Hydrofluoric acid

1,3,5-Benzentricarboxylic acid (95%), sulfuric acid-d₂ (96–98%), hydrofluoric acid (48%), copper(II) nitrate trihydrate (99–104%), iron(III) nitrate nonahydrate (98%), trifluoroacetic acid (99%), poly(vinylidene fluoride) (average MW: ~ 534,000), copper(II) acetate monohydrate (98%), sodium chloride (99%), potassium chloride (99%), copper(I) iodide (98%) were purchased from Sigma-Aldrich. Zirconium dichloride oxide octahydrate (98%), formic acid (99%), cobalt(II) nitrate hexahydrate (98–102%), hydrobromic acid (48%), hydroiodic acid (55–58%) were purchased from Thermo Fisher Scientific. Dimethyl sulfoxide-d₆ (99.9%) was purchased from Cambridge Isotope Laboratories. Nitric acid (60%), N,N-dimethylformamide (99.5%), acetone (99.5%), ethylenediaminetetraacetic acid disodium salt (99%), hydrochloric acid (35–37%) were purchased from DAEJUNG chemicals. Copper(II) fluoride (98%) was purchased from Tokyo Chemical Industry. All chemicals and solvents were of reagent grade and used without further purification.
X-ray powder diffraction (XRPD) patterns were collected on a Bruker D2 PHASER at 30 kV and 10 mA for Cu K_α (λ = 1.54050 Å), with a step size of 0.02° in 2 θ. Fourier transform-Infrared (FT-IR) spectra were recorded on a Bruker ALPHA II FT-IR spectrometer using the attenuated total reflection (ATR) mode. ¹H nuclear magnetic resonance (NMR) spectra were measured on a Bruker Advance III HD 300 MHz. For NMR sample preparation, 0.005 g of samples were digested using D₂SO₄ (20 μL) and DMSO-d₆ (600 μL) as solvents. The nitrogen adsorption-desorption isotherm was obtained using a Quantachrome Instruments Autosorb-iQ at 77 K. All samples ( ~ 60 mg) were activated under ultra-high vacuum at 130 °C for 24 h prior to each measurement. The surface areas were calculated using BETSI, following the Rouquerol criteria 1–4^{61 (link)}. Pore size distribution was calculated using quenched solid density functional theory (QSDFT) method. Scanning electron microscopy (SEM) images and energy dispersive X-ray spectroscopy (EDS) mapping were taken using JSM 7800 F Prime operating at 15 kV. For SEM imaging, the samples were placed on the carbon tape on an aluminum sample holder and coated using carbon-sputter coating. X-ray photoelectron spectroscopy (XPS) data were obtained by using an AXIS SUPRA and spectra were analyzed using XPSPEAK 4.1. Inductively coupled-atomic emission spectroscopy (ICP-AES) data were collected on a Perkin Elmer Optima 8300. For ICP-AES sample preparation, 0.01 g of samples were digested with 60 μL of hydrofluoric acid. The hydrofluoric acid was completely removed by vaporization before the samples were further dissolved with 4 mL of Nitric acid. The acid-digested samples were diluted with deionized water before measurement. UV-Vis-NIR spectra were recorded with a PerkinElmer Lambda 365 UV/Vis spectrophotometer for reflectance measurement. Raman spectroscopy data were obtained using a Thermo Fischer Scientific DXR2xi Raman imaging microscope with 532 nm laser source.

Styrene, acrylic acid, ammonium peroxodisulfate, gold (III) chloride hydrate (HAuCl₄, 99.995%), palladium (II) nitrate hydrate (Pd(NO₃)₂, 99.9%), sodium borohydride (NaBH₄, 99%), polyvinylpyrrolidone (PVP, MW 10 K), sodium citrate, 2-aminoethanethiol hydrochloride (AET, 98%), N-Ethyl-N′-(3-(dimethylamino)propyl) carbodiimide hydrochloride (EDAC, ≥99.0%) and 2-(N-morpholino)ethanesulfonic acid (MES, >99.5%), tetraethyl orthosilicate (TEOS), nitric acid (HNO₃ (aq), 67–70% w/w), hydrochloric acid (HCl (aq), 36.5−38.0% w/w and 0.1 M), hydrofluoric acid (HF, 50 %), acetone and sand (white quartz, 50–70 mesh particle size) were purchased from Sigma-Aldrich. Ethanol was obtained from Koptec. ICP-MS calibration samples of Au (10 PPM) and Pd (10 PPM) were obtained from Inorganic Ventures. All the chemicals were used as received. Triply distilled deionized (DI) water (18 MΩ) was used in all experiments. All glassware and teflon-coated magnetic stir bars used in the metal nanoparticle synthesis were thoroughly cleaned in aqua regia (3 parts HCl, 1 part HNO₃) (Caution: highly corrosive) and rinsed in DI water.
The synthesis of PVP-capped bimetallic Pd_0.04Au_0.96 nanoparticles (NPs) and raspberry colloids were reported in our previous publications^{9 (link),15 (link)}. In general, citrate capped Au nanoparticles (~5 nm) were prepared by reduction of HAuCl₄ with sodium borohydride NaBH₄ in DI water. As synthesized Au nanoparticle solution (40 mL) was used for the synthesis of Pd_0.04Au_0.96 by adding to it 5 mL of ascorbic acid aqueous solution (0.1 M) and 150 μL of Pd(NO₃)₂ aqueous solution (10 mM). The reaction mixture was stirred for 12 h at room temperature and stored at 4 °C. Carboxylic acid-functionalized polystyrene colloids (PS-COOH) with diameter of ~340 nm were synthesized by surfactant free emulsion polymerization, using acrylic acid as co-monomer and ammonium peroxodisulfate as an initiator following a recipe from the literature^{36 (link)}. Raspberry colloids were synthesized by adding specific amounts of Pd_0.04Au_0.96 nanoparticles to the colloidal dispersion of thiol-modified polystyrene colloids (PS-SH)^{9 (link),15 (link)}. Typically for ~1% metal loading, 2.5 mL of the Pd_0.04Au_0.96 solution was added to 1 mL of 1 wt.% PS-SH colloidal dispersion in DI water. The dispersion was stirred for 2 h, washed three times with water using centrifugation (9500 rpm for 40 min), and re-dispersed in water to give ~5 wt% PS@Pd_0.04Au_0.96 raspberry colloids. The backfilling method used to form RCT SiO₂-based structures was described in detail in our previous publications^{24 ,37 (link)}. In general, the raspberry colloidal dispersion was dried at 65 °C and then backfilled with prehydrolyzed TEOS solution. The backfilled samples were dried and finally calcined at 500 °C in air for 2 h to remove polymer colloids and organic volatiles, and to solidify the matrix into SiO₂.

All chemicals were of analytical
reagent grade. All samples and standards were diluted with deionized
water (Milli-Q Integral 3 Q-POD Water Purification System, Merck Millipore,
Darmstadt, Germany).
Selected geological reference materials
were analyzed to validate the proposed analytical procedure. They
include U.S. Geological Survey reference materials BHVO-2 (Hawaiian
basalt), GH (granite; Hoggar, Algeria), GL-O (glauconite; Normandy,
France), and IF-G (iron formation; West Greenland).
Hydrofluoric
acid (40%), nitric acid (65%; both Merck Suprapur,
Darmstadt, Germany), and phosphoric acid (≥85%; Sigma, Milwaukee,
WI, USA) were applied to dissolved geological SRMs.
EMSURE fuming
hydrochloric acid (37%) and chloroform for liquid
chromatography (both Merck, Darmstadt, Germany) were used in the extraction
procedure. Compressed helium (Air Products, Warsaw, Poland) was used
to purge samples after extraction.
Sodium borohydride (Sigma,
Milwaukee, WI, USA), sodium hydroxide
micropills (POCH, Gliwice, Poland), sodium acetate trihydrate (≥98.0%;
POCH, Gliwice, Poland), and glacial acetic acid (100%; Merck, Darmstadt,
Germany) were used for the generation of germanium hydride. NaBH₄ solution (1%, w/v) in 0.01 M NaOH was freshly prepared on
a daily basis^{31 (link)} by dissolving consecutively
0.24 g of sodium hydroxide and 6.0 g of Sodium borohydride in 600
mL of deionized water. To prepare the acetic acid–sodium acetate
stock buffer solution (1 M), 34 g of CH₃COONa·3H₂O was dissolved in ∼150 mL of deionized water, then
4.8 mL of glacial CH₃COOH was added, and the obtained solution
was diluted to 250 mL with water. Acetic buffer solution (0.1 M) was
prepared by an appropriate dilution of the stock solution.
Two
batch solutions of NIST 3120a standard (LOT 000411 and LOT
151115, both containing 10 g/L Ge) were used in the analysis, but
only LOT 000411 was applied as a standard reference material with
δ^74/70Ge equal to 0. Bracket solutions for measuring
delta values of Ge via the SSB procedure were prepared by spiking
0.1 M acetic buffer with NIST 3120a solution to a final Ge concentration
of 25–80 μg/L, trying to match the intensities of the
bracket and the sample.
Single-element nickel and copper ICP
standards (both Merck, Darmstadt,
Germany), iron atomic absorption standard (VHG Labs, Manchester, NH,
USA), and zinc calibration standard (CPAchem, Stara Zagora, Bulgaria),
as well as ICP multielement standard solution VI (Merck, Darmstadt,
Germany), were used in interference study by spiking the diluted NIST
3120a solution (70 μg/L Ge) to a final content of interfering
ions of 0.2–2.0 mg/L. The synthetic seawater was prepared similarly
as in ref^{32 (link)} by an appropriate dilution
of chloride salts of sodium (Sigma, Milwaukee, WI, USA), magnesium,
and potassium (both Merck, Darmstadt, Germany) with deionized water
with the only difference that sodium sulfate (Sigma, Milwaukee, WI,
USA) was also added to the mixture. The solution obtained had a comparable
composition to the natural seawater³³ (Table 1). This synthetic
seawater was spiked with NIST 3120a to a total Ge concentration of
80 μg/L.