Platinum nanoparticle
[9] Some common examples of platinum precursors include potassium hexachloroplatinate (K2PtCl6) or platinous chloride (PtCl2)[1][8] Different combinations of precursors, such as ruthenium chloride (RuCl3) and chloroplatinic acid (H2PtCl6), have been used to synthesize mixed-metal nanoparticles[9] Some common examples of reducing agents include hydrogen gas (H2), sodium borohydride (NaBH4) and ethylene glycol (C2H6O2), although other alcohols and plant-derived compounds have also been used.
[1][8][9] The size of the nanoparticles can also be controlled with small deviation by using a stepwise seed-mediated growth procedure as outlined by Bigall et al.
Hexadecylamine (HDA) was added to the purified reaction mixture and allowed to displace the THF and CO ligands over the course of approximately seven days, producing monodispersed spherical crystalline Pt nanoparticles with an average diameter of 2.1 nm.
When the same procedure was followed using a stronger capping agent such as triphenyl phosphine or octanethiol, the nanoparticles remained spherical, suggesting that the HDA ligand affects particle shape.
Research showed that alkylamine can coordinate with Pt2+ ion and form tetrakis(amine)platinate precursor and replace the original acac− ligand in Pt(acac)2, and oleic acid can further exchange with acac− and tune the formation kinetics of platinum nanoparticles.
[15] When Pt2(dba)3 was decomposed in THF under hydrogen gas in the presence HDA, the reaction took much longer, and formed nanowires with diameters between 1.5 and 2 nm.
Decomposition of Pt2(dba)3 under hydrogen gas in toluene yielded the formation of nanowires with 2–3 nm diameter independent of HDA concentration.
Reductive colloidal syntheses as such have yielded tetrahedral, cubic, irregular-prismatic, icosahedral, and cubo-octahedral nanoparticles, whose dispersity is also dependent on the concentration ratio of capping agent to precursor, and which may be applicable to catalysis.
[16] The precise mechanism of shape-controlled colloidal synthesis is not yet known; however, it is known that the relative growth rate of crystal facets within the growing nanostructure determines its final shape.
[16] Polyol syntheses of platinum nanoparticles, in which chloroplatinic acid is reduced to PtCl42− and Pt0 by ethylene glycol, have also been a means to shape-controlled fabrication.
[17] An ecologically-friendly synthesis of platinum nanoparticles from chloroplatinic acid was achieved through the use of a leaf extract of Diospyros kaki as a reducing agent.
Nanoparticles synthesized as such were spherical with an average diameter ranging from 212 nm depending on reaction temperature and concentration of leaf extract used.
[10] Another eco-friendly synthesis from chloroplatinic acid was reported using leaf extract from Ocimum sanctum and tulsi as reducing agents.
Being a free electron metal NP like silver and gold, its linear optical response is mainly controlled by the surface plasmon resonance (SPR).
This research attributed these absorption features to the generation and transfer of hot electrons from the platinum nanoparticles to the semiconductive material.
[25] The addition of small platinum nanoparticles on semiconductors such as TiO2 increases the photocatalytic oxidation activity under visible light irradiation.
By changing the size, shape and environment of metal nanoparticles, their optical properties can be used for electrontic, catalytic, sensing, and photovoltaic applications.
Nonenzymatic glucose sensors with Pt-based electrocatalysts offer several advantages, including high stability and ease of fabrication.
[29] Platinum catalysts are alternatives of automotive catalytic converters, carbon monoxide gas sensors, petroleum refining, hydrogen production, and anticancer drugs.
Depending on particle properties, nanoparticle may move throughout the human body are promising as site-specific vehicles for the transport of medicine.
In one study, platinum nanoparticles of diameter 58.3 nm were used to transport an anticancer drug to human colon carcinoma cells, HT-29.
The high acidity environment enables leaching of platinum ions from the nanoparticle, which the researchers identified as causing the increased effectiveness of the drug.
[36] Use of platinum in drug delivery hinges on its ability to not interact in a harmful manner in healthy portions of the body while also being able to release its contents when in the correct environment.
In one study, the authors compared the impact of different nanoparticle compositions on the red blood cells found in the human bloodstream.
In the same study it was found that 5–30 nm silver nanoparticles caused membrane damage, detrimental morphological variation, and haemagglutination to the red blood cells.
First, the authors found that platinum nanoparticles with spherical morphologies and sizes less than 3 nm showed biologically toxic properties; measured in terms of mortality, hatching delay, phenotypic defects and metal accumulation.
[41] Although this hypothesis needs to be further supported by future work, the authors did cite another paper which tracked the respiratory intake of platinum nanoparticles.
This group found that 10 μm platinum nanoparticles are absorbed by the mucus of the bronchi and trachea, and can travel no further through the respiratory tract.
However, their in vitro tests using human and lung epithelial cells found no cytotoxic or oxidative stress effects caused by the platinum nanoparticles despite clear evidence of cellular uptake.
