37 results about "Copper nanoclusters" patented technology

The invention discloses a multi-mode synergistic antibacterial nano material as well as a preparation method and application thereof. The multi-mode synergistic antibacterial nano material comprises a two-dimensional silylene nanosheet and a copper nanocluster loaded on the surface of the two-dimensional silylene nanosheet. According to the Si-coated Cu NSs composite material disclosed by the invention, copper nanoclusters (CuNCs) are loaded on the surface of a two-dimensional silylene nanosheet, the catalytic activity of copper is enhanced by utilizing a p-d orbital hybridization effect, and meanwhile, photo-thermal therapy (PTT) and chemical kinetic therapy (CDT) are combined to synergistically remove drug-resistant bacteria and biological membranes, so that the limitation of traditional two-dimensional silylene in antibacterial application is overcome.

The invention relates to an intelligent gel label integrating freshness monitoring and preservation as well as a preparation method and application of the intelligent gel label. The intelligent gel label is composed of a porous gel substrate, a plant source preservative eugenol and an aggregation-induced emission (AIE) copper nanocluster carried on the gel substrate. The cerium ions serve as a bridge between the gel and the copper nanoclusters, the copper nanoclusters are anchored to the gel, and indicator leakage is prevented. Besides, the porous gel structure realizes an embedding effect on eugenol, and cerium ions induce the copper nanoclusters to gather on the surface of the gel, so that eugenol is further blocked in a gel substrate. When the freshness of the aquatic product is reduced, the copper nano aggregate responds to the TVB-N, the structure disintegrates, the fluorescence intensity of the label is reduced, and the visual detection of the freshness is realized. In the aspect of preservation, a multi-factor trigger eugenol release mechanism is designed, so that the gel label can quickly respond to food quality change, and integration of food freshness monitoring and intelligent preservation is realized.

The present application mainly relates to a kind of preparation of sulfur-rich amino acid protein CMd-copper nanoclusters and its detection mercury ion method, comprising: a) by prokaryotic expression obtains CMd protein, and the protein concentration of 5 mg / mL-25 mg / mL CMd protein solution is obtained by purification.b) CMd is reacted with reducing agent TCEP after opening protein disulfide bond.c) the protein solution after reduction is reacted with anhydrous copper sulfate, and preparation high fluorescence CMd-copper nanocluster.d) CMd-copper nanocluster is applied to detect heavy metal mercury ion.The application method can be synthesized under mild aqueous conditions by "one-step method" structure controllable, stable CMd-copper nanocluster, widens the raw material of copper nanocluster synthesized with protein as template, avoids the use of organic solvent and strong reducing agent, and reduces the cost and environmental burden brought by noble metal raw material, and also has higher selectivity to mercury ion.

The invention discloses an application of a copper nano-cluster with stable ascorbic acid in detection of p-nitrophenol, the copper nano-cluster with stable ascorbic acid is used as a fluorescent probe, and the detection of p-nitrophenol is realized through a fluorescent sensing method. Due to the quenching effect of p-NP, the fluorescence intensity of the system is obviously reduced in the presence of p-NP. The p-NP concentration can be quantitatively detected by comparing the fluorescence intensity of the copper nano-cluster and the fluorescence intensity of a quenching system. The method is simple, sensitive and high in selectivity, does not need complex fluorescent dye labeling, shows remarkable potential for p-NP detection, and has a good application prospect in the aspects of food, medicine and the like.

Treatment of multiple sclerosis with copper nanoclusters (CuNCs).

The application relates to a universal fluorescence platform capable of realizing minute-level DNA companion logic operation and a preparation method and application thereof, and belongs to the technical field of fluorescence platform preparation. The universal fluorescence platform capable of realizing minute-level DNA companion logic operation is a fast, low-cost and universal platform constructed by taking a poly-T chain as a template of copper nanoclusters and double-stranded nucleic acid intercalating dye SYBR Green I as two universal output signals, and is used for various DNA companion logic operations. Benefited from the advantages of label-free and no complex TMSD reaction, the operation of all logic devices can be completed within 10 minutes, and the operation time and cost are 1 / 12 and 1 / 4 of previous work respectively. In addition, the in-vitro intelligent analysis of a disease marker poly-A polymerase is realized by utilizing the characteristics of positive and negative cross verification of opposite logic on the detection result.

This invention relates to the field of fluorescence detection technology, specifically disclosing a dual-colorimetric fluorescent probe for detecting methyl orange, its preparation method, and its application. The probe is prepared by in-situ synthesis of carbon dots and copper nanoclusters. The carbon dots are synthesized from Bermuda grass as a precursor via a hydrothermal method, and the copper nanoclusters are obtained by reducing copper ions with penicillamine and bovine serum albumin as dual stabilizers. The dual-colorimetric fluorescent probe provided by this invention has a detection limit for methyl orange as low as 0.06 μM, exhibiting good selectivity, stability, and anti-interference ability. It can be applied to the spiked recovery detection of methyl orange in actual water samples and can achieve visualized semi-quantitative analysis through filter paper loading, making it suitable for rapid on-site screening.

The application relates to an antibacterial self-repairing polyurethane material and a preparation method and application thereof, relates to the field of self-repairing polymer composite materials, and solves the problems that the self-repairing polyurethane material in the prior art is seriously dependent on external conditions, self-repairing efficiency is limited, the preparation process of introducing functional materials is complex and is easy to affect the micro-phase structure of the polyurethane, and mechanical properties, antibacterial function and self-repairing performance are difficult to be stably realized in cooperation. The application mixes isocyanate, polyol and a catalyst to perform a prepolymerization reaction, adds a pretreated chain extender solution to perform a chain extension reaction, adds a pretreated copper nanocluster dispersion solution, stirs, solidifies, and the antibacterial self-repairing polyurethane material is obtained; the polydopamine is used as the chain extender, the self-repairing efficiency of the polyurethane material is significantly improved through the synergistic effect of the polydopamine and the copper nanocluster, and the antibacterial performance and the mechanical performance are simultaneously optimized, and the application can be applied to the fields of medical devices, food packaging films, capsule materials, marine antifouling materials and biological protection materials.

The present application belongs to the field of nanomaterials, and particularly relates to a gold-copper nanocluster, a preparation method thereof and an optical device. n Cu 22‑n Y 18 wherein Y represents a dehydrogenated alkyne ligand, and 16<=n<=21. Thus, the gold-copper nanocluster has excellent quantum yield and optical properties.

The present invention discloses a method for preparing stable copper nanoclusters (CuNCs) based on glutathione (GSH) as a ligand. The method includes: first, preparing an aqueous solution of copper chloride, then adding a glutathione solution to the above solution in a certain proportion, fully stirring for five minutes at room temperature to form a white turbid solution, dropping a certain amount of sodium hydroxide solution until the solution becomes clear, then vigorously stirring at room temperature, transferring the solution into a dialysis bag for further dialysis, and then filtering through a microporous membrane. The copper nanoclusters prepared by the present invention have high sensitivity, good selectivity, strong anti-interference ability, a low detection limit for uranyl ions (the detection limit is 6.7 nM), and are used for real-time detection in real water samples including lake water, seawater, and pure water to evaluate the applicability of the copper cluster probe in the environment, having practical application value.

This application discloses a copper nanocluster, its preparation method, and its application. The copper nanocluster comprises copper atom aggregates and a stabilizer coated on the surface of the copper atom aggregates; the stabilizer includes casein. The copper nanocluster of this application not only improves the mechanical properties and hydrophobic properties of materials, making waterborne polyurethane materials hydrophobic, but also endows waterborne polyurethane materials with excellent flame-retardant and antibacterial properties. Furthermore, it simplifies the production process, reduces product costs, and the materials used have the advantages of being green and renewable.

This invention belongs to the technical field of composite nanomaterials and relates to a method for preparing a copper nanocluster-modified silver bromide nanoparticle / titanium dioxide photocatalyst. The method comprises: mixing a copper source and a silver source in deionized water to form a Cu ion-adsorbed AgCl (Cu / AgCl) turbid solution; dispersing TiO2, ascorbic acid, polyvinyl pyrrolidone, and potassium bromide in the deionized water by ultrasonication, transferring the solution to an oil bath, stirring and heating the solution, adding the Cu / AgCl turbid solution for reaction, and washing to remove impurities. The method is applied to the photocatalytic conversion of CO2 and H2O to produce C2H4 and H2O2. The Cu nanocluster-modified AgBr nanoparticles are directionally attached to a TiO2 substrate through an ion exchange process enhanced by electrostatic interactions. Utilizing the spatially confined structure, the Cu / AgBr / TiO2 ternary hybrid structure has a cascaded multi-step charge transfer mechanism, which provides a strong charge driving force for the catalyst. In addition, the adjacent heteronuclear sites of Cu and Ag provide an excellent synergistic catalytic effect for the entire reaction, realizing the light-driven conversion of CO2 and H2O to C2H4 and H2O2.

This invention discloses Cu NCs@ZIF-8 nanocomposite materials with AIE properties and Hg 2+ The detection application involves encapsulating Cu NCs in ZIF-8 using a one-pot method. This results in a copper nanocluster metal-organic framework composite (Cu NCs@ZIF-8) with aggregation-induced emission properties, used to detect trace amounts of Hg in environmental water samples via fluorescence mode. 2+ The fluorescence enhancement mechanism of the Cu NCs@ZIF-8 probe is Hg 2+ Induced AIE mechanism, with Hg 2+ The increase in [amount] enhances the fluorescence of the probe. CuNCs@ZIF-8, used as a probe, achieves specific and sensitive detection of Hg based on the aggregation-induced emission enhancement mechanism. 2+ The goal.

The invention belongs to the field of food safety detection, and particularly relates to a norfloxacin visual ratio fluorescence detection method based on an integrated detection device and application of the norfloxacin visual ratio fluorescence detection method. The integrated detection device provided by the invention comprises a filtering module and a detection module, the filtering module comprises a first container as well as modified sodium alginate hydrogel and glass wool which are filled in the first container; the modified sodium alginate hydrogel comprises a sodium alginate matrix and polyvinyl alcohol doped in the sodium alginate matrix; the detection module comprises a second container and a sodium alginate hydrogel bead which is filled in the second container and comprises a probe; the probe comprises a copper nano-cluster which is coordinated with terbium ions and modified by dithioerythrine. The integrated detection device provided by the invention is simple to operate and reliable in result, realizes rapid detection and visual response of norfloxacin, and has very high practicability and wide applicability.

The invention discloses a water antibiotic fluorescence detection method based on magnetic enrichment and copper nano-cluster in-situ generation, and belongs to the technical field of analytical chemistry and environmental monitoring. The method comprises the following steps: adding magnetic nanoparticles modified with antibiotic specific aptamers into a water sample, and selectively capturing target antibiotics; magnetically separating, enriching and washing to remove interferents; a copper source and a reducing agent are added, and the captured antibiotics serve as a template to induce in-situ generation of copper nano-clusters; and detecting a fluorescence signal of the copper nano-cluster for quantification. The target antibiotic is converted into a signal generation template from a detected object, so that the problem of poor stability of a pre-synthesized probe is solved; complex matrix interference is effectively eliminated through magnetic separation; and the internal standard of the gold nanoparticles improves the reproducibility among batches. The method is easy and convenient to operate, low in cost and suitable for rapid detection of antibiotic residues in complex water bodies such as breeding wastewater, hospital sewage and surface water.

The present application relates to the technical field of biomedical materials, and particularly relates to copper / oxygen defect barium titanate piezoelectric heterojunction nanoparticles and preparation and application thereof.The copper / oxygen defect barium titanate piezoelectric heterojunction nanoparticles of the present application take tetragonal phase barium titanate as a core, an oxygen defect amorphous layer as a shell, and a heterojunction is formed by depositing a non-valent copper nanocluster (Cu-Cu + ) on the surface of the shell layer; the copper / oxygen defect barium titanate piezoelectric heterojunction nanoparticles have an "electronic lever" effect, can be used for wound repair treatment by precisely regulating the "antibacterial-promoting repair" time sequence treatment under the action of ultrasound, and can rapidly and massively produce ROS and release copper ions under the action of ultrasound activation, so as to induce copper death of bacteria and achieve efficient antibacterial effect. Then, in the tissue repair stage, the ultrasound is turned off, and the intrinsic electric field of the heterojunction and the release of a small amount of copper ions are utilized to promote granulation tissue regeneration, collagen deposition, epithelial regeneration and angiogenesis, so as to synergistically accelerate tissue repair.

The application belongs to the field of nanomaterials, and provides a chiral copper nanocluster and a preparation method thereof. 20 X 12 Y6, wherein X represents a dehydrogenated alkyne ligand, Y represents a dehydrogenated acid ligand, and the acid ligand is R-2-phenylpropionic acid or S-2-phenylpropionic acid. The chiral copper nanocluster has high structural stability, and the provided preparation method has mild reaction and high yield.

The invention discloses a near-infrared fluorescent gold-copper nano-cluster and a preparation method and application thereof.The preparation method comprises the steps that a gold precursor, a sulfydryl ligand and a copper precursor are dissolved in a water-containing alcohol solvent, and a uniform mixed solution is obtained through oscillation; adding alkali into the mixed solution to change the color of the solution, dropwise adding a reducing agent NaBH4 under a stirring condition, and centrifuging, washing and drying to obtain solid powder after the reaction is finished; and re-dispersing the solid powder in water, carrying out ligand exchange reaction with Gln, and carrying out dialysis and filtration to obtain the brownish black near-infrared fluorescent gold-copper nano-cluster. The Gln-AuCu NCs prepared by the preparation method disclosed by the invention has relatively good dispersity and shows remarkable fluorescence emission capability in a near-infrared band, the absolute fluorescence quantum yield is 5.04%, and the optimal excitation wavelength and the optimal emission wavelength are 808nm and 1000nm respectively; the probe can be directly used for detecting melamine, has the advantages of simple synthesis method, rapid detection response, strong selectivity, high sensitivity and the like, and has good practical application value.

The application discloses a copper-based molecular sieve catalyst and a preparation method and application thereof. The copper-based molecular sieve catalyst comprises a molecular sieve carrier and copper nanoclusters encapsulated in the molecular sieve carrier; the molecular sieve carrier has CHA, MFI, BEA, FAU and MWW topological structures; the size of the copper nanoclusters is 0.02-5 nm; and the mass content is 0.025-5 wt%. The carrier has good hydrothermal stability, regularly adjustable channels and a high-crystallinity skeleton structure, can effectively limit the sintering and agglomeration of copper in the carrier, can inhibit the occurrence of polymerization and other side reactions through channel selection, and can improve the selectivity of furfuryl alcohol. The copper nanoclusters prepared by a coordination protection reduction method are uniform and easy to control in size, the structure of copper species is protected by a coordination agent in a subsequent crystallization process, and finally, the copper-based catalyst has high metal dispersion and good uniformity.

The invention provides a fluorescence detection method for detecting histamine, hydrogel and a preparation method and application thereof, and belongs to the technical field of biogenic amine detection. In particular to a fluorescence detection method for detecting histamine, which mainly comprises the following steps: mixing a copper nano-cluster solution, a carbon dot solution and histamine solutions with different concentrations, then fixing the volume, detecting the fluorescence emission spectrum of each system under the excitation wavelength of 365 nm, and calculating the fluorescence intensity of each system by taking the ratio F437 / F605 of the fluorescence intensity at the wavelength of 437 nm and 605 nm as the ordinate. Making a standard curve by taking the concentration of histamine in each system as an abscissa, and detecting the concentration of histamine in a sample to be detected; the invention also provides a hydrogel which is used for detecting histamine. The fluorescence detection method provided by the invention is used for detecting histamine, the histamine detection selectivity is strong, the specificity is good, and the hydrogel prepared by the invention realizes visual rapid detection of histamine.

This invention discloses an atomically precise copper nanocluster protected by pure phosphine ligands and its application in the electrocatalytic reduction of carbon dioxide. The molecular formula of the nanocluster is [Cu 18 H 17 (PPh2Et) 10 The preparation method of Cl includes: dissolving pure phosphine ligand PPh2Et with Cu(C5H7O2)2 in a mixed solvent of dichloromethane and methanol, reacting it, reducing it with sodium borohydride, and then obtaining orange cubic crystals by diffusion crystallization in a dichloromethane / n-hexane system. This cluster has a rich hydride content (Cu:H=18:17) and a surface hydride anion coverage as high as 94.4%. Using this cluster mixed with Ketjen black as a supported catalyst, the abundant hydride anions and its unique geometry effectively lower the reaction energy barrier of C-C coupling during the deep reduction of CO2, thereby efficiently improving the catalytic activity for the selective conversion of CO2 to ethylene at -1.4 V. RHE The ethylene Faraday efficiency reaches 70.5%, and it maintains high selectivity and catalytic stability even at industrial-grade current densities, providing an efficient solution for the electroreduction of carbon dioxide to produce high-value-added chemicals.

The application belongs to the technical field of environmental protection, and discloses a kind of ultra-small silver copper nanoclusters and its preparation and application.The preparation method of the ultra-small silver copper nanoclusters includes the following steps: (1) disperse copper salt in organic solvent to obtain copper salt suspension liquid; (2) add alkynyl ligand solution, silver salt solution to the copper salt suspension liquid obtained in step (1) in turn, stir, drop the reducing agent solution, continue to stir, solid-liquid separation, remove the organic solvent of the supernatant, wash, dry to obtain silver copper nanoclusters.The preparation method is simple in operation, and has good industrial application prospect;The particle size of the obtained silver copper nanoclusters is between 1.5-3 nanometers, and excellent catalytic activity and stability are shown in the electric synthesis of oxime reaction.

A method for preparing high quantum yield copper nanoclusters for alcohol detection by constructing hydrogen bond network with water molecules, 4,6-dihydroxy-2-mercaptopyrimidine is used as ligand, and copper sulfate is used as copper source to synthesize red light emitting R-CuNCs@TBA, and water molecules are introduced to prepare yellow light emitting Y-CuNCs@TBA with significantly enhanced fluorescence intensity. The application utilizes 4,6-dihydroxy-2-mercaptopyrimidine as ligand to synthesize CuNCs with multiple hydrogen bond sites on the surface, and after introducing water molecules, the intermolecular aggregation of CuNCs is more compact, the fluorescence intensity is enhanced by more than 15 times, the quantum yield is increased from 15.3% of R-CuNCs@TBA to 50.1% of Y-CuNCs@TBA, and the fluorescence wavelength is blue shifted from 638 nm to 573 nm. The significant "turn-on" fluorescence display effect of R-CuNCs@TBA on water molecules is used to detect whether different alcohols are adulterated with water.

Copper nanoclusters (CuNCs), thymine-modified hyaluronic acid (TMHA), and poly(copper nanoclusters) (PCuNCs) are disclosed. In certain embodiments, the TMHA is represented by formula I, wherein the degree of substitution of thymine in the HA is in a range of 1-50%, and wherein n for GlcA-GlcNAc repeats is an integer, from 10 to 10,000.

The present invention discloses a strong luminescent gold-copper nanocluster and its application in preparing luminescent ink, wherein the molecular formula of the strong luminescent gold-copper nanocluster is as shown in the following formula (1): Au2Cu6(R1)6(R2)2——Formula (1), wherein: R1 is C 10 H 15 S ‑ 、C4H9S ‑ R2 is one of (C6H5)2PCH2CH2P(C6H5)2, (C6H5)2PCH2CH2CH2P(C6H5)2, (C6H5)2PCH2CH2CH2CH2P(C6H5)2, (C6H5)2PCH2CH2CH2CH2CH2P(C6H5)2, (C6H5)2PCH2CH2CH2CH2CH2P(C6H5)2, (C6H5)2PCH2CH2CH2CH2CH2CH2P(C6H5)2, (C6H5)2PCH2CH2CH2CH2CH2CH2CH2P(C6H5)2. The gold-copper nanoclusters of the present invention have the characteristics of fluorescent and phosphorescent emission, high quantum yield, good stability, high yield, and easy synthesis. The gold-copper nanoclusters are combined with a high molecular polymer to form a luminescent ink, which can be used for printing anti-counterfeiting layers and two-dimensional codes. The luminescent ink based on gold-copper nanoclusters of the present invention has the advantages of clear printing, strong luminescence, good waterproofness, etc., and therefore has good practical application value.

The invention relates to a preparation method of a red light-emitting copper nano-cluster phosphorescent material, and belongs to the technical field of preparation of photoluminescence red light-emitting copper nano-clusters. The method comprises the following steps: dissolving a copper source in an alcohol-water solvent to obtain a mixed solution A; the preparation method comprises the following steps: dissolving aryl mercaptan serving as a protective agent and a reducing agent in an organic solvent according to a molar ratio of 1: (2-10) to a copper source to obtain a mixed solution B, uniformly mixing the mixed solution A and the mixed solution B, adjusting the pH value, stirring or carrying out ultrasonic treatment, reacting for 5-60 minutes to obtain a yellow suspension, centrifugally purifying, carrying out suction filtration, and carrying out vacuum pumping to obtain the red luminescent copper nano-cluster phosphorescent material. The luminescent property of the copper nano-cluster is enhanced by regulating and controlling the types, positions and quantity of substituent groups on aryl thiol of a reducing agent and an end-capping protective agent of the copper nano-cluster, the quantum yield reaches 10% or above, the fluorescence lifetime reaches the mu s level, and therefore the copper nano-cluster phosphorescent material is obtained.

The application discloses a method for constructing a copper nanocluster electrocatalyst based on amyloid fibers and application of the copper nanocluster electrocatalyst in chlorophenol wastewater, and comprises the following steps: dissolving lysozyme powder into water, adjusting the pH of the solution to 2 to prepare a lysozyme solution; taking titanium suboxide TiSO as a substrate, immersing the substrate into the lysozyme solution, heating and stirring to obtain an amyloid fiber AFs solution and a TiSO-AFs electrode; taking out the TiSO-AFs electrode, adding the amyloid fiber solution, adding a copper metal ion solution and a reducing agent, allowing the copper ions to be immobilized on the surface of the electrode and converted into copper single elements, cleaning the electrode with deionized water after standing, and drying to obtain a TiSO-AFs-Cu electrode; and the material is used to build an electrochemical reactor, so that chlorophenol wastewater can be efficiently purified.

The invention relates to a nano-copper cluster material with precise atoms, discloses a copper nano-cluster with an inhibiting effect on rhizoctonia cerealis as well as a preparation method and application of the copper nano-cluster, and belongs to the crossing field of nano-material chemistry and biochemistry. According to the invention, 1-benzyl-4, 4 '-dipyridyl chloride is used as a ligand, and the nano-copper cluster with high yield is synthesized by a room-temperature volatilization one-pot method. The chemical formula of the nano-copper cluster material is [Cu5I4 (L) 8 (I3) 2]. (I3) 7 (I2) 2 (L is 1-benzyl-4, 4 '-bipyridine chloride), abbreviated as Cu5I4, and the nano-copper cluster material belongs to a triclinic system; the space group is a chiral space group P21 / m. The nano-copper cluster material has good dispersity, good biocompatibility and excellent rhizoctonia cerealis resistance activity, the copper nano-clusters are adopted as antibacterial active components, the advantages of quantum size effect and high specific surface area of the copper nano-clusters are brought into full play, the copper ion release efficiency is high, and the inhibition rate on rhizoctonia cerealis can reach 90% or above.

This invention discloses a near-ultraviolet emitting copper nanocluster, its preparation method, and its applications. The chemical composition of the copper nanocluster is Cu4MPD7, and its fluorescence emission peak is located near 343 nm. The preparation method employs a simple one-pot aqueous phase method, using m-phenylenediamine as a reducing agent and ligand, reacting it with copper sulfate at room temperature followed by centrifugation. This nanocluster can be used as a fluorescent probe, emitting near-ultraviolet emission through its surface Cu... 2+ The specific binding with glyphosate induces fluorescence enhancement, enabling highly sensitive and selective detection of glyphosate, which has been successfully applied to the analysis of actual samples. Furthermore, due to its near-ultraviolet emission properties and excellent biocompatibility, this nanocluster also has significant application potential in fields such as biolabeling, in vivo imaging, disease treatment, catalytic materials, and the preparation of composite nanomaterials. This invention features a simple process, low cost, and environmental friendliness, providing new materials and methods for pesticide residue detection and the development of functional nanomaterials.

The invention discloses a supported gold-copper nanocluster catalyst and application, and the supported gold-copper nanocluster catalyst is obtained by supporting a gold-copper nanocluster (AuCu) 71 (SR) 46 on a carrier through an impregnation method, and is expressed as (AuCu) 71 / carrier. The catalyst (AuCu) 71 / carrier disclosed by the invention can catalyze a nitro compound and nitro of a nucleophilic raw material in a high-activity manner under a mild condition to eliminate cross coupling, the substrate is relatively wide in universality and can be recycled for at least ten times, and the TON (Transformation Number) can reach 2,800,000. The supported catalyst disclosed by the invention has a relatively great application prospect in the field of nitro elimination cross coupling.