Ligand Adsorption Research Articles

Natural and modified clays as low-cost and ecofriendly materials to remove salinomycin from environmental compartments

Antibiotics in the environment represent a substantial pollution threat. Among these emerging pollutants, ionophore anticoccidials are of special concern due to their potential ecological impact, persistence in the environment, and role in promoting antimicrobial resistance. To investigate the adsorption/desorption of the ionophore antibiotic salinomycin (SAL) on/from raw and modified clay adsorbents, batch-type experiments were performed using 0.5 g of clay adsorbent mixed with 10 mL of increasing doses of SAL solutions for each sample, at room temperature, with a contact time of 24 h. All measurements were conducted in triplicate employing HPLC-UV equipment. Three different natural (raw) and modified clay samples were investigated, which were denominated as follows: AM (with 51% calcite), HJ1 (with 32% kaolinite), and HJ2 (with 32% microcline). The experiments were carried out using three pH ranges: between 3.33 and 4.49 for acid-activated clays, 8.39–9.08 for natural clays, and 9.99–10.18 for base-activated clays. The results indicated that, when low concentrations of the antibiotic were added (from 5 to 20 μmol L−1), more than 98% of SAL was strongly adsorbed by almost all clays, irrespective of the physicochemical and mineralogical composition of the clays or their pH values. When higher SAL concentrations were added (40 and 100 μmol L−1), the adsorption of the antibiotic showed pH-dependent ligand adsorption mechanisms: (i) highly decreased as the pH raised (for the raw and base-activated AM and HJ1 clays), while (ii) slightly decreased as the pH decreased (on the acid-activated clays). Among the adsorption equations tested (Freundlich, Langmuir, and Linear), the Freundlich model was identified as the most suitable for fitting the data corresponding to SAL adsorption onto the studied clays. SAL desorption from clays was consistently below 10% for all the clay samples, especially for the acid-activated clays, due to cation bridging adsorption mechanisms, when the lowest concentration of the antibiotic was added. Additionally, it should be stressed that the desorption values can increase with rising SAL concentrations, but they always remain below 20%. Overall, the clays here investigated (both raw and modified) provide a cost-effective and efficient alternative for the removal of the veterinary anticoccidial antibiotic SAL, with potential positive and practical implications in environmental remediation and antibiotic pollution management, particularly by serving as amendments for contaminated soils to enhance their adsorption capacities against SAL. Additionally, using these clays in water treatment processes could improve the efficiency of mitigating antibiotic contamination in aquatic systems.

The Effect of the Capping Agents of Nanoparticles on Their Redox Potential.

Engineered metallic nanoparticles, which are found in numerous applications, are usually stabilized by organic ligands influencing their interfacial properties. We found that the ligands affect tremendously the electrochemical peak oxidation potentials of the nanoparticles. In this work, identical gold nanoparticles were ligand-exchanged and carefully analyzed to enable a precise and highly reproducible comparison. The peak potential difference between gold nanoparticles stabilized by various ligands, such as 2- and 4-mercaptobenzoic acid, can be as high as 71 mV, which is substantial in energetic terms. A detailed study supported by density functional theory (DFT) calculations aimed to determine the source of this interesting effect. The DFT simulations of the ligand adsorption modes on Au surfaces were used to calculate the redox potentials through the thermodynamic cycle method. The DFT results of the peak potential shift were in good agreement with the experimental results for a few ligands, but showed some discrepancy, which was attributed to kinetic effects. The kinetic rate constant of the oxidation of Au nanoparticles stabilized by 4-mercaptobenzoic acid was found to be twice as large as that of the Au nanoparticles stabilized by citrate, as calculated from Laviron's theory and the Tafel equation. Finally, these findings could be applied to some novel applications such as determining the distribution of nanoparticle population in a dispersion as well as monitoring the ligand exchange between nanoparticles.

Molecular-Scale Visualization of Steric Effects of Ligand Binding to Reconstructed Au(111) Surfaces.

Direct imaging of single molecules at nanostructured interfaces is a grand challenge with potential to enable new, precise material architectures and technologies. Of particular interest are the structural morphology and spectroscopic signatures of the adsorbed molecule, where modern probes are only now being developed with the necessary spatial and energetic resolution to provide detailed information at the molecule-surface interface. Here, we directly characterize the adsorption of individual m-terphenyl isocyanide ligands on a reconstructed Au(111) surface through scanning tunneling microscopy and inelastic electron tunneling spectroscopy. The site-dependent steric pressure of the various surface features alters the vibrational fingerprints of the m-terphenyl isocyanides, which are characterized with single-molecule precision through joint experimental and theoretical approaches. This study provides molecular-level insights into the steric-pressure-enabled surface binding selectivity as well as its effect on the chemical properties of individual surface-binding ligands.

Lithium Borohydride Nanorods: Self-Assembling Growth and Remarkable Hydrogen Cycling Properties.

Nanostructured metal hydrides with unique morphology and improved hydrogen storage properties have attracted intense interests. However, the study of the growth process of highly active borohydrides remains challenging. Herein, for the first time the synthesis of LiBH4 nanorods through a hydrogen-assisted one-pot solvothermal reaction is reported. Reaction of n-butyl lithium with triethylamine borane in n-hexane under 50bar of H2 at 40-100°C gives rise to the formation of the [100]-oriented LiBH4 nanorods with 500-800nm in diameter, whose growth is driven by orientated attachment and ligand adsorption. The unique morphology enables the LiBH4 nanorods to release hydrogen from ≈184°C, 94°C lower than the commercial sample (≈278°C). Hydrogen release amounts to 13wt% within 40min at 450°C with a stable cyclability, remarkably superior to the commercial LiBH4 (≈9.1wt%). More importantly, up to 180°C reduction in the onset temperature of hydrogenation is successfully attained by the nanorod sample with respect to the commercial counterpart. The LiBH4 nanorods show no foaming during dehydrogenation, which improves the hydrogen cycling performance. The new approach will shed light on the preparation of nanostructured metal borohydrides as advanced functional materials.

The addition of fluorine atoms and alkyl chains to aromatic ligand dipole for enhancing stability and photoelectronic properties of formamidinium perovskite surfaces

The long-term stability on perovskite surfaces limits the practical application of perovskite solar cells (PSCs). Adding multifunction ligand can deal with this issue, however, the structure diversity of ligand and perovskite surface leads to the complicated adsorptive interaction, affecting the improvement effect of the stability and photoelectric properties. In this work, strongly electronegative fluorine atoms and alkyl chain with different length are introduced into aromatic ligand dipole to modify the polarity, regulating the phase stability, energy state and photoelectric properties of formamidinium perovskite (FAPbI3) surfaces. The results show the adsorption and interaction energy of positive ligand dipoles on the I-terminated surface decrease with the increase of polarity, which displays stronger ordered π-π stack and adsorption anchoring of ligand dipoles and thus decreasing the formation energy to improve the phase stability. The positive 4-Trifluoromethyl-phenethylammonium (CF3-PEA) with the highest polarity obtains the highest stability and shifts work function (WF) upward from 6.21 eV to the highest 6.46 eV. The negative CF3-PEA adsorbs on the PbI2-terminated surface induced by CF3•••Pb and π•••I interaction, achieving the stable phase with lower formation energy and lowest WF 5.61 eV. This work provides tutorial for optimizing performance of PSCs by the addition of ligand dipoles.

Ligand-induced incompatible curvatures control ultrathin nanoplatelet polymorphism and chirality

The ability of thin materials to shape-shift is a common occurrence that leads to dynamic pattern formation and function in natural and man-made structures. However, harnessing this concept to rationally design inorganic structures at the nanoscale has remained far from reach due to a lack of fundamental understanding of the essential physical components. Here, we show that the interaction between organic ligands and the nanocrystal surface is responsible for the full range of chiral shapes seen in colloidal nanoplatelets. The adsorption of ligands results in incompatible curvatures on the top and bottom surfaces of the NPL, causing them to deform into helicoïds, helical ribbons, or tubes depending on the lateral dimensions and crystallographic orientation of the NPL. We demonstrate that nanoplatelets belong to the broad class of geometrically frustrated assemblies and exhibit one of their hallmark features: a transition between helicoïds and helical ribbons at a critical width. The effective curvature [Formula: see text] is the single aggregate parameter that encodes the details of the ligand/surface interaction, determining the nanoplatelets' geometry for a given width and crystallographic orientation. The conceptual framework described here will aid the rational design of dynamic, chiral nanostructures with high fundamental and practical relevance.

Assembly-promoted repeatable enhancement of photoluminescence from cesium lead tribromide nanocubes under light illumination.

A repeatable enhancement of the photoluminescence (PL) from CsPbBr3 nanocubes (NCs) is promoted by the assembling of NCs. The PL quantum yield (QY) of ordered NC arrays increases with photoirradiation and decreases in the dark. The repeatable enhancement of the PLQY cannot be observed from isolated NCs. The nanospaces between NCs in the ordered arrays allow a reversible change in thermally stimulated desorption and photo-induced adsorption of surface ligands that affect the PLQY.

A thermodynamic model for the formation of protein aggregates on a matrix

The development of many neurodegenerative diseases is associated with the formation of pathological protein aggregates. In some cases, these aggregates can be formed by multilayer adsorption of ligands on a matrix, for example, the set of membrane protein receptors. The paper proposes a thermodynamic model describing the formation of linear aggregates in which ligands can be stacked. The cases when these stacks consist of complexes of one or two different types are considered. The developed model can be applied to the study of pathological aggregation of proteins of different nature, primarily beta-amyloid and its isoforms. The mean, variance and entropy of the theoretical distributions of aggregate sizes are calculated. A comparison with other theoretical models of the formation of amyloid aggregates is made.

Computational Insights into the Adsorption of Ligands on Gold Nanosurfaces.

We study the adsorption process of model peptides, nucleobases, and selected standard ligands on gold through the development of a computational protocol based on fully atomistic classical molecular dynamics (MD) simulations combined with umbrella sampling techniques. The specific features of the interface components, namely, the molecule, the metallic substrate, and the solvent, are taken into account through different combinations of force fields (FFs), which are found to strongly affect the results, especially changing absolute and relative adsorption free energies and trends. Overall, noncovalent interactions drive the process along the adsorption pathways. Our findings also show that a suitable choice of the FF combinations can shed light on the affinity, position, orientation, and dynamic fluctuations of the target molecule with respect to the surface. The proposed protocol may help the understanding of the adsorption process at the microscopic level and may drive the in-silico design of biosensors for detection purposes.

Revealing the effect of Co/Cu (d7/d9) cationic doping on an electronic acceptor ZnO nanocage surface for the adsorption of citric acid, vinyl alcohol, and sulfamethoxazole ligands: DFT-D3, QTAIM, IGM-NCI, and MD analysis

The electron-spin duality and propagation of the active sites of free electrons are of interest for adsorbing the guests and fixing them with strong hydrogen bonds (HB). The coherence of the systems with the guests is one of the main parameters that favor the experimentation of new systems on primary column adsorption phenomena. The stability and the adaptable symmetries in all directions justify the use of a “nanocage” (ZnO) for studying adsorption phenomena. The formation of stable electronic charge transfer paths between sites occupied by very stable atomic orbitals ensures the success of the adsorption of the ligands. Electronic characterization (MES, FMO, DOS, and cationic doping) is used to describe the movement of the intra-Cu-Co/Zn19O20 electrons. The phenomena of charge transfer, stability, types of orbital occupations, adsorption sites, electron migration direction, conductivity, and reactivity of such systems are thoroughly explored. Based on these findings, the efficiency of a Cu–Co/Zn19O20 nanocage to adsorb three different ligands (medical ligands, prostate biomarkers, and antibiotics) is studied. From the reactivity parameter discussions, it is found that the copper or cobalt-doped nanocage-Citric Acid has a strongly electronegative index (4.40 eV and 4.91 eV) and hardness (1.99 eV and 1.82 eV) properties. The Fourier transform infrared analyses and orbital localizations (α and β) clearly demonstrate that the charge transfer occurs inter-surface, from nanocages to adsorbed ligands. Bader's theory analysis for the adsorption ligands VA (Vinyl Alcohol), CA (Citric Acid), and SMX (Sulfamethoxazole) by the doped copper and cobalt nanocages demonstrates that these systems are much more adequate for adsorbing the ligand antibiotics than the other hosts. The highly adsorbent energy of sulfamethoxazole by Cu–Zn19O20 is equal to −582.86 kJ.mol-1. The IGM-NCI/ELF analyses support these findings, revealing that the Cu/Co–Zn19O20 nanocages adsorb SMX via hydrogen bonding and van der Waals interactions, as they also did in DFT-D3 and FT-IR analyses. LOL analyses support this claim by visualizing single-pair spins in excess surrounding acceptor atoms (O) in the two systems. Molecular dynamics simulations show that SMX is quickly adsorbed by nanocages of Zn19O20 doped with copper (d9) or cobalt (d7).

Computational study on the adsorption of small molecules to surface-supported Ni-porphyrins

With their flexible oxidation and spin states, surface-supported metalloporphyrins are attractive building blocks for tuneable, periodic spin interfaces. A technique to manipulate the spin in such systems is based on the adsorption of external gas ligands to the chelated metal center. In the search for promising interfaces, computational studies allow for a convenient scan through potential ligand candidates. In this contribution, we perform density functional theory calculations to investigate the coordination of six exemplary gases (CH4, H2O, NH3, CO, NO and NO2) to nickel tetraphenylporphyrin interfaces. Analyzing the formed complexes, we distinguish four major interaction mechanisms between metal center and ligand: non-interacting, weak field d-splitting, competing surface trans-effect and redox reaction. We find that a surface-mediated redox reaction between a strong π-acceptor (e.g.: NO2) and an unusually reduced metal (e.g.: Ni d9) has the strongest potential to induce spin changes at ambient conditions. Furthermore, we demonstrate how commonly chosen theoretical approximations may influence the interpretation of DFT calculations for metalloporphyrins and their complexes. By highlighting the limitations and possibilities of theoretical approaches, we hope to contribute to a better understanding and more selective harnessing of the special properties of surface-supported metalloporphyrins.

Nanoimaging of Facet-Dependent Adsorption, Diffusion, and Reactivity of Surface Ligands on Au Nanocrystals.

Analysis of the influence of dissimilar facets on the adsorption, stability, mobility, and reactivity of surface ligands is essential for designing ligand-coated nanocrystals with optimal functionality. Herein, para-nitrothiophenol and nitronaphthalene were chemisorbed and physisorbed, respectively, on Au nanocrystals, and the influence of different facets within a single Au nanocrystal on ligands properties were identified by IR nanospectroscopy measurements. Preferred adsorption was probed on (001) facets for both ligands, with a lower density on (111) facets. Exposure to reducing conditions led to nitro reduction and diffusion of both ligands toward the top (111) facet. Nitrothiophenol was characterized with a diffusivity higher than that of nitronaphthalene. Moreover, the strong thiol-Au interaction led to the diffusion of Au atoms and the formation of thiol-coated Au nanoparticles on the silicon surface. It is identified that the adsorption and reactivity of surface ligands were mainly influenced by the atomic properties of each facet, while diffusion was controlled by ligand-metal interactions.

The design and adsorption behaviors study of Pd(II) removal materials deriving from quantitative electron transfer ratio evaluation

Currently searching for effective noble metal separation material is generally blind and time-consuming. Although theoretical calculation has been widely applied to explain the adsorption mechanism, the quantitative coordination effect between ligand and metal remains to be explored especially in the material screening stage. In this study, Pearson’s theory and Koopmans' theory were used to calculate the electron transfer ratio (ΔN) from different ligands containing N, S, and O to PdCl2. The quantitative evaluation contributed to the design of efficient ligands including EA (ΔN =0.5929), DB (ΔN =0.5483), and AT (ΔN =0.4885). And the corresponding polystyrene materials CMPS-EA, CMPS-AT, CMPS-DB were successfully synthesized via chemical modification. According to the adsorption experiment, the per mmol of ligand adsorption capacity from CMPS-EA, CMPS-DB and CMPS-AT for Pd(II) were 0.67 mmol/mmol, 0.17 mmol/mmol and 0.11 mmol/mmol, respectively, exhibiting a positive correlation with the results of ΔN. Moreover, CMPS-EA could efficiently remove 98.01% Pd(II) in the presence of multiple competing metal ions with five times concentration higher than Pd(II). In column study, the breakthrough point (Ct/C0 =0.05) for CMPS-EA was 666–676 BV in 1 mmol/L Pd(II) solution and up to 95% desorption efficiency within 50 BV. The adsorption differences and mechanism of CMPS-EA, CMPS-AT and CMPS-DB were further investigated by FTIR, XPS, ESP, and NBO.

Quantification, Exchange, and Removal of Surface Ligands on Noble-Metal Nanocrystals.

ConspectusSurface ligands are vital to the colloidal synthesis of noble-metal nanocrystals with well-controlled sizes and shapes for various applications. The surface ligands not only dictate the formation of nanocrystals with diverse shapes but also serve as a colloidal stabilizer to prevent the suspended nanocrystals from aggregation during their synthesis or storage. By leveraging the facet selectivity of some surface ligands, one can further control the sites for growth or galvanic replacement to transform presynthesized nanocrystals into complex structures that are otherwise difficult to fabricate using conventional methods. Furthermore, the presence of surface ligands on nanocrystals also facilitates their applications in areas such as sensing, imaging, nanomedicine, and self-assembly. Despite their popular use in enhancing the properties of nanocrystals and thus optimizing their performance in a wide variety of applications, it remains a major challenge to quantitatively determine the coverage density of ligand molecules, not to mention the difficulty of substituting or removing them without compromising the surface structure and aggregation state of the nanocrystals.In this Account, we recapitulate our efforts in developing methods capable of qualitatively or quantitatively measuring, exchanging, and removing the surface ligands adsorbed on noble-metal nanocrystals. We begin with an introduction to the typical interactions between ligand molecules and surface atoms, followed by a discussion of the Langmuir model that can be used to describe the adsorption of surface ligands. It is also emphasized that the adsorption process may become very complex in the case of a polymeric ligand due to the variations in binding configuration and chain conformation. We then highlight the capabilities of various spectroscopy methods to analyze the adsorbed ligands qualitatively or quantitatively. Specifically, surface-enhanced Raman scattering, Fourier transform infrared, and X-ray photoelectron spectroscopy are three examples of qualitative methods that can be used to confirm the absence or presence of a surface ligand. On the other hand, ultraviolet-visible spectroscopy and inductively coupled plasma mass spectrometry can be used for quantitative measurements. Additionally, the coverage density of a ligand can be derived by analyzing the morphological changes during nanocrystal growth. We then discuss how the ligands present on the surface of metal nanocrystals can be exchanged directly or indirectly to meet the requirements of different applications. The former can be done using a ligand with stronger binding, whereas the latter is achieved by introducing a sacrificial shell to the surface of the nanocrystals. Furthermore, we highlight three additional strategies besides simple washing to remove the surface ligands, including calcination, heating in a solution, and UV-ozone treatment. Finally, we showcase three applications of metal nanocrystals in nanomedicine, tumor targeting, and self-assembly by taking advantage of the diversity of surface ligands bearing different functional groups. We also offer perspectives on the challenges and opportunities in realizing the full potential of surface ligands.

Synthesis and characterization of binding interaction of ZnO nanoparticles with organic compounds

The current research investigated an unique type of fluorescent sensitive imidazole based on 2-(4-chlorophenyl)-4,5-dimethyl-1-(3,5-dimethylphenyl)-1H-imidazole(CPDPH) derivative ZnO nanoparticles has been synthesized by condensation reaction. The modified surface and structural behaviour of prepared CPDPH derivative ZnO nanoparticles has been investigated by FT-IR, SEM, and EDX spectra. The zinc oxide nanoparticles has been altered the CPDPH properties and binding interface examined. Thermodynamic electron transfer of CPDPH derivative ZnO nanoparticles were studied using absorption and fluorescence spectral techniques. All the synthesized CPDPH derivatives have been studied for their fluorescence analysis and strong ligand adsorption has been evaluate the HOMO and LUMO energy levels.

Influence of Capping Ligands, Solvent, and Thermal Effects on CdSe Quantum Dot Optical Properties by DFT Calculations.

Cadmium selenide nanomaterials are very important materials in photonics, catalysis, and biomedical applications due to their optical properties that can be tuned through size, shape, and surface passivation. In this report, static and ab initio molecular dynamics density functional theory (DFT) simulations are used to characterize the effect of ligand adsorption on the electronic properties of the (110) surface of zinc blende and wurtzite CdSe and a (CdSe)33 nanoparticle. Adsorption energies depend on ligand surface coverage and result from a balance between chemical affinity and ligand-surface and ligand-ligand dispersive interactions. In addition, while little structural reorganization occurs upon slab formation, Cd···Cd distances become shorter and the Se-Cd-Se angles become smaller in the bare nanoparticle model. This originates mid-gap states that strongly influence the absorption optical spectra of nonpassivated (CdSe)33. Ligand passivation on both zinc blende and wurtzite surfaces does not induce a surface reorganization, and thus, the band gap remains nonaffected with respect to bare surfaces. In contrast, structural reconstruction is more apparent for the nanoparticle, which significantly increases its highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap upon passivation. Solvent effects decrease the band gap difference between the passivated and nonpassivated nanoparticles, the maximum of the absorption spectra being blue-shifted around 20 nm by the effect of the ligands. Overall, calculations show that flexible surface cadmium sites are responsible for the appearance of mid-gap states that are partially localized on the most reconstructed regions of the nanoparticle that can be controlled through appropriate ligand adsorption.

Synchronous Metal Rearrangement on Two-Dimensional Equatorial Surfaces of Au-Cu Alloy Nanoclusters.

Understanding the growth of nanoclusters and the relationship between structure-activity depends on the precise arrangement of metals on their surface. In this work, we realized the synchronous rearrangement of metal atoms on the equatorial plane of Au-Cu alloy nanoclusters. Upon adsorption of the phosphine ligand, the Cu atoms on the equatorial plane of the Au52Cu72(SPh)55 nanocluster are irreversibly rearranged. The whole metal rearrangement process can be understood from a synchronous metal rearrangement mechanism initiated by the adsorption of the phosphine ligand. Furthermore, this metal rearrangement can effectively improve the efficiency of A3 coupling reactions without increasing the amount of catalyst.

Pd/Chitosan Nanoparticle Catalysts Prepared by Solid Mortar Grinding for Hydrogenation of Nitroarenes

Herein, we report a rational and highly sustainable strategy for the gram-scale synthesis of solid chitosan polymer-supported palladium nanoparticles (Pd/Chit) without the use of toxic solvents or expensive purification processes. Pd nanoparticles (NPs) are deposited onto a chitosan polymer using both ascorbic acid and NaOH. The former served as a mild reducing agent in the conversion of PdCl2 to Pd NPs, and the latter was crucial in anchoring the resulting Pd NPs to the chitosan support during solid grinding. The combination of ligand adsorption kinetics measurements and Langmuir adsorption isotherm studies of Pd/Chit reveals that the deposited Pd NPs have a higher available surface area and a large number of accessible active sites, which is in sharp contrast with other Pd NP catalysts reported using solution methods. As a result, in the presence of NaBH4 as a hydrogen source, the Pd/Chit demonstrated enhanced catalytic activity for the reduction of a range of nitroarenes into corresponding amines. Furthermore, a kinetics investigation of the reduction of nitroarenes under optimal reaction conditions showed that Pd/Chit has substantially lower activation energy than other reported Pd NP catalysts. Because of the novel interface structure at the Pd–chitosan site as well as the greater number of accessible active sites at the Pd NP sites, the Pd/Chit possesses excellent catalytic activity and selectivity. The development of more renewable biopolymer-supported metal catalysts for heterogeneous catalysis may therefore be encouraged by the present scalable solid-state method for the sustainable synthesis of Pd/Chit catalysts.

Complex ligand adsorption on 3D atomic surfaces of synthesized nanoparticles investigated by machine-learning accelerated ab initio calculation.

Nanoparticle surfaces are passivated by surface-bound ligands, and their adsorption on synthesized nanoparticles is complicated because of the intricate and low-symmetry surface structures. Thus, it is challenging to precisely investigate ligand adsorption on synthesized nanoparticles. Here, we applied machine-learning-accelerated ab initio calculation to experimentally resolved 3D atomic structures of Pt nanoparticles to analyze the complex adsorption behavior of polyvinylpyrrolidone (PVP) ligands on synthesized nanoparticles. Different angular configurations of large-sized ligands are thoroughly investigated to understand the adsorption behavior on various surface-exposed atoms with intrinsic low-symmetry. It is revealed that the ligand binding energy (Eads) of the large-sized ligand shows a weak positive relationship with the generalized coordination number . This is because the strong positive relationship of short-range direct bonding (Ebind) is attenuated by the negative relationship of long-range van der Waals interaction (EvdW). In addition, it is demonstrated that the PVP ligands prefer to adsorb where the long-range vdW interaction with the surrounding surface structure is maximized. Our results highlight the significant contribution of vdW interactions and the importance of the local geometry of surface atoms to the adsorption behavior of large-sized ligands on synthesized nanoparticle surfaces.

Defined Coadsorption of Prostate Cancer Targeting Ligands and PEG on Gold Nanoparticles for Significantly Reduced Protein Adsorption in Cell Media

A study on the surface chemistry of gold nanoparticles (AuNPs) utilizing gel electrophoresis is presented. The molecular design of targeting and stabilizing PEG ligands allows one to combine them in mixed ligand layers with control of relative composition. For all tested targeting and control ligands, coadsorption of PEG significantly reduces protein adsorption and matrix effects of cell media as compared to conjugates without PEG. Introducing carboxylic acid groups into the PEG ligand layer does not lead to increased protein adsorption as shown with carboxylic acid terminated PEG ligands. The controlled adsorption of PEG ligands with different molecular weights is used to disentangle the effects of particle charge and hydrodynamic diameter. Taken together, this study provides directions for the functionalization of nanoparticles to obtain conjugates which are well-defined in terms of composition and colloidally stable in complex media. This is in particular relevant for targeting applications and cell experiments.