Hollow Platinum Research Articles

Optical Fabrication of Hollow Platinum Nanospheres by Excavating the Silver Core of Ag@Pt Nanoparticles

Hollow platinum nanospheres (see figure) have been fabricated by optical excavation of the core silver metal of Ag@Pt core/shell nanoparticles. The surface plasmon resonances of the shell platinum metal were excited with picosecond laser pulses of 1064 nm. Thermalized photon energy induces the silver to melt and effuse rapidly through the shell, producing smooth hollow platinum nanospheres.

Galvanic replacement reaction: A simple and powerful route to hollow and porous metal nanostructures

Galvanic replacement reaction provides a remarkably simple and versatile route to metal nanostructures with controllable hollow interiors and porous walls. The key step of this process involves the replacement reaction between a suspension of nanoscale metal templates and a salt precursor containing a relatively less active metal. This method has been successfully applied to prepare gold-based hollow nanostructures with a wide range of different morphologies, including cubic nanoboxes, cubic nanocages, triangular nanorings, prism-shaped nanoboxes, single-walled nanotubes, and multiple-walled nanoshells or nanotubes. In addition to gold, hollow platinum and palladium nanostructures have also been prepared by using appropriate salt precursors for the replacement reaction. These hollow and porous metal nanostructures show intriguing optical and mechanical properties, with their surface plasmon resonance peaks tunable from the visible to the near-infrared region. These materials are expected to find applications in a number of areas, such as optical sensing, imaging contrast enhancement, photothermal cancer treatment, and catalysis.

Rapid Reduction of U(VI) on Activated Platinum Wire Gauze Electrode for the Primary Coulometric Determination of Uranium

A large enhancement in the active area of a hollow cylindrical platinum wire gauze electrode was achieved by repetitive multilayer growth of oxide followed by its reduction. Growth of oxide was obtained by a combination of chemical and electrochemical treatments. Enhancement in the active area of the electrode was checked by determining the time taken for the quantitative reduction of U(VI) to U(IV) at a controlled potential of −0.150 V vs SCE in 1 M H2SO4. A six-fold decrease in the reduction time was observed, indicating a corresponding six-fold increase in the active area of the electrode. The enhanced activity of the electrode was found to decay on ageing. Determination of uranium was carried out by a successive addition technique using the activated platinum wire gauze electrode and carrying out the reduction U(VI) to U(IV) at a controlled potential of −0.150 V vs SCE. Precision and accuracy of better than ±0.2% were obtained at 5 to 10 mg levels of uranium. This demonstrates the applicability of a platinum electrode, instead of the conventionally used Hg electrode, for determination of uranium by primary coulometry.

Synthesis of self-assembled nanoscale structures by focused ion-beam induced deposition

This paper presents the results of recent experiments that lead to the nanofabrication of hollow platinum structures in a focused ion beam microscope. The inclination of the substrate with respect to the ion beam is shown to control the growth direction of Pt on the surface of polysilicon.

Mesoporous microcapsules with noble metal or noble metal oxide shells and their application in electrocatalysis

A versatile peripheral-pore-nanocasting method is employed to fabricate a series of novel microcapsules with mesoporous shell of noble metal or noble metal oxides, including Pt, PdO, RuO2 and IrO2. The shell thickness of these hollow microcapsules can be adjusted by controlling the depth of 3-amino-propyltriethoxysilane (APS) modification. By pre-filling the guest species or their precursors into the 3-D pores of HMS (hexagonal mesoporous molecular sieves) spheres, an interesting material with a “sphere in shell” structure could be fabricated via the same method. Both the mesoporous platinum hollow microcapsules and carbon spheres encapsulated in platinum microcapsules have shown high mass-normalized activities as a catalyst in the oxidation of methanol, a fundemantal reaction in direct methanol fuel cells (DMFC).

Experimental and theoretical study of the hyperfine structure in the (5d+6s)96p configurations of Pt I

The hyperfine structure of the odd configurations 5d96p and 5d86s6p was studied with laser optogalvanic spectroscopy and high resolution interferometry in a platinum hollow cathode. A parametric hyperfine structure analysis for the configurations (5d+6s)96p with 10 excited odd-parity levels was performed for195Pt. We obtained one-electron hfs parameters,a 5d 01 =1160(320) MHz,a 6s 10 =35600(5300) MHz anda 6p 01 =1300(780) MHz for the configuration 5d86s6p. The corresponding\(\left\langle {r^{ - 3} } \right\rangle _{nl}^{k_s k_l } \) values are compared with those known for other 5d-elements.

Comparison of deuterium arc and Smith-Hieftje background correction for graphite furnace molecular absorption spectrometry of fluoride and chloride

Molecular absorption spectrometry (MAS) in a graphite furnace, which is a sensitive method for the determination of halides, involves the formation of a diatomic molecule containing a metal reagent and a halide (the analyte). Other reagents, called chemical modifiers, are also added to increase the number of molecules formed. However, the utility of the technique for practical analysis has been limited by spectral and chemical interferences. Large amounts of reagents (μg amounts) produce relatively large background signals. Previous MAS work has employed deuterium arc background correction to account for these signals, but this method has been shown to be unable to accurately correct for large backgrounds. In this work, Smith-Hieftje background correction was employed for the first time with molecular absorption spectrometry for the determination of fluoride and chloride. For fluoride, a platinum hollow cathode lamp (HCL) was employed as the light source; aluminum was added as a reagent to produce AlF, the molecule whose absorbance was measured; and barium was added as a chemical modifier. The chemical and furnace conditions were optimized, but no AlF signal was obtained with Smith-Hieftje background correction. The absence of a signal was attributed to the involatility of platinum, which is poorly self-reversed during the Smith-Hieftje correction step, the use of a high level HCL line that was poorly self-reversed, and to the large width of the AlF molecular line (0.08 nm). Using deuterium arc background correction, a detection limit of 200 pg, a characteristic mass of 370 pg, and a linear dynamic range of 1.6 orders of magnitude were obtained. This technique was employed for the determination of fluoride in oyster tissue and dental rinse, but poor recovery (< 50%) was obtained. Chloride was determined with a lead HCL, the AlCl molecule, and cobalt and strontium as modifiers. Smith-Hieftje and continuum source background correction were compared for the determination of chloride; characteristic masses were 0.6 and 1.0 ng, respectively. The successful use of Smith-Hieftje background correction for chloride was attributed to the increased self-reversal of the lead HCL compared to the platinum HCL employed for fluoride. The addition of nitric acid to aqueous standards was shown to severely degrade the absorption signal. Smith-Hieftje background correction was shown to be more accurate than deuterium arc background correction for the determination of chloride in a simulated rain water standard reference material.

Isotope shift investigations in the configurations 5d9nl and 5d8nln'l' of Pt I

The isotope shift in a platinum hollow cathode discharge was studied for transitions of the type 5d97s → 5d96p, 5d97s → 5d86s6p and 5d96p → 5d86s2 through laser optogalvanic spectroscopy and high resolution interferometry. Considering configuration mixing in each of the levels of 5d96s, 5d86s2, 5d86s6p and 5d96p of all known and the new evaluated level isotope shifts, we obtain average configuration isotope shift values for the even configurations ΔT(5d96s) = 2425 (90) MHz, ΔT(5d86s2) = 5960 (60) MHz, ΔT(5d97s) = 260 (160) MHz and for the odd configurations ΔT(5d96p) = −230 (380) MHz, ΔT(5d86s6p) = 2740 (250) MHz, ΔT(5d76s26p) = 9700 (4700) MHz. These experimental values compare well with the theoretically predicted configuration isotope shifts in platinum, based on pseudo-relativistic Hartree-Fock calculations.

Analysis of enloplatin by liquid chromatography and of platinum by atomic absorption spectrometry in various biological fluids

Analytical methods were developed and validated for the determination of enloplatin (an anticancer agent) in plasma by reversed-phase LC and for platinum (an elemental component of enloplatin) in plasma, plasma ultrafiltrate (PUF) and whole blood by flameless atomic absorption spectrometry (FAAS). The LC procedure involved protein precipitation with dilute perchloric acid. The supernatant was mixed with sodium phosphate buffer and injected into the LC system. A C18 or a cyano column was used, depending on sample matrix, with UV detection at 230 nm. The LC method was linear from 0.50 to 50.0 micrograms ml-1. Inter-day and intra-day precision (RSD%) and accuracy (relative error%) were < +/- 14%. The FAAS procedure utilized a graphite furnace, a hollow cathode platinum (Pt) lamp, and Zeeman background correction. An aliquot of plasma, PUF, or whole blood was mixed with a solution of Triton X-100 and Antifoam-B and injected into the FAAS system. The FAAS method showed goodness of fit from 0.05 to 10.0 micrograms Pt/ml. Inter-day and intra-day precision and accuracy were < +/- 15%. The methods were developed to support pharmacokinetic studies in humans, dogs and rats.

Determination of Fluorine, Chlorine, and Bromine by Molecular Absorption Spectrometry

Fluorine was determined by molecular absorption spectrometry (MAS) in a graphite tube furnace, and fluorine, chlorine, and bromine were determined in a flame. For the fluorine work, aluminum nitrate was added as a reagent to produce aluminum fluoride molecules whose absorbance was monitored with emission from a platinum hollow cathode lamp (HCL) at 227.45 nm. A deuterium arc lamp was employed for background correction. For the furnace work, barium nitrate was used as a chemical modifier to increase the absorption signal. After optimization of the chemical and furnace conditions, a detection limit of 160 pg F was obtained, with a linear dynamic range of two orders of magnitude. Graphite furnace MAS was used to accurately determine fluoride in dental rinse and National Institute of Standards and Technology oyster tissue, but the precision was between 21 and 23%. Low recoveries were obtained for the determination of trifluoroacetic acid and l,2,2,3-tetrafluoropropan-1-ol by graphite furnace MAS. The detection limit for F by flame MAS was 13 mg liter −1 which is a factor of 5 lower than the best reported flame MAS detection limit. Chlorine was determined by flame MAS with the aluminum chloride molecule. Excitation was done at 261.4 nm with a lead HCL. and a detection limit of 180mg liter −1 was obtained. Flame MAS of bromine was done by use of AlBr (excitation at 279.0 nm with an arsenic HCL) and InBr (excitation at 284.3 nm with a chromium HCL), but very poor detection limits were obtained: 24.5 g liter −1 and 500mg liter −1, respectively.

Energy levels of neutral platinum (Pt I)

The emission spectrum of a platinum hollow cathode lamp has been recently recorded by means of a grating spectrograph at the National Institute of Standards and Technology (N.I.S.T.) and by Fourier transform spectrometry at Kitt Peak National Observatory and at Laboratoire Aime Cotton. The classification of Pt I lines is revised and extended. One hundred-nineteen new energy levels have been added to the 83 earlier ones, four of which are assigned revised J-values. Seventy percent of the levels are interpreted theoretically by means of Slater-Condon type calculations of (5d + 6s)10, 5d96d, 5d97s, 5d97d, 5d98s and (5d96p + 5d86s6p + 5d76s26p + 5d97p). The ionisation limit 5d9 2D5/2 at $72~230\pm 50$ cm-1 (8.956±0.006 eV) has been derived from 5d9ns, 5d96f and 5d86s5f levels.

Wavelengths and intensities of a platinum/neon hollow cathode lamp in the region 1100-4000 A

The spectrum of a platinum hollow cathode lamp containing neon carrier gas was recorded photographically and photoelectrically with a 10.7 m normal-incidence vacuum spectrograph. Wavelengths and intensities were determined for about 3000 lines in the region 1100-4000 A. The uncertainty of the measured wavelengths is estimated to be + or - 0.0020 A. Ritz-type wavelengths are given for about 550 classified lines of Pt II with uncertainites varying from + or - 0.0004 A to + or - 0.0025 A. The uncertainty of the relative intensities is estimated to be about 20 percent.

Volume Expansion of Glass at High Temperatures

The determination of the volume expansion of glass at high temperatures required the development of a technique or method that would give reproducible results. The considerations necessary in developing such a technique are discussed, and the design and construction of the apparatus used are described. The volume expansion of a glass was determined by the change in buoyancy of a hollow platinum plummet over the temperature range 925° to 1300°C. Although no density measurements were made in the annealing range, previous findings which indicated that glass does not attain complete equilibrium when cooled by normal procedures are confirmed.