Charge transfer (CT) is governed by complex multiscale dynamics sensitive to environmental factors. In molecules, charge state and vibrational effects shape energy levels, charge distribution, and reactivity, thereby controlling CT efficiency. Quantifying these contributions in CT is experimentally challenging, as vibrational effects remain difficult to isolate due to limits in precision, sensitivity, and stability. In such context, the original Marcus theory, often lacks the refinement required to accurately capture CT rates in complex environments, necessitating new approaches that incorporate vibronic effects. Here, we examine a non-covalent H2TPP dyad on a semi-insulating CaF2/Si(100) surface. Using a low-temperature (9 K) scanning tunneling microscope (STM), we generate tunneling electrons that trigger CT events by creating locally cationic states while activating transient vibronic modes at specific molecular sites in one fragment. This initiates a meso N tautomerization serving as a CT signature in the second fragment. By tuning the tunnel electron energy, CT rates measurements reveal a periodic modulation. Quantitative analysis with the Marcus-Levich-Jortner model identifies key reorganization energies and resonant vibronic modes, while DFT provides complementary conformational and vibrational insights. Extending the Marcus-Antoniewicz models to explicit reaction coordinates reveals that CT is governed by the interplay between electronic and vibronic contributions, establishing surface-supported systems as a model framework.

Integrating nanoscale optoelectronic functions is vital for applications such as optical emitters, detectors, and quantum information. Lanthanide atoms show great potential in this endeavor due to their intrinsic transitions. Here, we investigate Er adatoms on Si(100)-2×1 at 9 K using a scanning tunneling microscope (STM) coupled to a tunable laser. Er adatoms display two main adsorption configurations that are optically excited between 800 and 1200 nm while the STM reads the resulting photocurrents. Our spectroscopic method reveals that various photocurrent signals stem from the bare silicon surface or Er adatoms. Additional photocurrent peaks appear as the signature of the Er adatom relaxation, triggering efficient dissociation of nearby trapped excitons. Calculations using density functional theory with spin-orbit coupling correction highlight the origin of the observed photocurrent peaks as specific 4f→4f or 4f→5d transitions. This spectroscopic technique can facilitate optoelectronic analysis of atomic and molecular assemblies by offering insight into their intrinsic quantum properties.

This article presents a study concerning the charge state control of single iron-tetraphenyl porphyrins (FeTPP) molecules when adsorbed on a semi-insulating monolayer of CaF2/Si(100) surface. The charge state of the FeTPP molecule is regulated by employing tunneling electrons from a low-temperature scanning tunneling microscope (STM) operating at 9 K. We show that once the charge is loaded into the FeTPP molecule, the molecule can be laterally manipulated across the surface without losing its charge state. The charge state change is reversible and the FeTPP molecule can be restored, at will, to its initial neutral state. A precise analysis of the STM topographies and dI/dV curves acquired on the FeTPP molecule before and after the electronic charge loading allows mapping the spatial charge state variations in the molecule as well as a conductance hysteresis effect, indicating the formation of an anion. Numerical simulation based on the density functional theory exploiting the virtual crystal approximation (VCA) method allows reproducing the trends of our experimental results and shows that the change in charge state affects specific areas of the molecule. Our theoretical investigations suggest that the molecular charge state variations can be monitored via STM topographies treatment and its local density of state distribution. This information can be related to the spatial distribution of the magnetic moment within the FeTPP molecule while the delocalization of the charge appears to depend on the total spin state of the central iron atom.

Ivermectin is an antiparasitic drug that results in the death of the targeted parasites using several mechanical actions. While very well supported, it can induce in rare cases, adverse effects including coma and respiratory failure in case of overdose. This problem should be solved especially in an emergency situation. For instance, the first pandemic of the 21th century was officially declared in early 2020, and while several vaccines around the worlds have been used, an effective treatment against this new strain of coronavirus, better known as SARS-CoV-2, should also be considered, especially given the massive appearance of variants. From all the tested therapies, Ivermectin showed a potential reduction of the viral portability, but sparked significant debate around the dose needed to achieve these positive results. To answer this general question, we propose, using simulations, to show that the nanovectorization of Ivermectin on BN oxide nanosheets can increase the transfer of the drug to its target and thus decrease the quantity of drug necessary to cope with the disease. This first application could help science to develop such nanocargo to avoid adverse effects. Communicated by Ramaswamy H. Sarma

The use and the study of semi-insulating layers on metals and semiconductors surfaces have found continuous interest in the past decades. So far, the control of the sizes and growth location of the insulating islands on the substrate is either ill-defined or usually constrained to the use of evaporation masks which size can easily exceed tenth of nanometers. Here, we show that it is possible to grow self-organized periodically spaced thin ribbons of semi-insulating stripes on the bare Si(100) surface. The epitaxial growth of these structures is obtained by the evaporation of CaF_2 molecules on the silicon surface with a coverage of 1.2 monolayers. They are investigated via scanning tunneling techniques at low temperature (9K). The obtained ribbons exhibit a surface bandgap of 3.2 eV as well as a resonant state at the central part of the ribbons at 2.0 eV below the Fermi level energy. The use of the density functional theory allows suggesting a model structure of the observed ribbons and reproducing the experimental STM topographies. The formation of the thin ribbons is discussed and we point out the influence of the mechanical forces inside and between the structures that may influence their periodicity.

Since 2020, the world is facing the first global pandemic of 21st century. Among all the solutions proposed to treat this new strain of coronavirus, named SARS-CoV-2, the vaccine seems a promising way but the delays are too long to be implemented quickly. In the emergency, a dual therapy has shown its effectiveness but has also provoked a set of debates around the dangerousness of a particular molecule, hydroxychloroquine. In particular, the doses to be delivered, according to the studies, were well beyond the acceptable doses to support the treatment without side effects. We propose here to use all the advantages of nanovectorization to address this question of concentration. Using quantum and classical simulations we will show in particular that drug transport on boron nitrogen oxide nanosheets increases the effectiveness of the action of these drugs. This will definitely allow to decrease the drug quantity needing to face the disease.

The synthesis of tetraphenylporphyrin erbium(III) acetylacetonate (acac) complexes is realized and their properties studied at the nanoscale when adsorbed on a semi-insulating CaF2/Si(100) surface. Our findings reveal that the ErTPP-(acac) molecules can adsorb in two main on-site conformations. Following precisely located dI/dV measurements at various specific positions [phenyls, pyrroles, and Er-(acac)], the relative locations of the Er cation and the apical ligand (acac) can be deciphered for each observed conformation. Hence, one of the adsorbate conformations presents the acac ligand parallel to the porphyrin plane with the Er atom outside the macrocycle plane. The second conformation is related to what is known in the gas phase, where the acac ligand is oriented vertically on top of the Er atom. This work is combined with a theoretical investigation that uses density functional theory methods to bring into light details of the two observed conformations. Additional proofs of our discoveries are related to the vibrational excitations of ErTPP-(acac). A comparison with a theoretical estimation of the vibrational modes reveals how the electronic resonance near the valence-band edge of the insulting layer is suitable to distinguish between the two adsorbed conformations.

The ability to precisely control the electronic coupling/decoupling of adsorbates from surfaces is an essential goal. It isimportant for fundamental studies not only in surface science but alsoin several applied domains including, for example, miniaturizedmolecular electronic or for the development of various devices suchas nanoscale biosensors or photovoltaic cells. Here, we provide atomic-scale experimental and theoretical investigations of a semi-insulatinglayer grown on a silicon surface via its epitaxy with CaF2. We showthat, following the formation of a wetting layer, the ensuing organizedunit cells are coupled to additional physisorbed CaF2molecules,periodically located in their surroundings. This configuration shapesthe formation of ribbons of stripes that functionalize the semi-conductor surface. The obtained assembly, having a monolayerthickness, reveals a surface gap energy of 3.2 eV. The adsorption of iron tetraphenylporphyrin molecules on the ribbons of stripes is used to estimate the electronic insulating properties of thisstructure via differential conductance measurements. Density functional theory (DFT) including several levels of complexity(annealing, DFT +U, and nonlocal van der Waals functionals) is employed to reproduce our experimental observations. Ourfindings offer a unique and robust template that brings an alternative solution to electronic semi-insulating layers on metal surfacessuch as NaCl. Hence, CaF2/Si(100) ribbon of stripe structures, whose lengths can reach more than 100 nm, can be used as aversatile surface platform for various atomic-scale studies of molecular devices.

We present a theoretical study of two different zinc phthalocyanine molecules, the 2-aminoethoxy-ZnPc (ZnPc-NH) and ZnPc-Lys molecules, covalently anchored on a graphene nanoflake to increase the stability of the system. By means of density functional theory calculations, we determine the atomic structure of the molecule/graphene nanoflake systems. Then, time-dependent density functional theory calculations show that the optical properties of the two molecules are preserved in water plus salt conditions, which is crucial for photodynamic therapy applications. In the case of the ZnPc-NH molecule, molecular dynamics (MD) simulations show that, whatever the chosen conformation, the adsorbed molecule lies on the substrate, which seems to be more favorable at the approach of the cell membrane. On the contrary, the three long arms of the ZnPc-Lys molecule allow to enhance the solubility and avoid molecule aggregation, but make the membrane approach harder. Finally, a balance between the diffusion of the ZnPc/graphene nanoflake system toward the membrane cell and the solubility, both related to the ligand length, should be found to optimize the PDT efficiency.

Reactions between the antibacterial fluoroquinolone agent ciprofloxacin (CIP) and organic hydrophilic nanoflakes (graphene oxide and boron nitride oxide) have been studied in aqueous medium using density functional theory (DFT), time-dependent density functional theory (TD-DFT), and molecular dynamics (MD) simulations. We found that CIP molecules in π-π electron donor–acceptor (EDA) reaction preserve their optical properties in water when adsorbed on hydrophilic nanoflakes. Moreover, MD calculations aimed at studying the diffusive translocation of CIP to lipid membrane showed that the choice of the hydrophilic nanovectors is primordial to stabilize the molecule on the cellular membrane and improve cytotoxic effects.

The ability to precisely control the electronic coupling/decoupling of adsorbates from surfaces is an essential goal. It is important for fundamental studies not only in surface science but also in several applied domains including, for example, miniaturized molecular electronic or for the development of various devices such as nanoscale biosensors or photovoltaic cells. Here, we provide atomic-scale experimental and theoretical investigations of a semi-insulating layer grown on a silicon surface via its epitaxy with CaF2. We show that, following the formation of a wetting layer, the ensuing organized unit cells are coupled to additional physisorbed CaF2 molecules, periodically located in their surroundings. This configuration shapes the formation of ribbons of stripes that functionalize the semiconductor surface. The obtained assembly, having a monolayer thickness, reveals a surface gap energy of ∼3.2 eV. The adsorption of iron tetraphenylporphyrin molecules on the ribbons of stripes is used to estimate the electronic insulating properties of this structure via differential conductance measurements. Density functional theory (DFT) including several levels of complexity (annealing, DFT + U, and nonlocal van der Waals functionals) is employed to reproduce our experimental observations. Our findings offer a unique and robust template that brings an alternative solution to electronic semi-insulating layers on metal surfaces such as NaCl. Hence, CaF2/Si(100) ribbon of stripe structures, whose lengths can reach more than 100 nm, can be used as a versatile surface platform for various atomic-scale studies of molecular devices.

We studied the behavior of doxorubicin (DOX; an anticancer drug) molecules loaded on a boron nitride oxide nanosheet (BNO-NS) using the density functional theory (DFT), time-dependent density functional theory (TDDFT), and molecular dynamic (MD) simulation methods. We found that DOX molecules in pi-pi or covalent interaction with BNO-NS preserve their optical properties in water. Moreover, the BNO-NS vector allowed stabilizing the DOX molecules on a cellular membrane contrary to isolated DOX that randomly moved in the solvent box without any interaction with the cell membrane. From these results, we conclude that hydrophilic BNO-NS represents a good candidate for DOX molecule transport and stabilization near a cell membrane. In this drug delivery system, the choice of BNO-NS as nanovector is important because it allows delivering an elevated therapeutic dose directly on the cancer cell target without hindrance of the DOX payload.

The confinement of anticancer carboplatin molecules (CBPT) in boron nitride nanotubes (BNNTs) with various sections was studied by means of density functional theory and molecular dynamic simulations. We show that the molecular insertion in BNNT is favored depending on the tube radius. The range of the energy adsorption varied from −1 eV to −2 eV depending on BNNT dimension. We also determined the critical diameter for the possible vectorization of the anticancer molecule. Indeed, the hydrophobicity of small BNNT radius R < 5.5 Å) is so large that CBPT encapsulation is impossible to achieve. On the contrary, a larger radius could offer an ideal situation to enhance drug delivery and allow a progressive release of the therapeutic near its target. Comparison with carbon nanotubes allowed us to draw conclusions on the best adapted nanovector for CBPT.

The controlled motion of magnetic impurities on semiconductor (SC) surfaces is of crucial importance for atomic scale magnetic devices. Still challenging because of their strong reactivity with SCs, magnetic impurities are usually studied in bulk SCs, thus preventing their manipulation. Here, we show that a single Co adatom can be steadied on the bare Si(100)-2 X 1 surface in a pedestal configuration at low temperature, 9 K, and moved along the reconstructed silicon dimer rows via the use of a scanning tunneling microscope. The electronic characteristics of the Co adatom and its surroundings are investigated via topography and dI/dV measurements. Our findings reveal that the Si Co bonding involves hybridization between the Si-p and the Co-p(x)p(y) orbitals. This configuration indicates that the Co-d orbitals remain weakly hybridized with the silicon atoms. These results are supported by density functional theory calculations where the role of the As dopant is discussed as well as the surface reconstruction. Therefore, we show that the motion direction of the Co adatom can be influenced by the surrounding c(4 X 2) or p(2 X 2) surface reconstruction phases, thus opening future interesting magnetic applications.

Cytotoxicity of cationic (NHC)Cu(I) complexes bearing 2,2′-dipyridylamine (dpa) type ligands has been evaluated toward 4 cancer cell lines, and compared to the one of neutral (NHC)Cu(I) complexes. The high cytotoxicity of these novel cationic (NHC)Cu(I) complexes, combined with the straightforward synthesis, and versatility of dpa type ligands may offer new prospects in cancer research, toward the development of novel carrier linked prodrugs.

In this study, the self-assembled molecular network and electronic properties of Ni-phthalocyanine (NiPc) molecules on monolayer graphene (MLG)/6H-SiC(0001) were studied by room temperature Scanning Tunnelling Microscopy (STM) and Density Functional Theory (DFT) calculations. In this study, a very weak electronic coupling between the graphene and the NiPc molecules is found. This is due to the very small charge transfer of only 0.035e- per molecule. The weak molecule-graphene interaction has two observable consequences: sub-molecular resolution was obtained in the STM spectroscopy at room-temperature with the molecules adsorbed directly on the graphene, and the occupied and unoccupied molecular resonance peaks were observed to shift their position in energy as a function of the tip-surface distance. This is due to the temporary local charging (either positive or negative) that is achieved by decreasing the surface voltage under the STM tip. This may have important consequences for future studies of the opto-electronic properties of such hybrid graphene-molecule systems.

Controlling the properties of quantum dots at the atomic scale, such as dangling bonds, is a general motivation as they allow studying various nanoscale processes including atomic switches, charge storage, or low binding energy state interactions. Adjusting the coupling of individual silicon dangling bonds to form a 2D device having a defined function remains a challenge. Here, we exploit the anisotropic interactions between silicon dangling bonds on n-type doped Si(100):H surface to tune their hybridization. This process arises from interactions between the subsurface silicon network and dangling bonds inducing a combination of Jahn-Teller distortions and local charge ordering. A three-pointed star-shaped device prototype is designed. By changing the charge state of this device, its electronic properties are shown to switch reversibly from an ON to an OFF state via local change of its central gap. Our results provide a playground for the study of quantum information at the nanoscale.

We propose a new approach to improving photodynamic therapy (PDT) by transporting zinc phthalocyanine (ZnPc) in biological systems via a graphene nanoflake, to increase its targeting. Indeed, by means of time-dependent density functional theory simulations, we show that the ZnPc molecule in interaction with a graphene nanoflake preserves its optical properties not only in a vacuum but also in water. Moreover, molecular dynamic simulations demonstrate that the graphene nanoflake/ZnPc association, as a carrier, permits one to stabilize the ZnPc/graphene nanoflake system on the cellular membrane, which was not possible when using ZnPc alone. We finally conclude that the graphene nanoflake is a good candidate to transport and stabilize the ZnPc molecule near the cell membrane for a longer time than the isolated ZnPc molecule. In this way, the choice of the graphene nanoflake as a nanovector paves the way to ZnPc PDT improvement.

Abstract Motivated by the widely reported anticancer activity of parthenolides and their derivatives, a series of new substituted parthenolides was efficiently synthesized. Structural modifications were performed at the C-9 and C-13 positions of 9α- and 9β-hydroxyparthenolide, which were isolated from the aerial parts of Anvillea radiata. Twenty-one derivatives were synthesized and evaluated for their in vitro cytotoxic activity against HS-683, SK-MEL-28, A549, and MCF-7 human cancer cell lines using the MTT colorimetric assay. Among the derivatives, seven exhibited excellent activity compared to 5-fluorouracil and etoposide against the four cell lines tested, with IC50 values ranging from 1.1 to 9.4 µM.

The diastereoselective Michael addition of TmsN 3 to parthenolide (I) gives the key intermediate (III), which undergoes regioselective 1,3-dipolar cycloaddition with various alkynes affording triazole derivatives.