Chiroptically Active Multi-Modal Calcium Carbonate-Based Nanocomposites

The development of multimodal nano- and micro-structures has become an increasingly popular area of research in recent years. In particular, the combination of two or more desirable properties within a single structure opens multiple opportunities from biomedicine, sensing, and catalysis, to a variety of optical applications. Here, for the first time, we report the synthesis and characterization of multimodal chiroptically active CaCO3 nanocomposites. These composites have been prepared by a modified microemulsion method in the presence of an amino acid (cysteine). Following this, additional modalities have been introduced by loading the composites with luminescent nanoparticles or doping with Eu3+ ions. The luminescent composites have been produced by the incorporation of CuInZnS/ZnS or CdSe@ZnS/ZnS core/shell quantum dots, or via doping with trivalent europium. In this manner, we have produced chiroptically active composites with orange, green, and red luminescence. Overall, this work demonstrates the unique advantage and potential of our approach and new class of chiroptically active CaCO3 nanocomposites, which display tunable functionality to specific requirements via the incorporation of desired ions, nanoparticles, and chirality of the structure.

On-signal amplification of silver nanosol RRS/SERS aptamer detection of ultratrace urea by polystyrene nanosphere catalyst

The catalytic amplification signal of polystyrene nanosphere (PN) is used to conveniently fabricate the resonance Rayleigh scattering (RRS)/surface-enhanced Raman scattering (SERS) dual-mode method to sensitively and selectively detect urea in food. PN has strong catalysis of the slow nanoreaction of citrate-Ag(I) to produce yellow silver nanoparticles (AgNP), which exhibit strong RRS effect and SERS effect with molecular probes. When aptamer (Apt) is present, the Apt is adsorbed on the PN surface, the catalysis is weakened, the AgNP is reduced, and the SERS/RRS signal is weakened. After adding urea to exhibit specific Aptamer reaction, the Apt is desorbed from the PN surface and the catalysis is restored. As urea increase, the desorbed PNs increase to produce more AgNPs indicator to increase SERS/RRS signal. The increase value △I of SERS/RRS is linearly to urea concentration. Therefore, a sensitive and selective SERS/RRS dual-mode method for urea is established based on aptamers-regulated the catalysis of PNs. This method is applied to the detection of urea in milk with satisfactory results. The relative standard deviation is 3.9-6.8% and the recovery rate is 94.5-102%.

Magnetic polymer bowl for enhanced catalytic activity and recyclability

This work introduces the fabrication of a magnetic polymer bowl for enhanced catalytic activity and recyclability, which involves the synthesis of silica-coated Fe3O4 magnetic clusters, seeded dispersion polymerization using the magnetic clusters, and transformation into a bowl-like structure via a phase separation route. The additional treatment with tannic acid (TA) on the bowls allows the in situ formation of silver nanoparticles (AgNPs) on their surfaces. The openness and larger surface area of the bowls, as compared with those of other structured particles, such as spheres and flowers, enable a considerably higher immobilization of AgNPs, thus leading to an excellent catalytic reduction for 4-nitrophenol (4-NP), methylene blue (MB), and rhodamine B. Furthermore, the strong magnetic response originating from the magnetic clusters inside the bowls endows a good magnetic recovery and an excellent reusability for the repeated reduction of the organic dyes without loss of catalytic activity.

A Smart Route for Encapsulating Pd Nanoparticles into a ZIF-8 Hollow Microsphere and Their Superior Catalytic Properties

The encapsulation of catalytically active noble metal nanoparticles (NM NPs) into metal-organic frameworks (MOFs) represents an effective strategy for enhancing their catalytic performance. Despite a myriad of reports on the nanocomposites consisting of NM NPs and MOFs, it remains challenging to develop a sustainable and convenient method for realizing confined integration of NM NPs within a porous and hollow zinc-based MOF. Herein, a simple and well-designed approach is reported to the fabrication of Pd@ZIF-8 hollow microspheres with a number of Pd nanoparticles immobilized on the inner surface. This method capitalized on the use of polyvinylpyrrolidone (PVP)-stabilized polystyrene (PS) microspheres as templates, to harness the dual functions of PVP for reducing PdCl₂ to generate Pd NPs and coordinating with zinc ions to grow ZIF-8 shells. Consequently, it avoids the complicated protocols involving surface treatment of template microspheres that conventionally adopts hazardous or costly agents. The obtained Pd@ZIF-8 hollow microspheres exhibit outstanding catalytic activity, size selectivity, and stability in the hydrogenation of alkenes. This study presents both the advances in the green synthesis and great potential of Pd@ZIF-8 hollow microspheres for catalytic applications.

Green synthesis of palladium nanoparticles using lentinan for catalytic activity and biological applications

The green synthesis of palladium nanoparticles (Pd NPs) for catalysis and biological applications has been gaining great interest. To replace complex plant extracts, lentinan (LNT) may be a good reducing and stabilizing agent. In this work, a simple and green method using LNT to reduce and stabilize palladium Pd NPs was verified. The resulting LNT stabilized palladium nanoparticles (Pd_n-LNT NPs) were characterized by UV-Vis spectroscopy, DLS, TEM, and XPS. The results indicated that Pd NPs inside of Pd_n-LNT NPs had a small size (2.35–3.32 nm). Pd_n-LNT NPs were stable in solution for 7 days. In addition, Pd_n-LNT NPs had higher catalytic activity towards the reduction of 4-nitrophenol than other catalysts. More importantly, Pd_n-LNT NPs had negligible cytotoxicity towards cells and showed good antioxidant activity. Taken together, the prepared Pd_n-LNT NPs have great potential bio-related applications.

Lentinan stabilized palladium nanoparticles had high catalytic activity, negligible cytotoxicity and good antioxidant activity.