Theory and experiment of optical absorption of platinum nanoparticles synthesized by gamma radiation

Simulation and Synthesis of Cobalt (Co) Nanoparticles by Gamma Radiation Technique

Cobalt nanoparticles were synthesized using the gamma radiolytic technique, and the particle size was found to be reduced from 12±1 to 7±1 nm by increasing the dose from 10 to 60 kGy. The UV-visible absorption spectra were measured and exhibited a steady absorption maxima at 517 nm in the UV region, which blue-shifted toward a lower wavelength with a decrease in particle size. By taking the conduction electrons of an isolated particle that are not entirely free but are instead bound to their respective quantum levels, the optical absorption of the cobalt nanoparticles can be calculated and simulated via intra-band quantum excitation for particle sizes comparable to the measured ones. We found that the simulated absorption maxima of electronic excitations corresponded to the measured absorption maxima. Moreover, the structural characterizations were performed utilizing dynamic light scattering (DLS), transmission electron microscopy (TEM), and X-ray diffraction (XRD).

Single Step Laser-Induced Deposition of Plasmonic Au, Ag, Pt Mono-, Bi- and Tri-Metallic Nanoparticles

Multimetallic plasmonic systems usually have distinct advantages over monometallic nanoparticles due to the peculiarity of the electronic structure appearing in advanced functionality systems, which is of great importance in a variety of applications including catalysis and sensing. Despite several reported techniques, the controllable synthesis of multimetallic plasmonic nanoparticles in soft conditions is still a challenge. Here, mono-, bi- and tri-metallic nanoparticles were successfully obtained as a result of a single step laser-induced deposition approach from monometallic commercially available precursors. The process of nanoparticles formation is starting with photodecomposition of the metal precursor resulting in nucleation and the following growth of the metal phase. The deposited nanoparticles were studied comprehensively with various experimental techniques such as SEM, TEM, EDX, XPS, and UV-VIS absorption spectroscopy. The size of monometallic nanoparticles is strongly dependent on the type of metal: 140–200 nm for Au, 40–60 nm for Ag, 2–3 nm for Pt. Bi- and trimetallic nanoparticles were core-shell structures representing monometallic crystallites surrounded by an alloy of respective metals. The formation of an alloy phase took place between monometallic nanocrystallites of different metals in course of their growth and agglomeration stage.

Laser-Induced Deposition of Plasmonic Ag and Pt Nanoparticles, and Periodic Arrays

Surfaces functionalized with metal nanoparticles (NPs) are of great interest due to their wide potential applications in sensing, biomedicine, nanophotonics, etc. However, the precisely controllable decoration with plasmonic nanoparticles requires sophisticated techniques that are often multistep and complex. Here, we present a laser-induced deposition (LID) approach allowing for single-step surface decoration with NPs of controllable composition, morphology, and spatial distribution. The formation of Ag, Pt, and mixed Ag-Pt nanoparticles on a substrate surface was successfully demonstrated as a result of the LID process from commercially available precursors. The deposited nanoparticles were characterized with SEM, TEM, EDX, X-ray diffraction, and UV-VIS absorption spectroscopy, which confirmed the formation of crystalline nanoparticles of Pt (3–5 nm) and Ag (ca. 100 nm) with plasmonic properties. The advantageous features of the LID process allow us to demonstrate the spatially selective deposition of plasmonic NPs in a laser interference pattern, and thereby, the formation of periodic arrays of Ag NPs forming diffraction grating

From platinum atoms in molecules to colloidal nanoparticles: A review on reduction, nucleation and growth mechanisms

Platinum (Pt) is one of the most studied materials in catalysis today and considered for a wide range of applications: chemical synthesis, energy conversion, air treatment, water purification, sensing, medicine etc. As a limited and non-renewable resource, optimized used of Pt is key. Nanomaterial design offers multiple opportunities to make the most of Pt resources down to the atomic scale. In particular, colloidal syntheses of Pt nanoparticles are well documented and simple to implement, which accounts for the large interest in research and development. For further breakthroughs in the design of Pt nanomaterials, a deeper understanding of the intricate synthesis-structures-properties relations of Pt nanoparticles must be obtained. Understanding how Pt nanoparticles form from molecular precursors is both a challenging and rewarding area of investigation. It is directly relevant to develop improved Pt nanomaterials but is also a source of inspiration to design other precious metal nanostructures. Here, we review the current understanding of Pt nanoparticle formation. This review is aimed at readers with interest in Pt nanoparticles in general and their colloidal syntheses in particular. Readers with a strongest interest on the study of nanomaterial formation will find here the case study of Pt. The preferred model systems and characterization techniques used to perform the study of Pt nanoparticle syntheses are discussed. In light of recent achievements, further direction and areas of research are proposed.