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Introduction of gas sensing materials and application of nano tin oxide for gas sensors

A gas-sensitive material is a material that is very sensitive to a certain gas in a certain environment, generally a certain type of metal oxide, which is semiconductive by doping or non-stoichiometric changes, and its resistance changes with the changing atmosphere. Different types of gas-sensitive materials are particularly sensitive to one or several gases, and their resistance will change regularly with the concentration (partial pressure) of the gas, and their detection sensitivity is in the order of one millionth, while some individuals can reach the order of one billionth, far exceeding the olfactory perception of animals, so known as “electronic nose”.

 

A sensor is a detection device that can sense the measured information, and can transform the sensed information into electrical signals or other required forms of information output according to certain rules, so as to meet the requirements of information transmission, processing, storage, display, recorde and control requirements. A gas sensor is a sensor that senses the physicochemical properties of specific components contained in a gas and converts it into an appropriate electrical signal to detect the type and concentration of the gas. Semiconductor metal oxides such as SnO2, ZnO, Fe2O3 have been widely used as gas-sensing materials, and In2O3 as a new gas-sensing material has also attracted the attention of researchers.

 

With the continuous development of science and technology,  SnO2 Tin Oxide Nanopowder, as a special and important industrial raw material with various uses, has been continuously expanded in its use and dosage. The application of materials, etc. has shown the actual and potential huge market as gas sensitive, light, white conductive, nano composite photocatalytic materials, etc. Therefore, it is of great significance to find a preparation method with simple process equipment, low cost, high product yield and stable performance.

 

Nano tin dioxide SnO2 is the earliest and most widely used gas-sensing material. Because tin oxide nano has high gas-sensitivity to various combustible gases, it is widely used in the detection and alarm of combustible gases. The combustible gas sensor designed and manufactured with it has the characteristics of high sensitivity, large output signal, high impedance to toxic gas, long life and low cost. Taking nano tin oxide as the matrix material and incorporating appropriate catalysts or additives, a tin oxide gas sensor with selective sensitivity to alcohol, hydrogen, hydrogen sulfide, carbon monoxide and methane can also be prepared.

 

Since the gas-sensing mechanism of tin oxide is surface-controlled, the gas sensitivity is related to the specific surface area of ​​the material. Generally, the larger the specific surface area, the higher the gas sensitivity. Therefore, nanometerization and thin filmization of tin oxide gas-sensitive materials have become two ways to improve the sensitivity ratio of tin oxide gas.

 

In recent years, many materials science and electronics workers have joined this field one after another, dedicated to the research on the adsorption characteristics and detection mechanism of SnO2 gas-sensitive materials, and their products have also penetrated into various fields of petrochemical industry and household civil use. Used as a gas sensor, tin dioxide has many properties superior to other materials, such as higher sensitivity and lower operating temperature. In the past, there have been many studies on sintered and membrane sensors, which are currently widely used for the detection of toxic gases and flammable gases. However, this kind of gas sensor has poor stability and selectivity, long response time and recovery time, unsatisfactory repeatability of the device, and is not conducive to integration and multi-functionality. Nanotechnology can be used to make a large surface area thin-film and powder sensors are used to miniaturize and integrate components, improve sensitivity, and shorten response and recovery time. On the other hand, the development of highly selective sensors requires the use of silicon-based microelectronics technology, and thin-film technology is the most suitable method to achieve this goal. Another method to modify the traditional gas sensor is to dope pure tin oxide with various elements and compounds to reduce the working temperature and improve the sensitivity and selectivity.

 

Currently, Hongwu Nano has successfully produced more fine-grained nanometer tin dioxide, of which size reach to 10nm, in good shape, narrow distribution.https://www.hwnanomaterial.com

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Application of Nano Inorganic Materials in Printing Ink

The printing industry is an important part of our country’s national economy, and vigorously developing printing technology is the current development trend of the international printing industry. The application of nano materials in ink, paper and printing machine can improve the performance of printing materials, the defects of printing materials, and bring new vitality to the development of printing industry.

 

Ink fineness is closely related to the quality of printed matter. The finer the ink is, the stronger the tinting strength, and the clearer and fuller the dots of the printed matter. Nano inks undoubtedly have special advantages in terms of fineness, because nanomaterials are the materials with the finest grains at present. The nanoparticles themselves have good surface wettability, they are adsorbed on the surface of the pigment particles in the ink, which significantly improves the lipophilicity and wettability of the ink, which can better improve the printing suitability of the ink. The so-called nano particles refer to metal-based particles, oxide particles thereof, and non-metallic-based particles. The composition and characteristics of the nanopowders are different, and the characteristics of the ink made are also different. Nano metal particles can absorb all light of various wavelengths, and they appear black, but have a scattering effect on light. Therefore, the ink added with metal nano powders has higher purity and density. This is a process effect that cannot be achieved by adding ordinary materials. This is the basic law of actual performance. Using novel technology to add nano particles in resins, pigments, fillers, etc. can also achieve the effect of reducing the amount of pigment without reducing the covering power of the ink. If it is added to the UV ink, it can also speed up its curing speed and effectively avoid the shrinkage and wrinkling of the ink film.

 

Adhesion of nano inks to substrates

Nano anti-counterfeiting ink, a researcher from Beijing University of Chemical Technology compounded a material mixed with nano zirconia (ZrO2) and rare earth elements in a conventional ink binder to prepare an ink for printing anti-counterfeiting labels. After the ink is printed on the substrate, the pattern appears in one color under visible light and another under infrared light, which can achieve anti-counterfeiting purposes. There is also a magnetic anti-counterfeiting ink, which is to add nano magnetic substances to the ink, and the pictures and texts printed with this ink can detect magnetic signals under a special detector.

 

Adding nano SiO2 and nano TiO2 to the ink, because these two substances have strong anti-ultraviolet and catalytic properties, the light fastness of the synthesized nano ink is improved by 2-3 grades, and the heat resistance and adhesion are improved to some extent.

 

Conductive ink is made by adding silver nano conductive powder into the ink. This ink can be printed on ceramics and metals, and can also be used for circuit layer printing of modern touch panel switches. It has good performance and smooth and uniform film.

 

Using the ink with addition of nano TiO2 for printing on the surface of metal, plastic and other substrates can produce visual flash effect, color transfer effect, additional color effect, etc., also can make the surface color of the printed matter change richly and play a decorative effect as nano TiO2 can continuously emit visible light and produce different visual effects.

 

There are also some specific nanoscale materials that can achieve some specific effects if added to the ink. Nano inorganic materials such as nano Al203 has good fluidity, and if added to the ink, the wear resistance can be greatly improved. When some substances are at the nano scale, the particle size is different so is the color. Thus the manufacture of color ink may no longer rely on chemical pigments, but select different nano size particles of appropriate volume to present different colors.

 

Times are advancing, and new demands will always require the market to provide new products. The emergence of nano-printing technology marks that our country has reached the international forefront in the field of printing, opened up a new way of green, environmentally friendly and efficient printing, and promoted the development of my country’s printing industry in the direction of “green, functional, three-dimensional, and device-based” and it will also spawn more strategic emerging industries.

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Antibacterial Mechanism of Nano Silver Powder–Most Cost-Effective Antibacterial Material

In nature, harmful bacteria, fungi, viruses and other microorganisms are widely distributed, and they grow, multiply or mutate under certain conditions, which are the main reasons for human infections and diseases. Therefore, the development and application of antibacterial materials and antibacterial products have attracted attention from all over the world. Compared with organic antibacterial agents, inorganic antibacterial agents have the characteristics of high safety, good heat resistance and antibacterial durability; in addition, with the in-depth research of nanotechnology, nanoparticles and nanomaterials have become one of the research hotspots in the field of materials science. , Studies have shown that the antibacterial performance will be greatly enhanced after the nanometerization of the antibacterial agent. Therefore, nano-scale inorganic antibacterial agents have a lot of room for development.

 

Compared with ordinary silver powder, nano-silver power has the unique surface effect, volume effect, quantum size effect and macro-quantum tunneling effect of nano-materials. It has a strong inhibitory and killing effect on dozens of pathogenic microorganisms such as Escherichia coli, Neisseria gonorrhoeae, Chlamydia trachomatis, and will not produce drug resistance. Animal experiments show that even if the amount of this nano-silver antibacterial powder reaches several thousand times the standard dose, the tested animals have no signs of poisoning. At the same time, it also promotes the repair of damaged epithelial cells. It is worth mentioning that the antibacterial effect of this product when exposed to water is increasingly enhanced, which is more conducive to the treatment of diseases.

 

The main application areas of nano silver antibacterial include environmental protection, textiles and clothing, fruit preservation, food hygiene, fibers (fabrics, finished products), information industry, ecological environment, daily necessities, etc. Its detailed applications: cotton, linen, silk, polyester, acrylic, spandex, viscose fiber, protein fiber, finished fabrics, clothing, bedding, daily textiles, toys, etc., aquaculture, gardening facilities, soil improvement, building materials, Decorative materials, detergents, glassware, packaging paper products, paper for special industries, deodorants, antibacterial gels for external use in medicine, and plastic products.

 

Antibacterial mechanism of inorganic nano silver antibacterial agent

The biggest difference between nano-silver inorganic antibacterial agents and organic antibacterial agents is that the use of organic antibacterial agents can easily make bacteria resistant, and improper use can cause harm to the human body, while the use of nano-silver inorganic antibacterial agents will not cause bacteria at any time Produce drug resistance and have antibacterial durability. The antibacterial mechanism generally has the following aspects:

 

  1. The effective ingredients in antibacterial fibers act on cell membrane proteins. It can directly destroy the bacterial cell membrane and cause the cell contents to ooze out. Nano silver and organic antibacterial agents are adsorbed on the cell membrane, hindering bacteria and other microorganisms from absorbing amino acids, uracil and other nutrients necessary for growth, thereby inhibiting their growth.
  2. The far infrared rays emitted from the surface of the antibacterial fabric have a certain wavelength range, which can inhibit the activity of bacteria and cause the death of bacteria.
  3. The surface catalysis of nano-silver affects the normal metabolism and reproduction of bacteria, leading to the death of bacteria.

 

Anti-microbial category

1) Common pathogenic bacteria: Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella, etc.

2) Common pathogenic fungi: pathogenic molds such as Aspergillus flavus, Aspergillus nidulans, Penicillium citrinum, etc.; yeasts such as Candida albicans, etc.

3) Common molds that pollute the environment: Aspergillus niger, Aureobasidium pullulans, Paecilomyces variabilis and Trichoderma viride, etc. https://www.hwnanomaterial.com