Exploration of stable metal single-site supported porous graphitic carbon nitride(PCN)nanostructures and the development of maximum atom utilization for enhanced photocatalytic oxidation of antibiotics remains a chall...Exploration of stable metal single-site supported porous graphitic carbon nitride(PCN)nanostructures and the development of maximum atom utilization for enhanced photocatalytic oxidation of antibiotics remains a challenge in current research.This work proposed a one-step thermal copolymerization to obtain Cu(Ⅰ)doping porous carbon nitride(CUCN)through a spontaneously reducing atmosphere by urea in a covered crucible.The obtained CUCN had crumpled ultrathin nanosheets and mesoporous structures,which possessed higher specific surface areas than PCN.From X-ray absorption near edge structure(XANES)and Fourier transform extended X-ray absorption fine structure(FT-EXAFS)spectra analysis,the Cu doping existed in the oxidation state of Cu(Ⅰ)as single atoms anchored on the 2D layers of CN through two N neighbors,thereby facilitating efficient pathways for the transfer of photoexcited charge carriers.Furthermore,the photoluminescence(PL)spectra,electrochemical impedance spectra(EIS)and transient photocurrent response test proved the improved separation and transfer of photoexcited charge carriers for Cu(Ⅰ)introduction.Consequently,the photocatalytic activity of CUCN was much better than that of PCN for antibiotics norfloxacin(NOR),with 4.7-fold higher degradation reaction rate constants.From species-trapping experiments and density function theory(DFT)calculations,the Cu single atoms in Cu-N_(2)served as catalytic sites that could accelerate charge transfer and facilitate the adsorption of molecular oxygen to produce active species.The stable Cu(Ⅰ)embedded in the layer structure led to the excellent recycling test and remained stable after four runs of degradation and even thermal regenerated treatment.The degradation paths of NOR by CUCN under visible light were also demonstrated.Our work sheds light on a sustainable and practical approach for achieving stable metal single-atom doping and enhancing photocatalytic degradation of aqueous pollutants.展开更多
In the generalized gradient approximation, the energy and electronic structure are investigated for a single copper atomic chain wrapped in （4, 4）, （5, 5） and （6, 6） armchair carbon nanotubes by using the first-...In the generalized gradient approximation, the energy and electronic structure are investigated for a single copper atomic chain wrapped in （4, 4）, （5, 5） and （6, 6） armchair carbon nanotubes by using the first-principles projector-augmented wave potential within the framework of density functional theory. The results show that the （4, 4） and （5, 5） tubes are too narrow to wrap a Cu chain, but the （6, 6） tube is nearly ideal to wrap a Cu chain on its centre axis. Wider tubes are anticipated to wrap more than one Cu chain spontaneously with forces amounting to a fraction of a nanonewton. Although the tube-chain interaction decreases with the increase of the tube diameter of （4, 4）, （5, 5） and （6, 6） successively, the charge density of the Cu@（6, 6） combined system still does not show complete superposition of that of the pristine （6, 6） tube and Cu chain. Successively reducing the restrictions of （4, 4）, （5, 5） and （6, 6） tubes on the Cu chain leads to a reduction in shift of the highest peak of the Cu chain towards lower energies, that is from -0.5177 eV of the isolated Cu chain to -1.36785 eV, -0.668 eV and -0.588 eV for the Cu@（4, 4）, Cu@（5, 5） and Cu@（6, 6） systems, respectively. In reverse, the strong metallic character of the Cu chain also enhances the metallic character of the combined systems so that the broader pseudogaps of the pristine carbon nanotubes around the Fermi level change into the narrow pseudogaps of the combined systems.展开更多
A micro-flow injection sorbent extraction preconcentration system was combined with a graphite furnace atomic absorption spectrometry that formed an integrated system for the determination of trace amounts of elements...A micro-flow injection sorbent extraction preconcentration system was combined with a graphite furnace atomic absorption spectrometry that formed an integrated system for the determination of trace amounts of elements. The analytical performances of the prospsed method for determining Cd, Cu and Mn were studied. The analytes were preconcentrated with a thiol resin(Type 190, produced by Nankai University, China) whose active group is -SH. The elements to be determined were preconcentrated onto the column for 60 s and then rinsed with deionized water and eluted with 30 μL of 1 mol/L HCl. The graphite furnace atomic absorption spectrometry(GFAAS) determination of the concentrated analyte was carried out in parallel with the next preconcentration cycle. Enrichment factors 41, 22 and 20 and detection limits(3 σ , n =10) 0.36, 3.8 and 7.0 ng/L for Cd, Cu and Mn, respectively, along with a sampling frequency of 20 h -1 , were obtained with a 60 s loading time at a sample flow rate of 3.5 mL/min. The analytical results for a number of water samples show that the flow-injection semi-online column preconcentration can not only eliminate the effect of some concomitant elements, such as Li, Na, K, Ca and Mg, on the determination of the analyte, but also enhance the sensitivity.展开更多
In the present work, an easy solid phase extraction method using alumina modified with polyethylenimine as a new adsorbent was applied to the simultaneous extraction of copper, silver, and palladium ions prior to thei...In the present work, an easy solid phase extraction method using alumina modified with polyethylenimine as a new adsorbent was applied to the simultaneous extraction of copper, silver, and palladium ions prior to their determination with electrothermal atomic absorption spectrometry. The analytical procedure involved the complex formation of these cations with polyethylenimine as a chelating agent in buffer media of pH 7.0. Under the optimum conditions, a preconcentration factor of 200, 150, and 200, precision of ~5.4%, ＋4.7%, and ＋5.2% and linear calibration ranges of 15.0-140, 4.0-93, and 7.5-125 ng/L （in original solution） for Cu, Ag, and Pd were obtained, respectively. Also detection limits of 3.9,1.1, and 2.0 ng/L were obtained for Cu, Ag, and Pd, respectively. The proposed method was applied to the determination of copper, silver, and palladium in some real samples with satisfactory results.展开更多
A novel approach was developed for the determination of ultratrace amounts of copper in water samples by using electrothermal atomic absorption spectrometry （ETAAS） after cloud point extraction （ CPE ）. 1-（ 2-Pyr...A novel approach was developed for the determination of ultratrace amounts of copper in water samples by using electrothermal atomic absorption spectrometry （ETAAS） after cloud point extraction （ CPE ）. 1-（ 2-Pyridylazo ） -2- naphthol was used as the chelating reagent and Triton X-114 as the mieellar-forming surfactant. CPE was conducted in a pH 8. 0 medium at 40 ℃ for 10 rain. After the separation of the phases by contrifugafion, the surfactant-rieh phase was diluted with 1 mL of a methanol solution of 0. 1 mol/L HNO3. Then 20μL of the diluted surfactant-rieh phase was injected into the graphite furnace for atomization in the absence of any matrix modifier. Various experimental conditions that affect the extraction and atomization processes were optimized. A detection limit of 5 ng/L was obtained after preconeentration. The linear dynamic range of the copper mass concentration was found to be 0-2.0 ng/mL, and the relative standard deviation was found to be less than 3. 1% for a sample containing 1.0 ng/mL Cu （ Ⅱ ）. This developed method was successfully applied to the determination of uhratraee amounts of Cu in drinking water, tap water, and seawater samples.展开更多
We report on the use of titanium dioxide nanoparticles (NPs) coated with poly-thiophene for the preconcentration of copper and silverions. The NPs were prepared by first modifying the surface of TiO2 NPs with vinyl gr...We report on the use of titanium dioxide nanoparticles (NPs) coated with poly-thiophene for the preconcentration of copper and silverions. The NPs were prepared by first modifying the surface of TiO2 NPs with vinyl groups and then copolymerizing them with vinyl thiophen. The resulting TiO2-polythiophene core-shell NPs were characterized by thermogravimetry, differential thermal analysis, scanning electron microscopy, Fourier transform infrared spectrometry and X-ray diffraction. The experimental conditions such as pH value, adsorption and desorption time, type, concentration and volume of the eluent, break through volume, and effect of potentially interfering ions were optimized. The ions were then desorbed with hydrochloric acid and determined by FAAS. The limits of detection are 0.4 and 1.2 μg·L_1 for Cu(II) and Ag(I), respectively, and recoveries and precisions are >98.0%展开更多
A novel,simple,rapid,efficient and environment-friendly method for the determination of trace copper in cereal samples was developed by using dispersive liquid-liquid microextraction based on solidification of floatin...A novel,simple,rapid,efficient and environment-friendly method for the determination of trace copper in cereal samples was developed by using dispersive liquid-liquid microextraction based on solidification of floating organic drop（DLLME-SFO） followed by flame atomic absorption spectrometry.In the DLLME-SFO,copper was complexed with 8-hydroxy quinoline and extracted into a small volume of 1-dodecanol,which is of low density,low toxicity and proper melting point near room temperature. The experimental parameters affecting the extraction efficiency were investigated and optimized.Under the optimum conditions, the calibration graph exhibited linearity over the range of 0.5—500 ng/mL with the correlation coefficient（r） of 0.9996.The enrichment factor was 122 and the limit of detection was 0.1 ng/mL.The method was applied to the determination of copper in the complex matrix samples such as rice and millet with the recoveries for the spiked samples at 5.0 and 10.0 u,g/g falling in the range of 92.0-98.0%and the relative standard deviation of 3.9-5.7%.展开更多
[ Objective] This study aimed to evaluate the uncertainty in detecting copper and zinc contents in maize flour by flame atomic absorption spectrometry. [ Method] Combined with the actual inspection experience, the unc...[ Objective] This study aimed to evaluate the uncertainty in detecting copper and zinc contents in maize flour by flame atomic absorption spectrometry. [ Method] Combined with the actual inspection experience, the uncertainty in detecting copper and zinc contents in maize flour by tame atomic absorption spec- trometry was evaluated to establish the mathematical model. The uncertainty sources in the experimental process were investigated to analyze several components af- fecting the uncertainty in sample detection, including sample weighing, standard material transfer, solution dilution and volume setting, curve fitting, and repeat- ability of measurement instruments. [ Result] Standard curve fitting and repeatability test were two major factors that significantly affected the combined standard uncertainty. However, in the actual detection process, standard curve calibration and repeated detection procedures should be controlled strictly. Finally, the ex- panded uncertainty of copper and zinc contents in maize flour was （ 1.38 ± 0.08） mg/kg and （ 10.20 ± 1.20） mg/kg, respectively. [ Conclusion] This study provided reference for improving the accuracy and reliability of the detection method.展开更多
The determination of copper by MIP-AES was investigated in detail. Aqueous samples were introduced from an ultrasonic nebulizer and the solvent was removed by a desolvation device before introduction of the aerosol in...The determination of copper by MIP-AES was investigated in detail. Aqueous samples were introduced from an ultrasonic nebulizer and the solvent was removed by a desolvation device before introduction of the aerosol into the MIP. The desolvation system consisted of a condenser associated with a concentrated H2SO4 absorption cell. Various experimental conditions and interferences from easily ionised elements (EIEs) were also studied and some practical samples were analyzed.展开更多
The principle and characteristics of the rapidly solidified centrifugal atomization technique are studied in present paper.It has been widely used to make fine,rapidly solidified precious metal powders for application...The principle and characteristics of the rapidly solidified centrifugal atomization technique are studied in present paper.It has been widely used to make fine,rapidly solidified precious metal powders for application as the electrical engineering materials,conductive coatings for electromagnetic shielding and brazing alloys.The silver powder,copper powder and some precious metal alloys powders are prepared by the new method.A comparative analysis is carried out with the conventional electrolytic silver powder and chemical deposition silver powder.The results show that rapidly solidified powders are fine and have higher solid solubility of the alloying elements,and their alloys have excellent properties in various aspects.展开更多
[Objectives] The contents of copper and lead in the soil of the Yellow River Wetland were determined by flame atomic absorption spectrometry, which provides a theoretical basis for the treatment of soil pollution. [Me...[Objectives] The contents of copper and lead in the soil of the Yellow River Wetland were determined by flame atomic absorption spectrometry, which provides a theoretical basis for the treatment of soil pollution. [Methods] The soil was digested with a concentrated nitric acid-hydrofluoric acid-perchloric acid system, and the contents of heavy metals such as copper and lead in the Yellow River Wetland of Shaanxi Province were determined by flame atomic absorption spectrometry. [Results] The correlation coefficients reached 0.999 5 in the range of 0.00-1.00 mg/L, indicating good linearity. [Conclusions] The method is simple in operation, good in reproducibility, high in sensitivity to most elements, and can be widely used.展开更多
By the decomposition of copper nitrate at 400 ℃, oriented islands of copperoxide crystals were successfully fabricated on the amorphous glass surface. X ray diffraction (XRD), atom force microscope (AFM), and X ray p...By the decomposition of copper nitrate at 400 ℃, oriented islands of copperoxide crystals were successfully fabricated on the amorphous glass surface. X ray diffraction (XRD), atom force microscope (AFM), and X ray photoelectron spectroscopy (XPS) confirm the presence of copper oxide islands. The formation of oriented island structures is attributed to the following reasons: 1) the mismatch between the glass substrate and the copper oxide crystals during the relaxation of thermal expansion leads to the formation of islands; 2) the preorganized copper nitrate particles in the voids of colloidal crystals determine their ordered spatial distribution; 3) the strain of the glass substrate developing during calcination provides the driven energy for the orientation of copper oxide crystals along the same direction.展开更多
Support substrates play important roles in the catalysis process.Herein,atomically dispersed CuN_(3)catalysts supported by two different types of zirconia(denoted as CuN_(3)/NC/T-ZrO_(2)and CuN_(3)/NC/M-ZrO_(2))have b...Support substrates play important roles in the catalysis process.Herein,atomically dispersed CuN_(3)catalysts supported by two different types of zirconia(denoted as CuN_(3)/NC/T-ZrO_(2)and CuN_(3)/NC/M-ZrO_(2))have been rationally fabricated to uncover the influence of the support.CuN_(3)/NC/T-ZrO_(2)exhibits outstanding performance for electrochemical CO_(2)reduction towards CO at a wide range of potentials(~96%,0.6-0.8 V vs.RHE)owing to the acidic uncoordinated Zr^(4+)sites of T-ZrO_(2),which facilitate CO_(2)accumulation,and N-doped carbon(NC),which enhances the conductivity of the catalyst.Moreover,density functional theory calculations prove that T-ZrO_(2)effectively decreases the Gibbs free energy for CO_(2)to CO conversion.Significantly,this study reports the effects of the substrate on the electrocatalytic CO_(2)RR and provides a promising strategy for tuning catalytic activity and selectivity during the process of converting CO_(2)into high-value products by controlling the phase of the support for the first time.展开更多
Atomically precise copper(I)nanoclusters(CuNCs)with high photoluminescence(PL)efficiency and a relatively short lifetime could be promising non-precious metal-based phosphorescent emitters for organic light-emitting d...Atomically precise copper(I)nanoclusters(CuNCs)with high photoluminescence(PL)efficiency and a relatively short lifetime could be promising non-precious metal-based phosphorescent emitters for organic light-emitting diodes(OLEDs),but the synthesis of such CuNCs still remains a great challenge.Herein,we have prepared a parallelepiped-like and green emissive atomically precise Cu_(10) alkynyl cluster with a moderate PLQY of 35% and lifetime(τav)of 8.4μs.Interestingly,upon addition of hexane to a DCM solution of Cu_(10),it turns into an hourglass-like,orange emissive Cu_(18) cluster with an enhanced PL efficiency(PLQY=63%,andτav=2.8μs)at room temperature,which is rarely achieved in high-nuclearity alkynyl-protected CuNCs.Experiments and theoretical calculations suggested that the excellent PL performance of Cu_(18) is due to reduced nonradiative transition,a larger d orbital contribution of Cu ions,an enhanced transition dipole moment and reduced HOMO–LUMO gap.This work will not only pave a novel approach for constructing alkynyl-protected CuNCs with a high PLQY and short lifetime,which might be explored for other CuNCs for fabricating high-performance OLEDs,but also shed light on the structure–luminescence relationship.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52070103 and 22102102)Zhejiang Provincial Natural Science Foundation of China(Nos.LY21E090004 and LQ22B050004)+1 种基金Ningbo Public Welfare Science and Technology Program(No.2021S025)Ningbo Youth Leading Talent Project(No.2024QL038).
文摘Exploration of stable metal single-site supported porous graphitic carbon nitride(PCN)nanostructures and the development of maximum atom utilization for enhanced photocatalytic oxidation of antibiotics remains a challenge in current research.This work proposed a one-step thermal copolymerization to obtain Cu(Ⅰ)doping porous carbon nitride(CUCN)through a spontaneously reducing atmosphere by urea in a covered crucible.The obtained CUCN had crumpled ultrathin nanosheets and mesoporous structures,which possessed higher specific surface areas than PCN.From X-ray absorption near edge structure(XANES)and Fourier transform extended X-ray absorption fine structure(FT-EXAFS)spectra analysis,the Cu doping existed in the oxidation state of Cu(Ⅰ)as single atoms anchored on the 2D layers of CN through two N neighbors,thereby facilitating efficient pathways for the transfer of photoexcited charge carriers.Furthermore,the photoluminescence(PL)spectra,electrochemical impedance spectra(EIS)and transient photocurrent response test proved the improved separation and transfer of photoexcited charge carriers for Cu(Ⅰ)introduction.Consequently,the photocatalytic activity of CUCN was much better than that of PCN for antibiotics norfloxacin(NOR),with 4.7-fold higher degradation reaction rate constants.From species-trapping experiments and density function theory(DFT)calculations,the Cu single atoms in Cu-N_(2)served as catalytic sites that could accelerate charge transfer and facilitate the adsorption of molecular oxygen to produce active species.The stable Cu(Ⅰ)embedded in the layer structure led to the excellent recycling test and remained stable after four runs of degradation and even thermal regenerated treatment.The degradation paths of NOR by CUCN under visible light were also demonstrated.Our work sheds light on a sustainable and practical approach for achieving stable metal single-atom doping and enhancing photocatalytic degradation of aqueous pollutants.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No 2004CB619302)
文摘In the generalized gradient approximation, the energy and electronic structure are investigated for a single copper atomic chain wrapped in （4, 4）, （5, 5） and （6, 6） armchair carbon nanotubes by using the first-principles projector-augmented wave potential within the framework of density functional theory. The results show that the （4, 4） and （5, 5） tubes are too narrow to wrap a Cu chain, but the （6, 6） tube is nearly ideal to wrap a Cu chain on its centre axis. Wider tubes are anticipated to wrap more than one Cu chain spontaneously with forces amounting to a fraction of a nanonewton. Although the tube-chain interaction decreases with the increase of the tube diameter of （4, 4）, （5, 5） and （6, 6） successively, the charge density of the Cu@（6, 6） combined system still does not show complete superposition of that of the pristine （6, 6） tube and Cu chain. Successively reducing the restrictions of （4, 4）, （5, 5） and （6, 6） tubes on the Cu chain leads to a reduction in shift of the highest peak of the Cu chain towards lower energies, that is from -0.5177 eV of the isolated Cu chain to -1.36785 eV, -0.668 eV and -0.588 eV for the Cu@（4, 4）, Cu@（5, 5） and Cu@（6, 6） systems, respectively. In reverse, the strong metallic character of the Cu chain also enhances the metallic character of the combined systems so that the broader pseudogaps of the pristine carbon nanotubes around the Fermi level change into the narrow pseudogaps of the combined systems.
文摘A micro-flow injection sorbent extraction preconcentration system was combined with a graphite furnace atomic absorption spectrometry that formed an integrated system for the determination of trace amounts of elements. The analytical performances of the prospsed method for determining Cd, Cu and Mn were studied. The analytes were preconcentrated with a thiol resin(Type 190, produced by Nankai University, China) whose active group is -SH. The elements to be determined were preconcentrated onto the column for 60 s and then rinsed with deionized water and eluted with 30 μL of 1 mol/L HCl. The graphite furnace atomic absorption spectrometry(GFAAS) determination of the concentrated analyte was carried out in parallel with the next preconcentration cycle. Enrichment factors 41, 22 and 20 and detection limits(3 σ , n =10) 0.36, 3.8 and 7.0 ng/L for Cd, Cu and Mn, respectively, along with a sampling frequency of 20 h -1 , were obtained with a 60 s loading time at a sample flow rate of 3.5 mL/min. The analytical results for a number of water samples show that the flow-injection semi-online column preconcentration can not only eliminate the effect of some concomitant elements, such as Li, Na, K, Ca and Mg, on the determination of the analyte, but also enhance the sensitivity.
文摘In the present work, an easy solid phase extraction method using alumina modified with polyethylenimine as a new adsorbent was applied to the simultaneous extraction of copper, silver, and palladium ions prior to their determination with electrothermal atomic absorption spectrometry. The analytical procedure involved the complex formation of these cations with polyethylenimine as a chelating agent in buffer media of pH 7.0. Under the optimum conditions, a preconcentration factor of 200, 150, and 200, precision of ~5.4%, ＋4.7%, and ＋5.2% and linear calibration ranges of 15.0-140, 4.0-93, and 7.5-125 ng/L （in original solution） for Cu, Ag, and Pd were obtained, respectively. Also detection limits of 3.9,1.1, and 2.0 ng/L were obtained for Cu, Ag, and Pd, respectively. The proposed method was applied to the determination of copper, silver, and palladium in some real samples with satisfactory results.
基金the Analysis and Testing Foundation of Zhejiang Province(No 04045)
文摘A novel approach was developed for the determination of ultratrace amounts of copper in water samples by using electrothermal atomic absorption spectrometry （ETAAS） after cloud point extraction （ CPE ）. 1-（ 2-Pyridylazo ） -2- naphthol was used as the chelating reagent and Triton X-114 as the mieellar-forming surfactant. CPE was conducted in a pH 8. 0 medium at 40 ℃ for 10 rain. After the separation of the phases by contrifugafion, the surfactant-rieh phase was diluted with 1 mL of a methanol solution of 0. 1 mol/L HNO3. Then 20μL of the diluted surfactant-rieh phase was injected into the graphite furnace for atomization in the absence of any matrix modifier. Various experimental conditions that affect the extraction and atomization processes were optimized. A detection limit of 5 ng/L was obtained after preconeentration. The linear dynamic range of the copper mass concentration was found to be 0-2.0 ng/mL, and the relative standard deviation was found to be less than 3. 1% for a sample containing 1.0 ng/mL Cu （ Ⅱ ）. This developed method was successfully applied to the determination of uhratraee amounts of Cu in drinking water, tap water, and seawater samples.
文摘We report on the use of titanium dioxide nanoparticles (NPs) coated with poly-thiophene for the preconcentration of copper and silverions. The NPs were prepared by first modifying the surface of TiO2 NPs with vinyl groups and then copolymerizing them with vinyl thiophen. The resulting TiO2-polythiophene core-shell NPs were characterized by thermogravimetry, differential thermal analysis, scanning electron microscopy, Fourier transform infrared spectrometry and X-ray diffraction. The experimental conditions such as pH value, adsorption and desorption time, type, concentration and volume of the eluent, break through volume, and effect of potentially interfering ions were optimized. The ions were then desorbed with hydrochloric acid and determined by FAAS. The limits of detection are 0.4 and 1.2 μg·L_1 for Cu(II) and Ag(I), respectively, and recoveries and precisions are >98.0%
基金supported by the Natural Science Foundation of Hebei(No.B2010000657)
文摘A novel,simple,rapid,efficient and environment-friendly method for the determination of trace copper in cereal samples was developed by using dispersive liquid-liquid microextraction based on solidification of floating organic drop（DLLME-SFO） followed by flame atomic absorption spectrometry.In the DLLME-SFO,copper was complexed with 8-hydroxy quinoline and extracted into a small volume of 1-dodecanol,which is of low density,low toxicity and proper melting point near room temperature. The experimental parameters affecting the extraction efficiency were investigated and optimized.Under the optimum conditions, the calibration graph exhibited linearity over the range of 0.5—500 ng/mL with the correlation coefficient（r） of 0.9996.The enrichment factor was 122 and the limit of detection was 0.1 ng/mL.The method was applied to the determination of copper in the complex matrix samples such as rice and millet with the recoveries for the spiked samples at 5.0 and 10.0 u,g/g falling in the range of 92.0-98.0%and the relative standard deviation of 3.9-5.7%.
文摘[ Objective] This study aimed to evaluate the uncertainty in detecting copper and zinc contents in maize flour by flame atomic absorption spectrometry. [ Method] Combined with the actual inspection experience, the uncertainty in detecting copper and zinc contents in maize flour by tame atomic absorption spec- trometry was evaluated to establish the mathematical model. The uncertainty sources in the experimental process were investigated to analyze several components af- fecting the uncertainty in sample detection, including sample weighing, standard material transfer, solution dilution and volume setting, curve fitting, and repeat- ability of measurement instruments. [ Result] Standard curve fitting and repeatability test were two major factors that significantly affected the combined standard uncertainty. However, in the actual detection process, standard curve calibration and repeated detection procedures should be controlled strictly. Finally, the ex- panded uncertainty of copper and zinc contents in maize flour was （ 1.38 ± 0.08） mg/kg and （ 10.20 ± 1.20） mg/kg, respectively. [ Conclusion] This study provided reference for improving the accuracy and reliability of the detection method.
基金Supported by the Natinoal Natural Science Foundation of China.
文摘The determination of copper by MIP-AES was investigated in detail. Aqueous samples were introduced from an ultrasonic nebulizer and the solvent was removed by a desolvation device before introduction of the aerosol into the MIP. The desolvation system consisted of a condenser associated with a concentrated H2SO4 absorption cell. Various experimental conditions and interferences from easily ionised elements (EIEs) were also studied and some practical samples were analyzed.
基金Project supported by national high technology research and development program(863)of China(2001AA337080).
文摘The principle and characteristics of the rapidly solidified centrifugal atomization technique are studied in present paper.It has been widely used to make fine,rapidly solidified precious metal powders for application as the electrical engineering materials,conductive coatings for electromagnetic shielding and brazing alloys.The silver powder,copper powder and some precious metal alloys powders are prepared by the new method.A comparative analysis is carried out with the conventional electrolytic silver powder and chemical deposition silver powder.The results show that rapidly solidified powders are fine and have higher solid solubility of the alloying elements,and their alloys have excellent properties in various aspects.
基金Supported by Scientific Research Program Funded by Shaanxi Provincial Education Department(16JK1275)Fund for Supporting National Undergraduate Scientific and Technological Innovation(16XK046)
文摘[Objectives] The contents of copper and lead in the soil of the Yellow River Wetland were determined by flame atomic absorption spectrometry, which provides a theoretical basis for the treatment of soil pollution. [Methods] The soil was digested with a concentrated nitric acid-hydrofluoric acid-perchloric acid system, and the contents of heavy metals such as copper and lead in the Yellow River Wetland of Shaanxi Province were determined by flame atomic absorption spectrometry. [Results] The correlation coefficients reached 0.999 5 in the range of 0.00-1.00 mg/L, indicating good linearity. [Conclusions] The method is simple in operation, good in reproducibility, high in sensitivity to most elements, and can be widely used.
文摘By the decomposition of copper nitrate at 400 ℃, oriented islands of copperoxide crystals were successfully fabricated on the amorphous glass surface. X ray diffraction (XRD), atom force microscope (AFM), and X ray photoelectron spectroscopy (XPS) confirm the presence of copper oxide islands. The formation of oriented island structures is attributed to the following reasons: 1) the mismatch between the glass substrate and the copper oxide crystals during the relaxation of thermal expansion leads to the formation of islands; 2) the preorganized copper nitrate particles in the voids of colloidal crystals determine their ordered spatial distribution; 3) the strain of the glass substrate developing during calcination provides the driven energy for the orientation of copper oxide crystals along the same direction.
基金funded by the NSFC(Grant No.21401004)Natural Science Foundation of Anhui Province(Grant No.1508085QB36,1908085QB58,2008085MB52)Open Foundation of Anhui Laboratory of Molecule-based Materials(fzj19005).
文摘Support substrates play important roles in the catalysis process.Herein,atomically dispersed CuN_(3)catalysts supported by two different types of zirconia(denoted as CuN_(3)/NC/T-ZrO_(2)and CuN_(3)/NC/M-ZrO_(2))have been rationally fabricated to uncover the influence of the support.CuN_(3)/NC/T-ZrO_(2)exhibits outstanding performance for electrochemical CO_(2)reduction towards CO at a wide range of potentials(~96%,0.6-0.8 V vs.RHE)owing to the acidic uncoordinated Zr^(4+)sites of T-ZrO_(2),which facilitate CO_(2)accumulation,and N-doped carbon(NC),which enhances the conductivity of the catalyst.Moreover,density functional theory calculations prove that T-ZrO_(2)effectively decreases the Gibbs free energy for CO_(2)to CO conversion.Significantly,this study reports the effects of the substrate on the electrocatalytic CO_(2)RR and provides a promising strategy for tuning catalytic activity and selectivity during the process of converting CO_(2)into high-value products by controlling the phase of the support for the first time.
基金support from the Guangdong Basic and Applied Basic Research Foundation(no.2019B151502024 and 2021A0505030037)Guangdong Province Pearl River Scholar Funded Scheme(2019)+1 种基金The National Natural Science Foundation of China(no.21975104,22150004 and 22101099)the Guangdong Major Project of Basic and Applied Research(no.2019B030302009)also supported this work financially.
文摘Atomically precise copper(I)nanoclusters(CuNCs)with high photoluminescence(PL)efficiency and a relatively short lifetime could be promising non-precious metal-based phosphorescent emitters for organic light-emitting diodes(OLEDs),but the synthesis of such CuNCs still remains a great challenge.Herein,we have prepared a parallelepiped-like and green emissive atomically precise Cu_(10) alkynyl cluster with a moderate PLQY of 35% and lifetime(τav)of 8.4μs.Interestingly,upon addition of hexane to a DCM solution of Cu_(10),it turns into an hourglass-like,orange emissive Cu_(18) cluster with an enhanced PL efficiency(PLQY=63%,andτav=2.8μs)at room temperature,which is rarely achieved in high-nuclearity alkynyl-protected CuNCs.Experiments and theoretical calculations suggested that the excellent PL performance of Cu_(18) is due to reduced nonradiative transition,a larger d orbital contribution of Cu ions,an enhanced transition dipole moment and reduced HOMO–LUMO gap.This work will not only pave a novel approach for constructing alkynyl-protected CuNCs with a high PLQY and short lifetime,which might be explored for other CuNCs for fabricating high-performance OLEDs,but also shed light on the structure–luminescence relationship.
