Palladiy nanozarrachalarining sonokimyoviy qisqarishi
Palladiy (Pd) katalitik xususiyatlari bilan mashhur bo'lib, materiallar tadqiqotlari, elektronika ishlab chiqarish, tibbiyot, vodorod tozalash va turli kimyoviy ilovalarda keng qo'llaniladi. Sonokimyoviy yo'l yordamida palladiy zarralarining o'lchami va morfologiyasi PVP/Pd nisbatini sozlash orqali nazorat qilinishi mumkin. Bu juda mayda, monodispers nanopartikulalar yoki katta palladiy agregatlarini ultratovush orqali sintez qilish imkonini beradi, bu esa zarracha o'lchamlarini optimal katalitik samaradorlikka moslashtirishga imkon beradi.
Palladiy nanozarralarini ultratovush yordamida ishlab chiqarish
Ultrasonik palladiy nanopartikullari kamayishi, akustik kavitatsiyadan foydalanib lokal yuqori energiyali sharoitlarni yaratish va eritmada radikallarni kamaytirish orqali Pd(0) nanopartikullariga tez va reagentlarni samarali yo‘l bilan erishish imkonini beradi, bu esa palladiy ionlarini oddiy yuqori haroratdagi ishlovsiz kamaytirishga imkon beradi.
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Sanoat nanopartikul ishlov berish UIP2000hdT sonikatori bilan
Namuna tayyorlash tartibi
Namunalar quyidagi tarzda tayyorlangan:
Namunalar uchun 30ml EG va 5·10 aralashmalari-6mol of PVP were preprared by magnetic stirring for 15 min. For the different samples, different amount of Pd(NO₃)₂ solution, 1.5mL and 2mL, were added. The sample mixtures were prepared with the ratio of 2·10-3mol Pd(NO₃)₂ in sample (a) and 2.66·10-3mol Pd(NO₃)₂ (b) namunasida. Ikkala aralashma ham 20mL flakonda zond turidagi ultrasonikator yordamida sonikatsiya qilindi. Namunalar sonikatsiya vaqtlari 30, 60, 90, 120, 150 va 180 daqiqadan so'ng olingan.
Tajriba natijalarini tahlil qilish shuni ko'rsatadiki:
- 1. Pd (II) ning Pd (0) ga sonokimyoviy qisqarishi sonikatsiya vaqtiga bog'liq.
- 2. Yuqori PVP/Pd(II) molyar nisbati dumaloq shaklga ega va o'rtacha diametri taxminan 5nm bo'lgan monodispers palladiy zarrachalarining shakllanishiga olib keladi.
- 3. Biroq, past PVP / Pd (II) molyar nisbati 20 nm markazida joylashgan katta o'lchamdagi taqsimotga ega palladiy nanozarrachalari agregatlarini olishni o'z ichiga oladi.
Palladiy (II) ionlarini kamaytirishning sonokimyoviy yo'li Pd(II) palladiy atomlariga Pd(0) quyidagilar deb taxmin qilish mumkin:
- (1) Suv pirolizi: H₂O → •OH+•H
- (2) Radikal hosil bo'lishi: RH (Reduksiyalovchi vosita) + •OH(•H) → •R + H₂O(H₂)
- (3) Ionlarning kamayishi: Pd(II) + qaytaruvchi radikallar (•H, •R) → Pd(0) + R•CHO + H+
- (4) Zarrachalar hosil bo'lishi: NPd(0) → Pdn
Natija: PVP/Pd(II) nisbatiga qarab dispers yoki agregatlangan PdN qo‘lga kiritildi.
Palladiyning sonokimyoviy reduksiyasi: namuna a (chapda) yuqori miqdorda PVP, namuna b (o'ngda) kam miqdorda PVP mavjud. UP100H bilan sonikatsiya vaqti: 180 daqiqa. Namuna a mono tarqalgan Pd nano zarralarini, b namunasi esa agregatsiyalangan Pd nano zarralarini ko'rsatadi.
Tasvirlar va tadqiqot: ©Nemamcha va Rehspringer, 2008
Tahlil va natijalar
UV nurida ko'rinadigan yutilish tahlillari palladiy (II) ionlarining palladiy (0) atomlariga sonokimyoviy qisqarishi va ultratovush maydonida ushlab turish vaqti o'rtasidagi bog'liqlikni tasdiqlaydi. Palladiy (II) ionlarining palladiy (0) atomlariga qisqarishi davom etadi va sonikatsiya vaqtining oshishi bilan to'liq erishish mumkin. Transmissiya elektron mikroskopining (TEM) mikrografiklari shuni ko'rsatadiki:
- When a high amount of PVP is added, the sonochemical reduction of palladium ions leads to the formation of monodispersed palladium particles with spherical shape and a mean diameter of approx. 5nm.
- The use of a small quantity of PVP involves the obtaining of aggregates palladium nanoparticles. The dynamic light scattering (DLS) measurements reveal that the palladium nanoparticles aggregates have a large size distribution centered at 20nm.
The lab sonicator UP100H paladium nano-zarralarini tayyorlash uchun ishlatilgan.
Palladiy (Pd) nano-zarrachalari sonication yordamida tayyorlanishi mumkin
Dizayn, ishlab chiqarish va konsalting – Germaniyada ishlab chiqarilgan sifat
Hielscher ultrasonikatorlari eng yuqori sifat va dizayn standartlari bilan mashhur. Mustahkamlik va qulay foydalanish ultratovush qurilmalarimizni sanoat ob'ektlariga silliq integratsiya qilish imkonini beradi. Qo'pol sharoitlar va talabchan muhit Hielscher ultrasonikatorlari tomonidan osonlik bilan hal qilinadi.
Hielscher Ultrasonics ISO sertifikatiga ega kompaniya bo'lib, eng zamonaviy texnologiya va foydalanuvchilarga qulaylik bilan ajralib turadigan yuqori samarali ultratovush apparatlariga alohida e'tibor beradi. Albatta, Hielscher ultrasonikatorlari Idoralar talablariga javob beradi va UL, CSA va RoHs talablariga javob beradi.
Adabiyot/Adabiyotlar
- Nemamcha, A.; Rehspringer, J. L. (2008): Morphology of dispersed and aggregated PVV-Pd nanoparticles prepared by ultrasonic irradiation of Pd(NO₃)₂ solution in ethylene glycol. Rev. Adv. Mater. Sci. 18;2008. 685-688.
- Prekob, Á., Muránszky, G., Kocserha, I. et al. (2020): Sonochemical Deposition of Palladium Nanoparticles Onto the Surface of N-Doped Carbon Nanotubes: A Simplified One-Step Catalyst Production Method. Catalysis Letters 150, 2020. 505–513.
- Haitao Zheng, Mphoma S. Matseke, Tshimangadzo S. Munonde (2019): The unique Pd@Pt/C core-shell nanoparticles as methanol-tolerant catalysts using sonochemical synthesis. Ultrasonics Sonochemistry, Volume 57, 2019. 166-171.
Bilishga arziydigan faktlar
Palladium nima?
Palladium - noyob, kumushrang oq qimmatbaho metall bo'lib, kimyoviy belgisi Pd va atom raqami 46. U platina guruhi metallarga kiradi va kimyoviy barqarorligi, elektr o'tkazuvchanligi, vodorod yutishi va ajoyib katalizator sifatida ishlashi sababli qadrlanadi. Mayda boʻlinib ketgan palladium ayniqsa vodorodlash va dehidrogenlash reaksiyalari uchun samaralidir, va isitilgan palladium orqali vodorod diffuziya qilishi mumkin, bu esa uni vodorodni ajratish va tozalash uchun foydali qiladi.
Palladium nanopartikullari nimalar uchun ishlatiladi?
Palladium nanoparticles are used mainly as high-surface-area catalysts. Because nanoparticles expose far more active surface area than bulk palladium, they can improve catalyst efficiency and reduce the amount of expensive noble metal required. Typical applications include chemical synthesis, hydrogenation reactions, carbon–carbon coupling reactions, electrocatalysis, fuel-cell research, hydrogen sensing and storage, environmental catalysis, and some biomedical research areas such as antimicrobial, photothermal, and anticancer systems. Palladium catalytic behavior depends strongly on particle size, morphology, and dispersion.
Palladium nanoparticles are also used to dope other particles in order to achieve catalytic functionalities. Pd/N-BCNT ni Fischer-Tropsch katalizatori sifatida sintezlash uchun ultratovush yo'li haqida ko'proq o'qing!
Palladiy zaharlimi?
Elemental metallic palladium is generally considered to have low toxicity and no known biological role, but palladium compounds, salts, dusts, and nanoscale forms should be handled carefully. Occupational or laboratory exposure can cause irritation or sensitization depending on the compound and route of exposure, and palladium chloride solutions, for example, may irritate mucous membranes. For industrial handling, the practical answer is: bulk metallic palladium is relatively low-risk, but palladium powders, soluble palladium salts, and palladium nanoparticles should be treated as potentially hazardous materials, with dust control, ventilation, gloves, eye protection, and proper waste handling.