266results about How to "The reaction conditions are mild and controllable" patented technology

The invention discloses a high temperature resistant modified starch filtration reducing agent and a preparation method thereof. The modified starch filtration reducing agent and the preparation method comprise that: with starch, a phenolic compound, alkenyl amide and alkenyl sulfonic acid as raw materials, an oil phase solution as a continuous phase and a nonionic surfactant as an emulsifying agent, and under catalytic actions of a reduction substrate and a hydrogen acceptor substrate, a starch graft copolymer is generated through a reaction. The filtration reducing agent provided by the invention is resistant to temperature of up to 175 DEG C, and simultaneously also has good salt and calcium resistance capabilities; and the preparation method is simple and easy to implement, and has mild and controllable reaction conditions, high grafting efficiency, fast reaction speed and low cost.

The invention relates to a method for preparing a sulfonated carbon solid acid catalyst, which uses a sulfonic aromatic compound to replace sulfuric acid. The method uses glucide as a raw material and an aromatic compound with sulfonic group as a sulfonating reagent to generate the carbon solid acid catalyst in one step through solvent heat treatment at a temperature of between 150 and 200 DEG C. The method has the advantages that the prepared solid acid has controllable surface acid content and good stability; the glucide as the raw material has rich resource and low price; the reaction condition is mild, and the preparation process is simple; and concentrated sulfuric acid or fuming sulfuric acid are not adopted as the sulfonating reagent, so equipment can be corroded less. The solid acid can be used as the catalyst of hydrolyzation of cellulose, alkylation reaction, biodiesel preparation and other reactions. Compared with the prior sulfuric acid catalyst, the catalyst has the advantages of non corrosion, easy separation, reusage and non production of waste acid or sewage, and has better advantages in the application field with special requirement, such as fine chemistry industry and pharmaceutical synthesis.

The invention provides a synthesis method of crisaborole, belongs to the technical field of drug synthesis, and relates to a synthesis method of a novel boron-containing anti-inflammatory preparation, namely crisaborole. 4-halobenzonitrile and benzo[c][1,2] oxaborolane-1,5(3H)-diol are reacted in an organic solvent in the presence of alkali, and the crisaborole is obtained. The synthesis methoid is simple, and the crisaborole is high in yield and high in purity. (The reaction formula is shown in the description).

The invention relates to a method for preparing nano boron powder. B203, Mg and KBH4 are taken as reaction materials, and mixed at the protection of argon at the temperature of 700-850 DEG C to trigger the self-propagating reaction; and the obtained reaction rough product is separated and purified to obtain the nano boron powder. The method of the invention has the following beneficial effects: (1) reactivity diluent KBH4 is added in a B203 / Mg system on the basis of synthesizing boron powder by traditional magnesiothermic reduction and by virtue of endothermic reaction, so as to control heat effect of the reaction system, realize energy conserving effect and control self-propagating reaction temperature, thus restraining side reaction and by-product impurities, effectively improving the purity of the product and acquiring amorphous boron powder with higher purity; (2) reaction product particles are avoided from sintering and agglomerating due to the generation of H2O and H2; realizing to refine and control boron powder granularity to prepare the nano boron powder; and (3) the method of the invention has moderate and controllable reaction conditions, simple process and reduced energy consumption, and is suitable for industrial production.

The invention relates to nitrogen-sulfur codoped fluorescent carbon dots with high quantum yield as well as a preparation method and an application of the nitrogen-sulfur codoped fluorescent carbon dots. According to the technical scheme, tartaric acid and L-cysteine are added to a hydrothermal reactor, a mixture is subjected to a heating reaction for 3-8 h at the temperature of 160-210 DEG C, naturally cooled to the room temperature ultrapure water is added for dissolving, a mixed solution is filtered, centrifuged, dialyzed and freeze-dried, and purified fluorescent carbon dot powder is obtained. The quantum yield of the fluorescent carbon dots can reach 19.1%. The nitrogen-sulfur codoped fluorescent carbon dots can be applied to fingerprint detection and Hg<2+> detection and have great significance for fingerprint development and extraction. Besides, sulfydryl in the nitrogen-sulfur codoped fluorescent carbon dots has strong affinity effect with Hg<2+>, and therefore, the nitrogen-sulfur codoped fluorescent carbon dots have great significance in study on the environmental chemistry. Finally, the fluorescent carbon dots can also be applied to degradation of methylene blue in printing and dyeing wastewater.

The invention discloses a breathable and waterproof multi-response fabric sensor. The sensor comprises a flexible elastic fabric base body, an interface layer, a functional layer and a protective layer from inside to outside, wherein the interface layer is a polydopamine layer, the functional layer is an MXene network, the protective layer is polydimethylsiloxane. In the invention, the elastic fabric is subjected to polydopamine interface modification, then the elastic fabric is subjected to dipping modification by using an MXene dispersion liquid, and finally hydrophobic treatment is performed by using the polydimethylsiloxane to obtain the MXene-based fabric sensor. The sensor disclosed by the invention is breathable and waterproof, and can show corresponding resistance response under different external strains and temperatures; the preparation method is simple, large-scale production can be achieved, and the multi-response fabric sensing device has excellent sensing performance andgood environmental stability and is of great significance in the field of intelligent wearable clothes.

The invention belongs to the technical fields of material separation and preparation and functional polymer materials and particularly provides a preparing method of a gel microsphere material absorbing molybdate. The method adopts (2-(acryloyloxy)ethyl)trimethylammonium chloride (DAC) as a monomer, adopts a reversed-phase suspension polymerization method and prepares cation gel microspheres CPDAC having a particle size of 200-300 [mu]m. The preparing method is characterized by high stability, mild conditions, simple process, and convenient and controllable operation. The gel microspheres CPDAC adsorb ammonium molybdate, and are high in exchange capacity and high in exchange speed. The gel microspheres CPDAC have a potential application prospect in the field of extraction and separation of anion materials, the field of drug controlled release, and even the field of removing toxic anions from a water environment.

The invention discloses a preparation method of an alpha-MnO2 catalyst for catalyzing oxidation of volatile organic compounds, relates to the preparation method of the alpha-MnO2 catalyst, and aims tosolve the problems that an existing manganese oxide catalyst is low in reaction activity and poor in stability and water resistance. The preparation method comprises the following steps: preparing apotassium permanganate solution and an ethylene glycol solution with the pH value of 7.0-12.0, mixing, reacting under water bath and stirring conditions, adding ethylene glycol, reacting under water bath and stirring conditions to obtain a turbid liquid, and sequentially filtering, washing, drying and calcining. According to the method, the alpha-MnO2 catalyst is obtained by taking the ethylene glycol as a reducing agent and potassium permanganate as a manganese source for the first time under the condition of room temperature or relatively low temperature, and compared with a traditional high-temperature hydrothermal method and a reflux method, the catalyst disclosed by the invention has the advantages of high activity, high stability and water resistance. The method is suitable for preparing the alpha-MnO2 catalyst.

The invention discloses a method for synthesizing trans-1,1,1,4,4,4-hexafluoro-2-butene. The method comprises the following steps: (a) in the presence of a telomerization catalyst, performing a reaction on 3,3,3-trifluoropropene and carbon tetrachloride to synthesize 1,1,1,3-tetrachloro-4,4,4-trifluorobutane, wherein the reaction temperature is 30-70 DEG C, and the reaction time is 1-10 h; and (b)under the action of a fluorination catalyst, performing gas phase fluorination on the 1,1,1,3-tetrachloro-4,4,4-trifluorobutane and HF to synthesize the trans-1,1,1,4,4,4-hexafluoro-2-butene, whereinthe reaction temperature is 200-300 DEG C, a molar ratio of the HF to the 1,1,1,3-tetrachloro-4,4,4-trifluorobutane is (5-50):1, the telomerization catalyst is composed of a main catalyst, a cocatalyst and an initiator, the main catalyst is a monovalent or divalent copper salt, the cocatalyst is an organic amine, and the initiator is p-hydroxyacetophenone or 1,1-azobis(cyanocyclohexane); and thefluorination catalyst is a supported catalyst with a composition of Nx / MgF2, N is an active component and selected from one of Al, Cu, Zn and Co, x is a molar ratio of N to MgF2, and a value of x satisfies the relationship of 0.05 <= x <= 0.15. The method provided by the invention is mainly used for synthesizing the trans-1,1,1,4,4,4-hexafluoro-2-butene.

The invention provides a hydrophilic modification method of PVA to polyester fiber, which belongs to the high-molecular technical field. The method comprises the following steps: pretreating the polyester fiber by a sodium hydroxide solution with 3-10% of mass fraction for 1 hour, wherein the solid liquid ratio is 1: 50, flushing and drying the polyester fiber, then placing the polyester fiber in a reaction container filled with a PVA solution with 0.2-0.3% of mass fraction, then adding acetate, methanol and sulfuric acid according to volume ratio of 3: 2: 1 in the reaction container, wherein the volume fraction of acetate, methanol and sulfuric acid are 10% respectively, adding GA with 25% of mass fraction in the reaction container, wherein the mol ratio of GA to PVA is 1: 4, performing mechanical stirring and reacting for 1-2 hours under the temperature of 50-70 DEG C, washing by water after the reaction is completed, and drying. Through representation and determination, the surface of the modified polyester fiber uniformly contains PVA, the contact angle is less than 10-50 DEG, hydrophilcity of the polyester fiber is greatly improved, the effect is stable, and the polyester fiber can be widely used in the fields of regeneration resource papermaking, clothes, decoration and industry and agriculture.

The invention provides a hydrophilic modification method for a polyester fiber by using sodium alginate, which belongs to the technical field of high polymer. The method comprises the following steps: stirring and pretreating the polyester fiber by using a sodium hydroxide solution with a mass fraction of 3 to 10% in a reaction container at a temperature of 70 to 90 DEG C for 1 h, wherein a solid-liquid ratio is 1: 50, then carrying out flushing with water after completion of a reaction and carrying out drying; and preparing a sodium alginate solution with a mass fraction of 1 to 4%, standing the sodium alginate solution at a temperature of 4 DEG C for 1 h, allowing sodium alginate to expand after sufficient water absorption, placing the sodium alginate solution in the reaction container, adding the dried polyester fiber into the reaction container, carrying out mechanical stirring at normal temperature for 1 to 2 h, adding a calcium chloride solution with a mass fraction of 2% during stirring and after completion of a reaction, successively carrying out flushing with water and then drying at 70 DEG C for 1 h. According to determination results, the contact angle of the modified polyester fiber is less than 10 to 60 DEG, hydrophilicity of the polyester fiber and products thereof are greatly improved, and the modified polyester fiber can be extensively applied to fields like papermaking with renewable resources, clothes, decoration, the industry and the agriculture.

The invention relates to a preparation method of a 3-substituted phenyl-4,5-dihydroisoxazole derivative and application and an intermediate thereof. A cyano compound (V) is converted into an N-hydroxybenzimidium compound (VII), and then 3-substituted phenyl-4,5-dihydroisoxazole intermediate (IX) is synthesized through a diazotization chlorination reaction and a dipolar cycloaddition reaction; a reaction condition is mild and controllable, the reaction selectivity in each step is good, the yield is relatively high, production of some byproducts is avoided, the product quality is guaranteed, andindustrialization of a whole technological route is easy to implement.

The invention belongs to the field of pharmacy, and discloses a synthesis method of a macrophage targeting carrier system and a preparation method of a gene delivery system. The macrophage targeting carrier system is characterized in that a macrophage targeting carrier is mannosylation protamine; electropositive mannosylation protamine loads electronegative nucleic acid to form a positively charged nano particle; and protamine modified by carubinose is prepared from formyl methyl mannopyranoside and protamine sulfate through a reductive amination reaction. Compared with non-viral gene carrier protamine, mannosylation protamine has a nuclear localization function and a macrophage targeting property, and can improve the gene transfection mediation efficiency of protamine in macrophage. The preparation method is simple, and mature in technology, and has good application prospects.

The invention relates to an alkyl phosphorus dihalide preparing method and belongs to the technical field of preparation of alkyl phosphorus halide. According to the method, hydrocarbon and phosphorus trihalide are taken as raw materials, alkali metal or alkaline-earth metal is taken as the initiator, and reaction is conducted at -30-170 DEG C. The initiator alkali metal or alkaline-earth metal reacts with the phosphorus trihalide to generate phosphorus dihalide free radicals, and free radical reaction is conducted between the phosphorus dihalide free radicals and the hydrocarbon to generate alkyl phosphorus dihalide, halogen hydride and a small amount of alkali halide or alkaline earth halide. The generated halogen hydride is low in solubility in a reaction system, and therefore the halogen hydride can be separated out in the gas form simply by conducting decompression on products. Compared with existing methods of preparing alkyl phosphorus dihalide with hydrocarbon and phosphorus trihalide as raw materials, the method has the advantage that due to the adoption of the initiator alkali metal or alkaline-earth metal, reaction temperature is reduced remarkably, so that the requirements of reaction for temperature and equipment are reduced, and then cost is reduced greatly.

The invention relates to a CT contrast agent with gold nanoparticles wrapped with zwitter-ion modified dendrimer and a preparation method and application of the CT contrast agent. The surface of the dendrimer is modified with the zwitter-ion carboxybetaine acrylic amide (CBAA), and the gold nanoparticles are wrapped with the dendrimer, wherein the dendrimer is fifth-generation polyimide dendrimer G5.NH2. The preparation method comprises the steps that the CBAA and the fifth-generation polyimide are stirred and reacted at the room temperature to obtain CBAA-G5.NH2, an HAuCl4 solution is added, NaBH4 is added for reduction, triethylamine and acetic anhydride are added finally, and then the CT contrast agent is obtained. Compared with a traditional contrast agent modified by mPEG, the consuming quantity of in-vitro macrophages is low, protein adsorption in the protein adsorption resistance experiment is low, the in-vivo rat blood circulation time is longer, liver gathering in the mouse CT experiment is low, the renal metabolism is slower, and the CT contrast agent can also be used for rat blood pool radiography and rabbit lymphonodus VT imaging.

The invention provides a phase change cold storage material for freshness retaining of partial-frozen chilled food and a preparation method. The phase change cold storage material for partial-frozen fruits and vegetables uses a mixed solution of decyl alcohol and dodecyl alcohol as main base liquid and uses hydroxylated multi-wall carbon nanotubes and sodium dodecylbenzenesulfonate as additives toimprove the thermal conductivity of the phase change cold storage material. The phase change temperature of the phase change cold storage material is -3.2 DEG C; and the latent heat of phase change is 171 J / g and the thermal conductivity is 0.3462 W / (m.K). After low and high temperatures are circulated for 100 times, the composite phase change cold storage material still has excellent thermal stability. The obtained phase change cold storage material can be applied to freshness retaining of foods such as meat and vegetables. The invention further provides a preparation method of a composite phase change cold storage material.

The invention provides an acidic texturing solution for texturing of a polycrystalline silicon chip and a using method thereof. The acidic texturing solution is characterized in that: when the acidic texturing solution is used for surface texturing of the polycrystalline silicon chip for a solar cell, excellent texturing effect can be achieved. The technical problems of environmental pollution of the texturing solution and textured surface non-uniformity caused by instable states of the texturing solution and the process conditions in the prior art are solved.

The invention belongs to the technical field of catalysis, in particular relates to a solid acid catalyst loaded with organic sulfoacid groups by an immersion method and a preparation method of the solid acid catalyst. The method for preparing the catalyst provided by the invention comprises the following steps: (1) throwing an activated carrier into an immersion solution prepared from styrene, an initiator and an organic solvent to immerse and load; (2) in the presence of protective gas, allowing styrene to conduct a polymerization reaction to obtain a load precursor loaded with polystyrene monomolecular film on the surface; and (3) mixing and sulfonating the load precursor and a sulfonating agent, and the like. The loaded organic sulfoacid solid catalyst utilizes the polymerization reaction of styrene for ensuring that the active groups of the catalyst partially form the structure of polystyrene, and after the sulfonating reaction, a plurality of sulfo group structures can be formed in each active group, so that the acid content of the whole catalyst is greatly improved; and the degree of polymerization of polystyrene in the catalyst can reach 2-100, and the quantity of the loaded sulfoacid groups is greatly increased.

The invention discloses dicyclohexylmethylmethane-4,4'-diisocyanate prepolymer used for paint curing agent and preparation method thereof, the prepolymer is mainly prepared from (A) 20-50 mass parts of dicyclohexylmethylmethane-4,4'-diisocyanate; (B) 5-60 mass parts of polyalcohol composition; (C) 30-300 mass parts of organic solvent with boiling point less than 200 DEG C; and selective (D) 0.01-1 mass part of organic metal catalyst; and the prepolymer is used for curing agent for alkyd resin paint and has better weathering resistance, yellowing resistance, chemicals resistance and water resistance.

The invention relates to the technical field of drug synthesis, in particular to a sugammadex sodium impurity and a preparing method thereof. A chemical structural formula of the impurity is shown ina formula I. The preparing method comprises the following steps that 1, sugammadex sodium is put in an aqueous solution, and after a reaction is carried out for a period of time at a certain temperature in the presence of an oxidizing agent, oxidation is conducted to generate a compound with the formula I, wherein the compound is a mixture of a compound II and a compound III; 2, the obtained mixture of the compound II and the compound III is subjected to preparative separation to obtain the single compound II and the single compound III. The preparing method has the advantages that operation is convenient, the reaction condition is mild and controllable, the stability of a reaction is high, and a reaction product is high in yield and purity; moreover, the compound with the formula I can provide an impurity reference substance which meets the requirement for quality control over the sugammadex sodium.

The invention discloses a method for ultrasonic wave assistant-catalyzed synthesis of grifolan sulphate. According to the method, the grifolan is used as a raw material, and sulfur trioxide-pyridine is used as a sulfonating agent, under the catalytic action of 4-dimethylaminopyridine, the grifolan sulphate can be prepared, further, the method includes the step of ultrasound swelling of grifolan in N,N-dimethylformamide. According to the method, as the synthesis of grifolan sulphate is realized through the ultrasonic wave assistant-catalysis method, the esterification temperature is reduced, the esterification time is shortened, and the degree of substitution of sulfuric acid groups is improved by 1.07-2.13; with the adoption of the method provided by the invention, the reaction condition is safe and controllable, and the reaction speed is higher.

The invention discloses a method for preparing high-purity lysophosphatidylcholine. The method comprises the steps of enabling soybean phospholipid to dissolve in water or a calcium chloride solution,adding phospholipase, and performing an enzymolysis reaction; pretreating enzymolysis reaction products, conveying the pretreated enzymolysis reaction products into a silica gel column, performing repeated eluting by using multi-halogeno low-carbon alkane-low-carbon alcohol-water as an eluant, collecting a solution of an object, and performing concentration and drying so as to obtain high-puritylysophosphatidylcholine products. According to the method disclosed by the invention, ordinary soybean phospholipid is used as a raw material, through the enzymolysis reaction, pretreatment after enzymolysis and column chromatography and refiningtechnology, and the high-purity lysophosphatidylcholine is prepared; and the high-purity lysophosphatidylcholine has the characteristics that the raw materials are cheap and easy to obtain, the technology is simple, the maneuverability is high and product yield is high, is suitable for industrialized production, and the produced lysophosphatidylcholineis high in purity, few in by-products and stable in product quality.

The invention belongs to the field of chemical synthesis, and relates to a method for preparing a compound zolpidem. The invention provides an effective new method for preparing zolpidem by a trimaceral serially reaction. The method for preparing the zolpidem provided by the invention has the advantages that the reaction step is short, the condition is moderate, atom economy and environmentally friendly are achieved, the yield is high, the cost is low, industrialized production is applicable, and the defects in the prior art that the synthetic route is long and the cost is high are overcome.

The invention discloses a synthetic process of methylacrolein. The synthetic process is characterized in that the methylacrolein is synthesized by adopting paraformaldehyde and propionaldehyde under the condition of taking a morpholine hydrochloride solution as a catalyst, and controlling the reaction temperature and the proportion of all reactants. The methylacrolein synthesized by adopting the process has the yield of 97 percent or more, the purity is equal to or greater than 97 percent and the selectivity is close to 100 percent; meanwhile, the catalyst can be recycled for 20 times or more at least; the problems that the yield and the selectivity cannot be combined, the recycling of the catalyst is poor, and the methyla crolein quality is poor in a traditional method are solved.

The invention discloses a catalyst for synthesis of amino-terminated polyether. The catalyst is load type, the carrier material has a porous structure, metal Ni and Co are taken as the main active components of the catalytic material, and any two of Cr, Fe and Mo are mixed in any proportion to serve as the assistant active component. The invention discloses a preparation method of the catalyst and application of the catalyst to synthesis of amino-terminated polyether. The catalyst provided by the invention is used for synthesis of amino-terminated polyether, and also has high conversion rate and high primary amine selectivity that are both greater than or equal to 99.0%. By using the catalyst provided by the invention, the reaction cost is lowered, and the catalyst has good catalytic effect in a batch kettle and a fixed bed reactor, and can meet different process requirements. By adding the catalyst, the reaction can be milder and more controllable, the temperature is lower than or equal to 230DEG C, the pressure is less than or equal to 10MPa, and the risk of the operation process is reduced.

The invention discloses a near-infrared silver-indium-selenium quantum dot and a preparation method thereof. The preparation method comprises the following steps: (1) dissolving cupric chloride or silver acetate, indium acetate, sodium hydrogen selenide and 3-mercaptopropionic acid according to the molar ratio of 1:1-5:10-20:34-36, so as to obtain a mixed solution, wherein the concentration of cupric chloride or silver acetate is 0.7-0.9 mmol / L; and (2) adjusting the pH value of the mixed solution obtained in the step (1) to 8-9, then heating the mixed solution at 93-98 DEG C for reaction for 55-65 min, and cooling to room temperature, so as to obtain the near-infrared silver-indium-selenium quantum dot. The prepared quantum dot has the advantages of being nontoxic, simple in method, mild and controllable in reaction conditions, short in reaction time, good in reappearance and the like. The prepared quantum dot is widely applicable to cell and tissue imaging as a fluorescent marker, and also is applicable to in vivo imaging research.

The invention discloses an electrochemical preparation method of a BiOBr / Bi12SiO20 composite film photocatalyst and application of the BiOBr / Bi12SiO20 composite film photocatalyst, belonging to the fields of in-situ preparation of Bi-based composite materials, solar photocatalyst immobilization technology and artificial photosynthesis. The problems that existing synthesis methods are high in energy consumption and have difficulty in separation of powder catalysts from reaction systems can be solved. According to the invention, a BiOBr / Bi12SiO20 immobilized composite film is through one-step electrochemical synthesis at room temperature with a Bi plate, NaBr and Na2SiO3.9H2O as raw materials, water / EG as a solvent, nitric acid or a sodium hydroxide solution as an agent for adjusting a pH value and a Ti plate as a negative pole. The preparation method has the advantages of usage of cheap and easily available raw materials, no need for high temperature and high pressure, mild and controllable reaction conditions, easy operation, environment-friendly process, and no generation of harmful byproducts.

The invention belongs to the field of pharmaceutical preparations, and in particular relates to an in-situ temperature-sensitive gel drug delivery system for combined chemotherapy and immune therapy. The delivery system consists of drug carrier peptide dendrimers (G4‑arg), antineoplastic drugs and thermosensitive gel matrix material PLGA‑PEG‑PLGA, and the antineoplastic drugs are entrapped in the cavity of peptide dendrimers to form The drug-loaded peptide dendrimers wrap the drug-loaded peptide dendrimers in a temperature-sensitive gel matrix through the swelling process to form an in-situ drug delivery system that is an injectable sol at room temperature and turns into a gel at body temperature. The in situ delivery system of the present invention can form a gel near the tumor, slowly release the drug-loaded peptide dendrimer molecules to act on the tumor tissue, and the peptide dendrimer molecules act on the macrophages in the tumor tissue to generate NO , together with anti-tumor drugs to act on tumors, forming a chemotherapy-immune combination therapy to inhibit the development of tumors.

The invention relates to a fluorescent carbon dot capable of realizing visible light excitation and long wavelength emitting, and a preparation method and application thereof. According to a technicalscheme in the invention, the method comprises the following steps of: putting quercetin and glycine in an ethanol system into a stainless steel reaction kettle lined with polytetrafluoroethylene at room temperature, carrying out heating at 180 DEG C for 7 hours, performing natural cooling to room temperature, adding a passivating agent, conducting heating at 160 DEG C for 12 hours, performing natural cooling to room temperature, and successively conducting filtering, centrifuging and dialyzing to obtain the fluorescent carbon dot. A solvothermal method is adopted, the fluorescent carbon dot is synthesized in one step, and the fluorescence property of the fluorescent carbon dot is enhanced through modification. The raw materials for preparing the carbon dot are easy to obtain, the method is simple, synthesis conditions are mild and controllable, and the obtained fluorescent carbon dot has the advantages of visible light excitation, long emission wavelength, good stability and high fluorescence quantum yield.