Br Anions Research Articles

An experimental study of low energy electrons attachment to CH2ClBr using ion mobility spectrometry

The rate constant of low-energy electron attachment to CH2ClBr was determined using atmospheric pressure nitrogen corona discharge electron attachment ion mobility spectrometry at ambient pressure and room temperature in the mean electron range between 0.35 and 0.69eV. The rate constants are in the order of magnitude of ∼10−9cm3molecule−1s−1 and agree well with the reported value. Only one peak was observed in the production of low-energy electron attachment to CH2ClBr and it might be the overlap of hydrated anions Cl−(H2O)n and Br−(H2O)m. In order to clarify the contribution of Cl and Br anions, acetic acid was utilized to react with the hydrated Cl/Br anions. The H2O molecules in the hydrated Cl/Br anions were substituted by CH3COOH molecules, and formed Cl−(CH3COOH)p and Br−(CH3COOH)q, respectively. The contribution of hydrated Cl anions of low-energy electron attachment to CH2ClBr was found to be negligible, whereas the hydrated Br anions were the main product ions.

Hydrogen Peroxide Production by Gamma Radiolysis of Sodium Chloride Solutions Containing a Small Amount of Bromide Ion

Gamma radiolysis experiments on solutions of a mixture of sodium chloride (NaCl) and sodium bromide (NaBr) were conducted to confirm the validity of radiolysis calculations for simulated seawater solutions and to determine the importance of bromide anion (Br−) in the production of hydrogen peroxide (H2O2) via water radiolysis. The H2O2 concentration in each solution was measured after irradiation and compared with that obtained from radiolysis calculations. It was found that the calculated and experimental results were in good agreement. The concentration of H2O2 in a 0.6 M NaCl solution increased approximately three times on the addition of 1 mM NaBr. The result showed that Br− plays an important role in the production of H2O2 by water radiolysis, presumably through the reactions of Br− with hydroxyl radical (•OH). For 1 mM NaCl solutions, there is a minimum production rate of H2O2 at pH 8, which increases when the pH changes to either lower or higher values. It was considered that the hydrated electron also plays an important role in H2O2 production under these acidic and alkaline conditions.

Solvothermal Subcomponent Self-Assembly of Cubic Metal-Imidazolate Cages and Their Coordination Polymers.

A series of Ni-imidazolate cubic cages, one-dimensional and two-dimensional coordination polymers based on the cubic cages, have been prepared by solvothermal subcomponent self-assembly of 5-methyl-4-formylimidazole, m-xylylenediamine, and Ni(II) salts with varied anions. These compounds have been characterized by single-crystal X-ray diffractions, elemental analysis, IR spectra, and powder X-ray diffractions. The formation of an oligomerized coordination cage or an infinite coordination polymer depends on the anions chosen. An oligomerized 8-nuclear Ni-imidazolate cubic cage is formed when the anion Cl(-), Br(-), I(-), SCN(-), NO2(-), or NO3(-) is utilized in the reactions, and a two-dimensional coordination polymer based on the Ni-imidazolate cubic cage will be obtained when N3(-), (CN)2N(-), or (CN)3C(-) act as the anions. When only ClO4(-) or both ClO4(-) and [Ni(C4N2S2)2](2-) (C4N2S2 = dimercaptomaleonitrile) as anions exist in the reaction mixture, a ladder-like one-dimensional coordination polymer based on the Ni-imidazolate cubic cage and formate is formed unpredictably.

Iridium ultrasmall nanoparticles, worm-like chain nanowires, and porous nanodendrites: One-pot solvothermal synthesis and catalytic CO oxidation activity

We report a facile one-pot solvothermal synthesis of monodisperse iridium (Ir) ultrasmall (1.5–2.5 nm in diameter) nanoparticles (NPs), worm-like chain nanowires (NWs), and porous nanodendrites (NDs), for which CO oxidation reaction has been employed as a probe reaction to investigate the effects of nanoparticle size and surface-capping organics on the catalytic activities. Time-dependent experiments revealed that an oriented attachment mechanism induced by the strong adsorption of halide anions (Br− and I−) on specific facet of Ir nanoclusters or by decreasing the reduction rate of Ir precursors with changing their concentrations during the synthesis was responsible for the formation of Ir NWs and NDs. Annealing tests indicated that an O2-H2 atmosphere treatment turned out to be an effective measure to clean up the surface-capping organics of Ir NPs supported on commercial SiO2. Catalytic CO oxidation reaction illustrated that a significant improvement in the catalytic activity of CO oxidation reaction was achieved together with the changing of activation energies after such atmosphere treatment for the supported catalysts of the ultrasmall Ir NPs. It is noteworthy that this enhancement in catalytic activity could be ascribed to the changes in the surface status (including populations of Ir species in metallic and oxidized states, removal of surface capping organics, the variety of active sites, and total effective active site number) for the supported nanocatalysts during the atmosphere treatment.

Ag@Au core-shell dendrites: a stable, reusable and sensitive surface enhanced Raman scattering substrate.

Surface enhanced Raman scattering (SERS) substrate based on fabricated Ag@Au core-shell dendrite was achieved. Ag dendrites were grown on Si wafer by the hydrothermal corrosion method and Au nanofilm on the surface of Ag dendritic nanostructure was then fabricated by chemical reduction. With the help of sodium borohydride in water, Au surface absorbates such as thiophene, adenine, rhodamine, small anions (Br– and I–), and a polymer (PVP, poly(N-vinylpyrrolidone)) can be completely and rapidly removed. After four repeatable experiments, the substrate SERS function did not decrease at all, indicating that the Ag@Au dendrite should be of great significance to SERS application because it can save much resource. Six-month-duration stability tests showed that the Ag@Au core-shell dendrite substrate is much more stable than the Ag dendrite substrates. We have also experimented on fast detection of Cd2+ at 10−8 M concentration by decorating single-stranded DNA containing adenine and guanine bases on the surface of this Ag@Au dendrite. Finite-difference time-domain simulations were carried out to investigate the influence of Au nanolayer on Ag dendrites, which showed that the local electric fields and enhancement factor are hardly affected when a 4 nm Au nanolayer is coated on Ag dendrite surface.

Temperature-Induced Molecular Rearrangement of an Ionic Liquid Confined in Nanospaces: An in Situ X-ray Absorption Fine Structure Study

A temperature-dependent X-ray absorption fine structure (XAFS) study was performed to investigate structural changes in the 1-hexyl-3-methylimidazolium bromine (C(6)mimBr) ionic liquid (IL) confined within the channels of multiwalled carbon nanotubes (MWCNTs). The XAFS spectra at room temperature confirmed the charge transfer from the bromine anion of the encapsulated IL to the MWCNTs. R-space analysis at ambient temperature revealed the reduced distance between the anions and cations in the confined IL compared with that in the bulk state. Interfacial-induced solidification and nanoconfinement in MWCNTs induced the self-assembly of ions in the confined IL to form a layered arrangement near the inner surface of MWCNTs. In situ XAFS analysis revealed that with increasing temperature charge transferred from MWCNTs to Br anions because of the damage from the conjugative effect between Br and MWCNTs and the relatively strong electronegativity of Br atoms. R-space analysis also showed gradual reduction in distance between cations and anions with increasing temperature. This finding indicated that the anion moved toward the ring planar, and ions rearranged from the layered to the near-planar structure. Raman and XRD experiments confirmed the structural transformation of the confined IL at increased temperature.

Hybrid Membrane of Agarose and Lanthanide Coordination Polymer: a Selective and Sensitive Fe(3+) Sensor.

A new hybrid membrane was prepared by a facile method based on a highly luminescent lanthanide coordination polymer and agarose. The soft membrane was characterized by FT-IR, PXRD, SEM and luminescence. It is found that the soft membrane is a highly selective and sensitive sensor, among 19 metal ion solutions of Fe(3+), Mg(2+), Li(+), Ca(2+), Zn(2+), Cu(2+), Ba(2+), Mn(2+), Ru(3+), Cr(3+), Ag(+), Sr(2+), Cd(2+), Na(+), Ni(2+), Pb(2+), Fe(2+), Hg(2+) and Ca(2+), only Fe(3+) quench the luminescence. The sensing results can be distinguished by the naked eye in daylight or by irradiation of a portable UV light at the scene. Mechanism studies reveal the sensing is due to the decomposition of the coordination polymer 1 which induced by slow permeation of Fe(3+). Further studies found anions of BO3(-), CO3(2-), H2PO4(-), Br(-), Cl(-), ClO4(-), H2PO4(-), I(-), IO3(-) and NO3(-) will not quench the luminescence of the hybrid membrane, which imply that other anions in water would not disturb the detection result.

ChemInform Abstract: Regio‐ and Stereoselective Synthesis of (E)‐1‐Bromo‐2‐iodoalkenes Through Iodobromination of Internal Alkynes.

AbstractThe key to the presented approach is a well matching pair of anionic Br from Tms‐Br and cationic iodide from NIS.

Hypobromous acid, a powerful endogenous electrophile: Experimental and theoretical studies

Hypobromous acid (HOBr) is an inorganic acid produced by the oxidation of the bromide anion (Br−). The blood plasma level of Br− is more than 1,000-fold lower than that of chloride anion (Cl−). Consequently, the endogenous production of HOBr is also lower compared to hypochlorous acid (HOCl). Nevertheless, there is much evidence of the deleterious effects of HOBr. From these data, we hypothesized that the reactivity of HOBr could be better associated with its electrophilic strength. Our hypothesis was confirmed, since HOBr was significantly more reactive than HOCl when the oxidability of the studied compounds was not relevant. For instance: anisole (HOBr, k2=2.3×102M−1s−1, HOCl non-reactive); dansylglycine (HOBr, k2=7.3×106M−1s−1, HOCl, 5.2×102M−1s−1); salicylic acid (HOBr, k2=4.0×104M−1s−1, non-reactive); 3-hydroxybenzoic acid (HOBr, k2=5.9×104M−1s−1, HOCl, k2=1.1×101M−1s−1); uridine (HOBr, k2=1.3×103M−1s−1, HOCl non-reactive). The compounds 4-bromoanisole and 5-bromouridine were identified as the products of the reactions between HOBr and anisole or uridine, respectively, i.e. typical products of electrophilic substitutions. Together, these results show that, rather than an oxidant, HOBr is a powerful electrophilic reactant. This chemical property was theoretically confirmed by measuring the positive Mulliken and ChelpG charges upon bromine and chlorine. In conclusion, the high electrophilicity of HOBr could be behind its well-established deleterious effects. We propose that HOBr is the most powerful endogenous electrophile.

Computer simulation of electron states of the isoelectronic substitutional impurities in quantum wire of KCl with edge dislocation

The electron states of quantum wires KCl, KCl : Br, and KCl : I with an edge dislocations were investigated. The main problem was in study of dislocation influence on localized electron states connected with substitutional isoelectronic impurities Br− and I− in the neighborhood of edge dislocation line. The tight-binding semi-empirical band approximation, semi-empirical and non-empirical cluster approach were used. Semi-empirical calculations were carried out in framework of model [1,2]. Besides, the algorithms for electronic levels calculations of polar nanosystems with the partial self-consistency [3] were used. The computer simulation results lead to the conclusion that the substitutional isoelectronic impurity anions Br− and I− located near the dislocation line capture the holes more efficiently than in bulk of systems without dislocations.

Cyclic voltammetric studies of adsorption of cetyltrimethylammonium bromide and HBr on Pt(100) towards understanding their effects in shape-controlled synthesis of nanomaterials

Adsorption of CTAB and HBr on Pt(100) in acid solutions were studied by using cyclic voltammetry (CV). The effects of bromide anion (Br−), and cetyltrimethylammonium cation (CTA+) together with Br− (CTAB) on the long-range ordered structure of Pt(100) were investigated systematically and analyzed quantitatively. It has demonstrated that adsorption of both CTA+ and Br− can protect the long-range ordered structure of Pt(100). The upper limit potential of CV below which the long-range ordered structure of Pt(100) is starting to be disturbed was measured at 0.6V in 0.1M H2SO4, and it was shifted positively to 0.9V in 0.1M H2SO4+1mM HBr; this potential has been further postponed to even a higher potential of 1.1V in 0.1M H2SO4+1mM CTAB solution, demonstrating that the ability of protecting the long-range ordered structure of Pt(100) is CTAB>HBr. The adsorbed Br− can desorb simultaneously with proton adsorption, while the CTA+ has adsorbed firmly on Pt(100). It has demonstrated that the irreversibly adsorbed CTA+ could be mostly removed by CO adsorption/stripping. The results revealed that the origin of protecting the long-range ordered (100) structure by HBr is mainly through the inhibition of oxygen adsorption, while that by CTAB comes from both the inhibition of oxygen adsorption and the CTA+ irreversible adsorption. The study has thrown insights in understanding the interaction of Br− and CTA+ with Pt(100), and interpreted that using CTAB as shape-tuning agent is more favorable to yield Pt nanomaterials with long-range ordered (100) surface structure.

Geophysical and geochemical site investigation of eastern part of Lagos metropolis, southwestern Nigeria

Geophysical and geochemical studies were carried out in the eastern part of Lagos metropolis to determine the possible contamination of subsurface soils and groundwater as a result of dumping of waste into the canal. The geophysical method involved the use of 2D electrical resistivity imaging which was acquired along five (5) traverses, while the geochemical method involved the physicochemical analysis of water samples from nine (9) wells within the study area. The geochemical study includes the analysis of physical parameters like total dissolved solids (TDS), electrical conductivity (EC), pH and temperature. Seventy elements which include trace elements (such as As, B, Ba, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, U and Zn), major cations (such as Ca, K, Mg and Na) and anions (Cl and Br) were analysed, and the concentrations of the elements were compared with the World Health Organization (WHO) and Nigerian Standard for Drinking Water Quality (NSDWQ) permissible level for drinking water. Geophysical results show that the lithology is composed of topsoil, clayey sand, peat and sand. 2D electrical resistivity tomography revealed that the leachate and polluted water from the canal have percolated to the subsurface soil down to a depth of about 37 m with low resistivity values of 1–13 Ω m. In addition to this, result of physicochemical analysis of water samples shows that Mn, Br, TDS, and EC were high in some wells, above the WHO and NSDWQ standard. It was deduced that the subsurface has been invaded by the polluted water from the canal consequently, making the groundwater unsuitable for human consumption.

FTIR and quantum chemical study of LiBr solvation in acetonitrile solutions

FTIR spectroscopy and quantum chemical calculations at the RTF+MP2/6-311G** level of theory with solvation model density (SMD) corrections were used to study ion solvation and association in LiBr/acetonitrile solutions. The aim of this study was to establish the composition and geometry of the predominant ionic species solvated by acetonitrile molecules and to analyse their spectroscopic signatures. The results obtained make it possible to propose an equilibrium between Li+Br−(CH3CN)3, Li+(CH3CN)4, and anionic Br−(CH3CN)n complexes with an undetermined n value and bent coordination of the solvent molecules. The calculated wavenumbers and the geometric parameters of the solvated ionic species were found to be in excellent agreement with the experimental data.

H2S–CO2 Separation Using Room Temperature Ionic Liquid [BMIM][Br

Solubility and selective absorption of hydrogen sulfide (H2S) over carbon dioxide (CO2) in a room temperature ionic liquid, 1-butyl-3-methylimidazolium bromide ([BMIM][Br]) has been evaluated under ambient temperature and pressure. [BMIM][Br] demonstrated its potential as a solvent for selective removal of H2S from CO2/H2S mixture. Our investigation indicated that H2S solubility in [BMIM][Br] is comparable to or better than that in commercially available MDEA-based solvents. Meanwhile, CO2 solubility in [BMIM][Br] is lower than that in the same amine resulting in H2S/CO2 absorption selectivity of within 3.5 to 3.75. The solubility behavior is relatively maintained after 4 times absorption-desorption cycles. A computational molecular study suggested that intramolecular hydrogen bonding interaction between anion Br and hydrogen atom of H2S could stabilize the complex and resulted lower complexation energy than CO2 interaction with [BMIM][Br]. Based on the experiment results, a separation process employing [BMIM][Br] is proposed to control the CO2/H2S ratio existing in a natural gas feed.

Development of single‐step liquid chromatography methods with ultraviolet detection for the measurement of inorganic anions in marine waters

Although a number of techniques exist to measure the major and minor inorganic anions Cl‐, NO2‐, Br‐, NO3‐, or SO42‐ in marine waters and sediment porewaters, a single method that can quantify all five anions in a single step with a sufficiently low detection limit has yet to be developed. In this work, a novel ion‐chromatographic separation procedure was developed that exploits the UV‐absorbing properties of Br‐, NO3‐, and NO2‐, as well as the suppression of eluent absorbance by high concentrations of Cl‐ and SO42‐ to quantify all these anions simultaneously in marine waters. If additional sensitivity for the minor anions Br‐, NO3‐, and NO2‐ is needed, NaCl can be used as eluent in a matrix elimination method that no longer allows for Cl‐ and SO42‐ determination. These methods are isocratic, require no chemical or electronic suppression, are not subject to interferences, and can resolve the anions in less than 18 min. The decrease in analysis time and the number of analyses required compared with conventional methods lowers the costs associated with laboratory analysis of marine samples. Last, the simplicity and good limits of detection make this separation method suitable for in situ analyses of marine waters and porewaters, and an in situ liquid chromatograph is currently under development for these applications.

Synthesis and structural characterization of two heterometallic hybrids containing 0-D and 1-D bromoplumbate anions

Two novel heterometallic organic–inorganic hybrids, [Co(terpy)2]4[Pb8Br24·2(DMF)]·8(DMF) (1) and {[Co(terpy)2]4[Pb16Br40]·H2O}n (2), with unprecedented structures have been prepared from the reactions of cobalt(II) salts with 2,2′:6′,2′′-terpyridine (terpy), PbBr2 and KBr. Compound 1 contains a novel octanuclear Pb–Br anion formed from six coordinate Pb–Br units, representing the highest nuclearity for Pb–Br cluster anions. Compound 2 exhibits 1-D infinite chains consisting of five-, six and seven-coordinate Pb units.

A Decade of Dinuclear Technetium Complexes with Multiple Metal–Metal Bonds

AbstractTransition metal complexes with multiple metal–metal bonds exhibit interesting catalytic and biological properties. One element whose metal–metal bond chemistry has been poorly studied is technetium. Currently, only 25 technetium complexes with multiple metal–metal bonds have been structurally characterized. The nature of metal–metal interactions in these complexes, as well as the influence of ligands on the bonding in the Tc2n+ unit (n = 6, 5, 4) are not well understood. In order to better understand the influence of ligands on the Tc–Tc bonding, a study of the solid‐state and electronic structure of dinuclear complexes with the Tc2n+ unit (n = 6, 5, 4) has been performed. Dinuclear technetium complexes (nBu4N)2Tc2X8, Tc2(O2CCH3)4X2, Tc2(O2CCH3)2Cl4, cesium salts of Tc2X83–, and Tc2X4(PMe3)4 (X = Cl, Br) were synthesized; their molecular and electronic structures, as well as their electronic absorption spectra, were studied by a number of physical and computational techniques. The structure and bonding in these systems have been investigated by using multiconfigurational quantum calculations. For all these complexes, the calculated geometries are in very good agreement with those determined experimentally. Bond order analysis demonstrates that all these complexes exhibit a total bond order of approximately 3. Analysis of individual effective bond order (EBO) components shows that these complexes have similar σ components, while the strength of their π components follows the order Tc2X4(PMe3)4 > Tc2X83– > Tc2(O2CCH3)2Cl4 > Tc2X82–. Calculations indicate that the δ components are the weakest bond in Tc2X8n– (n = 2, 3) and Tc2(O2CCH3)2Cl4. Further analysis of Tc2X83– and Tc2X4(PMe3)4 (X = Cl, Br) indicates that the electronic structure of the Tc25+ and Tc24+ units is insensitive to the nature of the coordinating ligands. The electronic absorption spectra of Tc2X8n– (n = 2, 3), Tc2(O2CCH3)2Cl4, and Tc2X4(PMe3)4 (X = Cl, Br) were studied in solution, and assignment of the transitions was performed by multiconfigurational quantum chemical calculations. For the Tc2X8n– (n = 2, 3; X = Cl, Br) anions and Tc2(O2CCH3)2Cl4, the lowest‐energy band is attributed to the δ→δ* transition. For Tc2X4(PMe3)4, the assignment of the transitions follow the following order in energy: δ*→σ* < δ*→π* < δ→σ* < δ→π*.

Pd–Rh Nanocrystals with Tunable Morphologies and Compositions as Efficient Catalysts toward Suzuki Cross-Coupling Reactions

Delicate elaboration of the nanostructures of multimetal catalytic materials with well-defined shapes and compositions to reveal their potential use as heterogeneous nanocatalysts for organic synthetic reactions with the combined merits of heterogeneous and homogeneous catalysis is both scientifically and technologically important, but this type of investigation has remained rarely pursued. In this work, we demonstrated a facile hydrothermal approach toward the one-pot shape-selective syntheses of Pd–Rh nanocrystals with tunable compositions and morphologies, including hollow nanocubes (NCs), nanoicosahedrons (NIs), and nanotruncated octahedrons (NTOs), using poly(vinylpyrrolidone) as both reductant and capping agent and halide anions (Br–/I–) as shape control agents. The formation of Pd–Rh hollow NCs was induced by an iodine adsorbate-induced reconstruction mechanism with KI, whereas the formation of Pd–Rh NIs and NTOs were realized by controlling the selective nucleation of twinned seeds or single crystal seeds and their relative growth rates along different facets (e.g., (111) and (100) facets) through finely adjusting the Pd/Rh ratio and the amount of KBr added in the absence of KI. Due to the great significance of Pd-catalyzed organic reactions, the catalytic performances of Pd–Rh nanocrystals for Suzuki cross-coupling reactions with different reactants were evaluated. The measured turnover frequencies (TOFs) suggested that Pd–Rh hollow NCs held considerably enhanced catalytic activities (at least 3 times) than other Pd-based solid nanocrystals including Pd–Rh NIs, Pd–Rh NTOs, Pd–Rh NCs, Pd NCs, and commercial Pd/C, with iodobenzene as the reactant. In addition, even for more inert reactants such as bromobenzene or 4-bromotoluene, the catalytic activities of Pd–Rh hollow NCs were still impressive (showing similar TOFs to those of other shapes for reactions with iodobenzene as the reactant), indicating the promising application of Pd-based nanocatalysts for other powerful Pd-catalyzed organic synthesis reactions. Meanwhile, Pd-based solid NCs, enclosed with (100) facets only, showed better catalytic performance than NIs as well as NTOs, which had a larger fraction of (111) facets other than (100) ones, further suggesting that morphology differences were vitally significant to tune the catalytic performances of bimetallic nanocatalysts.

Two Conformational Isomers in a Crystal of trans-Dibromobis(2,2-dimethyl-1,3-propanediamine)chromium(III) Bromide

A new salt complex, trans-[Cr(Me2tn)2Br2]Br (Me2tn = 2,2-dimethyl-1,3-propanediamine), was prepared and characterized by elemental, IR spectroscopic, and single-crystal X-ray diffraction analyses. The title complex crystallized in the space group C2/c of the monoclinic system with eight mononuclear formula units in a cell of dimensions a = 19.991(4), b = 11.489(2), c = 17.278(4) A, and β = 111.94(3)°. The chromium ion was in a distorted octahedral coordination with four N atoms of two chelating Me2tn and two bromine atoms in trans axial positions. The structural analysis showed that a single crystal contained two crystallographically independent complex ions which were anti and syn conformational isomers of each other. The mean Cr–N(Me2tn) and Cr–Br bond lengths are 2.091(1) and 2.476(1) A, respectively. The crystal lattice was stabilized by hydrogen bonding interactions between Br ligand, Br anion and NH groups of the Me2tn ligand. The X-ray crystallography result of trans-[Cr(Me2tn)2Br2]Br shows that the chromium atom is in a distorted octahedral environment, coordinated by two bidentate, 2,2-dimethyl-1,3-propanediamine ligands and two Br ligands in trans positions.

In Situ Non-DLVO Stabilization of Surfactant-Free, Plasmonic Gold Nanoparticles: Effect of Hofmeister’s Anions

Specific ion effects ranking in the Hofmeister sequence are ubiquitous in biochemical, industrial, and atmospheric processes. In this experimental study specific ion effects inexplicable by the classical DLVO theory have been investigated at curved water-metal interfaces of gold nanoparticles synthesized by a laser ablation process in liquid in the absence of any organic stabilizers. Notably, ion-specific differences in colloidal stability occurred in the Hückel regime at extraordinarily low salinities below 50 μM, and indications of a direct influence of ion-specific effects on the nanoparticle formation process are found. UV-vis, zeta potential, and XPS measurements help to elucidate coagulation properties, electrokinetic potential, and the oxidation state of pristine gold nanoparticles. The results clearly demonstrate that stabilization of ligand-free gold nanoparticles scales proportionally with polarizability and antiproportionally with hydration of anions located at defined positions in a direct Hofmeister sequence of anions. These specific ion effects might be due to the adsorption of chaotropic anions (Br(-), SCN(-), or I(-)) at the gold/water interface, leading to repulsive interactions between the partially oxidized gold particles during the nanoparticle formation process. On the other hand, kosmotropic anions (F(-) or SO4(2-)) seem to destabilize the gold colloid, whereas Cl(-) and NO3(-) give rise to an intermediate stability. Quantification of surface charge density indicated that particle stabilization is dominated by ion adsorption and not by surface oxidation. Fundamental insights into specific ion effects on ligand-free aqueous gold nanoparticles beyond purely electrostatic interactions are of paramount importance in biomedical or catalytic applications, since colloidal stability appears to depend greatly on the type of salt rather than on the amount.