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CIQTEK is the manufacturer and global supplier of high-performance scientific instruments, such as Electron Microscopes, Electron Paramagnetic Resonance (Electron Spin Resonance), Gas Adsorption Analyzers, quantum sensors, quantum computers, etc.
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Environmental Contaminant Detection - EPR (ESR) Applications
Environmental Contaminant Detection - EPR (ESR) Applications
Environmental pollution is one of the global crises and is affecting the quality of living and health of the entire population. A new class of harmful substances, the environmentally persistent free radicals (EPFRs). These pollutants are pervasive and can be found in air, water, and soil. The EPFRs can be recognized as biohazard since it can produce reactive oxide species (ROS), which causes cell and tissue damages and ultimately cancer. To mitigate and eventually find a solution to this problem, tracing the origin of such pollutants is needed. Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool and can be used for such tasks.   What are EPFRs   The conventionally recognized free radicals are often transient with a short lifetime. On the contrary, EPFRs can be stable in the environment for tens of minutes to tens of days without being oxidized or quenched. The commonly found EPFRs include, cyclopentadienyl, semiquinone, phenoxy, and other radicals.     Common EPFRs     Where do EPFRs come from?   EPFRs are found in a wide range of environmental media, such as atmospheric particulate matter (e.g. PM 2.5), factory emissions, tobacco, petroleum coke, wood and plastic, coal combustion particulates, soluble fractions in water bodies, and organically contaminated soils, etc. EPFRs have a wide range of transport pathways in environmental media and can be transported through vertical ascent, horizontal transport, vertical deposition to water bodies, vertical deposition to land, and landward migration of water bodies. In the process of migration, new reactive radicals may be generated, which directly affects the environment and are precursors to other pollutants.   Formation and Multimediated Transfer of EPFRs (Environmental Pollution 248 (2019) 320-331)     Application of EPR Technique for the Detection of EPFRs   EPR spectroscopy is extremely sensitive to unpaired electrons, and a directly measurement of signals from these radicals make it an ideal method for monitoring the presence of EPFRs in different samples.  . For the detection of EPFRs, EPR (ESR) spectroscopy provides information in both spatial and temporal dimensions. By measuring and analyzing the continuous-wave EPR spectra of samples, the researchers are able to not only verifying the presence of radicals but also obtain g-values and hyperfine coupling constants of electrons, which can be used for inferring electronic structure of measured molecules. The temporal resolution refers to the half-life of EPFRs, which can also be obtained from monitoring their EPR signals over time.     Application of EPR Technology in Detecting EPFRs in the Soil Environment   Petroleum processing, storage, transportation, and possible leakage from storage tanks are all susceptible to soil contamination. Although thermal treatment techniques can be used to remediate soils contaminated by various volatile, semi-volati...
Study of EPR Signals in Corals - EPR (ESR) Applications
Study of EPR Signals in Corals - EPR (ESR) Applications
The name coral comes from the Old Persian sanga (stone), which is the common name for the coral worm community and their skeleton. Coral polyps are corals of the phylum Acanthozoa, with cylindrical bodies, which are also called living rocks because of their porosity and branching growth, which can be inhabited by many microorganisms and fish. Corals flourish in tropical ocean. The chemical composition of white coral is mainly CaCO3 and contains organic matter, called carbonate type. Golden, blue, and black coral is composed of keratin, called keratin type. Red coral (including pink, flesh red, rose red, light red to deep red) shell has more keratin and CaCO3. Cora, based on  the skeletal structure characteristics, can be divided into plate bed coral, four-shot coral, six-shot coral, and eight-shot coral. Modern coral is mostly the latter two categories. Coral is an important carrier to record the marine environment, for the determination of paleoclimatology, ancient sea level change and tectonic movement and other studies have important significance.   Electron paramagnetic resonance spectroscopy is a powerful tool for studying substances with unpaired electrons. This technique utilizes microwave irradiation to probe the energy separation of unpaired electrons created by an external magnetic field.  A special application of EPR spectroscopy is developed for analyzing corals, which is a valuable method marine environmental studies.   The information regarding paleoclimate is reflected in the Mn2+ concentration in coral reef. Using EPR spectroscopy, the signal of Mn2+ can be easily analyzed and interpreted, since its concentration is relatively high during a warm period and decreases sharply during a period of rapid cooling. Another set of substances in coral that can be measured by EPR spectroscopy is lattice defects and impurities produced by natural irradiation. Such lattice defects trap unpaired electrons, which produces observable EPR signals. The lineshape of such signals are indicative to the composition of minerals and trapped impurities, and therefore can be used for inferring the information about age of formation as well as crystallization condition of samples.   The EPR signal in the coral will be analyzed using a CIQTEK X-Band EPR (ESR) spectroscopy EPR100 to provide information on the composition and defect vacancies in the coral.   CIQTEK X-Band EPR100   Experimental Sample The sample was taken from white coral in the South China Sea, treated with 0.1 mol/L dilute hydrochloric acid, crushed with a mortar, sieved, dried at 60°C, weighed about 70 mg, and tested on the CIQTEK EPR100.   White Coral Sample   Electron Paramagnetic Resonance Spectroscopy The CIQTEK EPR100 was used to test the EPR signal in white coral. To achieve accurate measurement of the EPR signal, the specific experimental conditions were as follows.   Experimental Conditions ...
JACS Approved Article! CIQTEK EPR Contributes to 27 High-level Research Publications
JACS Approved Article! CIQTEK EPR Contributes to 27 High-level Research Publications
We are pleased to announce that the CIQTEK EPR spectrometer products have contributed to 27 high-level research publications to date!     One of the Selected Results    Vanadium-Catalyzed Dinitrogen Reduction to Ammonia via a [V]═NNH2 Intermediate.Journal of the American Chemical Society (2023) Wenshuang Huang, Ling-Ya Peng, Jiayu Zhang, Chenrui Liu, Guoyong Song, Ji-Hu Su, Wei-Hai Fang, Ganglong Cui, and Shaowei Hu     Abstract   The Earth's atmosphere is rich in N2 (78%), but the activation and conversion of nitrogen have been a challenging task due to its chemical inertness. The ammonia industry uses high-temperature and high-pressure conditions to convert N2 and H2 to NH3 on the surface of solid catalysts. Under ambient conditions, certain microorganisms can bind and convert N2 to NH3 via Fe(Mo/V)-based nitrogen fixation enzymes. Although great progress has been made in the structure and intermediates of nitrogen fixation enzymes, the nature of N2 binding to the active site and the detailed mechanism of N2 reduction remains uncertain. Various studies on the activation of N2 with transition metal complexes have been carried out to better understand the reaction mechanism and to develop catalysts for ammonia synthesis under mild conditions. However, so far, the catalytic conversion of N2 to NH3 by transition metal complexes remains a challenge. Despite the crucial role of vanadium in biological nitrogen fixation, there are few well-defined vanadium complexes that can catalyze the conversion of N2 to NH3. In particular, the V(NxHy) intermediates obtained from the proton/electron transfer reactions of ligated N2 remain unknown. Herein, this paper reports the vanadium metal complex-catalyzed reduction of nitrogen to ammonia and the first isolation and characterization of a neutral hydrazide complex intermediate ([V]=NNH2) from a nitrogen-activated system, with the cyclic conversion process simulated by the reduction of the protonated vanadium amino complex ([V]-NH2) to obtain a dinitrogen compound and release of ammonia. These findings provide unprecedented insights into the mechanism of N2 reduction associated with FeV nitrogen-fixing enzymes by combining theoretical calculations to elucidate the possible conversion of nitrogen to ammonia via the distal pathway in this catalytic system.   The group of Prof. Dr. Shaowei Hu at Beijing Normal University is dedicated to the development of transition metal complexes for the activation of inert small molecules. Recently, in collaboration with Prof. Dr. Ganglong Cui's group, we reported the reduction of nitrogen to ammonia catalyzed by vanadium metal complexes through a combination of theoretical calculations and experimental studies. The results of this study were published in the Journal of the American Chemical Society, and Wenshang Huang (M.S. student) and Lingya Peng (Ph...
Relative & Absolute Quantification - EPR (ESR) Applications
Relative & Absolute Quantification - EPR (ESR) Applications
The electron paramagnetic resonance (EPR or ESR) technique is the only method available for directly detecting unpaired electrons in samples. Among them, the quantitative EPR (ESR) method can provide the number of unpaired electron spins in a sample, which is essential in studying the reaction kinetics, explaining the reaction mechanism and commercial applications. Therefore, obtaining the unpaired electron spin numbers of samples by electron paramagnetic resonance techniques has been a hot topic of research.  Two main quantitative electron paramagnetic resonance methods are available: relative quantitative EPR (ESR) and absolute quantitative EPR (ESR).     Relative Quantitative EPR (ESR) Method   The relative quantitative EPR method is accomplished by comparing the integrated area of the EPR absorption spectrum of an unknown sample with the integrated area of the EPR absorption spectrum of a standard sample. Therefore, in the relative quantitative EPR method, a standard sample with a known number of spins needs to be introduced. The size of the integrated area of the EPR absorption spectrum is not only related to the number of unpaired electron spins in the sample, but also to the settings of the experimental parameters, the dielectric constant of the sample, the size and shape of the sample, and the position of the sample in the resonant cavity. Therefore, to obtain more accurate quantitative results in the relative quantitative EPR method, the standard sample and the unknown sample need to be similar in nature, similar in shape and size, and in the same position in the resonant cavity.   Quantitative EPR Error Sources     Absolute Quantitative EPR (ESR) Method   The absolute quantitative EPR method means that the number of unpaired electron spins in a sample can be obtained directly by EPR testing without using a standard sample. In absolute quantitative EPR experiments, to obtain the number of unpaired electron spins in a sample directly, the value of the quadratic integral area of the EPR spectrum (usually the first-order differential spectrum) of the sample to be tested, the experimental parameters, the sample volume, the resonance cavity distribution function and the correction factor are needed. The absolute number of unpaired electron spins in the sample can be directly obtained by first obtaining the EPR spectrum of the sample through the EPR test, then processing the EPR first-order differential spectrum to obtain the second-integrated area value, and then combining the experimental parameters, sample volume, resonant cavity distribution function and correction factor.   CIQTEK Electron Paramagnetic Resonance Spectroscopy   The absolute quantification of unpaired electron spins of the CIQTEK EPR (ESR) spectroscopy can be used to obtain the spin number of unpaired electrons in a sample directly without the use of a reference or standard sample. The resonant cavity distribution funct...
CIQTEK EPR (ESR) boosts nano-spin sensor research
CIQTEK EPR (ESR) boosts nano-spin sensor research
Based on quantum properties, electron spin sensors have high sensitivity and can be widely used to probe various physicochemical properties, such as electric field, magnetic field, molecular or protein dynamics, and nuclear or other particles. These unique advantages and potential application scenarios make spin-based sensors a hot research direction at present. Sc3C2@C80 has a highly stable electron spin protected by a carbon cage, which is suitable for gas adsorption detection within porous materials. Py-COF is a recently emerged porous organic framework material with unique adsorption properties, which was prepared using a self-condensing building block with a formyl group and an amino group. prepared with a theoretical pore size of 1.38 nm. Thus, a metallofullerene Sc3C2@C80 unit (~0.8 nm in size) can enter one of the nanopores of Py-COF.   A nanospin sensor based on metal fullerene was developed by Taishan Wang, a researcher at the Institute of Chemistry, Chinese Academy of Sciences, for detecting gas adsorption within a porous organic framework. The paramagnetic metal fullerene, Sc3C2@C80, was embedded in the nanopores of a pyrene-based covalent organic framework (Py-COF). The adsorbed N2、CO、CH4、CO2、C3H6 and C3H8 within the Py-COF embedded with the Sc3C2@C80 spin probe were recorded using the EPR technique ( CIQTEK EPR200-Plus).It was shown that the EPR signals of the embedded Sc3C2@C80 regularly correlated with the gas adsorption properties of the Py-COF. The results of the study were published in Nature Communications under the title "Embedded nano spin sensor for in situ probing of gas adsorption inside porous organic frameworks".     Probing gas adsorption properties of Py-COF using molecular spin of Sc3C2@C8     In the study, the authors used a metallofullerene with paramagnetic properties, Sc3C2@C80 (~0.8 nm in size), as a spin probe embedded into one nanopore of pyrene-based COF (Py-COF) to detect gas adsorption within Py-COF. Then, the adsorption properties of Py-COF for N2、CO、CH4、CO2、C3H6 and C3H8 gases were investigated by recording the embedded Sc3C2@C80 EPR signals. It is shown that the EPR signals of Sc3C2@C80 regularly follow the gas adsorption properties of Py-COF. And unlike conventional adsorption isotherm measurements, this implantable nanospin sensor can detect gas adsorption and desorption by in situ real-time monitoring. The proposed nanospin sensor was also used to probe the gas adsorption properties of metal-organic framework (MOF-177), demonstrating its versatility.     Relationship between gas adsorption properties and EPR signals     Effect of gas pressure on EPR signal     EPR signal line width analysis   Spin-based sensors have attracted considerable attention owing to their high sensitivities. Herein, we developed a metallofullerene-based nano spin sensor to probe gas adsorption within porous organi...
Electron-Electron Double Resonance (DEER) in DNA Structure Analysis - EPR (ESR) Applications
Electron-Electron Double Resonance (DEER) in DNA Structure Analysis - EPR (ESR) Applications
Since the 1950s, when Watson and Crick proposed the classical double helix structure of DNA, DNA has been at the heart of life science research. The number of the four bases in DNA and their order of arrangement lead to the diversity of genes, and their spatial structure affects gene expression.In addition to the traditional DNA double helix structure, studies have identified a special four-stranded DNA structure in human cells, the G-quadruplex, a high-level structure formed by the folding of DNA or RNA rich in tandem repeats of guanine (G), which is particularly high in rapidly dividing G-quadruplexes are particularly abundant in rapidly dividing cells (e.g., cancer cells). Therefore, G-quadruplexes can be used as drug targets in anticancer research. The study of the structure of the G-quadruplex and its binding mode to binding agents is important for the diagnosis and treatment of cancer cells.   Schematic representation of the three-dimensional structure of the G-quadruplex.Image source: Wikipedia   Electron-Electron Double Resonance (DEER)   The Pulsed Dipolar EPR (PDEPR) method has been developed as a reliable and versatile tool for structure determination in structural and chemical biology, providing distance information at the nanoscale by PDEPR techniques. In G-quadruplex structure studies, the DEER technique combined with site-directed spin labeling (SDSL) can distinguish G-quadruplex dimers of different lengths and reveal the binding pattern of G-quadruplex binding agents to the dimer.Differentiation of G-quadruplex Dimers of Different Lengths Using DEER TechnologyUsing Cu(pyridine)4 as a spin label for distance measurement, the tetragonal planar Cu(pyridine)4 complex was covalently bound to the G-quadruplex and the distance between two paramagnetic Cu2+ in the π-stacked G quaternary monomer was measured by detecting dipole-dipole interactions to study the dimer formation.[Cu2+@A4] (TTLGGG) and [Cu2+@B4] (TLGGGG) are two oligonucleotides with different sequences, where L denotes the ligand. The DEER results of [Cu2+@A4]2 and [Cu2+@B4]2 are shown in Figure 1 and Figure 2. From the DEER results, it can be obtained that in [Cu2+@A4]2 dimers, the average distance of single Cu2+ -Cu2+ is dA=2.55 nm, the G-quadruplex 3′ end forms G-quadruplex dimer by tail-tail stacking, and the gz-axis of two Cu2+ spin labels in G-quadruplex dimer is aligned parallel.The [Cu2+@A4]2 π stacking distance is longer (dB-dA = 0.66 nm) compared to the [Cu2+@A4]2 dimers. It was confirmed that each [Cu2+@B4] monomer contains an additional G tetramer, a result that is in full agreement with the expected distances. Thus, distance measurements by the DEER technique can distinguish G-quadruplex dimers of different lengths.     Fig. 1 (A) The pulsed EPR differential spectrum (black line) of [Cu2+@A4]2 dimer and its corresponding simulation (red line) (34 GHz, 19 K); (B) After background correction, four phases in a-d DEER time-domain ...
Lithium-ion Batteries - EPR (ESR) Applications
Lithium-ion Batteries - EPR (ESR) Applications
Li-Ion Batteries (LIBs) are widely used in electronic devices, electric vehicles, power grid storage, and other fields due to their small size, lightweight, high battery capacity, long cycle life, and high safety.Electron paramagnetic resonance (EPR or ESR) technology can non-invasively probe the inside of the battery and monitor the evolution of electronic properties during the charging and discharging of electrode materials in real-time, thus studying the electrode reaction process close to the real state. It's gradually playing an irreplaceable role in the study of the battery reaction mechanism.     Composition and Working Principle of Lithium-ion Battery   A lithium-ion battery consists of four main components: the positive electrode, the negative electrode, the electrolyte, and the diaphragm. It mainly relies on the movement of lithium ions between the positive and negative electrodes (embedding and de-embedding) to work.   Fig. 1 Lithium-ion Battery Working Principle   In the process of battery charging and discharging, the changes of charging and discharging curves on the positive and negative materials are generally accompanied by various microstructural changes, and the decay or even failure of performance after a long time cycle is often closely related to the microstructural changes. Therefore, the study of the constitutive (structure-performance) relationship and electrochemical reaction mechanism is the key to improving the performance of lithium-ion batteries and is also the core of electrochemical research.     EPR (ESR) Technology in Lithium-ion Batteries   There are various characterization methods to study the relationship between structure and performance, among which, the electron spin resonance (ESR) technique has received more and more attention in recent years because of its high sensitivity, non-destructive, and in situ monitorability. In lithium-ion batteries, using the ESR technique, transition metals such as Co, Ni, Mn, Fe, and V in electrode materials can be studied, and it can also be applied to study the electrons in the off-domain state.   The evolution of electronic properties (e.g., change of metal valence) during the charging and discharging of electrode materials will cause changes in EPR (ESR) signals. The study of electrochemically induced redox mechanisms can be achieved by real-time monitoring of electrode materials, which can contribute to the improvement of battery performance.   EPR (ESR) Technology in Inorganic Electrode Materials   In lithium-ion batteries, the most commonly used cathode materials are usually some electrodeless electrode materials, including LiCoO2, Li2MnO3, etc. The improvement of cathode material performance is the key to improving the overall battery performance.   In Li-rich cathodes, reversible O redox can generate additional capacity and thus increase the specific energy of oxide cathode materials. Hence, the s...
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