355 results about "Fluorescence sensing" patented technology

The invention relates to a Schiff base compound and a method for detecting an aniline compound thereof, belonging to the technical field of chemical sensor materials. The Schiff base compound is characterized by being prepared in such a way that an aromatic aldehyde compound with ortho-position hydroxyl reacts with monoamine or polyamine and has the structural formula shown as the figure, wherein n1 is an integer from 1 to 100, and n2 is an integer from 1 to 6; R is an aliphatic hydrocarbon substituted group, an aryl substituted group, heteroatom-substituted aliphatic alkyl or heteroatom-substituted aryl alkyl; and R1 and R2 are electron-withdrawing groups or electron-donating groups. The compound has stable solid fluorescence luminous performance, the fluorescence strength of the compound is changed by the aniline compound, the aniline compound can be detected according to the change of the fluorescence strength of the compound, and the compound is a novel fluorescence sensing material for detecting aniline.

The invention relates to organic-ligand-based multifunctional zinc complexes and application thereof. The molecular formulae of the complexes are as follows: {[Zn(L1)(mip)].H2O}n, {[Zn2(L1)2(hip)2].H2O}n, {[Zn(L1)(oba)].H2O}n, {[Zn(L1)(chda)].H2O}n, [Zn(L2)(mip)]n, {[Zn(L2)(hip)(H2O)].3H2O}n and [Zn(L2)(oba)]n. The preparation method comprises the following steps: adding deionized water into Zn(NO3)2.6H2O, tripyridine derivative ligand and V-type dicarboxylic acid, regulating the value, and carrying out hydrothermal synthesis to obtain the product. The complexes have the advantages of high affinity for water-soluble pollutants, favorable catalytic degradation effect, low environmental pollution and favorable fluorescence sensing behavior.

The invention relates to a nano-crystal cellulose fluorescent probe for detecting metal ions and a preparation method thereof, and belongs to the technical field of nanometer materials and fluorescence sensing crossing. The method comprises the steps that firstly, an active functional group is introduced into the surface of nano-crystal cellulose, the nano-crystal cellulose fluorescent probe is constructed through covalent bonding fluorescent dye, by means of the synergic complexing action of the surface active functional group, the fluorescence emission mechanism of the fluorescent dye is changed, and selectivity and sensitivity detection for metal ions are achieved. The nano-crystal cellulose fluorescent probe is an environment-friendly green material and is good in hydrophilia, safe, free of toxin, capable of being completely degraded and capable of being applied to the fields of metal ion sensing detection, fluorescence tracking, bioimaging and the like.

The invention relates to a fluorescence biosensor, and a preparation method and a purpose thereof. On the basis of a two-dimensional manganese dioxide nanometer sheet as a fluorescence sensing platform, morpholineethanesulfonic acid is used for reducing potassium permanganate for synthesizing the manganese dioxide nanometer sheets; the manganese dioxide nanometer sheets adsorb FAM-ssDNA and quench FAM fluorescence; under the effect of alkaline phosphatase, vitamin C magnesium L-ascorbate-2-phosphate is hydrolyzed to generate ascorbic acid; the two-dimensional manganese dioxide nanometer sheets are reduced into manganese ions by the ascorbic acid; FAM-ssDNA is released; the fluorescence is recovered; the fluorescence sensor using the manganese dioxide nanometer sheets and the alkaline phosphatase to regulate the fluorescence intensity is built and is used for detecting the activity of the alkaline phosphatase. Compared with the prior art, the fluorescence biosensor has the characteristics of simplicity, high speed, low background signal, high sensitivity, low detection limit and good selectivity by using the change of the two-dimensional manganese dioxide nanometer sheets on the fluorescence signal, i.e., the off-on mode for detecting the alkaline phosphatase.

The invention discloses a preparation method of a quantum dot@Cu nano-cluster ratiometric fluorescent sensor and application thereof in Cu<2+> detection, belonging to the technical field of fluorescence sensing. According to the preparation method, CuNCs prepared by taking polyethyleneiminen as a template is coupled to the surface of silicon dioxide coated CdSe QDs to prepare CdSe QDs@CuNCs ratiometric fluorescent sensor having CdSe QDs and CuNCs double-fluorescence emission signals. When Cu<2+> exists in a solution, amino of polyethyleneimine and Cu<2+> are subjected to complexing to form a copper-amine complex, thereby avoiding the problem that CuNCs fluorescence quenching is caused but the fluorescence intensity of CdSe QDs is unchanged because electrons are transferred from amino to CuNCs. With the increase of Cu<2+> concentration, the intensity ratio of two fluorescence emission peaks of CdSe QDs and CuNCs is reduced gradually, thereby realizing sensitive fluorescent and visual detection on Cu<2+>.

The invention discloses an organic ligand for synthesizing metal organic frames. The chemical nomenclature of the organic ligand is 2-(3, 5-bis (4-pyridyl) phenyl) benzoglioxaline. The chemical formula of the organic ligand is represented in the description. The invention also discloses a synthetic method of the organic ligand and a Cu (I) ion-based bright yellow metal organic frame (MOF-1) and a Cu (I) ion-based dark red metal organic frame (MOF-2), and the chemical formulas are {[Cu(L)I].0.5CH3CN.0.5CH3OH.0.75H2O}n, (n=1,2,3...'8') and {[Cu(L)I].2H2O}n(n=1,2,3...'8'). The invention also provides a synthetic method for dark red Cu (I) ion metal organic frame (MOF-2) and a synthetic method for organic matters of the Cu (I) ion metal organic frame. The invention also provides application of the organic ligand and metal organic frames serving as alcohols small organic molecule fluorescence sensing materials. The application operation is simple, the cost is low, the respond is quick, and the obvious fluorescence response for methanol, ethanol, isopropanol , n-propanol under the liquid phase and the gas phase can be achieved.

The present invention relates to methods for functionally modifying a polymeric surface for subsequent deposition of metallic particles and / or films, wherein the polymeric surface is modified by increasing hydroxyl and / or amine functional groups thereby providing an activated polymeric surface for deposition of metallic particles to form a fluorescence sensing device. The device can be used for metal-enhanced fluorescence of fluorophores positioned above the metallic particles that can be readily applied to diagnostic or sensing applications of metal-enhanced fluorescence.

The invention provides a preparation method for a fluorescence sensing material based on molecular imprinting and carbon dots. The method comprises the following steps: adding a substitute template and a functional monomer into a mixed solution composed of chloroform, acetonitrile and toluene, carrying out stirring and allowing the mixed solution to fully dissolve and react, then adding the carbon dots, carrying out stirring and then adding a crosslinking agent and an initiator, carrying out ultrasound and then introducing nitrogen for water bath and incubation, carrying out filtering, carrying out placing in a vacuum drying oven for aging, carrying out washing with an extracting solvent so as to remove template molecules, and carrying out vacuum drying so as to obtain a molecular imprinting and carbon dot fluorescent sensing material. The preparation method for the fluorescence sensing material provided by the invention has the advantages of high stability, light-free bleaching, low toxicity and capability of directly forming a sensing material by embedding into molecular imprinting polymer through polymerization reaction without the need of subsequent modification; and the sensing material in the invention is simple in preparation process, and has specific recognition effect of the molecular imprinting polymer, strong fluorescence characteristic of the carbon dots, and selective recognition effect to sterigmatocystin.

The present invention discloses a novel fluorescent probe capable of specifically recognizing cysteine, wherein the molecular structure formula is defined in the specification. According to the present invention, the fluorescent probe can distinguish the mercapto-containing cysteine from the mercapto-free amino acid region, can distinguish the cysteine from the homocystine and the glutathione having the similar structure, emits red light during cysteine detection, can reduce the background interference and the damage of light on tissue cells in biological applications, exhibits great Stokes shift, can reduce self-absorption so as to improve the sensitivity, can be used for the fluorescence sensing analysis of the cysteine in environments or biological samples, and has advantages of good selectivity to cysteine, high sensitivity, strong interference resistance, and good application prospect.

The invention provides a preparation method of a pH-sensitive dual-emission carbon quantum dot, and belongs to the technical field of nanomaterials. The pH-sensitive dual-emission carbon quantum dot is prepared from a common organic micro-molecule by using a solvothermal reaction through changing a traditional production process, and has emission peaks at 445 nm and 555 nm respectively, the fluorescence intensity and the fluorescence peak position change with the pH environment, and when the pH value increases, the emission peak at 555 nm weakens, the emission peak at 445 nm strengthens, the fluorescence becomes blue from blue green, and the pH-sensitive dual-emission carbon quantum dot is easily applied to the fields of pH sensors and cell fluorescence imaging, and an organic composite film produced after compounding the pH-sensitive dual-emission carbon quantum dot with an organic polymeric matrix can be applied to fluorescence sensing of acidic and alkaline solvents or gases I orderto carry out food detection.

The invention relates to a fluorescence imaging detection device, and particularly provides a directional emission fluorescence imaging detection device, which is provided with an optical laser beam-expanding system, a sample system and a detecting system, wherein the optical laser beam-expanding system is provided with a laser light source, a microobjective, a needle hole, a plano-convex lens, an attenuator and a rectangular diaphragm, the excitation light emitted by the laser light source sequentially passes by the microobjective, the needle hole and the plano-convex lens for beam expanding and collimation to form parallel light beams, and the parallel light beams sequentially pass by the attenuator and the diaphragm to obtain light spots; the sample system is provided with a rotating stage, a sample rack, a prism and an optical quartz substrate, the prism is placed on the sample rack and fixed at the center of the rotating stage, a nanoscale metallic film is arranged on the surface of the quartz substrate, a fluorescence sensing film is arranged on the surface of the metallic film, and solution is coated between the quartz substrate and the prism; and the detecting system is provided with a CCD rotating arm, a CCD receiver and an optical filter, the CCD rotating arm is fixed on the stage board of the rotating stage, the CCD rotating arm is connected onto the stage board of the rotating stage, and the CCD receiver used for collecting images and the optical filter are arranged on the CCD rotating arm.

The invention relates to the field of fluorescent probes, and in particular relates to a coumarin 2-hydrazinobenzothiazole Schiff base fluorescent probe and an application thereof. The fluorescent probe has a specific structure shown in the description. The fluorescent probe provided by the invention can recognize Cd<2+> in an EtOH-H2O (95:5, v / v, and HEPES 20 mmol / L) solution, and has the advantages of exhibiting excellent selectivity in competition with other ions, and having higher fluorescence sensing properties, low detection limit, high detection sensitivity and a high fluorescence quantum yield.

The invention relates to the field of fluorescence probes, particularly to an Eu (III)-metal-organic framework and preparation and application methods thereof. The Eu (III)-metal organic framework isapplied to detection of quintozene. The Eu (III)-metal-organic framework has a chemical formula of {[(CH3)2NH2][Eu(cppc)2*2H2O]}n. The Eu (III)-metal-organic framework saves post-synthesis purification and can be directly applied to fluorescence detection of quintozene, thereby having the advantages of simple design, low cost and the like and being applicable to online sensitive and rapid analysis. The Eu (III)-metal-organic framework achieves a quintozene detecting limit of 1.67*10<-6> M and meanwhile is short in response time, and meanwhile, can be thoroughly separated through simple filtering, thereby being high in reutilization rate. Besides, the Eu (III)-metal-organic framework achieves universality in the field of fluorescence sensing and facilitates practical application.

A method of preparing monomolecular layer polysilane fluorescence sensing thin film sensitized to nitroarene includes steps of: cutting substrate, preparing lotion, preparing active substrate, preparing silanized substrate, preparing polysilane, and preparing monomolecular layer polysilane fluorescence sensing thin film. The invention assembles a monolayer of silanization agent with chlorine functional group at terminal to a glass substrate surface, polysilane with lithium at terminal reacts with the alkyl chloride to be chemically combined on the surface of the substrate, conjugated fluorescence macromolecule is introduced into the sensing thin film, hypersensitization of the thin film sensor is realized, and problem of stability and permeability for solid fluorescence sensor is solved. Advantages of the invention are: stability is good, life time is long, sensitivity is high, the fluorescence sensing thin film can be used on sensor and detection instrument for detecting nitroarene-containing compound, and the fluorescence sensing thin film sensed nitroarene compound can be directly detected by fluorescence instrument.

The invention pertains to the technical field of nanometer supramolecular materials, and relates to a nanometer supramolecular assembly of a perylene diimide derivate modified by full methylated Beta-cyclodextrin loaded by polyvinylidene fluoride membrane and a preparation method thereof. The chemical formula of the molecular assembly is C138H226N2O72, and the structure thereof is shown as in an attached drawing. The perylene diimide derivate modified by the red fully methylated Beta-cyclodextrin is dissolved to obtain the nanometer supramolecular assembly. The method adopts the strong fluorescence of solid perylene as a detecting singnal, takes an empty chamber of the fully methylated Beta-cyclodextrin as a receptor of an air molecule, thereby solving two difficulties of strong fluorescence in a solid state in the construction of a fluorescence sensor and the introduction of a suitable air molecular receptor. The nanometer supramolecular assembly of the perylene diimide derivate modified by full methylated Beta-cyclodextrin loaded by PVDF member realizes quick detection of the fluorescence sensing function of the air molecules of nitromethane, nitroethane and nitrobenzene in 10s.

The invention discloses a three-dimensional fluorescent covalent organic framework material as well as a preparation method and application thereof. A hexamethyl biphenyl aldehyde derivative and a series of pyrenylamine derivatives are used as raw materials, o-dichlorobenzene and mesitylene are used as solvents, acetic acid is used as a catalyst, and solvothermal reaction is carried out for several days. After the reaction is finished, suction filtration and washing are sequentially carried out by using DMF and THF, carrying Soxhlet extraction is carried out for 24 hours, and vacuum drying iscarried out to obtain yellow powder, namely a target product. Hexamethyl biphenyl tetraaldehyde based on a steric effect and pyrenyl tetramine with fluorescent property are used as construction monomers, the synthesized Turn-on type three-dimensional fluorescent covalent organic framework has a rich cavity structure and a conjugated three-dimensional skeleton, the aggregation-induced quenching effect of fluorophores is avoided, the sensitivity of host-guest response of the material is improved, the material has a good application prospect in the field of fluorescence sensing, and the three-dimensional covalent organic framework is applied to the field of VOCs molecular decoding for the first time.

The invention relates to a material heat conduction analysis device based on a fluorescence method, and belongs to the field of material thermal property analysis. The material heat conduction analysis device comprises a probe (1), a photoelectric module and a data processing module. The probe (1) is used for detecting fluorescence sensing materials (7) on an object to be tested and transmitting detected optical signals to the photoelectric module through optical fibers (2). The photoelectric module coverts the received optical signals into electric signals, and converts the electric signals into temperature signals and then transmits the temperature signals to the data processing module. The data processing module obtains a temperature change curve according to the temperature signals, obtains a thermal diffusion coefficient of the detected object through comparison with standard data, and transmits the thermal diffusion coefficient to an upper computer for heat conduction analysis. The material heat conduction analysis device can be applied to measurement of thermal diffusion coefficients of gas, liquid and solid, is simple in structure, high in flexibility, and has the advantages of being better in measurement accuracy and anti-electromagnetic interference capacity, and achieving functions of miniaturization, intellectualization and online monitoring.

The invention relates to a real-time online optical fiber oxygen sensor. A high power light-emitting diode or pulse lamp is adopted as the excitation light source. The excitation light is transmitted by an exciting optical fiber to irradiate an oxygen fluorescence sensing membrane, and the generated fluorescence is collected by a launching optical fiber after passing through an optical filter and is transmitted to an optoelectronic conversion device to be detected. In a probe of the optical fiber oxygen sensor, the exciting optical fiber and the launching optical fiber forms an angle of 50-70 degrees, thus effectively reducing interference of media. The maximal fluorescence receiving efficiency can be obtained near the angle of 60 degrees. The oxygen fluorescence sensing membrane is placed in the sensor and can continuously detect the oxygen content in the gas and the dissolved oxygen in the water on line in real time. The sensor has the advantages of long service life, wide measurement range, high sensitivity, good stability and repeatability, easy miniaturization and the like.

The invention discloses a carboxymethyl lysine fluorescence imprinting material and a preparing method and application thereof .According to the preparing method, thin layer nano material graphene is used as a carrier, a fluorescence nano material namely quantum dots excellent in optical performance is used as a response element, a molecularly imprinting polymer high in selectivity and specificity is used as a recognition element, an efficient, portable, fast and sensitive molecularly imprinting fluorescence sensing system is set up, carboxymethyl lysine is used as template molecules, 3-aminopropyl triethoxy silane is used as a functional monomer, tetraethoxy-silicane is used as a crosslinking agent, and ammonia water is used as a catalyst .The surface molecularly imprinting material based on graphene and quantum dots is prepared through a reversed-phase microemulsion synthesis method, and carboxymethyl lysine residues can be detected from food fast and easily .

The invention relates to a preparation method of a polymer fluorescence sensing film containing cholesterol. According to the invention, the cholesterol is introduced into the side chain of a conjugated fluorescence molecule through utilizing the characteristics of supermolecule self-assembly, rigid construction and good film-forming properties of the cholesterol, and the molecule and diamine are polymerized, so that the polymer which contains the cholesterol and has a fluorescence property is obtained; and the novel polymer is utilized as a sensing element so as to prepare the fluorescence sensing film, thereby realizing hypersensitization of a thin film sensor and solving the stability and the permeability of a solid fluorescence sensor. The preparation method provided by the invention has the advantages that the operation is simple, and the reaction conditions are mild; and the prepared fluorescence sensing film is good in stability, long in service life, and high in hydrogen chloride gas detection sensitivity, can be applied to a sensor for detecting the hydrogen chloride gas, and can also be used in a detection instrument for detecting the hydrogen chloride gas by utilizing a fluorescence principle; and the fluorescence sensing film senses the hydrogen chloride gas so as to carry out detection directly through a fluorescence instrument.

The invention relates to an aza-fluorine organic semiconductor material and preparation and application methods thereof, belonging to the organic photoelectric material scientific field, in particular to the aza-fluorine organic semiconductor material and the preparation method. And the material is applied to organic electronic fields of organic light emitting display, fluorescence sensing, flash memory devices, solar cells, and etc. With the structure shown above, the material has the advantages that: (1) the aza-fluorine has special electron acceptor electronic structure and opto-electrical properties; (2) the material can interact or react with metal mutually and can be applied to the sensing field; (3) synthetic route is simple, etc.

The invention discloses a sensitive predictive coat material with the phenylfluorone sensitive material used in the aluminum alloy surface, which is made up of the 0.2-0.8 weight of phenylfluorone fluorescence sensing material, 0.01-0.05 weight of activating agent and residue agglomerant. The invention uses the fluorescence corrosion sensing intelligent coat as the monitoring instrument; the fluorescence compound is as the corrosion sensing material. By using the character of fluorescence change after compounding with the special metal ion in different oxidation, reducing and pH value, it combines with the coat to monitor. The technology has the high sensitivity to monitor the aluminum alloy corrosion, which can detect the aluminum ion of ppm. So it can provide the ability to appraise the corrosion state and get the important corrosion environment information.

The invention discloses a DGT-PO composite membrane for in-situ simultaneous monitoring of labile phosphorus and dissolved oxygen. The composite membrane is characterized by comprising a transparent supporting body, a fluorescence sensing layer and a DGT fixing layer; the fluorescence sensing layer is obtained by uniformly mixing fluorochrome octaethyl porphilin platinum and fluorescein 10-GN, and fixing the two fluorochromes to the surface of a transparent supporting body through chemical embedding; the DGT fixing layer adopts submicron ZrO particles as a fixing agent and adopts polyurethane as a matrix, and the DGT fixing layer is obtained on the fluorescence sensing layer through a coating method. According to the composite membrane, on the basis of a slab photoelectrode and a film diffusion gradient principle, two channels are adopted for obtaining DO and SRP information, and SRP fixation and DO induction in the matrix such as water or sediments or soil or the like can be achieved.

The invention discloses a fluorescence-sensing-based method for rapidly detecting explosives such as nitrobenzene in water and applications thereof. The self-assembling nano-micelle serves as a carrier for embedding and protecting a fluorescent conjugated polymer and comprises block polyether, grafting cellulose amphiphilic derivatives and the like, and the self-assembling nano-micelle / conjugated polymer compounds with excellent water dispersibility are explosives such as nitrobenzene in water detected by a fluorescence probe. The fluorescence-sensing-based method for rapidly detecting explosives such as nitrobenzene in water provides technical support for developing test paper and kits for rapidly detecting the explosives, and the method is expected to play a role in emergency safety detection, airport check, environmental detection and biological cell imaging and has a wide application prospect.

The invention belongs to the technical field of environmental monitoring, and relates to a method for detecting oxytetracycline fluorescence based on surface passivated and DNA covalent coupling modified metal organic skeleton nanosheets. The covalent coupling of the surface of the two-dimensional MOF nanosheets with DNA effectively utilizes the limited adsorption sites on the surface of the MOF nanosheets to enhance the ability of the nanosheets to adsorb DNA molecules and reduce the background fluorescence signal. At the same time, the use of short-chain DNA molecules as signal reporter molecules effectively improves the efficiency of fluorescence recovery, and the addition of surface passivator sodium polystyrene sulfonate in the reaction system further weakens the adsorption capacity of nanosheets to signal reporter molecules, thereby making the MOF nanosheet sensor improve the linear response to low-concentration OTC and enhancing the detection performance of the OTC. The detection method provided by the invention can effectively reduce the fluorescence background value, improve the signal response value induced by the target, and effectively improve the detection performanceof the oxytetracycline on the fluorescence sensing platform constructed based on the physical adsorption principle.

The present invention discloses a fluorescence sensing film based on boron dipyrromethene-phenyl boronic acid (BODIPY-PBA), wherein the fluorescence sensing film comprises, by weight, 0.18% of BODIPY-PBA, 0.14% of tridodecyl methyl ammonium chloride, 33.23% of polyvinyl chloride, and the balance of 2-nitrophenyl octyl ether. The present invention further discloses a preparation method for the fluorescence sensing film based on the BODIPY-PBA, and an application of the fluorescence sensing film. According to the present invention, the new synthesis route is adopted to prepare a series of BODIPY-PBA derivatives, wherein the BODIPY-PBA derivatives have different emission wavelengths and high quantum yields. With application of the BODIPY-PBA in fluorescent probes, monosaccharide can be detected in homogeneous phases and polymer optical sensing films, the fructose selectivity is particularly good, the response time is short (20 minutes), and the glycogen can be directly detected in homogeneous phases.

The invention relates to a fluorescence sensing material for Cu2+ and Fe3+ detection and a preparation method and application thereof. The preparation method includes dissolving polyphenylene vinylene precursor and polymethyl methacrylate into N, N-dimethyl-formamide solvent, obtaining polyphenylene vinylene precursor / polymethyl methacrylate nanofiber membrane after electrostatic spinning, and subjecting the obtained nanofiber membrane to a heat eliminating treatment under a vacuum state at the temperature of 110 to 130 DEG C to obtain the fluorescent sensing material. The fluorescent sensing material has a high specific surface area, so that the contact surface of the fluorescent sensing material and detection molecule can be effectively enlarged to obtain greatly improved detection sensitivity. The fluorescent sensing material has no specific receptor and has a special porous nanofiber structure formed by high temperature elimination to realize identification of the substance to be detected. When subjected to optical excitation, the fluorescent sensing material shows high selectivity and sensitivity to Cu2+ and Fe3+ and has different responsiveness. The fluorescent sensing material can be reused and has a good application prospect.

The invention discloses polyvinyl thioether ester as well as a preparation method and application thereof. The polyvinyl thioether ester is obtained through solution polymerization reaction by takinga binary acetylene acid ester internal alkyne monomer and a binary sulfydryl monomer as raw materials. The reaction raw materials are easy to obtain, no by-product is generated in the polymerization reaction process, and the atom economy is met; the polymerization reaction has wide substrate applicability and good functional group compatibility, and various functional groups can be conveniently introduced; no catalyst is used in the polymerization reaction, so that the influence of catalyst residues on photoelectric and biological properties of the polymer material can be eliminated. The polyvinyl thioether ester prepared by the invention has good processability, high thermal stability and aggregation-induced emission performance, and has application value in the aspects of optical plastics, biomedical materials, fluorescence sensing and the like.

The invention relates to an organic fluorescence sensing composite material with ultrahigh sensitivity response for explosives as well as preparation and application thereof. The material is a blended one-dimensional organic semiconductor nanowire obtained by compositing one or more metallorganics complexes based on carbazole molecules and an organic fluorescence sensing material based on a series of carbazole molecules by a self-assembly method; the material has the characteristics of being porous, being large in superficial area, high in fluorescence quantum efficiency, uniform in mixing and the like, is suitable for fluorescence detection for the explosives and is particularly very efficient in detection for trace explosives.

The invention belongs to the field of metal ion detection and nucleic acid reagent preparation and in particular relates to a fluorescent nanosilver nucleinate cluster as well as a preparation method and application thereof. A novel fluorescent DNA nanosilver cluster is synthesized by taking micromolecular nucleic acid as a template; the nanosilver cluster is 2-4nm in size; a water solution of the nanosilver cluster is light yellow, the nanosilver cluster is excited by red light of 600nm, relatively strong fluorescent light is emitted at the position of 660nm, the fluorescence quantum yield is 0.2 (compared with bipyridine ruthenium), fluorescent light at the position of 660nm can be quenched by trivalent and divalent iron ions, fluorescent light of DNA-AgNCs has remarkable different fluorescent inductions on trivalent and divalent iron ions, and the sensitivity on divalent iron is much higher than the sensitivity on trivalent iron, so that the total amount of trivalent and divalent iron can be qualitatively and quantitatively analyzed and low-concentration divalent iron (10<-9> to 10<-5> mu M) and trivalent iron (10<-6> to 10<-1> mu M) can be qualitatively analyzed.