Polyhedral Oligomeric Silsesquioxane Derivatives Research Articles

Encapsulated Atomic Hydrogen in Octamethyl-POSS cages: a Pulsed EPR Study.

Encapsulated atomic hydrogen in polyhedral oligomeric silsesquioxane (POSS) cages is a promising candidate for spin-based quantum technologies. Key parameters such as spin relaxation times and magnetic interactions with surrounding electron and nuclear spins can be typically probed with advanced electron paramagnetic resonance (EPR) methods. Here we present a detailed pulsed EPR study of the species H@Si8O12R8 with R=CH3, namely encapsulated atomic hydrogen in the octamethyl POSS derivative. The temperature dependence of the spin-lattice relaxation rate 1/T1 is analyzed in terms of a Raman process with a Debye temperature of ΘD=145 K and a thermally activated process with Ea=794 K (552 cm-1), whereas, the phase memory time TM shows the typical shortening behaviour at T<150 K observed for all methyl-containing derivatives. The hyperfine coupling of the cage 29Si nuclei is measured by hyperfine sublevel correlation (HYSCORE) spectroscopy and is found to fulfil the so-called "matching condition" at the low-field EPR transition. The potential of this paramagnetic molecule to perform one-qubit quantum operations is probed by room-temperature Rabi oscillations.

Phenyl-Substituted Cage Silsesquioxane-Based Star-Shaped Giant Molecular Clusters: Synthesis, Properties, and Surface Segregation Behavior.

The crystallinity, solubility, and physical properties of polyhedral oligomeric silsesquioxane (POSS) compounds are highly dependent on their organic substituents. We previously synthesized a series of isobutyl-substituted star-shaped POSS derivatives with aliphatic chain linkers of different length. In this study, we prepared C3- and C6-linked phenyl-substituted star-shaped POSS derivatives (3Ph-C3 and 3Ph-C6) by the hydrosilylation of heptaphenylallyl- and hexenyl-POSS (1a and 1b) and octadimethylsiloxy-Q8-silsesquioxane (Q8M8H) (2), respectively, and their properties were compared with those of the corresponding isobutyl-substituted derivatives (5iBu-C3 and 5iBu-C6). Although 3Ph-C6 was only soluble in chloroform and insoluble in tetrahydrofuran (THF) and toluene, 3Ph-C3 was soluble even in THF and toluene, suggesting that the shorter linkers of the derivative afford a wider range of solvents for dissolution. Differential scanning calorimetry analysis showed that 3Ph-C3 exhibited a baseline shift at 190 °C and an endothermic peak at 316 °C. However, no clear baseline shift was observed for 3Ph-C6. Thermogravimetric analysis showed that the shorter linker in the phenyl-substituted star-shaped POSS derivative significantly increased the decomposition temperature compared with the longer linker. The annealed cast film of 3Ph-C3 at 340 °C above its melting temperature formed a transparent film even after cooling to room temperature. However, an opaque whitish film was formed in the case of 3Ph-C6. Poly(methyl methacrylate) (PMMA) films containing 2 wt % 3Ph-C3 and 3Ph-C6 were prepared by casting their chloroform solutions onto glass substrates overnight at room temperature. The static water contact angle measurements and XPS analysis for the castings film containing 3Ph-C3 and 3Ph-C6 suggested that degree of the segregation amount of 3Ph-C3 was larger than that of 3Ph-C6. The shorter linker length in the phenyl-substituted star-shaped POSS derivative, 3Ph-C3, with its greater predicted solubility in PMMA, exhibited entropy-driven surface segregation.

POSS derivatives containing extremely different surface properties as emulsifiers in colloidal systems

The role of functionalized polyhedral oligomeric silsesquioxane (POSS) in emulsion systems is still insufficiently researched. Therefore, this paper presents two aspects. First, the effect of the sequence of olefin introduction and the olefins chemical character on the course and efficiency of hydrosilylation was studied. The use of olefins of drastically different properties was expected to maximally expose their impact on the efficiency of hydrosilylation. The second involve the application of the obtained compounds to be used as emulsifier. Functionalized silsesquioxanes were obtained by subsequent hydrosilylation of spherosilicate with two olefins that is allyl-octafluoropentyl ether and allyl polyether. The hydrosilylation process was monitored by IR spectroscopy in real time. All obtained compounds were used as emulsifiers and the stability of colloidal systems was analyzed using multiple light scattering. Moreover, emulsion stability index over time was also determined. According to the results, both the sequence and the type of introduced substituents have impact on the rate of hydrosilylation. Moreover, it has been shown that the moment of the catalyst addition also influences the character of the process. The results proved that the introduction of fluoroalkyl groups and polyether substituents significantly changed the emulsifying properties of POSS.

Interfacial Behavior of Giant Amphiphiles Composed of Azobenzene and Polyhedral Oligomeric Silsesquioxane.

Giant amphiphiles containing azobenzene and polyhedral oligomeric silsesquioxane (POSS) units are synthesized by linking 4,4'-azodianiline (ADA) and POSS derivatives by stepwise amidation and further modification. The synthesized giant amphiphiles are photoresponsive and show trans-cis isomerization under ultraviolet (UV) irradiation. These giant amphiphiles are spread on the air-water interface and compressed by the barrier without and under UV irradiation. By compression, the giant amphiphiles undergo a phase transition from gas (G), liquid expanded (LE), liquid condensed (LC), and solid (S) to a final collapse on the water surface. The giant amphiphiles are cis-isomer-rich under UV irradiation and are trans-isomer-rich without UV irradiation. The trans-isomers are straight-shaped, while the cis-isomers are bent, and hence, their phase transition behaviors on the water surface exhibit a distinct difference.

Unsymmetric Dumbbell-Shaped Polyhedral Oligomeric Silsesquioxane (POSS) Compound as a Single-Component POSS Hybrid.

Dumbbell-shaped polyhedral oligomeric silsesquioxane (POSS) derivatives, in which two POSS units are linked through a bridge, have attracted attention in the last decade. Here, we prepared an unsymmetric dumbbell-shaped POSS derivative (3Ph-iBu) in which isobutyl- and phenyl-substituted POSS units are linked by a disiloxane unit and compared its thermal properties with those of the corresponding symmetric isobutyl- and phenyl-substituted dumbbell-shaped POSS derivatives (3iBu-iBu and 3Ph-Ph, respectively). The symmetric isobutyl- and phenyl-substituted dumbbell-shaped POSS derivatives, 3iBu-iBu and 3Ph-Ph, were almost completely phase-separated during a mixing process. This phase separation is due to the limited solubility of phenyl-substituted POSS compounds, which are only soluble in tetrahydrofuran (THF) and insoluble in hydrocarbons such as n-hexane and toluene, while the isobutyl-substituted POSS derivatives exhibit a wider spectrum of soluble solvents. The unsymmetric dumbbell-shaped POSS, 3Ph-iBu, showed hybrid properties of solubility in solvents and thermal behaviors. Differential scanning calorimetric (DSC) analysis showed that enthalpy of the phase transition of 3Ph-iBu was significantly lower than those of the mixture of 3iBu-iBu and 3Ph-Ph. No apparent melting behavior was observed above the phase transition. The thermal degradation of the weakest isobutyl substituents improves in the present single-component hybrid structure.

Langmuir and Langmuir Blodgett films of zinc oxide (ZnO) nanocrystals coated with polyhedral oligomeric silsesquioxanes (POSS)

HypothesisThe type and properties of ligands capping nanoparticles affect the characteristics of corresponding Langmuir and Langmuir-Blodgett films. When ligands are firmly anchored to the surface, as in zinc oxide nanocrystallites (ZnO NCs), compression at the air/water interface might cause ligands interdigitation and then the formation of supra-structures. Here, we evaluate how the introduction of bulky ligands, namely polyhedral oligomeric silsesquioxanes (POSSs), influences the self-assembly of POSS@ZnO NCs and the properties of corresponding thin films. ExperimentsZnO NCs capped with asymmetrical POSS derivatives are prepared via a one-pot two-step self-supporting organometallic (OSSOM) method. POSS@ZnO NCs are characterized by employing STEM, DLS, TGA, NMR, IR, UV–VIS, and photoluminescence spectroscopy. Changes in surface pressure, surface potential, and morphology (using BAM) are recorded upon compression at the air/water interface. Films transferred onto solid substrates are examined utilizing XRR and AFM. FindingsAll studied POSS@ZnO NCs form stable Langmuir films. POSSs prevent the interdigitation of ligands capping neighboring NCs. Thus, POSS@ZnO NCs films resemble those composed of classical amphiphiles but without any visible structural source of amphiphilicity. We suggest that the core provides enough hydrophilicity to anchor NCs at the air/water interface. POSS ligands provide enough hydrophobicity for the NCs not to disperse into the subphase upon compression.

Zirconium‐Embedded Polyhedral Oligomeric Silsesquioxane Containing Phosphaphenanthrene‐Substituent Group Used as Flame Retardants for Epoxy Resin Composites

AbstractA zirconium hybrid polyhedral oligomeric silsesquioxane derivative (Zr–POSS–bisDOPO) is synthesized by the corner‐capping and Kabachnik–Fields reactions. It is characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR), and then used as a flame retardant in diglycidyl ether of bisphenol A (DGEBA) to endow epoxy resin (EP) with flame retardancy. The flame retardancy, thermal stability, and mechanical properties of the cured EP/Zr–POSS–bisDOPO composites are investigated. The results show that when Zr–POSS–bisDOPO is added by 5–7 wt%, the EP/Zr–POSS–bisDOPO composites pass the UL‐94 V‐0 rating test. In addition, they have a better flame‐retardant effect than pure EP. The combination of Zr atom embedded in the SiO cubic cage and the two phosphaphenanthrene substituent groups in one corner of cubic cage is expected to realize the Zr/Si/P ternary intramolecular hybrid synergistic effect and achieve the possibility of dispersing metal–POSS cages at a sub‐micrometer‐scale level into polymer matrix. It also proves that Zr–POSS–bisDOPO produces phosphorus‐containing free radicals and terminates the chain reactions in gas phase. Meanwhile the SiOSi and ZrO units are retained in the solid phase, which promote the char formation and enhance the flame retardancy. This kind of Zr‐doped POSS will be helpful for developing the new metal–POSS hybrid flame‐retardant and polymer composites.

UV cured transparent coatings with good thermal stability prepared from a liquid polyhedral oligomeric silsesquioxane with allyl sulphur−containing carbosilane substitutes

It is necessary to develop novel silicone materials with high transparency and excellent thermal stability to meet increasing demands from demands from next generation electronic devices. Polyhedral oligomeric silsesquioxane (POSS) was widely used to improve thermal properties of silicone materials, however, when solid POSS derivatives were used, the toxic organic solvents are needed to facilitate the dispersion of POSS, which will inevitably hinder the practical application. To overcome these shortcomings, a kind of liquid POSS with allyl sulphur−containing carbosilane substitutes was fabricated to improve thermal stability of transparent silicone coatings prepared by UV initiated thiol–ene reaction. These silicone materials exhibit transparency higher than 88 % (400–800 nm). The coatings also show transmittance higher than 80 % (400−800 nm) even being immersed in acid(10 wt% HCl) and salt(10 wt% NaCl) aqueous for 20 days. TGA analysis shows the start thermal decomposition temperature and the degradation residual yield at 800 °C under N2 atmosphere are as high as 337.2–377.9 °C and 51.7–60.8 % respectively. By comparison with the materials improved thermal properties by POSSs reported previously, the materials obtained also have excellent thermal stability. It can be concluded that it is a good method to improve thermal stability of silicone materials by combining the advantages of liquid POSS and carbosilane.

Molecular fillers for increasing the refractive index of polystyrene hybrids by chain assembly at polyhedral oligomeric silsesquioxane

We developed a molecular filler based on polyhedral oligomeric silsesquioxane (POSS) containing halogenated aromatic substituents to increase the refractive indices (RIs) of polystyrene (PS). PS hybrid films with a series of POSS derivatives were prepared through the solution method, and RI measurements were performed. Accordingly, it was revealed that these halogenated POSS fillers can increase the RI of the films. In particular, the degree of increase was larger than those estimated by theoretical prediction, suggesting that the accumulation of polymer chains around the POSS filler plays a key role in the increasing effect. In addition, it was shown that critical losses of thermal and mechanical properties were barely observed by adding POSS fillers. Preparation without the conventional sol‒gel method for the single-molecule-type filler with high-RI polymer hybrids based on chain assembly can be demonstrated. The halogenated polyhedral oligomeric silsesquioxane (POSS) fillers can increase the refractive indices (RIs) of the films. In particular, the degree of increases was larger than those estimated by the theoretical prediction, suggesting that accumulation of polymer chains around the POSS filler plays a key role in the increasing effect. Moreover, critical losses of thermal and mechanical properties were hardly observed. Preparation without the conventional sol‒gel method for the single-molecule-type filler with high-RI polymer hybrids based on the chain assembling can be demonstrated.

Monodispersed hybrid microparticles based on polyhedral oligomeric silsesquioxane with good UV resistance and high thermal stability: From organic to inorganic

Polyhedral oligomeric silsesquioxane (POSS) is an attractive nano-building block for the preparation of organic-inorganic hybrid materials with diverse applications. However, hybrid microparticles based on POSS have rarely been reported as their preparation remains a challenge. In this work, we describe a facile approach for the fabrication of monodispersed organic-inorganic hybrid microparticles based on POSS (MBOPs) through thiol-Michael dispersion polymerization method. By adjusting the polymerization conditions and the monomer combinations, not only the size and uniformity, but also the POSS content of MBOPs can be tuned. The varied POSS content result in the enhanced UV resistance and thermal stability of hybrid MBOPs compared to purely organic microparticles. In addition, MBOPs could be regarded as precursors for formation of the inorganic SiOC ceramic microparticles with uniform size, well-defined micropore and good alkali resistance after high temperature removing the organic components. Considering the vast selection of POSS derivatives and the vast adaptability of chemical conversion that are possible, we believe that this work provides a platform for material chemists to fabrication of advanced microparticles with unique structures and performances from organic to inorganic.

Modification of poly-HEMA with nonreactive POSS derivatives by in situ photopolymerization

Photo-induced polymerization of 2-hydroxyethyl methacrylate (HEMA) in the presence of various amounts of nonreactive polyhedral oligomeric silsesquioxanes (POSS) functionalized with glycidyl, fluoroalkyl or hydroxyl groups was investigated. HEMA/POSS systems were characterized before, during and after the photocuring, with the special emphasis on the photopolymerization kinetics (measured by isothermal differential scanning calorimetry). It was found that the introduction of tested POSS derivatives into HEMA strongly affects the photopolymerization kinetics (enhancement of the gel effect, increase in the polymerization rate and conversion), mainly due to the increase in the viscosity of the initial formulation which leads to a reduction in the termination rate coefficient. However, interactions HEMA–POSS cause also a slight increase in the propagation rate coefficient. The behavior of the polymerization rate coefficients during the reaction suggests that POSS cages may mitigate the inhibitory effect of viscosity on the diffusion of macroradicals by exerting a slip effect. The materials produced are microcomposites due to the partial phase separation occurring during the curing process. Small amounts of added POSS modifiers cause plasticization of the material; at higher loads, POSS domains behave like nanofiller aggregates that increase the glass temperature. The nonreactive POSS have very little effect on thermal decomposition of the poly-HEMA matrix, which can result in a degree from the phase separation; the latter is also the main cause of the deterioration of the mechanical properties of composites compared to a pure polymer matrix.

Modification of polyhedral oligomeric silsesquioxane derivatives with heck reaction as possible new bio-hybrid materials

The regioselective synthesis of Polyhedral oligomeric silsesquioxane (POSS)-based norbornyl imide derivatives through palladium catalyzed Heck coupling reaction was reported on an effective synthetic method to organic–inorganic bio-hybrids serving as advanced materials. The reaction of POSS-based imide derivatives with various aryl iodides catalyzed by palladium acetate in the presence of triethyl amine, as the base, in DMF afforded the products in moderate yields. All new POSS derivatives were structurally characterized by FTIR, 1H, 13C NMR, HRMS and GC/MS analyses.

Synthesis of new polyhedral oligomeric silsesquioxane derivatives as some possible antimicrobial agents

1,3-Dipolar cycloaddition reactions were studied to synthesize Polyhedral oligomeric silsesquioxane (POSS)-based norbornyl imide derivatives containing izoxazoline groups in good yields. And also 1,3-dipolar cycloaddition reactions of azomethine ylides with POSS-based norbornene dipolarophiles for a synthesis of the novel POSS-based norbornane-fused spiro-1,3-indandionolylpyrrolidines are reported. All newly synthesized POSS compounds were structurally characterized by FTIR, 1H, 13C NMR, HRMS and GC/MS analyses.

Optical, Electrical and Thermal Properties of Organic⁻Inorganic Hybrids with Conjugated Polymers Based on POSS Having Heterogeneous Substituents.

Preparation of organic–inorganic hybrids with conventional conjugated polymers such as polyfluorene (PF) and poly(3-hexylthiophene) (P3HT) were demonstrated via the facile blending in solution by employing polyhedral oligomeric silsesquioxane (POSS) having heterogeneous alkyl substituents. From the optical measurements, it was shown that the modified POSS derivatives played a critical role in facilitating amorphous state of polymer matrices. Interestingly, although inter-strand interaction decreased after POSS addition in the hybrid films, thermal stability can be enhanced in the presence of the modified POSS with long alkyl chains. Furthermore, it was demonstrated that carrier mobilities through the hybrid film was minimally reduced by POSS. These results suggest that POSS should be a versatile building block to form hybrid with various types of polymers for enhancing durability without loss of electronic properties of organic components.

PCL/POSS Nanocomposites: Effect of POSS Derivative and Preparation Method on Morphology and Properties.

The incorporation of polyhedral oligomeric silsesquioxanes (POSS) molecules as nanoparticles into polymers can provide improved physico-chemical properties. The enhancement depends on the extent of dispersion of the nanofiller, which is determined by the compatibility with the polymer that is by the POSS type, and the processing method. In this study, poly(ε-caprolactone)/POSS derivatives nanocomposites (PCL/POSS) were obtained via solution-casting and melt compounding. Two amino-derivatives containing different alkyl substituents, and ditelechelic POSS-containing hybrid PCL masterbatch were used as nanofillers. The effect of preparation method, POSS content and type on the morphology, thermal, mechanical, and surface properties of nanocomposites were studied. Morphological analysis evidenced the formation of POSS crystalline aggregates, self-assembled POSS molecules of submicrometer size dispersed in the polymer matrix. The best dispersion was achieved using the ditelechelic POSS-containing hybrid PCL masterbatch, and comparing the two amino-POSS derivatives, the one with longer alkyl chain of substituents exhibited better degree of dispersion independent of preparation method. DSC analysis showed the role of POSS derivatives as nucleating agents for PCL. The incorporation of POSS derivatives into the PCL matrix improved thermal stability. The preparation method, POSS type and content had influence on mechanical properties of nanocomposites. POSS nanoparticles enhanced the surface hydrophobicity of PCL.

Fluoroalkyl POSS with Dual Functional Groups as a Molecular Filler for Lowering Refractive Indices and Improving Thermomechanical Properties of PMMA.

The dual-functionalized polyhedral oligomeric silsesquioxane (POSS) derivatives, which have the seven fluorinated alkanes and the single acrylate ester on the silica cube, were designed as a filler for lowering the refractive index (RI) and improving thermomechanical properties in poly(methyl methacrylate) (PMMA). The desired dual-functionalized POSS fillers were prepared, and because of its high miscibility, homogeneous films were readily obtained, by the casting method, with the mixture solutions containing the modified POSS and the polymers. From optical measurements, it was found that the larger effects of lowering the RIs of the PMMA matrices were observed from the modified POSS than those of the octa-substituted POSS derivatives with the homogeneous substituents. It should be mentioned that the degradation temperatures and the storage moduli were able to be greatly elevated by loading the present POSS fillers. Finally, it was demonstrated that the methacrylate ester-tethered POSS should be the most effective filler for modulating PMMA (Δn = −0.020, ΔTd20 = +53 °C, ΔE’/E’ = +72%).

Ion Conducting Behavior of Silsesquioxane-Based Materials Used in Fuel Cell and Rechargeable Battery Applications

The worldwide energy demand is expected to be double of the current consumption in the near future. This huge energy demand increases the importance of energy conversion and storage devices. A fuel cell needs an electrolyte which can be used under high temperature conditions for increasing the system efficiency. In the case of rechargeable batteries, the ion-conducting properties of the electrolyte should possess long-term sustainability. However, available electrolytes for a fuel cell can efficiently work only at temperatures below 100 °C. On the other hand, commercially used electrolytes are usually liquids and may cause serious leakage and safety problems, thus their sustainability is limited for Li-ion battery applications. Although their ionic conductivities are relatively low, solid and gel type electrolytes are safer and therefore become more favorable. More recently, compatible hybrid organic-inorganic polyhedral oligomeric silsesquioxane (POSS) derivatives have attracted much attention of researchers in order to obtain solid or gel type electrolytes. These materials combine the intrinsic mechanical and thermal properties owing to the inorganic core and the compatibility owing to the organic coronae. Therefore POSS derivatives are a promising family that can allow the design of alternative energetic materials. Here, the objective is to increase the awareness of the role of POSS-based materials for fuel cell and rechargeable battery applications.

Effect of chemical structure of fluorinated polyhedral oligomeric silsesquioxanes on formation of Langmuir monolayers and Langmuir-Blodgett films

Fluorinated polyhedral oligomeric silsesquioxanes (F-POSS) due to their nanoscale hybrid structure coupled with hydrophobic substituted chains have drawn significant attention as highly hydrophobic and oleophobic materials. That is why the surface properties of such compounds at the molecular level should be analyzed in details. Therefore we studied four different fluorinated closed cage polyhedral oligomeric silsesquioxanes (POSS) using Langmuir and Langmuir-Blodgett (LB) techniques. The monolayer behavior was investigated by measurements of the surface pressure-area (π-A) isotherm and morphology of the films was visualized using Brewster angle microscopy (BAM). The rheological behavior was investigated using interfacial shear rheometer (ISR). The unusual properties of these silsesquioxanes result from their unsymmetrical structure. The hydrophobic character of their fluorinated substituents, combined with the hydrophilicity of the trimethoxysilane moieties lead to specific monolayer properties. The compounds were found to form stable monolayers at the air/water (A/W) interface however the surface activity of POSS derivatives decreases with increasing content of fluorinated moieties in the POSS structure. The monolayers of the studied POSS compounds were also successfully transferred onto the solid substrates as Y-type Langmuir-Blodgett films. The wettability and the structure of the LB film were investigated by measuring the static water contact angle on the glass surface. The presence of fluorinated moieties in the structure of POSS molecules governs the enhanced hydrophobic properties of solid substrate modified by the LB film.

POSS functionalized with mixed fluoroalkyl and methacryloxy substituents as modifiers for UV-curable coatings

UV-curable acrylate-based coatings were modified by copolymerization of base resins with polyhedral oligomeric silsesquioxanes (POSS) containing four methacryloxy and four fluoroalkyl substituents in one molecule (4M4F-POSS), giving hybrid organic–inorganic coatings. Such modifiers are covalently linked to the matrix (by methacryloxy groups) preventing them from exuding onto the surface, and fluoroalkyl substituents (along with the POSS cages) improve scratch resistance and hydrophobicity. Two types of POSS derivatives differing with the length of the fluoroalkyl chain were tested. These compounds were applied in two types of formulations: wood-derived and aluminum substrates. Modification of the coatings led to a substantial increase in the hydrophobicity and enhanced scratch resistance after incorporation of only 1.5 wt% of the modifier. Water contact angle increased by up to 14–160% of the initial value, whereas the scratch hardness for the first surface stripping improved by about 30–170% in the presence of 5 wt% of POSS. The latter can be associated with the increase in the surface sliding properties caused by the presence of fluoroalkyl substituents of the modifier. Better results were obtained for POSS containing shorter fluoroalkyl substituents.

Surface Modification Enhanced Reflection Intensity of Quartz Crystal Microbalance Sensors upon Molecular Adsorption.

Molecular adsorption on a sensing surface involves molecule-substrate and molecule-molecule interactions. Combining optical systems and a quartz crystal microbalance (QCM) on the same sensing surface allows the quantification of such interactions and reveals the physicochemical properties of the adsorbed molecules. However, low sensitivity of the current reflection-based techniques compared to the QCM technique hinders the quantitative analysis of the adsorption events. Here, a layer-by-layer surface modification of a QCM sensor is studied to increase the optical sensitivity. The intermediate layers of organic-inorganic molecules and metal-metal oxide were explored on a gold (Au) surface of a QCM sensor. First, polyhedral oligomeric silsesquioxane-derivatives that served as the organic-inorganic intermediate layer were synthesized and modified on the Au-QCM surface. Meanwhile, titanium oxide, fabricated by anodic oxidation of titanium, was used as a metal-metal oxide intermediate layer on a titanium-coated QCM surface. The developed technique enabled interrogation of the molecular adsorption owing to the enhanced optical sensitivity.