Search

Background Self-assembly monolayers (SAMs) had been used widely to tailor the surface properties; and alkanthiols were the most common molecules which have been intensively studied. However, the assembly behavior of amine molecules and the characteristics of the SAMs are not well understood. Method In this study, dodecylamine (DDA) is used as a model molecule to study the self-assembly behavior of amine molecules from HClO4 solution onto an Au(111) surface. The adsorption process and the SAM characteristics are studied via cyclic voltammetry (CV), in-situ surface-enhanced infrared absorption spectroscopy (SEIRAS) and scanning tunneling microscopy (STM). Significant findings The CV spectra show that the current densities of Fe+2/Fe+3 redox reaction decrease slightly after the treatment of DDA, implying the formation of a DDA adlayer. The in-situ SEIRAS spectra demonstrate that the adsorption of DDA performed slowly. These results imply a weak interaction of DDA with the gold surface. The STM observation in the HClO4 solution demonstrates that the adsorbed molecules arranged in an orderly manner, forming a flat-lying orientation. The lift-off orientation commonly found for thiol molecules doesn't occur for the DDA adlayer. On the basis of this study, the self-assembly ability of DDA on a gold surface is confirmed, and a weak DDA-Au interaction is verified.

The electrolyte pH has been determined to be an important factor that has a direct influence on the formation of film morphologies. Herein, we investigate the effect of electrolyte pH on the formation of nickel oxide (NiOx) films in borate solutions and examine their corresponding electrochromic characteristics. The result shows that the formation of hexa-aquo Ni complexes due to an appropriate electrolyte pH can aid the electrodeposition of NiOx films and produce a film of small grains. Raman and in situ X-ray absorption fine structure (XAFS) measurements indicate that the structure of the NiOx films in their oxidized state is similar to γ-NiOOH, regardless of the electrolyte pH, although the grain size of the films is dependent on the electrolyte pH. The different grain size results in significant differences in electrochromic performance. The film made of small grain size exhibits the best electrochromic performance. The optical contrast of the NiOx film achieved 87%. The coloration efficiency increased by about 50% to 51 cm2/C and the switching time reduced to 5.4 s for bleaching. These results demonstrate the imperative for an appropriate electrolyte pH to enable sustained electrochemical activity, reactive site formation, and functional stability.

High-efficiency and stable quasi-solid-state dye-sensitized solar cells (QS-DSSCs) are fabricated using printable polymer gel electrolytes for application under room light conditions. The printable electrolytes are prepared based on 3-methoxypropionitrile liquid electrolytes containing iodide/triiodide redox mediator, polyethylene oxide/polyvinylidene fluoride gelator, and titanium dioxide nanofillers. To obtain the optimal performance of the DSSCs, the composition of the printable electrolytes and the thickness of the photoelectrode are regulated. The results show that the polymers composition has little effect on the conversion efficiency of the QS-DSSCs under ambient-light conditions. However, the iodine concentration and the thickness of the titanium dioxide film are important parameters. The experimental results indicate that the printable electrolyte containing 0.01 M iodine, and a titanium dioxide photoelectrode with the thickness of 4 µm main layer and 4 µm scattering layer are the optimal condition to obtain high cell efficiencies. It also shows that the best QS-DSSCs have high recombination resistance and high incident photon to current efficiency values, which contribute, respectively, to the high open circuit voltage and the current density of the corresponding cells. Therefore, the cells can achieve efficiencies of 15.39% and 20.63% under 200 and 600 lx illuminance, respectively. These efficiencies are almost similar to the conversion efficiencies of the corresponding liquid-state DSSC. By applying this printable electrolyte to a sub-module cell, an energy conversion efficiency of 12.23% is achieved under 200 lx illuminance. The study of long-term stability shows that the efficiency of the QS-DSSC can retain 97% of its initial performance after 1000 h testing under 200 lx illuminance, exhibiting high stability of the cells.

The behavior of ethanol oxidation reaction on composite electrodes prepared by deposition platinum on a gold surface (Pt/Au) were studied by cyclic voltammetry and surface enhanced infrared absorption spectroscopy (SEIRAS) analysis. The results show that the Pt electrode has high oxidation activity and significant poison behavior; on the contrary, the Au electrode demonstrates low activity without a poison peak. The SEIRAS analyses reveal that both carbon monoxide (CO) and carbon dioxide (CO

Major challenges in the development of lithium metal batteries (LMBs) are nonuniform Li deposition and substantial variation in Li volume, resulting in Li dendrite growth and Li consumption. A networked solid-state polymer electrolyte (NSPE) that comprises poly(ethylene oxide-co-propylene oxide) (P(EO-co-PO)) and poly(dimethylsiloxane) diglycidyl ether (PDMSDGE) chains and a lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt is developed for resolving the Li deposition challenges. The methyl pendants on P(EO-co-PO) and PDMSDGE chains render the NSPE a low-surface-energy film for complete coverages on the high-energy Li electrode and regulating Li+ transport. The low-surface-energy characteristics induces overspreading of the highly lithiophilic C-F ends of the TFSI− anion at the Li electrode–NSPE interface, forming Li−F bonds and facilitating uniform Li deposition. The elastic PDMS chains enable the NSPE to accommodate Li volume changes. Liquid-phase Li||LiFePO4 and Cu||LiFePO4 cells with the NSPE as an artificial interface or a solid-state Li||LiFePO4 cell with the NSPE as solid electrolyte had uniform anodic Li deposition, resulting in long cycle life and high coulombic efficiency. Our study demonstrated that (a) low surface energy to completely cover the Li anode and (b) the presence of interfacial Li − F bonds are two essential requirements for uniform Li deposition in LMBs.

A graphene oxide sponge (GOS) is prepared and utilized as a nanofiller (NF) of an iodide liquid electrolyte for dye-sensitized solar cell (DSSC) application. The concentration effects of the GOS NFs on the conductivity of the electrolyte, and the performance of the DSSCs are studied. The results indicate that the inclusion of GOS NFs markedly enhances the conductivity of the liquid electrolyte. The electrochemical impendence spectroscopy (EIS) analysis shows that the presence of GOS NFs may increase the recombination resistance (Rct) at the photoelectrode/electrolyte interface and, furthermore, decreases the charge transfer resistance at the Pt counter electrode/electrolyte interface (Rpt). Therefore, the current density (Jsc), open circuit potential (Voc), and fill factor (FF) of the DSSCs can be improved by controlling the concentration of GOS NFs. In this study, the DSSC with 0.50 wt% GOS NFs can achieve the highest energy conversion efficiency of 9.44%, which is higher than that obtained for the corresponding cell without GOS NFs (8.84%).

All-solid-state polymer electrolytes (SPEs) are key for improving lithium-ion battery (LIB) safety and the practical application of metallic Li anodes. The major challenges of developing SPEs are their ionic conductivity, interfacial affinity, and flammability. In this article, synthesis of an SPE comprising lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and poly(ethylene oxide) networked with an acylamino-functionalized crosslinker is reported. The acylamino sites, urethane and biuret linkages, dissociate LiTFSI and may form deep-eutectic-solvent domains to facilitate ion transport. This SPE is fire-retarding because CO2 evolves when the urethane decomposes at high temperatures. When operated at room temperature, the all-solid-state Li|SPE|LiFePO4 cell exhibits a high rate capability and long lifespan. Due to the high elasticity of the SPE, the polymers can self-rearrange during operation to reduce the Li–SPE interfacial resistance and regulate Li+-ion transport for uniform Li deposition. The rearrangement may involve migration of the low-energy alkane chains in the crosslinker toward the Li-anode, resulting in overspreading of lithiophilic carbonyl groups and F-atoms of TFSI− at the interface. This rearrangement property enables the SPE to act as an artificial interlayer in liquid-electrolyte LIBs. The advantages of using an acylamino-functionalized crosslinker to synthesize a networked SPE for high ionic conductivity and interfacial compatibility are demonstrated.

Electrochemical methodologies including constant current, constant potential and cyclic voltammetry (CV), as well as the sputter coating, are utilized to fabricate the poly(3,4-ethylene dioxythiophene) (PEDOT), platinum (Pt), and their composite films with layer-by-layer (Pt/PEDOT) and homogenous (PEDOT-Pt) structures. These films are utilized as counter electrodes of dye-sensitized solar cells (DSSCs). To achieve high cell efficiencies, the thickness of Pt and PEDOT, as well as the structure of composite films are regulated. The results show that PEDOT/Pt and PEDOT-Pt films demonstrate, respectively, the best and worst cell efficiencies. The X-ray diffraction and X-ray photoelectron spectroscopy analysis indicate that PEDOT and Pt have slight interaction in the PEDOT/Pt film, and the Pt preserves a crystalline structure. On the contrary, the interaction of PEDOT and Pt in the PEDOT-Pt film is high, resulting in an amorphous Pt structure. The crystalline Pt and its interaction with PEDOT are considered to be the main reason resulting in the high efficiencies of the corresponding cells. By applying this PEDOT/Pt counter electrode on DSSCs, the charge transfer at the counter electrode/electrolyte interface is significantly increased, and the cells can achieve efficiencies as high as 8.97% and 15.35%, respectively, under one-sun and room-light (200 lux) conditions.

Dye-sensitized solar cells (DSSCs) are a promising alternative for conventional silicon solar cells in terms of high energy conversion efficiency and low production cost. However, liquid-state DSSCs exhibit poor long-term stability since volatile liquid electrolytes are utilized. An effective, simple approach to improving the stability as well as the photovoltaic performance of DSSCs, is by replacing liquid electrolytes with nanocomposite electrolytes. This paper reviews various state-of-the-art nanocomposite electrolytes in view of their physical and electrochemical properties for application in DSSCs. This review mainly focuses on various types of inorganic materials such as clays, metal oxides, metal nitrides, metal carbides, metal sulfides and carbonaceous materials as nanofillers (NFs) in nanocomposite electrolytes. The influence of the sizes, shapes, and surface functional groups of these NFs on the properties of the nanocomposite electrolytes are described. The working mechanism of the DSSCs based on the interactions of these NFs with the electrolytes are presented. The long-term stability of the DSSCs using nanocomposite electrolytes at different temperatures is reviewed. In addition, the methods used to evaluate the mechanical, electrochemical, thermal and long-term stability of the electrodes, electrolytes, and DSSCs are summarized.

Cyclic voltammetry (CV) and in-situ Surface-Enhanced Infrared Absorption Spectroscopy (SEIRAS) are used to study the adsorption behavior of an electroplating additive, 3,3 thiobis-(1-propanesulfonic acid sodium salt) (TBPS), on a polycrystalline Au(111) surface. The effects of the applied potentials on the adsorption behavior of TBPS are investigated and compared to that obtained by in-situ scanning tunneling microscopy (STM) in a previous work. The results show that TBPS molecules can adsorb on the Au surface at 0.05 V (RHE) and approach an equilibrium state after ca. 200 sec. For the IR spectrum detected in the air, the most pronounced peaks of TBPS are symmetric S O (ss-SO) and asymmetric S O (as-SO) stretching modes. Upon adsorption on the Au surface, the ss-SO peak still keeps a sharp and intense shape, while the as-SO peaks appear as a broad peak with much lower intensity. Since the ss-SO vibration mode is parallel to the long molecular axis, these results imply that the TBPS molecules mainly adsorb with a lift-up conformation at 0.05 V. With the increase in electrode potential, the ss-SO peak intensities first increase slightly due to further adsorption of the TBPS, and then, decrease steadily, ascribing to a conformation change of adsorbed TBPS molecules from an upright to a lie-down orientation. On the contrary, the as-SO band intensity first stays constant, and then, increases with increasing potential, consistent with the inference of the conformation change. Accompanying the adsorption and conformation change in the TBPS molecules, the peak corresponding to the bending mode of the adsorbed water δ(HOH) reflects that water molecules move away from the surface when TBPS molecules are adsorbed at low potentials, but will become closer again as the molecular conformation shifts to a lie-down orientation. The adsorption behavior of TBPS with respect to the potential change is reversible.

In the literature, so far, in-situ chemical cross-linking methods have been utilized for the preparation of Al2O3 or ZnO-composite polymer gel electrolytes (PGEs). Such PGEs have shown poor performance in quasi-solid-state dye-sensitized solar cells (QS-DSSCs) under one-sun conditions. Moreover, the QS-DSSCs using ZnO-PGEs had higher open-circuit voltages (Voc) than the cell using Al2O3-PGEs; but their conversion efficiencies are much lower. To solve this problem, for the first time, composite printable electrolytes (CPEs) are fabricated by dispersion Al2O3 and ZnO nanofillers (NFs) in the quasi-solid-state electrolytes. The electrochemical properties of the CPEs and their effects on the QS-DSSCs performance are systematically studied and compared. The results show that the diffusion coefficients of ions in Al2O3 CPEs are much higher than in ZnO CPEs. However, the introduction of ZnO NFs significantly decreases the charge recombination at the photoelectrode/electrolyte interface than do by the Al2O3. Therefore, the QS-DSSCs using Al2O3 CPE and ZnO CPE have, respectively, higher current density and higher Voc; and the highest efficiencies achieved are 8.73% and 7.59%. These efficiencies are significantly higher than those reported for the QS-DSSC PGEs using the two NFs. The mechanisms of the two NFs are proposed by analysis the iodide ions on the two NFs using X-ray photoelectron spectroscopy and ultraviolet-visible spectroscopy.

Propionitrile (PPN) solvent based iodide/triiodide liquid-electrolyte is utilized to prepare highly efficient poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) polymer gel electrolytes (PGEs) of dye-sensitized solar cells, aiming at improving the energy conversion efficiency as well as the stability of gel-state DSSCs. The concentrations effect of the PVdF-HFP on the properties of PGEs and the performance of the corresponding cells are studied. The results show that the in-situ gelation is performed for the PVdF-HFP concentration range of 8–18% at room temperature. However, increasing the concentration of polymer in the PGEs triggers a decrease in the diffusivity and conductivity of the PGEs, but an increase in the phase transition temperature of the PGEs. A high phase transition temperature is obtained for the PGEs with 18 wt% PVdF-HFP, which increase the long-term stability of the gel-state DSSC. By using the 18 wt% PVdF-HFP in the presence of 5 wt% TiO2 nanofillers (NFs), gel-state cells with an efficiency of 8.38% can be obtained, which is higher than that achieved by liquid-state cells (7.55%). After 1000 h test at room temperature (RT) and 50 °C, the cell can retain 96% and 82%, respectively, of its initial efficiency.

Carbon black (CB) thin films are prepared using a doctor blade process and utilized as counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). Poly(vinylidene fluoride) (PVDF) is used as a binder to regulate the viscosity of the CB paste to facilitate the doctor blade process. The PVDF is then removed via thermal treatment at 350 or 450 °C. The effects of CB composition (8-15 wt%) and the heat-treatment temperature on the electrochemical properties of the CB electrodes are studied, as well as on the performance of the corresponding DSSCs. The results show that, after the heat treatment, all CB films demonstrate a mesoporous structure. Film thickness increases with increased CB concentration. CB films heat-treated at 350 °C exhibit low electrochemical activity, high charge transfer resistance, and poor performance when utilized in DSSCs. These results are attributed to the presence of residual PVDF. By elevating the treating temperature to 450 °C, PVDF is completely removed and the electrochemical properties of the resultant CB films resemble closely those of platinum (Pt) film. The DSSCs using these CB CEs achieve conversion efficiencies (8.27–8.35%) comparable to cells using Pt (8.29%).

Sodium acetate (NaAc) is utilized as an additive in cationic precursors of the successive ionic layer adsorption and reaction (SILAR) process to fabricate CdS quantum-dot (QD)-sensitized photoelectrodes. The effects of the NaAc concentration on the deposition rate and distribution of QDs in mesoporous TiO 2 films, as well as on the performance of CdS-sensitized solar cells are studied. The experimental results show that the presence of NaAc can significantly accelerate the deposition of CdS, improve the QD distribution across photoelectrodes, and thereby, increase the performance of solar cells. These results are mainly attributed to the pH-elevation effect of NaAc to the cationic precursors which increases the electrostatic interaction of the TiO 2 film to cadmium ions. The light-to-energy conversion efficiency of the CdS-sensitized solar cell increases with increasing concentration of the NaAc and approaches a maximum value (3.11%) at 0.05 M NaAc. Additionally, an ionic exchange is carried out on the photoelectrode to transform the deposited CdS into CdS 1−x Se x ternary QDs. The light-absorption range of the photoelectrode is extended and an exceptional power conversion efficiency of 4.51% is achieved due to this treatment.

This study proposes incorporating nitrogen-doped graphene oxide dots (NGODs) with graphene oxide (GO) sheets to form a stable and effective NGOD:GO composite for photocatalytic H 2 production through water splitting under visible light illumination. Although Pt-deposited NGOD catalysts were active in the photocatalytic H 2 production reaction, they were only moderately stable. Introducing GO sheets in light-absorbing NGODs effectively mediated the transfer of photogenerated electrons from the NGODs to the GO sheets. This vectorial electron transfer, confirmed by a photoluminescence spectroscopy analysis, led to the relocation of the reaction sites from the NGODs to the GO sheets, protecting the NGODs from attack by reaction intermediates. Moreover, the GO sheets acted as an electron sink, facilitating charge separation in the NGODs. When 3 wt% Pt was deposited on the developed NGOD:GO catalyst, the catalyst steadily catalyzed H 2 production from a 10 vol% aqueous solution of triethanolamine under visible light illumination for 96 h, unlike a NGOD catalyst that exhibited an activity decay of 50% within 96 h. The apparent quantum yield of H 2 under 420-nm light irradiation was 16.0%, demonstrating the high activity of the NGOD:GO catalyst.

Cyclic voltammetry (CV) and in situ scanning tunneling microscopy (STM) are used to study the electrodeposition of copper on an ordered Au(111) electrode modified with mercaptoacetic acid (MAA) in 0.1 M H 2 SO 4 + 0.1 mM CuSO 4 . A CV experiment with potential ramping at 5 mV/s from 0.4 to 0 V (vs. Ag/AgCl) results in a monolayer of Cu on this electrode, demonstrating a minor effect of MAA on Cu deposition, an atypical behavior for a thiol modifier on gold electrode. The MAA-modified Au(111) is imaged by STM, which reveals ordered structures on atomically smooth terraces punctured by steps and pits one atom deep. Cu deposition starts at these defective sites and grows to the entire electrode. The MAA modifier prompts uniform Cu deposition, leading to a smooth Cu film on Au(111). On top of the Cu film there is a major striped phase due to MAA molecules and a minor Moire pattern due to bisulfate anions. These ordered surface structures suggest a crystalline Cu substrate, possibly a face-centered cubic (fcc) structure with its (111) plane lying parallel to the Au(111) substrate. Triangular Cu blocks with their apexes pointing in opposite directions are observed, which implies twinned fcc Cu crystallites. Anodic stripping of the Cu deposit restores the MAA adlayer with a notable amount of defects in the film, which implies a simultaneous loss of MAA and Cu.

The Langmuir-Blodgett (LB) deposition technique is employed to prepare nano-composite films consisting of glucose oxidase (GOx) and gold nanoparticles (AuNPs) for glucose sensing applications. The GOx and AuNPs are co-adsorbed from an aqueous solution onto an air/liquid interface in the presence of an octadecylamine (ODA) template monolayer, forming a mixed (GOx-AuNP) monolayer. Alternatively, a composite film with a cascade architecture (AuNP/GOx) is also prepared by sequentially depositing monolayers of AuNPs and GOx. The architecture effects of the composite LB films on the glucose sensing are studied. The results show that the presence of AuNPs in the co-adsorption system does not affect the adsorption amount and preferred conformation (α-helix) of GOx. Furthermore, the incorporation of AuNPs in both composite films can significantly improve the sensing performance. However, the enhancement effects of the AuNPs in the two architectures are distinct. The major effect of the AuNPs is on the facilitation of charge-transfer in the (GOx-AuNP) film, but on the increase of catalytic activity in the (AuNP/GOx) one. Therefore, the sensing performance can be greatly improved by utilizing a film combining both architectures (AuNP/GOx-AuNP).

In this study, novel double-layered electrolyte architecture is first demonstrated for quasi-solid-state dye-sensitized solar cells (DSSCs). The experimental results show that the electrolyte prepared using 9 wt% polymer blends has rheological characteristics suitable for the printing process, and the corresponding DSSC with a double-layered electrolyte architecture reveals an efficiency (7.99%) comparable to that of a common liquid-state cell under 1 sun irradiation. Moreover, when zinc oxide (ZnO) nanoparticles are introduced as the additives in electrolytes, the open-circuit voltage (Voc) increases, whereas the short-circuit current density (Jsc) decreases. This phenomenon is attributed to the ZnO effects on the two electrodes, i.e., upward shift of the TiO2 conduction band at the photoelectrode and suppression of interfacial charge transfer at the counter electrode. A solution which takes advantage of the double-layered architecture is proposed herein to overcome the above dilemma. Electrolytes with and without the ZnO additives are printed onto the photoelectrode and counter electrode, respectively. The DSSC prepared by this solution maintains the high Voc, and furthermore, the Jsc increases, thus achieving an improved efficiency of 8.50%. A similar quasi-solid-state DSSC also outperforms its liquid-state counterpart under indoor fluorescent-light conditions, demonstrating impressive efficiencies beyond 15%.

The use of gel polymer electrolytes (GPEs) in electric double layer capacitors (EDLCs) is limited by the liquid injection assembly line currently used in EDLC manufacturing. This paper proposes a postinjection gelated GPE, which can be synthesized by mixing a polymer blend of poly(acrylonitrile-co-methyl acrylate) and poly(ethylene glycol) (i.e., PANMA:EG) with a conventional liquid electrolyte (LE). The as-synthesized GPE is in liquid state and can be applied in the liquid injection assembly line. The gelation time can be tuned by varying the composition of the polymer blend. The functionalities on the polymer chains facilitate the dissociation of ion pairs and suppress the formation of ion–solvent complexes; thus, the GPE has an ionic conductivity that is three times that of the LE. Under polarization for dielectric analysis, the GPE exhibits high storage permittivity and low loss permittivity because of its swift ion motion and polymeric dipole orientation. Owing to its superior permittivity performance, the resulting GPE-EDLC outperforms the LE-EDLC in terms of the ultimate capacitance, rate capability, and charge–discharge cycling stability. The postinjection gelation feature and outstanding permittivity characteristics indicate the suitability of this GPE in industrial-scale assembly lines and practical applications.

This paper reports a gel polymer electrolyte (GPE) that is synthesized as a liquid solution and transforms into a gel on-site after injection into lithium-ion batteries (LIBs). The GPE is produced by mixing poly (acrylonitrile-co-methacrylate) (P(AN-co-MA)) and polyethylene glycol (PEG) with a conventional carbonate-solvated LiPF6 liquid electrolyte (LE). P(AN-co-MA) dissociates counter-ion pairs and PEG promotes polymer-crosslinking for electrolyte gelation. The GPE has a high dielectric constant and low dielectric loss because of ion-pair dissociation and facilitated ion motion. When incorporated with a separator, the GPE exhibits an ionic conductivity of 1.7 × 10−3 S cm−1 and a Li transference number (tLi+) of 0.62. The corresponding values for the LE are 9.1 × 10−4 S cm−1 and 0.37, respectively. The high dielectric permittivity and tLi+ render the GPE stable at 5.2 V (vs. Li/Li+). The GPE outperforms the LE when assembled into Li||LiFePO4 batteries, exhibiting superior capacity, high rate retention, and cycling stability. Moreover, the GPE has low flammability such that a graphite|GPE|LiFePO4 pouch-cell battery operates smoothly under folding or after truncation. The on-site coagulation design ensures that the developed GPE can be used in existing LIB assembly lines to produce high-quality LIBs that can be applied in diverse power devices.

High-performance printable electrolytes (PEs) containing Co+2/Co+3 or I−/I3− redox-couple are prepared to fabricate quasi-solid-state (QS) dye-sensitized solar cells (QS-DSSCs) for room light environment applications. Polyethylene oxide (PEO) and poly(methyl methacrylate) (PMMA) are utilized to prepare PEs. Various parameters are regulated to obtain the optimal power conversion efficiencies (PCEs). For the I−/I3− system, the QS-DSSCs using PEO and PEO/PMMA PEs achieve nearly identical PCEs (16.32% and 16.40%, respectively) under the optimal conditions. However, the PCEs obtained for the Co+2/Co+3 system are markedly higher and the cell using PEO PE has a higher PCE (21.06%) than that using PEO/PMMA (18.14%). This difference is ascribed to the different composition of Li+ and Co+3 around the photoelectrode. The presence of Li+ around the interface will repel Co+3 away from the interface, decreasing the recombination of excited electrons to Co+3. According to the molecular structure, PMMA has more lone pair electrons to coordinate with Li+ ions, which will decrease the concentration of free Li+ more significantly than does by PEO. Therefore, the presence of PMMA will decrease and increase, respectively, the Li+ and Co+3 concentrations at the photoelectrode/electrolyte interface, resulting in more significant recombination of electrons to the Co+3. Consequently, the PCE of the PEO/PMMA cell is lower than that of the PEO cell. This effect doesn’t occur in I−/I3− system because the concentration variation of negatively charged ions did not affect significantly the electrons recombination at the interfacial. By using this cobalt PE, a bifacial QS-DSSC can achieve PCEs of 17.22% and 14.25%, respectively, under front-side and back-side illumination by 200 lx T5 light. A sub-module QS-DSSC using the cobalt PE can attain a PCE of 12.56%.

Printable electrolytes for dye-sensitized solar cells (DSSCs) are prepared using a low volatile solvent, gamma-butyrolactone (gBL). Various polymers including polyvinyl acetate (PVA), polyacrylonotrile (PAN), and poly(acrylonitrile-co-vinylacetate) (PAN-VA) are used to regulate the viscosity of the electrolytes. The results show that PAN is the best polymer interms of viscosity, conductivity, and performance of the DSSCs. Increasing the concentration of PAN increases the viscosity of the electrolyte paste, which is advantageous to the operation of a printing process but decreases the electrolyte conductivity and cell performance. This drawback can be compensated by introducing of TiO2 or TiC nanofillers. The quasi-solid-state DSSC prepared using a printing process achieves a conversion efficiency (7.85%) similar to that of the corresponding liquid cell (7.87%). The stability test shows that the presence of TiO2 nanofillers triggers a gradual desorption of dye, decreasing DSSC performance. However, this problem does not appear for the electrolyte using TiC nanofillers, with cell efficiency retaining 96% of its initial value after a 500 h test.

Propionitrile (PPN) or 3-methoxypropionitrile (MPN) is mixed with acetonitrile (ACN) to prepare ACN/PPN and ACN/MPN co-solvents and used to fabricate polymer gel electrolytes (PGEs) of dye-sensitized solar cells (DSSCs), aiming at improving the stability of gel-state DSSCs. Co-solvents with various ratios are utilized to prepare PGEs using poly(acrylonitrile-co-vinyl acetate) (PAN-VA) as the gelator. The ratio effects of the co-solvents on the properties of PGEs and the performances of the corresponding DSSCs are studied. The results show that in-situ gelation of the gel-electrolytes can still be performed at the presence of 40% PPN or 30% MPN. However, increasing the composition of PPN and MPN in the co-solvents triggers a decrease in the diffusivity and conductivity of the PGEs, but an increase in the viscosity. Therefore, the energy conversion efficiencies of the cells decrease as a result. However, the introduction of PPN and MPN elevates the gel-to-liquid transition temperature (Tp) of the PGEs which significantly increases the stability of the gel-state DSSCs. Comparing between the effects of the two co-solvents, PPN and MPN have similar effect on elevation of Tp, but the conductivity of PGEs and the corresponding cell efficiency are higher for the ACN/PPN system, attributed to its lower viscosity compared with ACN/MPN system. By using the ACN/PPN (60/40) co-solvent at the presence of TiO2 fillers, gel-state cell with an efficiency of 8.3% can be achieved, which is even higher than that obtained by the liquid state cell (8%). After 500 h test at 60 °C, the cell can retain 95.4% of its initial efficiency.

This study reports a networked solid polymer electrolyte (N-SPE) containing no solvent, ionic liquid, oligomer, or semisolid additives for lithium-ion batteries (LIBs). The N-SPE comprises a lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt as well as a polymer framework constructed using cage-like polyhedral oligomeric silsesquioxane (POSS) and serving as hubs to network poly(ethylene oxide-co-polypropylene oxide) (P(EO-co-PO)) chains. The networking prevents polymer chain twisting that hinders ion transport. Raman analysis indicates that the POSS hubs improve the dissociation of LiTFSI and localize TFSI− anions. The N-SPE exhibits a low glass transition temperature of −43 °C, a high 25 °C ionic conductivity of 1.1 × 10−4 S cm−1, and a small activation energy of 3.5 kJ mol−1 for ion conduction. The localization of TFSI− results in a high lithium transference number of 0.62, which is determined to be beneficial to Li+ transport. By incorporating the N-SPE into the LiFePO4 cathode and using a free-standing N-SPE membrane, this study assembles a Li|N-SPE|LiFePO4 battery, which delivers a high capacity of 160 mAh g−1 at 25 °C and exhibits excellent charge−discharge cycling stability. The free-standing feature of the N-SPE makes roll-to-roll assembly of LIBs readily scalable for industrial applications.

Poly (vinylidene fluoride-co-hexafluropropylene) (PVDF-HFP) and poly (acrylonitrile-co-vinyl acetate) (PAN-VA) are used as gelator to prepare gel- and solid-state polymer electrolytes for dye sensitized solar cells (DSSCs) applications. The electrolytes prepared using PVDF-HFP have higher conductivities than those prepared using PAN-VA. In blended polymers, the conductivities of the electrolytes increase with increasing composition of PVDF-HFP; at 75% PVDF-HFP, conductivity of the blended polymer surpassed that of pure polymers. It is also found that the viscosity of the electrolyte prepared by PAN-VA (1.2 kPaS) is much lower than that by PVDF-HFP (11 kPaS). Therefore, increasing PAN-VA composition can decrease the viscosity of the electrolyte, improving the penetration of electrolytes in the TiO2 matrix. By controlling the ratio of PVDF-HFP/PAN-VA, the conductivity and viscosity of the electrolyte can be regulated and an optimal ratio based on the conversion efficiency of the gel- and solid state DSSCs is obtained at the ratio of 3/1. The highest efficiency achieved by the gel- and solid-state cells using the blending polymers are 6.3% and 4.88%, respectively, which are higher than those prepared using pure polymers (5.53% and 4.56%, respectively). The introduction of TiO2 fillers to the solid electrolyte can further increase the cell efficiency to 5.34%.

Regioregular poly(3-hexyl thiophene) (rr-P3HT) and mixed P3HT/octadecyl amine (ODA) were used as template monolayers to adsorb the gold nanoparticles (AuNPs) dispersed in subphase. The behaviors of P3HT and P3HT/ODA monolayers were investigated by surface pressure area per molecule ( π – A ) isotherms, transmission electron microscopy (TEM) and atomic force microscopy (AFM). The experimental results show that P3HT does not form a homogeneous film and tends to aggregate at the air/water interface. Meanwhile, the amount of AuNPs adsorbed by the P3HT monolayers is low, attributable to the weak interaction between AuNPs and P3HT. By introduction of ODA molecules into the P3HT monolayer, the spreading of P3HT molecules at the air/water interface is improved and the aggregation of P3HT is significantly inhibited. A nearly uniform and homogeneously mixed P3HT/ODA monolayer can be obtained when 50% of ODA is introduced. It is also found that the introduction of ODA can significantly increase the adsorption of AuNPs. For the mixed monolayer with low ratio of ODA (P3HT/ODA = 1/0.2), a higher concentration of adsorbed AuNPs was observed on the corresponding monolayer. However, when the ODA/P3HT ratio increases to 1/1, the AuNPs tend to form three-dimensional (3D) aggregates and the AuNPs cannot distribute well as a homogeneous monolayer. This result is ascribed to the increasing hydrophobicity of the adsorbed AuNPs because of capping of more ODA molecules.

A novel method is developed to prepare orderly arranged mono-molecular layers of poly(3,4-ethylenedioxythiophene) (PEDOT) by surface polymerization of adsorbed 3,4-ethylenedioxythiophene (EDOT) monomers on Au(111) surfaces. To decrease the EDOT-substrate adhesion force, obtaining a highly ordered EDOT monolayer, the adsorption is performed in a phosphate buffer solution (PBS), rather than the acid solutions commonly utilized in the literature. Furthermore, potentials are applied on the electrode to regulate the adsorption rate of EDOT, and to simultaneously control the adsorption/polymerization mechanism of EDOT molecules. According to the observation of an in-situ electrochemical scanning tunneling microscopy (EC-STM), a highly ordered EDOT monolayer can be prepared by performing the adsorption in a PBS solution, as well as by slowly increasing the electrode potential, attributed to the slow adsorption of EDOT. In the following polymerization of the EDOT monolayer, if the reaction is performed at a constant potential (0.5 V vs. Ag/AgCl reference) or in an acid solution, the EDOT in the solution will take part in the reaction on the surface, leading to a disordered and multilayered structure of PEDOT film. Alternatively, by applying cyclic potentials between 0.0 and 0.5 V, as well as the utilization of a PBS solution, the polymerization could perform only on the pre-adsorbed EDOT monolayer, and an ordered PEDOT monolayer can be prepared. Impedance spectroscopy analysis indicates that the ordered PEDOT monolayer has a charge transfer resistance not only much lower than that of an EDOT monolayer, but also lower than that of the disordered PEDOT multilayer.

A new mechanism is proposed against the Grotthuss-type exchange reaction, to interpret the TiO2 nanofiller effect in quasi-solid-state dye-sensitized solar cells. Generally, the inclusion of TiO2 nanofillers in a polymer gel electrolyte causes an enhanced diffusion coefficient and a reduced charge transfer resistance at the electrolyte/counter-electrode interface, thereby improving the photovoltaic performance of the corresponding solar cell. Herein, liquid electrolytes are treated by TiO2 nanoparticles, and the resultant electrolytes yield similar effects on both the electrolyte properties and cell performance. This result suggests a facilitated movement of the triiodide species; however, it cannot be elucidated by the Grotthuss-type mechanism, because of the absence of nanoparticles in such liquid electrolytes. The X-ray photoelectron spectroscopy analysis shows that the TiO2 particles can adsorb iodide ions through their acidic surfaces. The adsorption of iodide ions leads to negatively charged surfaces, which further induces attraction to cations. As a result, cation concentrations in the electrolyte are reduced, and furthermore, the triiodide species can move more easily owing to the attenuated electrostatic interaction with cations. This mechanism is considered to be a dominant reason for the TiO2 nanofiller effect in quasi-solid-state dye-sensitized solar cells.

A novel copolymer, poly(acrylonitrile- co -vinyl acetate) (PAN-VA), is used as the solidification agent to prepare solid-state redox electrolytes for dye-sensitized solar cell (DSSC) applications. TiO 2 nano-particles are used as the fillers to enhance the performance of the solid electrolytes. Furthermore, to improve the penetration of solid electrolytes in the mesoporous TiO 2 matrixes, an external pressure is applied on the electrodes during the solvent evaporation process. The results show that the ionic conductivities of the solid-state electrolytes are comparable with those of gel electrolyte, indicating that the PAN-VA matrix itself may contribute to the charge transfer through the Grotthuss charge transfer mechanism. Based on the temperature-controllable viscosity of the polymer electrolytes, as well as the effect of an applied force, the solid electrolyte can penetrate well in the TiO 2 film, making good contact with the photoelectrode. It is also found that the introduction of TiO 2 fillers does not affect the conductivity of the electrolyte, but greatly enhance the charge transfer at the interface of the electrolyte and Pt counter electrode. On based of the high performance of the electrolyte system, an energy conversion efficiency of 8.65% is achieved for the solid-state DSSC.

Glucose oxidase (GOx) molecules were adsorbed from aqueous solution onto template monolayer of octadecylamine (ODA) or stearic acid (SA) at the air/liquid interface. The effects of the template layers on the GOx adsorption and the characteristics of the mixed template/GOx monolayers are studied. The monolayers at the air/liquid interface were then transferred onto Pt substrates to prepare GOx Langmuir–Blodgett (LB) films for glucose sensing study. The results show that the SA/GOx monolayer has a pressure–area isotherm resembles that of a SA monolayer, indicating that only a small amount of GOx was incorporated in the mixed film. On the contrary, the ODA/GOx monolayers exhibit high expanded and high compressible characteristics, attributed to the high incorporation amount of GOx induced by the electrostatic interaction between ODA and GOx. The glucose sensing experiments demonstrate that the ODA/GOx LB films have much better performance than SA/GOx films in terms of current sensitivity and current responding rate. Furthermore, an ODA/GOx film prepared after approaching the second equilibrium stage of GOx adsorption (8 h adsorption) shows a better performance than that prepared at the first equilibrium stage. Good linear relationship between response current and glucose concentration was obtained for the GOx-LB films between 0.1 and 5 mM.

TiO 2 terpineol-based pastes with nanorods (NRs) of over 25 μm thickness have been prepared for the photoactive electrodes of the dye-sensitized solar cells (DSSCs). The NRs, with a length of approximately 80 nm and an aspect ratio of about 3, are made by a two-step hydrothermal process. They have the single crystalline anatase structure and can be dispersed well in water and ethanol. With a high thermal stability and larger surface area (47.2 m 2 g − 1 ) than commercial TiO 2 particles (P25, 39.1 m 2 g − 1 ), the well-dispersed anatase NR films with aggregate-free morphology are transparent. For the photocurrent–voltage measurements, the NR cell exhibits high short-circuit photocurrent (J SC ) under 1 Sun AM 1.5 simulated sunlight due to the higher surface area and transmittance. The open-circuit voltage (V OC ) of NR films is not obviously reduced with incremental thickness, which results from the one-dimensional single crystalline structure of NR due to less surface defects. As compared with the P25 cell, DSSCs made with NRs have a higher fill factor (FF) because of the uniform void spaces. An enhancement of conversion efficiency from 4.88% for P25 to 5.67% for NR is achieved. The P25 particles are incorporated in NR films as light-scattering centers, while the R1P1 containing 50 wt.% of P25 has a high V OC and FF as compared with P25, but the J SC is still lower than that of the NR.

Gold nanoparticles were prepared by two different methods. The first method was chemically grafting the particles with different lengths of alkylthiol (C 6 SH, C 12 SH and C 18 SH). For the second method, the Au particles were surface modified first by mercaptosuccinic acid (MSA) to render a surface with carboxylic acid groups which play a role to physically adsorb cationic surfactant in chloroform. This method was termed physical/chemical method. In the first method, the effects of alkyl chain length and dispersion solvent on the monolayer behavior of surface modified gold nanoparticles was evaluated. The gold nanoparticles prepared by 1-hexanthiol demonstrated the narrowest size distribution. Most of them showed narrower particle size distributions in chloroform than in hexane. For the physical/chemical method, the particles can spread more uniformly on the water surface which is attributed to the amphiphilic character of the particles at the air/water interface. However, the particles cannot pack closely due to the relatively weak particle–particle interaction. The effect of alkyl chain length was also assessed for the second method.

The sidewall structure of multi-walled carbon nanotubes (MWNTs) was successfully functionalized with poly(3-hexylthiophene) (P3HT) by a non-covalent bond method. P3HT plays an important role in dispersing MWNTs, and assists them to have a stable existence at the air/water interface. The behavior of mixed MWNT/P3HT monolayer at the air/water interface was investigated after obtaining a homogeneously dispersed solution. The effect of MWNT concentration on the mixed MWNT/P3HT monolayer was investigated using the pressure–area ( π – A ) isotherm, relaxation curve and transmission electron microscopy (TEM). The mixed MWNT/P3HT monolayer was transferred onto a solid substrate using the Langmuir–Blodgett (LB) technique with horizontal or vertical deposition. The multilayer film was delicately fabricated by repeated deposition of the ultra-thin film. Scanning electron microscopy (SEM) images revealed non-uniformity in morphology of the ultra-thin MWNT/P3HT films. The absorption intensity at 250 nm by UV/vis spectroscopy illustrates that a uniform formation of mixed MWNT/P3HT monolayer into multilayer film was successfully obtained by horizontal deposition. The current–voltage characteristic of the ultra-thin MWNT/P3HT film shows that the current increases linearly with the increasing voltage, which indicates that MWNT/P3HT film forms an ohmic contact with gold. And, the electric current was estimated to be mainly contributed by MWNTs.

A self-assembled monolayer (SAM) of 3-mercaptopropyl-trimethyoxysilane (MPTMS) is pre-assembled onto a mesoporous TiO2 film and is used as a surface-modified layer to induce the growth of CdSe QDs in the successive ionic layer adsorption and reaction (SILAR) process. Due to the specific interaction of the terminal thiol groups to CdSe, the MPTMS SAM is found to increase the nucleation and growth rates of CdSe in the SILAR process, leading to a well covering and higher uniform CdSe layer which has a superior ability, compared with the electrode without MPTMS, in inhibiting the charge recombination at the electrode/electrolyte interface. Furthermore, the performance of the CdSe-sensitized TiO2 electrode can further be improved by an additional heat annealing after film deposition, attributable to a better interfacial connection between CdSe and TiO2, as well as a better connection among CdSe QDs. The CdSe-sensitized solar cell prepared by the present strategy can achieve an energy conversion efficiency of 2.65% under the illumination of one sun (AM 1.5, 100 mW cm−2).

The hydrophilic characteristic of the polyelectrolyte, poly(4-styrenesulfonic acid) (PSS), was modified by associating with the surfactant, dodecyltrimethylammonium bromide (DTMAB), to form polyelectrolyte–surfactant (PSS–DTMA) Langmuir layers at air/liquid interfaces. The interfacial behavior of the PSS–DTMA complexes was investigated with the Langmuir trough technique. The mixed PSS–DTMA Langmuir layers were then used as the two-dimensional templates to incorporate with silver precursors from the subphase, and were transferred onto mica substrates with the Langmuir–Blodgett (LB) deposition technique. The silver nanoparticles were fabricated in the resulting LB films with UV irradiation, and the morphology of the silver nanoparticle structures was analyzed by atomic force microscopy (AFM). The results indicated that increasing the DTMA + content in the mixed PSS–DTMA system would enhance the hydrophobic characteristic of the complexes and then form stable PSS–DTMA Langmuir layers at interfaces. In addition, by varying the DTMA + content, one could adjust the charge density in the Langmuir layer templates and thus control the association behavior between the two-dimensional templates and the silver precursors in the subphases. The AFM images demonstrated that the formation of the silver nanoparticle structures in the UV-treated LB films could be regulated with the DTMA + content in the Langmuir layer templates. It is inferred that the polyelectrolyte–surfactant template offers a potential of designing structures of polyelectrolyte–nanoparticle materials with a template-synthesis procedure.

Mixed Langmuir monolayers containing dipalmitoyl phosphatidylcholine (DPPC) were applied as two-dimensional templates to incorporate with gold precursor AuCl 4 − in the subphases. The organic monolayer templates were then transferred onto solid substrates to form ultra-thin films by the Langmuir–Blodgett (LB) deposition technique. With an UV irradiation approach, gold nanoparticles were thus fabricated in the LB films of monolayer templates. Characteristics of the monolayer templates were studied by the surface pressure–area isotherm measurements and Brewster angle microscopy (BAM) observation. The factors affecting the formation of gold nanoparticle structures in the LB films of organic monolayer templates were elucidated by the atomic force microscopy (AFM). The monolayer isotherms and BAM images suggested that by changing the gold precursor concentration in the subphase, one could control the adsorption behavior of the gold precursor onto the monolayer templates. It was found that the association of the gold precursor with a pure DPPC monolayer template resulted in an unstable Langmuir monolayer, which was inappropriate for the following LB deposition. With the presence of n -hexadecanol in a DPPC monolayer, the monolayer template stability and corresponding LB deposition quality could be tremendously improved. Moreover, the distribution of DPPC molecules in the monolayer templates was possible to be regulated by the addition of n -hexadecanol, and the association behavior of the gold precursor with the monolayer templates was thus controlled. The AFM analysis then indicated that the number and size of gold nanoparticles fabricated in the LB films of the mixed DPPC/ n -hexadecanol monolayer templates by a photoreduction reaction could be manipulated by the mole fraction of n -hexadecanol and UV irradiation time.

Based on the hole-transport characteristic of poly(3-hexylthiophene) (P3HT), self-assembled thin layer of P3HT was employed to modify the Ag anode of a top-emissive polymer light-emitting diodes (T-PLEDs) to enhance the hole-injection from the Ag anode. The experimental results show that introduction of a P3HT thin layer significantly decreases the threshold voltage of a T-PLED. However, only slightly increase of the work function was achieved due to this modification. To increase the work function of the P3HT modified Ag anode (Ag/P3HT), 1-fluoro-2-nitro-4-azidobenzene (FNAB) was introduced into the terminal tail (–C 6 H 13 ) of P3HT thin layer, which leads to a work function increment of 0.23 eV and a further enhancement in the hole-injection. The luminous efficiency achieved by this modified anode (Ag/P3HT/FNAB) is about fourfold higher than the efficiency obtained from the base device.

System characteristics of a two-unit repairable system are studied from a Bayesian viewpoint with different types of priors assumed for unknown parameters, in which the coverage factor for an operating unit failure is possibly considered. Time to failure and time to repair of the operating units are assumed to follow exponential distributions. In addition, the recovery time and reboot time of the failed units also follow exponential distributions. When time to failure, time to repair, recovery time and reboot time are with uncertain parameters, a Bayesian approach is adopted to evaluate system characteristics. Monte Carlo simulation is used to derive the posterior distribution for the mean time to system failure and the steady-state availability. Some numerical experiments are performed to illustrate the results derived in this paper.

A polysulfide electrolyte considering simultaneously the penetration of the electrolyte in a mesoscopic TiO2 film and the ion dissociation in the solution is developed for application in a CdS-sensitized solar cell (CdS-DSSC). A methanol/water (7:3 by volume) solution was found to be a good solvent for fitting the requirement mentioned above. The optimal composition of the electrolyte, based on the performance of the CdS-DSSCs, was found to contain 0.5 M Na2S, 2 M S, and 0.2 M KCl. By using a photoelectrode prepared after 4 cycles of chemical bath deposition, FTO/TiO2/CdS-4, the efficiency of the CdS-DSSC obtained for this polysulfide electrolyte is 1.15% under the illumination of 100% sun (AM1.5, 100 mW cm−2). This efficiency is less than that obtained using I−/I3− redox couple (1.84%), mainly caused from the smaller values of fill factor and open circuit potential. However, the CdS sensitizer is stable and, furthermore, a much higher short circuit current and IPCE (80%) are obtained by using the polysulfide electrolyte.

An organic solvent, tetrahydrofuran (THF), was employed to modify the Ag anode of a top-emissive polymer light-emitting diode (T-PLED) for improving the hole injection capability and the performance of a T-PLED device. The X-ray photoelectron spectroscope analysis shows that the THF molecules were chemically adsorbed on the Ag surface, forming oxygen-rich species by substrate-catalyzed decomposition. The THF-modification were found to enhance the hole injection on the Ag anode, decrease the threshold voltage, and increase the light intensity and luminous efficiency of a T-PLED device, attributing mainly to the increase of work function of the Ag anode.

System characteristics of a repairable system are studied from a Bayesian viewpoint with different types of priors assumed for unknown parameters, in which the system consists of one active component and one standby component. The detection of standby, the coverage factor and reboot delay of failed components are possibly considered. Time to failure of the components is assumed to follow exponential distribution. Time to repair and time to reboot of the failed components also follow exponential distributions. When time to failure, time to repair and time to reboot have uncertain parameters, a Bayesian approach is adopted to evaluate system characteristics. Monte Carlo simulation is used to derive the posterior distribution for the mean time to system failure and the steady-state availability. Some numerical experiments are performed to illustrate the results derived in this paper.

Three silane derivatives including dodecyltrichlorosilane (DDTS), phenyltriethoxysilane (PTES) and 3-aminopropyl-methyl-diethoxysilane (APMDS) were used to modify the indium tin oxide (ITO) surfaces. The effects of various terminal groups of the self-assembled monolayers (SAMs) on the growth behavior and interfacial morphologies of N,N′-di(naphthalene-1-yl)-N,N′-diphenylbenzidine (NPB) film deposited on the SAM-modified ITO were studied, as well as their effects on the performance of organic light-emitting diodes (OLED) devices. The results show that the growth behavior of NPB film over-deposited on the SAM-modified ITO is mainly determined by the wettability of the surface. The covering ability and thermal stability of NPB film on the SAM-modified ITO decrease in the order: bare ITO > ITO/PTES > ITO/APMDS > ITO/DDTS. However, the covering characteristic of NPB films on these substrates did not show direct relation to the transport of carriers across the anode/NPB interface as evaluated from the cyclic voltammogram and OLED performance. The turn-on voltages for these SMA-modified OLED devices increase in the order: ITO/PTES

Silica particles are hydrophobized either by chemical graft of alkyl chains or by physical adsorption of cationic surfactants, alkyltrimethylammonium bromide. The effects of the two modification methods on the monolayer behavior of silica particles at the air/water interface are studied, as well as the packing structure of the particulate films. The results show that the hydrophobicity of particles chemically modified by octanol (SiO2-C8) and dodecanol (SiO2-C12) are similar and higher than that modified by butanol (SiO2-C4). The monolayer composed of particles with higher hydrophobicity shows a large lift-off area, higher compressibility, and significant hysteresis due to the higher particle-particle interaction. As a result, the particulate films exhibit 2-dimensional (2D) aggregative domains of closely-packed structure, but with particle free regions presenting among the domains. The monolayer prepared by SiO2-C4 shows a contrary behavior resulted from the higher particle-water interaction. The particles modified by adsorption of cationic surfactants have an amphiphilic property at the air/water interface. Such monolayer exhibits lower compressibility and hysteresis, higher re-spreading characteristic, and a lower collapse pressure compared with those of the chemically modified particles. A particulate film with high uniformity and closely-packed structure can be obtained by using the octyltrimethylammonium bromide (OTAB) modified particles. When the alkyl chain of surfactant increases, the packing of the particles becomes looser. Such phenomenon is probably caused from the higher probability for the long-chain surfactants to stay at the air/water interface which obstructs the intimate contact of particles.