longstanding human health hazard. The limitations of current detection strategies have created a high demand for effectively monitoring the concentrations of these ions in water systems. A facile fluorescent bioassay for Cu2+ and S2- was developed in this study based on “on-off-on” fluorescent nitrogen-doped carbon dots (N-CDs). N-CDs were synthesized for the first time via thermal treatment using hexamethylene-tetramine and ammonium citrate precursors. The obtained CDs were highly stable in aqueous solution, with a strong green emission and a 51.2% quantum yield. The maximum fluorescence emission peak was observed at 478 nm for a 360-nm excitation. Notably, the fluorescence intensity of N-CDs can be quenched by a factor of 6 by Cu2+, which can be applied to Cu2+ assays ranging from 0.05 to 5 μM with a limit of detection (LOD) of 25 nM. Interestingly, further addition of S2- recovered the fluorescence of the N-CD@Cu2+ nanocomplex, which can be used to quantify S2- in a broad range from 0.05 to 10 μM with an LOD of 32 nM. The N-CD and N-CD@Cu2+ nanocomplexes were also demonstrated to be highly specific towards Cu2+ and S2-, respectively. Finally, the sensor was successfully applied to lake water for detecting both Cu2+ and S2-, demonstrating excellent application prospects for analytical chemistry and environmental remediation.

Facile microwave-assisted synthesis of Ti3C2 MXene quantum dots for ratiometric fluorescence detection of hypochlorite.

Adual-channel "naked-eye" colorimetric and ratio fluorescent probe has been developedbased on titanium carbide quantum dots for the detection of curcumin and hypochlorite (ClO-). The fluorescence emission of Ti3C2 MXene quantum dots (Ti3C2 MQDs) is in the range 350-600nm, and the maximum emission peak is at 430nm that overlaps with the UV absorption of curcumin at 430nm to a large extent. This facilitates the fluorescence resonance energy transfer (FRET) between Ti3C2 MQDs and curcumin. When ClO- is added, the phenolic and methoxy groups of curcumin are oxidized to quinones, resulting in the restoration of the fluorescence of Ti3C2 MQD. In addition, the probe designed makes it easier to distinguish colors with the naked eye to detect curcumin and ClO-. The linear detection range of curcumin was 0.05-10μM, and the detection limit was 20nM. The linear detection ranges of ClO- are 25-150μM and 150-275μM, and the detection limit is 5μM. This study is the first report on the determination of curcumin and ClO- based on Ti3C2 MQDs by dual-channel "naked-eye" colorimetric and ratio fluorescence method.

Green synthesis of carbon quantum dots from sumac: characterization and investigation with cyclic voltammetry technique

Carbon dots, due to their minimal size, non-toxicity, simple, cheap and easy synthesis; Among the studies on nanostructured materials that have attracted attention in recent years; has become a popular study topic for researchers. In this study, for the first time, Sumac was used as a source of carbon, and carbon dots were obtained by using the hydrothermal synthesis method in a one-pot reaction at 175 ° C for 8 hours without using any chemical reagents. The characterizations of the obtained carbon dots were illuminated by various analytical instruments (High-Resolution Transmission Electron Microscope (HR-TEM), X-ray Diffractometer (XRD), Raman, Photoluminescence, Infrared, and Uv-vis spectrometer). According to the TEM results, the average diameter of carbon dots was found as 10.48 nm. The maximum emission peak of the carbon dots was monitored at 428 nm when excited at 350 nm. In the next step, the electrochemical properties of the carbon dots were examined by cyclic voltammetry technique. According to cyclic voltammetry results, the substance transport on the electrode surface by diffusion controlled.

Optical study of clustering in III-V semiconductor quaternary solid solutions

Multicomponent epitaxially grown III-V semiconductor solid solutions are frequently non-uniform, but have a tendency of clustering. Optical studies can be used to reveal the complex internal structure of the epitaxial layer. Here we analyze the temperature dependence of the linear polarization of the photoluminescence (PL) emission from different GaInP and GaInAsP epilayers in a temperature range from 10 K to 300 K. At room temperature the PL emission is not polarized, whereas at low temperature the PL emission from the GaInAsP epilayers is linearly polarized with a degree of polarization of approximately 0.2 at 10 K. When the temperature increases, the PL polarization decreases and becomes insignificant at approximately 100–150 K. Additionally, from 10 K to 100 K, the temperature dependence of the energy of the GaInAsP PL emission peak maximum follows a characteristic S-shaped curve. We calculated the PL polarization degree taking into account the change in crystal symmetry caused by local biaxial and uniaxial strain in the emitting clusters. According to the calculations, the PL emission from uniaxially strained regions is polarized and the strain depends on temperature, which is consistent with the measured data. These results show that the epitaxial GaInAsP solid solution is not homogeneous, but includes elastically strained clusters, which are consequence of atomic content fluctuations.

Homochiral coordination architectures based on a series of pyridyl-alanine derivatives with varied configurations: Structural diversity, photoluminescence and magnetic properties

Six homochiral coordination polymers based on a series of designed pyridyl-alanine derivatives ligands (x,y-H2PDBAla, x, y ​= ​2, 6; 2, 5; 3, 5) and different divalent cations in the absence/presence of ancillary ligands, including [Zn (2,6-PDBAla)]∙3H2O (1), [Cd (2,6-PDBAla)] (2), [Cd (2,5-PDBAla) (H2O)3]·2H2O (3), [Cu3(2,5-PDBAla)2 (bipy)2(H2O)2]·10H2O (4), [Co(3,5-PDBAla) (bpea) (H2O)] (5), [Ni(3,5-PDBAla) (bpee) (H2O)2]·5H2O (6) (H2PDBAla ​= ​pyridine-dicarbonyl-bis(l-alanine), bipy ​= ​4,4′-bipyridine, bpea ​= ​1,2-bis(4-pyridyl)ethane, bpee ​= ​1,2-bis(4-pyridyl)ethylene), were prepared and characterized. Three kinds of pyridyl-alanine derivatives ligands with versatile coordination modes bridge metal ions to generate the diverse structures. In the absence of ancillary ligand, the 2,6-H2PDBAla ligands and Zn(II)/Cd(II) ions react to get the compounds 1 and 2.1 exhibits a one-dimensional (1D) “loop” chain structure with the 14-membered rings, whereas a 3D framework with the qtz topology was observed in 2, in which the right-handed single-stranded and the left-handed double-stranded helical chains coexist. The 2,5-H2PDBAla ligands coordinate with Cd(II)/Cu(II) ions to yield the compounds 3 and 4.3 shows 1D right-handed single-stranded helical chain, and 4 shows a 2D layer constructed from right-handed single-stranded helical chain. The integration of 3,5-H2PDBAla ligands and Co(II)/Ni(II) ions leads to the compounds 5 and 6.5 displays a 2D wavy layer, consisting of the [Co(3,5-PDBAla)] right-handed single-stranded helical chain and the [Co(bpea)]2+ zigzag chain, and 6 displays a 2D layer with sql topology. The photoluminescence spectra of 1, 2 and 3 reveal the corresponding emissions of organic ligands, their maximum emission peaks appear at 402, 401 and 433 ​nm, respectively. Magnetic susceptibility mensuration of 5 gives the J of −12.35 ​cm−1, indicating strong antiferromagnetic interactions between the Co(II) ions.

Green synthesis of water-soluble fluorescent carbon dots from rosemary leaves: Applications in food storage capacity, fingerprint detection, and antibacterial activity

Blue fluorescent carbon dots are synthesized via a one-step hydrothermal method using rosemary leaves as a carbon source. The obtained carbon dots are characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis, FTIR, and fluorescence spectrometry. The results show that carbon dots gave a maximum emission peak at 422 nm when excited at 332 nm. The average particle diameter of the synthesized spherical carbon dots is found to be 16.13 nm with a 4.6-nm standard deviation. The diameters of the produced carbon dots vary, as is evident from standard deviation heights, resulting in multicolor emission spectra. The fruit storage experiment is carried out by investigating the qualitative antioxidant ability of the produced carbon dots. The results obtained for polyvinyl alcohol–carbon dot–coated samples differ remarkably compared to polyvinyl alcohol–coated samples only. The polyvinyl alcohol–carbon dot composition is used in latent fingerprint detection applications. In analyses made on a glass surface, fingerprints cannot be monitored on the glass surface with the polyvinyl alcohol layer under ultraviolet light, while they are observed on the surface covered with the polyvinyl alcohol–carbon dot composition. Moreover, biological activity against Gram-positive, Gram-negative, and yeast strains are investigated.

High Efficiency Sky-Blue Gold(III)-TADF Emitters*.

Highly efficient sky-blue luminescent gold(III) complexes with emission quantum yields up to 82 %, lifetimes down to 0.67 μs and emission peak maxima at 470-484 nm were prepared through a consideration of pincer gold(III) donor-acceptor complexes. Photophysical studies and time-dependent density functional theory (TDDFT) calculations revealed that the emission nature of these gold(III) complexes is most consistent with TADF. Solution-processed OLEDs with these gold(III) complexes as dopants afforded electroluminescence maxima at 465-473 nm with FWHM of 64-67 nm and maximum external quantum efficiencies (EQEs) of up to 15.25 %. This research demonstrates the first example of gold(III)-OLEDs showing electroluminescence maxima at smaller than 470 nm, and highlights the potential of using gold(III)-TADF emitters in the development of high efficiency blue OLEDs and blue emissive dopant in WOLEDs.

Fabrication of novel bifunctional nanohybrid based on layered rare-earth hydroxide with magnetic and fluorescent properties

We demonstrate the fabrication of a novel magnetic nanohybrid involving the drug molecule 5-aminolevulinic acid (5-ALA) intercalated Gd-Eu layered rare-earth hydroxide (LRH) coated on magnesium ferrite particles (MgFe2O4). The structure, thermostability, morphology, luminescence properties, cytotoxic effect and magnetism are investigated. The 5-ALA intercalated composite may correspond to a monolayered vertical arrangement, and the thermal stability of organics is enhanced after intercalation. The LRH precursor shows red emission of Eu3+ and the maximum emission peak of the composite is at 451 nm, corresponding to the blue emission. The detection of drug molecules can be realized through the change of luminescence. The magnetic nanohybrid shows strong magnetic sensitivity, which provides an easy and efficient way to separate 5-ALA-MgFe2O4@LGd0.95H:Eu0.05 particles from a sol or a suspension system and to carry drugs to targeted locations under an external magnetic field. The cytotoxic effect of MgFe2O4@LRH is observed with a sulforhodamine B (SRB) colorimetric assay, which has low cytotoxic effects on selected cells. The fabrication of novel bifunctional drug carriers based on LRH with magnetic and fluorescent properties has potential applications in drug detection and drug delivery.

Convenient and highly sensitive detection of Cu2+ using chitosan solid film with g-C3N4 nanosheets

Abstract A solid fluorescence sensor composed of g-C3N4 nanosheets and chitosan solid film was fabricated by electrostatic interaction. The g-C3N4 nanosheet/chitosan solid film showed selectivity and sensitivity to Cu2+ which was higher than that of other metal ions in common use. Cu2+ ions were found to efficiently bind and quench the fluorescence of the g-C3N4 nanosheet/chitosan solid film. The absorption band of the g-C3N4 nanosheet/chitosan solid film was at 240 nm in the presence of Cu2+, and the maximum emission peak was at 380 nm. Copper ion concentrations were between 0 and 3.1 × 10−5 mol/L at pH 7, the detection limit is 5 nM, compared with previous reports, it was much lower than before. Good linear relationships existed between the metal ion concentration and fluorescence intensity of g-C3N4 nanosheets in the quenching and recovering processes. This is the first study to report on the detection of Cu2+ by utilizing g-C3N4 nanosheet/chitosan composite film. The as-prepared films were conveniently prepared, easy to operate, and recyclable, as well as sensitive and selective to detect Cu2+ in water. All these features indicate the sensor’s potential application in disease diagnosis.

Efficient Violet Organic Light‐Emitting Diodes with CIEy of 0.02 Based on Spiro Skeleton

AbstractOrganic materials with violet electroluminescence are highly interesting for organic light‐emitting diode (OLED) application. However, the design and synthesis of new molecules combining with desirable violet emission and high luminous efficiency are a challenging task. Here, three novel organic molecules consisting of a pyrene unit and a highly rigid skeleton, namely TFPy2, TFPy3, and TFPy4, are developed for violet‐emitting OLEDs (VOLEDs). These emitters exhibit excellent thermal stability and violet emission with a narrow full width at half‐maximum (FWHM) and high photoluminescence quantum yields (PLQYs). Photophysical results show that the emission peaks can be tuned by the introduction of pyrene units at different positions, and the emission will have a blue shift with increasing steric hindrance. Moreover, OLEDs fabricated with TFPy2, TFPy3, and TFPy4 as the emitters exhibit maximum external quantum efficiencies (EQEs), emission peaks, and CIEs (x,y) of 3.8%, 414 nm, and (0.15, 0.03); 4.8%, 406 nm, and (0.16, 0.02); and 5.1%, 404 nm, and (0.16, 0.02), respectively. The two molecules TFPy3 and TFPy4 exhibit violet emissions with EL peaks at ≈405 nm with a record low CIEy of 0.02. Therefore, these materials and their construction strategy are promising for future VOLEDs with wide‐color‐gamut display and potential biological applications.

Carbazole‐based colorimetric and fluorescent probe for Cu2+ and its utility in bio‐imaging and real water samples

AbstractA new carbazole functionalized Schiff base CBM was synthesized and characterized. CBM can selectively recognize Cu2+ via UV–vis and fluorescence signal among common biologically relevant metal ions. When Cu2+ was added to CBM, there was a significant enhancement at the maximum absorption wavelength of 393 nm and with a distinct blue shift. The maximum emission peak was significantly attenuated by a factor of about 15 times at 535 nm and the blue shift of emission wavelength was observed. When other metal ions were added, there was no remarkable change at the maximum absorption and emission peak. Under the illumination of 365 nm ultraviolet lamp, the color of the CBM solution changed from light blue to dark blue after the addition of Cu2+. The combination mechanism of CBM with Cu2+ was nicely explored by density functional theory studies. The probe CBM has good cell permeability, fluorescence electron microscopy experiments show that CBM can be used as a fluorescent probe to detect the presence or absence of Cu2+ in Hela cells. Furthermore, the probe CBM can also be used for the detection of copper ions in actual water samples.

Synthesis and characterization of homoleptic triply cyclometalated iridium(III) complex containing 6-(pyridin-2-yl)isoquinoline moiety for solution-processable orange-phosphorescent organic light-emitting diodes

The design and synthesis of a novel homoleptic triply cyclometalated iridium(III) complex containing the 6-(pyridin-2-yl)isoquinoline moiety [Ir(pyiq)3] was demonstrated for the first time. The performance of a phosphorescent organic light emitting diode (PHOLED) based on Ir(pyiq)3 is described with adoption of tris(4-carbazoyl-9-ylphenyl)amine (TCTA) and 2,2′,2"-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) which are co-host materials showing excellent compatibilities as well as CBP host with the prepared phosphorescent dopants. The photoluminescence (PL) of Ir(pyiq)3 produced orange emission with maximum emission peak at 583 nm. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital energy (LUMO) levels of Ir(pyiq)3 were −5.41 eV and −3.20 eV. An optimized solution-processed device doped with Ir(pyiq)3 had a maximum external quantum efficiency (EQE) of 8.71% and a maximum current efficiency (CE) of 22.51 cd/A. This correspond to 17% higher efficiency than that with bis(2-phenylbenzothiozolato-N,C2′)iridium(acetylacetonate) (bt)2Ir(acac), which is commonly used in orange PHOLEDs. This study rationalizes the promising application of new trimeric organometallic complex that possesses isoquinoline and pyridine in solution-processed PHOLEDs with good quantum and power efficiency.

P‐179: Design and Synthesis of Blue Thermally Activated Delayed Fluorescent Emitter with Strong PyCN Acceptor and Multi Donors

A thermally activated delayed fluorescence (TADF) emitter of 234CzPyCN was synthesized to study the effect of strong acceptor (PyCN) and strong multi donors on the TADF properties. Electrical and Photophysical properties of the TADF emitters were characterized by the electron donating and accepting strength of the molecule. The material was designed by uniting multiple carbazoles which are substituted at ortho, meta, and para positions relative to the PyCN that is applied as electron accepting unit. Energy band gap between the highest occupied molecular orbital (HOMO) and the lowest occupied molecular orbital (LUMO) was measured to be 2.97 eV. The maximum photoluminescence emission peak of 234CzPyCN was 479 nm. 234CzPyCN device presented maximum external quantum efficiency of 20.8% with a CIE color coordinate of (0.18, 0.37).

Green and Efficient Synthesis of Fluorescent Bis(pyrazolyl)methanes in Choline Chloride/Urea Deep Eutectic Solvent

A series of pyrazole-based heteroaromatic compounds were synthesized by the reaction of 3-methyl-5-pyrazolone and aromatic aldehydes in Choline chloride/urea DES as a green solvent. This simple and green procedure has advantages such as easy operation, short reaction times, efficient yields, low cost and minimum use of hazardous solvents and catalysts. The structure of compounds was determined by IR, 1H and 13C NMR spectra, and the crystal structure of 4a was confirmed using X-ray crystallographic analysis. The optical properties of Pyrazole derivatives 4a-g have also been studied with UV/vis and fluorescence spectroscopy. All of these pyrazole-containing heteroaromatic compounds displayed maximum emission peak from 340 to 360 nm.

Luminescent europium(III)-organic framework for visual and on-site detection of hydrogen peroxide via a tablet computer

A luminescent metal-organic framework of type Eu(III)-MOF has been fabricated for visual and on-site fluorometric determination of hydrogen peroxide (H2O2) via atabletcomputer. The maximum excitation and emission peaks of type Eu(III)-MOF were found at λex = 290nm and λem = 615nm, respectively. The average length of Eu-MOF is 1.21 ± 0.07μm. In the presence of the target H2O2, Fe2+ is transmitted into Fe3+ via Fenton reaction, leading to a fluorescence quenching of Eu-MOF. Therefore, visible color change occurred from bright red into colorless. Interestingly, by means of tablet computer's digital camera and ImageJ software, fluorescent signals were captured and transduced into digital parameters, resulting ina linear relationship between fluorescence intensity and the concentration of H2O2. As a result, the determination of H2O2 without the aid of complicated instruments is achieved in therange 2.0μM to 0.2mM with a detection limit of1.02μM. Our approach has beensuccessfully applied to quantify H2O2 in serum, urine, and waste water with good recovery and precision (< 2.5% RSD). Besides, our assay has beenexploited for visual detection of H2O2 released from HepG2 cells with the advantages of portability and accuracy. Moreover, the strategy displays acceptable selectivity and stability. Hence, our assay provides an alternative practical method for on-site determination of H2O2 without the need for instruments. Graphical abstract Schematic representation of the synthesis procedure of a luminescent Eu-MOF, which has been successfully applied for on-site detection of H2O2 via Fenton reaction and imaging analysis technique. The method exhibits handheld and accuracy for H2O2 determination, holding the potential for biochemical and clinical applications in remote regions.

Investigating the Properties of Cetyltrimethylammonium Bromide/Hydroxylated Graphene Quantum Dots Thin Film for Potential Optical Detection of Heavy Metal Ions.

The modification of graphene quantum dots (GQDs) may drastically enhance their properties, therefore resulting in various related applications. This paper reported the preparation of novel cetyltrimethylammonium bromide/hydroxylated graphene quantum dots (CTAB/HGQDs) thin film using the spin coating technique. The properties of the thin film were then investigated and studied. The functional groups existing in CTAB/HGQDs thin film were confirmed by the Fourier transform infrared (FTIR) spectroscopy, while the atomic force microscope (AFM) displayed a homogenous surface of the thin film with an increase in surface roughness upon modification. Optical characterizations using UV-Vis absorption spectroscopy revealed a high absorption with an optical band gap of 4.162 eV. Additionally, the photoluminescence (PL) spectra illustrated the maximum emission peak of CTAB/HGQDs thin film at a wavelength of 444 nm. The sensing properties of the as-prepared CTAB/HGQDs thin film were studied using a surface plasmon resonance technique towards the detection of several heavy metal ions (HMIs) (Zn2+, Ni2+, and Fe3+). This technique generated significant results and showed that CTAB/HGQDs thin film has great potential for HMIs detection.

A fluorescent probe for distinguish detection of formaldehyde and acetaldehyde

A new fluorescent chemosensor DTH for distinguish detection formaldehyde (FA) and acetaldehyde (AA) has been synthesized based on 2, 5-dihydroxy-p-benzenedicarbonamide as fluorophore and hydrazine as reaction group. DTH is a ratiometric probe for formaldehyde with fluorescence quantum yield is 0.055 and a turn on probe for acetaldehyde with a higher fluorescence quantum yield (0.122) due to different electron donating property of –H (formaldehyde) and –CH3 group (acetaldehyde), FA-DTH and AA-DTH, which were products of formaldehyde and acetaldehyde with DTH, respectively, showed different fluorescence variation. Interestingly, the maximum fluorescence emission peak wavelength varies with different molar ratio of the mixture solution of FA/AA and it was found that the wavelength is linear with the molar ratio of FA/AA, demonstrating that DTH fluorescence probe can be used not only to distinguish detect formaldehyde and acetaldehyde, but also to analyze the approximate content of formaldehyde and acetaldehyde in the mixed solution. Therefore, DTH is an excellent probe, which is expected to be applied in cells and distinguish detection of formaldehyde and acetaldehyde in the environment.

Fluorescent Determination of Mercury(II) by Green Carbon Quantum Dots Synthesized from Eggshell Membrane

Carbon quantum dots (CQDs), as a new carbonaceous nanomaterial, have attracted considerable attention due to their excellent properties. In this work, eggshell membrane (ESM), an excellent carbon source that is very easy to obtain, was used to synthesize water-soluble and fluorescent CQDs with a rapid, environmentally friendly and waste-recycling hydrothermal method. The synthesized functionalized CQDs showed superior water dispersibility and stability with a maximum fluorescence emission peak at 420 nm. The fluorescence quantum yield was approximately 9.6% under the selected synthesis conditions. A new label-free fluorescent method for the selective determination of Hg2+ was developed with a detection limit of 2.6 μM using the inhibition of the CQDs fluorescence by the ions. The linear range of the detection is from 10 to 100 μM. The prepared CQDs have also been successfully applied to the determination of Hg2+ in water samples.

Fluorescent Determination of Mercury (II) and Glutathione Using Amino-MIL-53(Al) Nanosheets

Amino-MIL-53(Al) nanosheets were synthesized by a hydrothermal reaction and were employed as a fluorescent probe because of their high quantum yield and excellent stability. The amino-MIL-53(Al) nanosheets have a maximum fluorescence emission peak at 435 nm using an excitation wavelength of 335 nm. The fluorescent intensity of luminophor at 435 nm was linearly quenched when mercury (II) (Hg2+) was added, which occurred due to the adsorption of Hg2+ onto the luminophor surface. Under these conditions, the fluorescent signal of the system is in the “turn-off” state. Following the addition of glutathione (GSH) into the system, the quenched fluorescence intensity may be partially restored based on the reaction between glutathione and Hg2+. In this condition, the fluorescent signal of the amino-MIL-53(Al)-Hg2+ system is in the “turn-on” state. Therefore, the amino-MIL-53(Al) nanosheets were successfully used as a “turn-off-on” fluorescent sensing system to determine the concentrations of Hg2+ in Tibetan medicine and glutathione in rabbit serum. A good correlation coefficient was obtained between the quenching of the fluorescence intensity of luminophor and the concentration of Hg2+ using the optimized conditions. A linear range was acquired from 1.96 nM to 38.27 μM with a detection limit of 0.23 nM of Hg2+ based upon a signal-to-noise ratio of three. For glutathione, the linear dynamic range was from 210 nM to 15.25 μM with a detection limit equal to 8.11 nM based upon a signal-to-noise ratio of three. This developed sensor system has the advantages of high selectivity, favorable sensitivity and simple operation for the determination of Hg2+ and glutathione in real samples.

Single-atom iron containing nanozyme with peroxidase-like activity and copper nanoclusters based ratio fluorescent strategy for acetylcholinesterase activity sensing

Single-atom nanozymes (SAzymes) have attracted extensive interests in bio-catalysis filed because of their robustness, excellent catalytic activity and unique feature of maximum atomic utilization. Herein, the peroxidase-like activity of single-atom iron anchored on N-doped porous carbon (Fe-SAs/NC) SAzyme was successfully demonstrated and a ratio fluorescence method for acetylcholinesterase (AChE) activity sensing was constructed based on Fe-SAs/NC and polyvinylpyrrolidone protected copper nanoclusters (PVP-CuNCs) for the first time. With H2O2 presence, Fe-SAs/NC with peroxidase-like activity catalyzed oxidation of nonfluorescent o-phenylenediamine (OPD) to fluorescent 2,3-diaminophenazine (DAP) with maximum fluorescence emission peak at 566 nm. Meanwhile, the generated DAP efficiently quenched PVP-CuNCs fluorescence at 438 nm through fluorescence resonance energy transfer (FRET). However, AChE possessed function of catalyzing the hydrolysis of acetylthiocholine (ATCh) to generate thiocholine (TCh), which can inhibit the Fe-SAs/NC peroxidase-like activity to block DAP generation and preserve PVP-CuNCs fluorescence. Therefore, the fluorescence intensity ratio F566/F438 of the system can serve as signal output for AChE activity sensing ranging from 2 to 70 U L−1 with a detection limit of 0.56 U L−1. Moreover, Fe-SAs/NC and PVP-CuNCs based system was utilized for AChE determination in human serum sample.