Functional Organophosphonate Interfaces for Nanotechnology: A Review

Nanomolecularly-induced Effects at Titania/Organo-Diphosphonate Interfaces for Stable Hybrid Multilayers with Emergent Properties

Nanoscale hybrid inorganic-organic multilayers are attractive for accessing emergent phenomena and properties through superposition of nanomolecularly-induced interface effects for diverse applications. Here, we demonstrate the effects of interfacial molecular nanolayers (MNLs) of organo-diphosphonates on the growth and stability of titania nanolayers during the synthesis of titania/MNL multilayers by sequential atomic layer deposition and single-cycle molecular layer deposition. Interfacial organo-diphosphonate MNLs result in ∼20-40% slower growth of amorphous titania nanolayers and inhibit anatase nanocrystal formation from them when compared to amorphous titania grown without MNLs. Both these effects are more pronounced in multilayers with aliphatic backbone-MNLs and likely related to impurity incorporation and incomplete reduction of the titania precursor indicated by our spectroscopic analyses. In contrast, both MNLs result in two-fold higher titania nanolayer roughness, suggesting that roughening is primarily due to MNL bonding chemistry. Such MNL-induced effects on inorganic nanolayer growth rate, roughening, and stability are germane to realizing high-interface-fraction hybrid nanolaminate multilayers.

Hybrid Materials Based on Imidazo[4,5-b]porphyrins for Catalytic Oxidation of Sulfides

Heterogenized metalloporphyrin catalysts for oxidation reactions are extensively explored to improve chemical production. In this work, manganese meso-tetraarylporphyrins were immobilized on hydrated mesoporous titanium dioxide (SBET = 705 m2 g−1) through carboxylate or phosphonate anchoring groups separated from the macrocycle by the 2-arylimidazole linker fused across one of the pyrrolic rings of the macrocycle. The element composition of two mesoporous hybrid materials thus obtained were investigated and the integrity of the immobilized complexes was shown by different physicochemical methods. Finally, the catalytic efficiency of the more stable material Mn(TMPIP)/TiO2 with the phosphonate anchor was evaluated in the selective oxidation of sulfides to sulfoxides by molecular oxygen in the presence of isobutyraldehyde (IBA). The heterogenized complex has shown excellent catalytic activity exhibiting a turnover (TON) of ~1100 in a single catalytic run of the sulfoxidation of thioanisole. The catalyst was successfully reused in seven consecutive catalytic cycles.

Molecular Orientation of -PO3H2 and -COOH Functionalized Dyes on TiO2, Al2O3, ZrO2, and ITO: A Comparative Study

Modification of transparent metal oxide (MO_x) surfaces with organic monolayers is widely employed to tailor the properties of interfaces in organic electronic devices, and MO_x substrates modified with light-absorbing chromophores are a key component of dye-sensitized solar cells (DSSCs). The effects of an organic modifier on the performance of a MO_x-based device are frequently assessed by performing experiments on model monolayer|MO_x interfaces, where an "inert" MO_x (e.g., Al₂O₃) is used as a control for an "active" MO_x (e.g., TiO₂). An underlying assumption in these studies is that the structure of the MO_x-monolayer complex is similar between different metal oxides. The validity of this assumption was examined in the present study. Using UV-Vis attenuated total reflection spectroscopy, we measured the mean dipole tilt angle of 4,4'-(anthracene-9,10-diyl)bis(4,1-phenylene)diphosphonic acid (A1P) adsorbed on indium tin oxide (ITO), TiO₂, ZrO₂, and Al₂O₃. When the surface roughness of the MO_x substrate and the surface coverage (𝛤) of the A1P film were constant, the molecular orientation of A1P was the same on these substrates. The study was extended to 4,4'-(anthracene-9,10-diyl)bis(4,1-phenylene)dicarboxylic acid (A1C) adsorbed on the same group of MO_x substrates. The mean tilt angle of A1C and A1P films on ITO was the same, which is likely due the intermolecular interactions resulting from the high and approximately equal 𝛤 of both films. Comparing A1C films at the same 𝛤 on TiO₂ and Al₂O₃ having the same surface roughness, there was no difference in the mean tilt angle. MD simulations of A1C and A1P on TiO₂ produced nearly identical tilt angle distributions, which supports the experimental findings. This study provides first experimental support for the assumption that the structure of the MO_x-modifer film is the same on an "active" substrate vs. a "inert" control substrate.

Biofunctionalization of Porous Titanium Oxide through Amino Acid Coupling for Biomaterial Design

Porous transition metal oxides are widely studied as biocompatible materials for the development of prosthetic implants. Resurfacing the oxide to improve the antibacterial properties of the material is still an open issue, as infections remain a major cause of implant failure. We investigated the functionalization of porous titanium oxide obtained by anodic oxidation with amino acids (Leucine) as a first step to couple antimicrobial peptides to the oxide surface. We adopted a two-step molecular deposition process as follows: self-assembly of aminophosphonates to titanium oxide followed by covalent coupling of Fmoc-Leucine to aminophosphonates. Molecular deposition was investigated step-by-step by Atomic Force Microscopy (AFM) and X-ray Photoemission Spectroscopy (XPS). Since the inherent high roughness of porous titanium hampers the analysis of molecular orientation on the surface, we resorted to parallel experiments on flat titanium oxide thin films. AFM nanoshaving experiments on aminophosphonates deposited on flat TiO₂ indicate the formation of an aminophosphonate monolayer while angle-resolved XPS analysis gives evidence of the formation of an oriented monolayer exposing the amine groups. The availability of the amine groups at the outer interface of the monolayer was confirmed on both flat and porous substrates by the following successful coupling with Fmoc-Leucine, as indicated by high-resolution XPS analysis.

Selective Pd recovery from acidic leachates by 3-mercaptopropylphosphonic acid grafted TiO2: does surface coverage correlate to performance?

Modification of metal oxides with organophosphonic acids (PAs) provides the ability to control and tailor the surface properties. The metal oxide phosphonic acid bond (M-O-P) is known to be stable under harsh conditions, making PAs a promising candidate for the recovery of metals from complex acidic leachates. The thiol functional group is an excellent regenerable scavenging group for these applications. However, the research on organophosphonic acid grafting with thiol groups is very limited. In this study, four different metal sorbent materials were designed with different thiol surface coverages. An aqueous-based grafting of 3-mercaptopropylphosphonic acid (3MPPA) on mesoporous TiO₂ was employed. Surface grafted thiol groups could be obtained in the range from 0.9 to 1.9 groups per nm². The different obtained surface properties were studied and correlated to the Pd adsorption performance. High Pd/S adsorption efficiencies were achieved, indicating the presence of readily available sorption sites. A large difference in their selectivity towards Pd removal from a spend automotive catalyst leachate was observed due to the co-adsorption of Fe on the titania support. The highest surface coverage showed the highest selectivity (K _d: 530 mL g^-1) and adsorption capacity (Q _max: 0.32 mmol g^-1) towards Pd, while strongly reducing the co-adsorption of Fe on remaining TiO₂ sites.

Two Steady-State Adsorption Modes of Phosphonic Acids on Aluminum Surfaces

The phosphonic acid (PA) surface treatment on various metal substrates is of high industrial relevance, and the PA molecular structure significantly affects its quality. In this work, systematic variation of the PA molecular steric and electron environment helps discern two steady-state adsorption modes on an aluminum surface. The PA molecular structure was varied systematically, which included inorganic phosphorus acid, alkyl phosphonic acids, and phenyl phosphonic acids. To explore their in situ dynamics of adsorption/desorption on the electrochemically unstable aluminum, techniques such as electrochemical impedance spectroscopy and inductively coupled plasma optical emission spectrometry were employed. A range of different types of interfacial layers are formed on the aluminum surface, namely, from the dissolution-limiting physisorbed layer to a quasi-inhibiting chemisorbed layer on the aluminum surface in acidic (pH ≈ 2.2) solution. Presented findings establish the dynamic steady-state nature of this type of interface. They reveal fundamental relationships among adsorbent steric or electronic effects, the steady-state interface morphology, and the steady-state aluminum dissolution rate. The study brings also a more differentiated molecular structure-related description of the aluminum dissolution inhibition of PAs and relates it to molecular density functional theory calculations.

Conductance Switching in Liquid Crystal-Inspired Self-Assembled Monolayer Junctions

We present the prototype of a ferroelectric tunnel junction (FTJ), which is based on a self-assembled monolayer (SAM) of small, functional molecules. These molecules have a structure similar to those of liquid crystals, and they are embedded between two solid-state electrodes. The SAM, which is deposited through a short sequence of simple fabrication steps, is extremely thin (3.4 ± 0.5 nm) and highly uniform. The functionality of the FTJ is ingrained in the chemical structure of the SAM components: a conformationally flexible dipole that can be reversibly reoriented in an electrical field. Thus, the SAM acts as an electrically switchable tunnel barrier. Fabricated stacks of Al/Al₂O₃/SAM/Pb/Ag with such a polar SAM show pronounced hysteretic, reversible conductance switching at voltages in the range of ±2-3 V, with a conductance ratio of the low and the high resistive states of up to 100. The switching mechanism is analyzed using a combination of quantum chemical, molecular dynamics, and tunneling resistance calculation methods. In contrast to more common, inorganic material-based FTJs, our approach using SAMs of small organic molecules allows for a high degree of functional complexity and diversity to be integrated by synthetic standard methods, while keeping the actual device fabrication process robust and simple. We expect that this technology can be further developed toward a level that would then allow its application in the field of information storage and processing, in particular for in-memory and neuromorphic computing architectures.

Design, Fabrication, and Characterisation of a Label-Free Nanosensor for Bioapplications

In this paper, we present a hybrid semiconductor structure for biosensing applications that features the co-integration of nanoelectromechanical systems with the well-known metal oxide semiconductor technology. The proposed structure features an MOSFET as a readout element, and a doubly clamped beam that is isolated from the substrate by a thin air gap, as well as by a tunnel oxide layer. The beam structure is functionalised by a thin layer of biotargets, and the main aim is to detect a particular set of biomolecules, such as enzymes, bacteria, viruses, and DNA/RNA chains, among others. In here, a three-dimensional finite element analysis is performed in order to study the behaviour of the functionalised, doubly clamped beam. Preliminary results for the fabrication and characterisation processes show good agreement between the simulated and measured characteristics.

C-P bond formation of cyclophanyl-, and aryl halides via a UV-induced photo Arbuzov reaction: a versatile portal to phosphonate-grafted scaffolds

A new versatile method for the C–P bond formation of (hetero)aryl halides with trimethyl phosphite via a UV-induced photo-Arbuzov reaction, accessing diverse phosphonate-grafted arenes, heteroarenes and co-facially stacked cyclophanes under mild reaction conditions without the need for catalyst, additives, or base is developed. The UV-induced photo-Arbuzov protocol has a wide synthetic scope with large functional group compatibility exemplified by over 30 derivatives. Besides mono-phosphonates, di- and tri-phosphonates are accessible in good to excellent yields. Mild and transition metal-free reaction conditions consolidate this method's potential for synthesizing pharmaceutically relevant compounds and precursors of supramolecular nanostructured materials.

UV-induced C–P bond formation of aryl halides via photo Arbuzov reaction: a versatile portal to phosphonate-grafted scaffolds.

Modular Assembly of Vibrationally and Electronically Coupled Rhenium Bipyridine Carbonyl Complexes on Silicon

Hybrid inorganic/organic heterointerfaces are promising systems for next-generation photocatalytic, photovoltaic, and chemical-sensing applications. Their performance relies strongly on the development of robust and reliable surface passivation and functionalization protocols with (sub)molecular control. The structure, stability, and chemistry of the semiconductor surface determine the functionality of the hybrid assembly. Generally, these modification schemes have to be laboriously developed to satisfy the specific chemical demands of the semiconductor surface. The implementation of a chemically independent, yet highly selective, standardized surface functionalization scheme, compatible with nanoelectronic device fabrication, is of utmost technological relevance. Here, we introduce a modular surface assembly (MSA) approach that allows the covalent anchoring of molecular transition-metal complexes with sub-nanometer precision on any solid material by combining atomic layer deposition (ALD) and selectively self-assembled monolayers of phosphonic acids. ALD, as an essential tool in semiconductor device fabrication, is used to grow conformal aluminum oxide activation coatings, down to sub-nanometer thicknesses, on silicon surfaces to enable a selective step-by-step layer assembly of rhenium(I) bipyridine tricarbonyl molecular complexes. The modular surface assembly of molecular complexes generates precisely structured spatial ensembles with strong intermolecular vibrational and electronic coupling, as demonstrated by infrared spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy analysis. The structure of the MSA can be chosen to avoid electronic interactions with the semiconductor substrate to exclusively investigate the electronic interactions between the surface-immobilized molecular complexes.

Improvement of the froth flotation of LiAlO2 and melilite solid solution via pre-functionalization

In this work froth flotation studies with LiAlO₂ (lithium-containing phase) and Melilite solid solution (gangue phase) are presented. The system was optimized with standard collectors and with compounds so far not applied as collectors. Furthermore, the principle of self-assembled monolayers was introduced to a froth flotation process for the first time resulting in excellent yields and selectivities.

Functionalization and Characterization of Silicon Nanowires for Sensing Applications: A Review

Silicon nanowires are attractive materials from the point of view of their electrical properties or high surface-to-volume ratio, which makes them interesting for sensing applications. However, they can achieve a better performance by adjusting their surface properties with organic/inorganic compounds. This review gives an overview of the main techniques used to modify silicon nanowire surfaces as well as characterization techniques. A comparison was performed with the functionalization method developed, and some applications of modified silicon nanowires and their advantages on those non-modified are subsequently presented. In the final words, the future opportunities of functionalized silicon nanowires for chipless tag radio frequency identification (RFID) have been depicted.

Mechanofluorochromic Anthryl Phosphonate/Benzoic Acid Cocrystals with a Large Blue Shift: The Role of P=O⋅⋅⋅H Interactions

Organophosphonates have a rich and diverse chemistry, but their mechanofluorochromic features have rarely been documented. Herein, we report on cocrystals of anthranylphosphonate with (E)-4-(2-(anthracen-9-yl)vinyl)benzoic acid that exhibit reversible mechanofluorochromic properties with large blue shifts. Anisotropic grinding (or pressure of just 25 kPa) maintains the co-crystals emission features but leads to a pronounced 59 nm (2087 cm^-1 ) blue-shift. Such an impressive blue-shift for a cocrystal has not been reported to date. The underlying causes for the blue-shift were validated by X-ray diffraction (powder and single crystal) studies and Hirshfeld surface analysis. Twisted molecular conformations and P=O⋅⋅⋅ H/C=O⋅⋅⋅H/C⋅⋅⋅H noncovalent interactions afford molecular arrangements via slip-stacks with two different pitch angles and relatively larger interlayer distances. The new compound was established as a potential medium for optical recording and security display.

Phosphonic Acid Modified ZnO Nanowire Sensors: Directing Reaction Pathway of Volatile Carbonyl Compounds

Surface molecular transformations on nanoscale metal oxides are inherently complex, and directing those reaction pathways is still challenging but important for designing their various applications, including molecular sensing, catalysts, and others. Here, a rational strategy to direct a reaction pathway of volatile carbonyl compounds (nonanal: biomarker) on single-crystalline ZnO nanowire surfaces via molecular modification is demonstrated. The introduction of a methylphosphonic acid modification on the ZnO nanowire surface significantly alters the surface reaction pathway of nonanal via suppressing the detrimental aldol condensation reaction. This is directed by intentionally decreasing the probability of two neighboring molecular activations on the nanowire surface. Spectrometric measurements reveal the correlation between the suppression of the aldol condensation surface reaction and the improvement in the sensor performance. This tailored surface reaction pathway effectively reduces the operating temperature from 200 to 100 °C while maintaining the sensitivity. This is because the aldol condensation product ((E)-2-heptyl-2-undecenal) requires a higher temperature to desorb from the surface. Thus, the proposed facile strategy offers an interesting approach not only for the rational design of metal oxide sensors for numerous volatile carbonyl compounds but also for tailoring various surface reaction pathways on complex nanoscale metal oxides.

Contact Architecture Controls Conductance in Monolayer Devices

The architecture of electrically contacting the self-assembled monolayer (SAM) of an organophosphonate has a profound effect on a device where the SAM serves as an intermolecular conductive channel in the plane of the substrate. Nanotransfer printing (nTP) enabled the construction of top-contact and bottom-contact architectures; contacts were composed of 13 nm thin metal films that were separated by a ca. 20 nm gap. Top-contact devices were fabricated by assembling the SAM across the entire surface of an insulating substrate and then applying the patterned metallic electrodes by nTP; bottom-contact ones were fabricated by nTP of the electrode pattern onto the substrate before the SAM was grown in the patterned nanogaps. SAMs were prepared from (9,10-di(naphthalen-2-yl)anthracen-2-yl)phosphonate; here, the naphthyl groups extend laterally from the anthracenylphosphonate backbone. Significantly, top-contact devices supported current that was about 3 orders of magnitude greater than that for comparable bottom-contact devices and that was at least 100,000 times greater than for a control device devoid of a SAM (at 0.5 V bias). These large differences in conductance between top- and bottom-contact architectures are discussed in consideration of differential contact-to-SAM geometries and, hence, resistances.

Energy Conversion and Biocompatibility of Surface Functionalized Magnetite Nanoparticles with Phosphonic Moieties

Magnetite nanoparticles (MNPs) were synthesized using two distinctly different approaches, co-precipitation (CP) and thermal decomposition (TD), and further surface functionalized with organophosphonic ligands containing different numbers of phosphonic groups. We have shown that it is possible to fabricate flower-like assemblies of MNPs through TD at lower temperatures, whereas CP MNPs formed agglomerates of particles with broad size distribution and irregular shapes. The effect of the organophosphonic ligands on the heating efficiency of the TD and CP MNPs under dual mode stimulation (simultaneous action of AMF and NIR laser radiation) was studied for the first time. It was found that in the case of the cost-effective CP MNP synthesis surface functionalization with chosen phosphonic ligands leads to higher heating efficiency upon laser stimulation, whereas better performance of TD MNPs was found under the action of AMF due to the significant difference of nanoparticle properties. The biocompatibility of surface functionalized MNPs with organophosphonic ligands was evaluated through thorough studies of the metabolic activity of MNPs in normal human foreskin fibroblasts as well as oxidative stress induction and oxidation stress response which has not been previously reported for most of the organophosphonic moieties used in this study.

Interface Engineering in Organic Field-Effect Transistors: Principles, Applications, and Perspectives

Heterogeneous interfaces that are ubiquitous in optoelectronic devices play a key role in the device performance and have led to the prosperity of today's microelectronics. Interface engineering provides an effective and promising approach to enhancing the device performance of organic field-effect transistors (OFETs) and even developing new functions. In fact, researchers from different disciplines have devoted considerable attention to this concept, which has started to evolve from simple improvement of the device performance to sophisticated construction of novel functionalities, indicating great potential for further applications in broad areas ranging from integrated circuits and energy conversion to catalysis and chemical/biological sensors. In this review article, we provide a timely and comprehensive overview of current efficient approaches developed for building various delicate functional interfaces in OFETs, including interfaces within the semiconductor layers, semiconductor/electrode interfaces, semiconductor/dielectric interfaces, and semiconductor/environment interfaces. We also highlight the major contributions and new concepts of integrating molecular functionalities into electrical circuits, which have been neglected in most previous reviews. This review will provide a fundamental understanding of the interplay between the molecular structure, assembly, and emergent functions at the molecular level and consequently offer novel insights into designing a new generation of multifunctional integrated circuits and sensors toward practical applications.

Robust Polymer Nanocomposite Membranes Incorporating Discrete TiO2 Nanotubes for Water Treatment

Polyethersulfone (PES) is a polymeric permeable material used in ultrafiltration (UF) membranes due to its high thermomechanical and chemical stability. The hydrophobic nature of PES membranes renders them prone to fouling and restricts the practical applications of PES in the fabrication of water treatment membranes. The present study demonstrates a non-solvent-induced phase separation (NIPS) approach to modifying PES membranes with different concentrations of discrete TiO₂ nanotubes (TNTs). Zeta potential and contact angle measurements showed enhanced hydrophilicity and surface negative charge in TNTs/PES nanocomposite membranes compared to unmodified PES membranes. To discern the antifouling and permeation properties of the TNTs/PES membranes, steam assisted gravity drainage (SAGD) wastewater obtained from the Athabasca oil sands of Alberta was used. The TiO₂ modified polymer nanocomposite membranes resulted in a higher organic matter rejection and water flux than the unmodified PES membrane. The addition of discrete TNTs at 1 wt% afforded maximum water flux (82 L/m² h at 40 psi), organic matter rejection (53.9%), and antifouling properties (29% improvement in comparison to pristine PES membrane). An enhancement in fouling resistance of TNTs/PES nanocomposite membranes was observed in flux recovery ratio experiments.

Controlled grafting of dialkylphosphonate-based ionic liquids on γ-alumina: design of hybrid materials with high potential for CO2 separation applications

In this work we provide a detailed study on grafting reactions of various dialkylphosphonate-based ILs. Special attention has been devoted to a comprehensive investigation on how the nature of the anion and the organic spacer composition (hydrophilic or hydrophobic groups) could impact the grafting densities and bonding modes of phosphonate-based ILs anchored to γ-alumina (γ-Al₂O₃) powders. For the first time, the bonding of phosphonate-based ILs with only surface hexacoordinated aluminum nuclei was established using both solid-state ³¹P–²⁷Al D-HMQC and ³¹P NMR experiments. It has been demonstrated that the grafting of dialkylphosphonate-based ILs is competing with a hydrolysis and/or precipitation process which could be attractively hindered by changing the anion nature: bis(trifluoromethane)sulfonylimide anion instead of bromide. In additon, independently of the chosen spacer, similar reaction conditions led to equivalent grafting densities with different bonding mode configurations. The CO₂ physisorption analysis on both pure ILs and grafted ILs on alumina powders confirmed that the initial sorption properties of ILs do not change upon grafting, thus confirming the attractive potential of as-grafted ILs for the preparation of hybrid materials in a form of selective adsorbers or membranes for CO₂ separation applications.

Grafting of diethylphophonate-based ILs onto γ-Al₂O₃ powder in solvothermal condition was achieved on mesoporous γ-alumina powder and membrane (A = organic spacer).

One-Pot, Three-Component Approach to Diarylmethylphosphonates: A Direct Entry to Polycyclic Aromatic Systems

A new type of three-component reaction was developed consisting of aldehydes, electron-rich (hetero)arenes, and trialkyl phosphite, which provided facile access to a wide range of diarylmethylphosphonates under mild reaction conditions. Simple one- or two-step synthetic manipulation of the resulting compounds enabled us to reach several polycyclic (hetero)aromatic systems efficiently.

Role of Different Receptor-Surface Binding Modes in the Morphological and Electrochemical Properties of Peptide-Nucleic-Acid-Based Sensing Platforms

Label-free detection of charged biomolecules, such as DNA, has experienced an increase in research activity in recent years, mainly to obviate the need for elaborate and expensive pretreatments for labeling target biomolecules. A promising label-free approach is based on the detection of changes in the electrical surface potential on biofunctionalized silicon field-effect devices. These devices require a reliable and selective immobilization of charged biomolecules on the device surface. In this work, self-assembled monolayers of phosphonic acids are used to prepare organic interfaces with a high density of peptide nucleic acid (PNA) bioreceptors, which are a synthetic analogue to DNA, covalently bound either in a multidentate (^∥PNA) or monodentate (^⊥PNA) fashion to the underlying silicon native oxide surface. The impact of the PNA bioreceptor orientation on the sensing platform's surface properties is characterized in detail by water contact angle measurements, atomic force microscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Our results suggest that the multidentate binding of the bioreceptor via attachment groups at the γ-points along the PNA backbone leads to the formation of an extended, protruding, and netlike three-dimensional metastructure. Typical "mesh" sizes are on the order of 8 ± 2.5 nm in diameter, with no preferential spatial orientation relative to the underlying surface. Contrarily, the monodentate binding provides a spatially more oriented metastructure comprising cylindrical features, of a typical size of 62 ± 23 × 12 ± 2 nm². Additional cyclic voltammetry measurements in a redox buffer solution containing a small and highly mobile Ru-based complex reveal strikingly different insulating properties (ion diffusion kinetics) of these two PNA systems. Investigation by electrochemical impedance spectroscopy confirms that the binding mode has a significant impact on the electrochemical properties of the functional PNA layers represented by detectable changes of the conductance and capacitance of the underlying silicon substrate in the range of 30-50% depending on the surface organization of the bioreceptors in different bias potential regimes.

Straightforward Immobilization of Phosphonic Acids and Phosphoric Acid Esters on Mesoporous Silica and Their Application in an Asymmetric Aldol Reaction

The combined benefits of moisture-stable phosphonic acids and mesoporous silica materials (SBA-15 and MCM-41) as large-surface-area solid supports offer new opportunities for several applications, such as catalysis or drug delivery. We present a comprehensive study of a straightforward synthesis method via direct immobilization of several phosphonic acids and phosphoric acid esters on various mesoporous silicas in a Dean–Stark apparatus with toluene as the solvent. Due to the utilization of azeotropic distillation, there was no need to dry phosphonic acids, phosphoric acid esters, solvents, or silicas prior to synthesis. In addition to modeling phosphonic acids, immobilization of the important biomolecule adenosine monophosphate (AMP) on the porous supports was also investigated. Due to the high surface area of the mesoporous silicas, a possible catalytic application based on immobilization of an organocatalyst for an asymmetric aldol reaction is discussed.

Localized Light-Au-Hyperthermia Treatment for Precise, Rapid, and Drug-Free Blood Clot Lysis

Thrombus diseases, induced by blood stasis or vascular embolization normally, frequently occur with high disability and mortalities worldwide. At present, drug thrombolysis, a primary clinical therapy for blood clot lysis, could increase the lethal risk for hemorrhage when thrombolysis agents are overused in the whole body. Therefore, a novel and advanced therapy for blood clot lysis, based on remote physical signals, is helpful for assisting clinical therapy. Here, we used the localized light-Au-hyperthermia (LAH) treatment, induced by gold nanorods (Au NRs) irradiated with near-infrared light (808 nm), for precise, rapid, and drug-free blood clot lysis. The LAH technology was first introduced in the murine hematoma model and the murine myocardial infarction model for blood clot lysis. Compared with traditional therapy, LAH was assured to shorten the time of detumescence in the murine hematoma model owing to their precise and localized hyperthermia. Meanwhile, we also discovered that LAH was a benefit to vascular recanalization in the murine myocardial infarction model. In addition, the Au NRs used in LAH present ideal biocompatibility in the murine model, which endows it to be suitable for blood clot lysis in vivo.

Platinum(ii) and palladium(ii) complexes with electron-deficient meso-diethoxyphosphorylporphyrins: synthesis, structure and tuning of photophysical properties by varying peripheral substituents

The luminescence quenching by O₂ and photodegradation of Pt(ii) and Pd(ii) phosphorylporphyrins are reported.

Hydrophobic Attraction Measured between Asymmetric Hydrophobic Surfaces

The interaction forces between silica surfaces modified to different degrees of hydrophobicity were measured using colloidal probe atomic force microscopy (AFM). A highly hydrophobic silica particle was prepared with octadecyltrichlorosilane (OTS), and the interaction forces were measured against silica substrates modified to produce surfaces of varying hydrophobicity. The interaction forces between the highly hydrophobic particle and a completely hydrophilic silicon wafer surface fitted well to the DLVO theory, indicating that no additional (non-DLVO) forces act between the surfaces. When the silicon wafer surface was treated to produce a contact angle of water on surface of 40°, an additional attractive force that is longer ranged than the van der Waals force was observed between the surfaces. The range and magnitude of the attractive force increase with the contact angle of water on the substrate. Beyond the effect on the contact angle, the hydrocarbon chain length and the terminal groups of hydrophobic layer on the substrate only have a minor effect on the magnitude of the force, even when the substrate is terminated with polar carboxyl groups, provided the hydrophobicity of the other surface is high.