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[Display omitted] • Cd chemical adsorption on Ag n @Cdots (n = 1–3) surfaces was studied. • Stability and electronic structure are systematically analyzed using DFT. • Cd sensing is feasible based on band gap changes after Cd adsorption. • The bond study shows that Cd/Ag n clusters remain anchored on functionalized Cdot. Density functional theory (DFT) calculations were carried out to evaluate the interaction between a Cd atom and silver clusters supported on functionalized and non-functionalized carbon dots (Cdots) surfaces modeled by coronene. The stability and electronic structure is systematically studied through energy, density of states and frontier orbitals analysis in order to establish the changes in the electronic structure and the feasibility of Cd adsorption. Additionally, a bonding investigation is also performed with the aim to determine if the Cd-Ag bond occurs and to verify if after this process the silver clusters remain anchored on Cdots surfaces. This study was also complemented through the calculation of chemical descriptors that allow inferring the electron affinity of the systems. Moreover, sensitivity parameters were evaluated with the aim to characterize the capabilities of the composite silver and Cdots structures for their application on the detection of Cd. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cdots surfaces were modeled by coronene and functionalized coronene. • Ag n (n = 1–3) small cluster interaction with Cdot was studied using DFT calculations. • Ag and O orbitals overlap, increasing Ag n and Cdot chemical interaction. • Epoxi group improves silver anchor enhancing the charge transfer to support. Density functional theory (DFT) calculations were carried out to evaluate the interaction of silver nanostructures on non-functionalized and functionalized carbon dots (Cdots) surfaces. Coronene and coronene with an epoxy functional group are used to model the Cdots surfaces and small size clusters of Ag n (n = 1.0.3) are employed to represent the silver nanostructures. A theoretical study of the stability and structure of the composite Ag@Cdots material is performed. The essential role of oxygenated functional groups of Cdots functionalized surfaces to attach silver clusters is systematically evaluated with focus on the understanding of the mechanism intervening on the Cdots surfaces and silver nanostructures interaction. The electronic structure and charge distribution are analyzed. Additionally a bonding investigation is also developed as an attempt to characterize the most relevant bonds contributing to anchor silver nanostructures on Cdots surfaces. [ABSTRACT FROM AUTHOR]

Silica based materials find applications as excipients and particularly as drug delivery agents for pharmaceutical drugs. Their performance can be crucially affected by surface treatments, as it can modify the adsorption (and release) of these formulations. The role of surface modification on the features of 4-formaminoantipyrine (FAA) adsorbed on β -cristobalite (001) surface is studied by means of simulations based on the Density Functional Theory (DFT). Starting from the results of FAA in interaction with a dehydroxylated surface; a fully hydroxylated surface and a functionalized surface with benzalkonium chloride (BC) surfactant have been added to study the configurational landscape. Calculations suggest that the trend for FAA preferential adsorption on silica surfaces is: dehydroxylated > hydroxylated > BC-functionalized. The potential for hydrogen bonding causes the main contribution to the bonding while dispersion forces present an additional contribution independently of whether the drug is hydrogen-bonded or BC-bonded to the surface. Adsorption takes mainly place through nitrogen atoms in the heterocyclic ring, the carbonyl and amine functional groups. Associated mode’s shifts and concurrent changes in bond length are also observed showing accordance between electronic and geometrical structure results. BC surfactant reduces the number of formed H-bonds and lowers the attractive molecule-surface interaction being it useful to prevent particle agglomeration and could favor drug release in therapies that requires faster but controlled delivery. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • SiO 2 (0 0 1) surface allows nedaplatin chemical attachment without drug degradation. • The adsorption strength follows the trend deshydrated > hydrated > TMS-functionalized. • H-bonds have vital influence in adsorption mechanism on hydrated and TMS-functionalized silica. • Nedaplatin is stabilized on deshydrated silica by N O, O O bonds and H partial dissociation. Abstract The interaction of nedaplatin drug with modified SiO 2 (0 0 1) surfaces has been investigated within the framework of Density Functional Theory. Nedaplatin molecule is adsorbed spontaneously onto silica surfaces. Silica surface prevents drug degradation allowing the chemical attachment without any impact on the drug structure itself. The nedaplatin sorption is mainly governed by H-bonding interactions on hydrated and trimethylsilane-functionalized surfaces, while the drug is major stabilized by N O, O O interactions and H partial dissociation on dehydrated silica. The differences on the adsorption strength could be used in future studies to control the drug release, developing delivery silica systems according therapy requirements. [ABSTRACT FROM AUTHOR]

Silica-based mesoporous materials have been recently proposed as an efficient support for the controlled release of a popular anticancer drug, 5-fluorouracil (5-FU). Although the relevance of this topic, the atomistic details about the specific surface-drug interactions and the energy of adsorption are almost unknown. In this work, theoretical calculations using the Vienna Ab-initio Simulation Package (VASP) applying Grimme's—D2 correction were performed to elucidate the drug–silica interactions and the host properties that control 5-FU drug adsorption on β-cristobalite (1 1 1) hydroxylated surface. This study shows that hydrogen bonding, electron exchange, and dispersion forces are mainly involved to perform the 5-FU adsorption onto silica. This phenomenon, revealed by favorable energies, results in optimum four adsorption geometries that can be adopted for 5-FU on the hydroxylated silica surface. Silanols are weakening in response to the molecule approach and establish H-bonds with polar groups of 5-FU drug. The final geometry of 5-FU adopted on hydroxylated silica surface is the results of H-bonding interactions which stabilize and fix the molecule to the surface and dispersion forces which approach it toward silica (1 1 1) plane. The level of hydroxylation of the SiO 2 (1 1 1) surface is reflected by the elevated number of hydrogen bonds that play a significant role in the adsorption mechanisms. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cyclopropane adsorbs parallel to the Pt (111) surface. [•] The Bridge adsorption site is 0.50eV more stable than the Top site. [•] The interaction of c-C3H6 with the metallic surface is week (less than 1eV). [•] The main bonding interaction comes from the hydrogen atoms pointing toward the surface. [•] Pt 5pz orbitals are the major contributions to the overall adsorbate-surface bonding. [ABSTRACT FROM AUTHOR]

Abstract: In the present work we analyzed the geometry and the chemical interactions of c-C5H8 after adsorption on a semiconductor surface: Si(001), by density functional theory calculations (DFT). Using a slab model, we studied the changes in the atomic and orbital interactions corresponding to the system. We examined overlap population values for specifics bonds during the adsorption. We considered two cases, the cyclopentene adsorption on dimers on the surface and on dimer vacancies on Si(001). We found an average h name="sbnd" />Si distance of 1.96Å on dimer Sin average Hlyph name="sbnd" />Cce:glyph name="dbnd" />Cces of 1.59Å, 1.83Å, and 1.57Å respectively on dimer vacancies. We also studied the density of states (DOS) and the crystal orbital overlap populations (OPDOS) corresponding to Clyph name="sbnd" />Si, C The main contribution to the adsorption are the Cbond in both cases and the H’s belonging to this double bonds in the case of adsorption on dimer vacancies (DV). The orbital contribution includes participation of the 2p z orbitals corresponding to C atoms and 3p z orbitals corresponding to Si in the case of adsorption on Si(001)-2×1 surface, and 2p x , 2p y , and 2p z orbitals corresponding to C atoms, and the 3p x , 3p y , and 3p z orbitals corresponding to Si for cyclopentene adsorption on DV. The adsorption of cyclopentane on Si(001)-2×1 produce several vibrational frequencies similar to that of c-C5H10, a molecule with sp3 hybridization. After C5H8 adsorption no frequencies coming from a Ce computed which also support the idea of re-hybridization. On DV the Sicy increase 35cm−1, indicating a stronger bond with the surface. [ABSTRACT FROM AUTHOR]

Abstract: In this work we analyzed the geometry and the chemical interactions for c-C5H8 adsorption on Ge (001), using density functional theory calculations (DFT). We examined the changes in the atomic interactions using a slab model. We considered two cases, the cyclopentene adsorption on Ge(001) and on dimer vacancies on the surface. We found an average distance H–Ge, –C–Ge and Ge of 1.50, 1.70 and 1.65Å, respectively, on dimer vacancies; and an average Ge distance of 2.05Å on Ge–Ge dimer. We also computed the density of states (DOS) and the DOS weighted overlap populations (OPDOS) corresponding to C–C, C–Ge, C–H, and Ge–Ge bonds. During adsorption the main contribution are the Cbond in both cases, and the next C and the H''s belonging to this bonds in the case of adsorption on dimer vacancies. The orbital contribution includes participation of the 2py and 2pz orbitals corresponding to unsaturated C atoms, 2pz corresponding to side saturated C, and the 4p orbitals of Ge for the adsorption on dimer vacancies; 2s and 2pz orbitals corresponding to double bond C atoms, 4s and 4pz orbitals of Ge for the adsorption on Ge(001). [Copyright &y& Elsevier]

[Display omitted] • Solution-state NMR spectroscopy suggests PDs and/or PCDs Cdots structures. • DFT calculations propose a core–shell structure which explains experimental features. • The methodology employed could structurally characterize other kinds of Cdots. A combination of experimental and theoretical results was used for the structural characterization of Carbon dots (Cdots). The synthesis of the Cdots was performed using glucose as a precursor and via the microwave method ("bottom-up" route) as a simple and environmentally friendly method. The experimental data obtained by UV–visible, fluorescence, IR and solution-state NMR spectroscopy techniques were correlated with density functional theory calculations results. Particularly, the results obtained by solution-state NMR spectroscopy suggested Cdots structures of Polymer dots (PDs) and/or polymer Carbon dots (PCDs) kind. PDs are characterized by being formed only of polymer structures and PCDs by being formed of a small carbonized core surrounded by polymer structures. Calculations allow us to predict the UV–visible absorption and IR spectra behavior of the species detected by the NMR technique, and propose a structure that can explain the experimentally observed features and infer the presence or absence of a carbon core in the proposed structures. Density of states curves were used to analyze and interpret the theoretical spectra peaks. Additionally, a calculation of the IR spectra for the models proposed, was performed. The complement of experimental and theoretical results represents a useful tool for the structural characterization of Cdots. [ABSTRACT FROM AUTHOR]