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  • Introduction Recently the development of

    2018-10-22

    Introduction Recently, the development of hybrid metal nanoparticles (NPs) with organic and biological components has gained enormous attention than ever before due to the possibility of tailored shape, size and novel properties. Among others, silver NPs (Ag-NPs) are commonly used in biomedical devices due to antimicrobial properties; in solar chemokine receptor antagonist and conductive adhesives due to electrical conductivity; and in many other technological applications such as catalysis, memory devices, and inkjet printing. In literature there are many synthesis processes that have been reported to prepare Ag-NPs, namely bio-synthesis, ultrasonic spray pyrolysis, laser ablation, green synthesis, microwave plasma, reduction method, colloidal or solvo-thermal synthesis. One of the most frequently used protective agents in metal nanoparticles synthesis is poly(N-vinyl-2-pyrrolidone) (PVP). This water-soluble polymer has been extensively exploited as protecting agent against agglomeration of metal colloids in the well-known polyols-based process. In this synthetic procedure, the alcohol (normally ethylene glycol (EG)) works contemporary as solvent and as reducing agent of the metal ions. PVP has also been used in the reduction of silver and gold in water or ethylene glycol/water mixtures. In most of the papers about the synthesis of nanoparticles, the PVP polymer plays the role of stabilizer or protecting agent against particles sticking and agglomeration, which is still a challenge to be fixed in most of the synthesis methods proposed for the preparation of Ag-NPs, mainly due to its light sensitivity. Many surfactants and protecting agents have been used such as poly ethylene glycol (PEG), Triton X-100, citrate, water-soluble bifunctional surfactant. Leading works in the synthesis of AgNPs have focused on the shape control of silver nanocrystals via different approaches. Wiley et al. controlled the shape of silver nanocrystals by varying reaction condition such as the precursor concentration molar ratio of the surfactant and silver ions. In the polyols-based process, PVP helps in the control of the shape. Chou et al. compared the ability of PVP to stabilize silver colloids in the presence of NaOH or Na2CO3. Liu et al. also proposed that the crystal structure shape was related to the capping modes between PVP with different molecular weights (MWs) and silver nanocrystals. On the other hand, Protoporphyrin IX (PP) (its structure is reported in Scheme 1) is a tetrapyrrole macrocycle, produced in heme biosynthesis of biological systems; which has attracted considerable attention due to its efficiency in photodynamic therapy of skin tumors. PP shows 22π electrons and two propionic groups in the same direction, perpendicular to the porphyrin plane. Some authors have demonstrates the effect of porphyrins molecules and their assemblies onto silver nanoparticles in surface enhanced Raman scattering. In this paper, we propose an alternative route to the synthesis of hybrid AgNPs, on basis of the simultaneous presence of the organic substances (i.e. the polymer PVP and the macromolecule PP) and their combinations. In particular, PP with three side chains, such as methyl, propionic acid and vinyl, enhances the stabilization of AgNPs. We have investigated the role of PP molecules also in the nucleation solution, with the aim to examine and discuss the possible involvement of PP molecules in the synthesis process, as surfactant, reducing and shape-modulating agent. The obtained hybrid Ag-PP, Ag-PVP and Ag-PP-PVP nanoparticles have been fully characterized by means of spectroscopic measurements, such as PM-IRRAS, UV–Visible, X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), revealing how the main intrinsic properties of organic molecules influence on the formation of silver nanostructures, in terms of particles stability and biocompatibility.
    Experimental
    Results and discussion
    Conclusion