Zinc oxide (ZnO) semiconductors are renowned for their cost-effective synthesis and superior catalytic attributes, making them prominent in environmental remediation applications. This study presents the synthesis of ZnO nanoparticles (NPs) with distinct morphologies, achieved by modulating citric acid concentrations in an ultrasonic-assisted hydrothermal process. The photocatalytic efficacy of these ZnO NPs in degrading malachite green (MG), a persistent environmental pollutant, was thoroughly investigated. Our findings reveal a strong correlation between the morphological features of ZnO catalysts and their photodegradation performance. Among the synthesized NPs, the chrysanthemum-shaped ZnO (denoted as USZ-0.1) demonstrated exceptional photocatalytic activity, attributed to its enhanced surface area and optimized nano-crystal aggregation. This structure facilitated the generation of a higher concentration of reactive oxygen species, leading to over 96.5% degradation of MG within 40 min under simulated sunlight in an acidic medium. This study underscores the potential of morphological manipulation in enhancing the photocatalytic properties of ZnO NPs for environmental applications.
Ting Liu,Yongxin Liu,Lili Yao,Wenxiu Yang,Long Tian,Huiling Liu,Dan Liu,Cheng Wang
Citric acid (CA) is introduced to modulate the synthesis of octahedral HKUST-1 (also known as Cu3(BTC)2, BTC = benzene-1,3,5-tricarboxylate) particles with hierarchical micro, meso- and/or macropores (noted as HP-HKUST-1 particles) under mild conditions. The particle size of the resultant product could be tuned from 300 nm to 2.4 μm by varying the amount of CA added, solvents, reaction time and so on. The intrinsic microporous structure of HKUST-1 is maintained despite the strong chelation capability of CA towards Cu2+ while the larger pores’ size is in the range of 30 to 100 nm. The possible formation mechanism of these octahedral HP-HKUST-1 particles is proposed on the basis of our systematic investigations. The resulting micrometer HP-HKUST-1 particle is employed to encapsulate phosphomolybdic acid hydrate (HPMo), a catalyst for the methanolysis of styrene oxide. After encapsulation, a superior catalytic activity with a high conversion rate (99.6%) is achieved when the reaction is carried out at 40 °C for 20 min.
Rui Wang,Xiaohui Ji,Zhenzhen Huang,Yurui Xue,Dayang Wang,Wensheng Yang
In this work, SiO2@Au core–shell particles under ambient conditions were prepared by using 120 nm SiO2 spheres with ca. 4 nm Au nanoparticles decorated on the surfaces as seeds, the aqueous solutions of sodium citrate/HAuCl4 mixtures as growth solutions, and hydroxylamine as reducing agent. The morphology of the Au shells obtained on the SiO2 spheres was readily regulated only by the citrate-to-HAuCl4 molar ratio; no deliberate adjustment of the temperature and pH of the reaction media was needed. When the citrate-to-HAuCl4 molar ratio in the growth solution was below 4:1, the surfaces of the SiO2 spheres were covered with sparsely packed Au nanoparticles with sizes in the range of 20–40 nm, depending on the citrate-to-HAuCl4 molar ratio. When the citrate-to-HAuCl4 molar ratio in the growth solution was above 8:1, the surfaces of the SiO2 spheres were coated by complete, uniform Au nanoshells. Concomitant with this citrate-regulated morphology, the localized surface plasmon resonance peaks of the resulting SiO2@Au particles shifted from 611 nm for the sparse Au nanoparticle coating to 784 nm for the complete Au nanoshell coating. Furthermore, the sparsely packed Au nanoparticle coating showed stronger surface enhancement Raman spectroscopic signals than the uniform Au nanoshell coating, while the latter exhibit higher photothermal efficiency than the former.
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