Applications

Spin trapping technique has been widely used in biology and chemistry because it can achieve the detection of short-lived radicals. For spin trapping experiments, many factors such as the time of trapping agent addition, trapping agent concentration, system solvent and system pH can affect the experimental results. Therefore, for different radicals, it is necessary to select the trapping agent and design the experimental scheme reasonably to achieve the best experimental results.   1.Trapping Agent and Solvent Selection   The common O-center radicals are hydroxyl radicals, superoxide anion radicals, and singlet oxygen.   Hydroxyl radicals (∙OH)   For hydroxyl radicals, they are usually detected in aqueous solutions and captured using DMPO, which forms adducts with DMPO with half-lives of minutes to tens of minutes.   Superoxide anion radicals (∙O2-)   For superoxide anion radicals, if DMPO is chosen as the trapping agent, the detection needs to be performed in a methanol system. This is because the binding ability of water and DMPO is higher than that of superoxide radicals to DMPO. If superoxide radicals are detected in water, the binding speed of water to DMPO will be greater than that of superoxide radicals to DMPO, resulting in superoxide radicals not being easily captured. Of course, if the superoxide radicals are produced in large amounts, they may also be captured by DMPO. If one wants to trap superoxide radicals in aqueous solution, BMPO needs to be chosen as the trapping agent because the half-life of adducts formed by BMPO trapping superoxide radicals in aqueous solution can be up to several minutes.   Single-linear state (1O2)   For single-linear state oxygen detection, TEMP is usually selected as the capture agent, and its detection principle is shown in Figure 1. Single-linear state oxygen can oxidize TEMP to form TEMPO radicals containing single electrons, which can be detected by electron paramagnetic resonance spectrometry. Since TEMP is easily oxidized and prone to background signal, TEMP needs to be tested before detecting single-linear state oxygen as a control experiment. Figure 1 Mechanism of TEMP for detecting singlet oxygen     Table 1 Common O-center radical detection trapping agent and solvent selection   2、Addition Time of Trapping Agent         In photocatalytic reactions, when light irradiates the catalyst, the valence band electrons are excited to the conduction band, producing electron/hole pairs. Such experiments generally require the addition of the trapping agent before the light irradiation, and in combination with the in situ light system, the variation of the radical signal with the light irradiation time can be studied, as shown in Figure 2, with different light irradiation times, the ∙OH content generated varies.   Fig. 2 Results of CIQTEK in-situ illumination experiments   In the warming reaction, if the reaction temperature...

Ceramic capacitors, as a kind of basic passive components, are an indispensable member of the modern electronic industry. Among them, chip multilayer ceramic capacitors (MLCC) occupy more than 90% of the ceramic capacitor market due to their characteristics of high temperature resistance, high voltage resistance, small size, and wide range of capacitance, and are widely used in the consumer electronics industry, including home appliances, communications, automotive electronics, new energy, industrial control, and other application areas.   The use of CIQTEK SEM can assist in completing the failure analysis of MLCC, finding the origin of failure through micro-morphology, optimizing the production process, and achieving the goal of high product reliability.   Application of CIQTEK SEM in MLCC   MLCC consists of three parts: inner electrode, ceramic dielectric and end electrode. With the continuous updating of the market demand of electronic products, MLCC product technology also presents the development trend of high capacity, high frequency, high temperature and high voltage resistance, high reliability and miniaturization. Miniaturization means the need to use smaller-sized, more uniform ceramic powders. The microstructure of the material determines the final performance, and the use of scanning electron microscope to characterize the microstructure of ceramic powders, including particle morphology, particle size uniformity, and grain size, can help in the continuous improvement of the preparation process.      Scanning electron microscope imaging of different types of barium titanate ceramic powders /25kV/ETD   Scanning Electron Microscope Imaging Different types of barium titanate ceramic powders /1kV/Inlens   High reliability means that a deeper understanding of the failure mechanism is required, and therefore failure analysis is indispensable. The root cause of MLCC failure is the presence of various microscopic defects, such as cracks, holes, delamination, etc., either externally or internally. These defects will directly affect the electrical performance and reliability of MLCC products, and bring serious hidden danger to product quality. The use of scanning electron microscope can assist in completing the failure analysis of capacitor products, find the origin of the failure through the microscopic morphology, optimize the production process, and ultimately achieve the goal of high reliability of the product.   MLCC's internal is a multi-layer structure, each layer of ceramics whether there are defects, multi-layer ceramics thickness is uniform, whether the electrodes are covered uniformly, all of these will affect the life of the device. When using SEM to observe the internal multilayer structure of MLCC or to analyze their internal failures, it is often necessary to perform a series of pre-treatments on the samples before they can be tested. These include resin embedding, mechanical grinding, ...

Drug powders are the main body of most pharmaceutical formulations, and their efficacy depends not only on the type of drug, but also to a large extent on the properties of the powders composing the pharmaceutical formulations. Numerous studies have shown that physical parameters such as specific surface area, pore size distribution and true density of drug powders are related to the properties of powder particles such as particle size, hygroscopicity, solubility, dissolution and compaction, and play an important role in the purification, processing, mixing, production and packaging capabilities of pharmaceuticals. Especially for APIs and pharmaceutical excipients, parameters such as specific surface area are important indicators of their performance.   The specific surface area of API, as the active ingredient of a drug, affects its properties such as solubility, particle size and solubility. Under certain conditions, the larger the specific surface area of the same weight of API, the smaller the particle size, dissolution and dissolution rate is also accelerated. By controlling the specific surface area of the API, it can also achieve a good uniformity and fluidity, to ensure uniform distribution of drug content.   Pharmaceutical excipients, as excipients and additional agents used in the production of drugs and prescriptions, specific surface area is one of the important functional indicators, which is important for diluents, binders, disintegrants, flow aids, and especially lubricants. For example, for lubricants, the specific surface area significantly affects their lubrication effect, because the prerequisite for lubricants to play a lubricating effect is to be able to be uniformly dispersed on the surface of the particles; generally speaking, the smaller the particle size, the larger the specific surface area, and the easier it is to be uniformly distributed during the mixing process.   Thus, accurate, rapid and effective testing of physical parameters such as specific surface area and true density of pharmaceutical powders has always been an indispensable and critical part of pharmaceutical research. Therefore, the methods for the determination of specific surface area and solid density of pharmaceutical powders are clearly defined in the United States Pharmacopoeia USP<846> and USP<699>, the European Pharmacopoeia Ph. Eur. 2.9.26 and Ph. Eur. 2.2.42, as well as in the second additions of the physical and chemical analysis contents 0991 and 0992 to the four general rules of the Chinese Pharmacopoeia, 2020 edition.   01 Gas adsorption technique and its application   Gas adsorption technique is one of the important methods for material surface property characterization. Based on adsorption analysis, it can accurately analyze the specific surface area, pore volume and pore size distribution, true density and other parameters of APIs, pharmaceutical excipients and drug formulations. In turn, it can do some...

Environmental catalysts are broadly defined as all catalysts that can improve environmental pollution. In recent years, environmental protection has become more and more popular, and the research and application of environmental catalysts have become more and more in-depth. The environmental catalysts for processing different reactants have corresponding performance requirements, among which the specific surface area and pore size are one of the important indexes for characterizing the properties of environmental catalysts. It is of great significance to use gas adsorption technology to accurately characterize the physical parameters such as the specific surface area, the pore volume and the pore size distribution of the environmental catalysts for the research and optimization of their performance.   01Environmental protection catalyst   Currently, oil refining, chemical and environmental protection industries are the main application fields of catalysts. Environmental catalysts generally refer to the catalysts used to protect and improve the surrounding environment by directly or indirectly treating toxic and hazardous substances, making them harmless or reducing them, broadly speaking, catalysts capable of improving environmental pollution can be attributed to the category of environmental catalysts. Environmental catalysts can be divided into exhaust gas treatment catalysts, wastewater treatment catalysts and other catalysts according to the direction of application, such as molecular sieve catalysts that can be used for the treatment of exhaust gases such as SO2, NOX, CO2, and N2O, activated carbon that can be used as a typical adsorbent for the adsorption of liquid/gas-phase pollutants, as well as semiconductor photocatalysts that can degrade organic pollutants, and so on.   02 Specific surface and pore size analysis and characterization of environmental catalysts   Catalyst surface area is one of the important indexes to characterize catalyst properties. The surface area of catalyst can be divided into outer surface area and inner surface area. Since the majority of the surface area of environmental catalyst is inner surface area and the active center is often distributed on the inner surface, generally, the larger the specific surface area of environmental catalyst is, the more activation centers are on the surface, and the catalyst has a strong adsorption capacity for reactants, which are all favorable to the catalytic activity. In addition, the type of pore structure has a great influence on the activity, selectivity and strength of the catalyst. Before the reactant molecules are adsorbed, they must diffuse through the pores of the catalyst to reach the active center on the inner surface of the catalyst, and this diffusion process is closely related to the pore structure of the catalyst, and different pore structures show different diffusion laws and apparent reaction kinetics, for example, the strong selectivity of ...

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 ...

I. Lithium-ion battery   The lithium-ion battery is a secondary battery, which mainly relies on lithium ions moving between the positive and negative electrodes to work. During the charging and discharging process, lithium ions are embedded and de-embedded back and forth between the two electrodes through the diaphragm, and the storage and release of lithium-ion energy are achieved through the redox reaction of the electrode material.   Lithium-ion battery mainly consists of positive electrode material, diaphragm, negative electrode material, electrolyte, and other materials. Among them, the diaphragm in the lithium-ion battery plays a role in preventing direct contact between the positive and negative electrodes, and allows the free passage of lithium ions in the electrolyte, providing a microporous channel for lithium ion transport.   The pore size, degree of porosity, uniformity of distribution, and thickness of the lithium-ion battery diaphragm directly affect the diffusion rate and safety of the electrolyte, which has a great impact on the performance of the battery. If the pore size of the diaphragm is too small, the permeability of lithium ions is limited, affecting the transfer performance of lithium ions in the battery, and making the battery resistance increases. If the aperture is too large, the growth of lithium dendrites may pierce the diaphragm, causing accidents such as short circuits or explosions.   Ⅱ. The application of field emission scanning electron microscopy in the detection of lithium diaphragm   The use of scanning electron microscopy can observe the pore size and distribution uniformity of the diaphragm, but also on the multi-layer and coated diaphragm cross-section to measure the thickness of the diaphragm. Conventional commercial diaphragm materials are mostly microporous films prepared from polyolefin materials, including polyethylene (PE), polypropylene (PP) single-layer films, and PP/PE/PP three-layer composite films. Polyolefin polymer materials are insulating and non-conductive, and are very sensitive to electron beams, which can lead to charging effects when observed under high voltage, and the fine structure of polymer diaphragms can be damaged by electron beams. The SEM5000 field emission scanning electron microscope, which is independently developed by GSI, has the capability of low voltage and high resolution, and can directly observe the fine structure of the diaphragm surface at low voltage without damaging the diaphragm.   The diaphragm preparation process is mainly divided into two types of dry and wet methods. The dry method is the melt stretching method, including the unidirectional stretching process and bidirectional stretching process, the process is simple, has low manufacturing costs, and is a common method of lithium-ion battery diaphragm production. The diaphragm prepared by the dry method has flat and long microporous (Figure 1), but the prepared diaphragm is thicke...

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...

Powders are today's raw materials for the preparation of materials and devices in various fields and are widely used in lithium-ion batteries, catalysis, electronic components, pharmaceuticals, and other applications.   The composition and microstructure of the raw material powders determine the properties of the material. The particle size distribution ratio, shape, porosity, and specific surface of the raw material powders can match the unique properties of the material.   Therefore, the regulation of the microstructure of the raw material powder is a prerequisite for obtaining excellent performance materials. The use of scanning electron microscopy allows observation of the specific surface morphology of the powder and precise analysis of the particle size to optimize the preparation process of the powder.   Application of scanning electron microscopy in MOFs materials   In the field of catalysis, the construction of metal-organic backbone materials (MOFs) to substantially improve the surface catalytic performance has become one of the hot research topics today. MOFs have the unique advantages of high metal loading, porous structure and catalytic sites, and have great potential as cluster catalysts. Using the CIQTEK Tungsten Filament Scanning Electron Microscope, it can be observed that the MOFs material shows regular cubic shape and the presence of fine particles adsorbed on the surface (Figure 1). The electron microscope possesses a resolution of up to 3 nm and excellent imaging quality, and uniform high-brightness SEM maps can be obtained in different fields of view, which can clearly observe the folds, pores, and particle loading on the surface of MOFs materials.     Figure 1 MOFs material / 15 kV/ETD   Scanning electron microscopy in silver powder materials   In the manufacture of electronic components, electronic paste, as a basic material for manufacturing electronic components, has certain rheological and thixotropic properties, and is a basic functional material integrating materials, chemical and electronic technologies, and the preparation of silver powder is the key to manufacturing silver conductive paste. Using the SEM5000 field emission scanning electron microscope independently developed by CIQTEK, relying on the high voltage tunneling technology, the space charge effect is drastically reduced, and irregular silver powder clustering with each other can be observed (Figure 2). And the SEM5000 has high resolution, so that details can still be seen even at 100,000x magnification.     Figure 2 Silver powder/5 kV/Inlens   Scanning electron microscopy in lithium iron phosphate   Lithium-ion batteries are rapidly occupying the mainstream market because of their high specific energy, long cycle life, no memory effect, and high safety. The use of electron microscopy to observe the positive and negative electrode morphology of lithium-ion batteries is important to improve t...