Palladiy nanozarrachalarining sonokimyoviy qisqarishi

Palladiy (Pd) o'zining katalitik funktsiyalari bilan mashhur, lekin ko'pincha materiallarni tadqiq qilish va elektronika, tibbiyot, vodorodni tozalash va boshqa kimyoviy dasturlarda qo'llaniladi. Sonokimyoviy yo'l orqali mono-dispersli, shuningdek yig'ilgan palladiy nanozarrachalarini ishlab chiqarish mumkin.

Palladiy nanozarralarini ultratovush yordamida ishlab chiqarish

Nemamcha and Rehspringer have investigated the sonochemical production of dispersed and aggregated palladium nanoparticles. Therefore, a Pd(NO₃)₂ solution has been sonicated with the ultrasonic lab homogenizer UP100H in presence of ethylene glycol (EG) and polyvinylpyrrolidone (PVP).

Sample Preparation Procedure

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 in sample (b). Both mixtures were sonicated in a 20mL vial using a probe-type ultrasonicator. Samples were taken after sonication times of 30, 60, 90, 120, 150, and 180 min.

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) Water pyrolysis: H₂O → •OH+•H
• (2) Radical formation: RH (Reducing agent) + •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 Pd_N qo‘lga kiritildi.

Palladiyning sonokimyoviy qisqarishi: a namunasi (chapda) yuqori miqdorda PVP, b namunasi (o'ngda) kam miqdorda PVP. Sonikatsiya vaqti bilan lab sonicator UP100H: 180 min.
Sample a shows mono dispersed Pd nano particles, sample b aggregated Pd nano particles. [Nemamcha; 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:

1. 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.
2. 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.