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Cracks are common in nature. Cracking is known as an irreversible and uncontrollable process. To control the cracking patterns, many researchers have proposed methods to prepare notches for stress localization on films. In this work, we investigate a method of controlling cracks by making microscale pyramid patterns that have notches between the pyramids. After preparing pyramid patterns consisting of colloidal particles with organic residue, we annealed them to induce volume shrinkage and cracking between the pyramids. We studied the effect of film thickness on cracking and the generation of rectangular fragments consisting of multiple pyramids. The area of rectangular fragments was in good agreement with the results of scaling analysis. The concept of controlling cracks by imprinting notches on a film and the relationship with the film thickness can guide the study of cracking phenomena.

Major research efforts have recently focused on the fabrication of supraparticles from primary nano/micro colloidal particles. A relatively new and key development in this field was surface-templated evaporation driven synthesis (STED), which is a method to synthesize supraparticles by drying droplets of colloidal dispersions on liquid repellent surfaces. This method permits various colloidal particles to be assembled into supraparticles. Specifically, the low contact line friction of the dispersion-containing droplets on liquid repellent surfaces promotes the assembly of primary colloidal particles at the end of evaporation, yielding supraparticles. The STED method is advantageous by enabling the synthesis of supraparticles of various functions, sizes, shapes, compositions, and morphologies. Here, we present an overview of the STED method for supraparticle syntheses, including the (i) fundamental principles of the method and (ii) strategies to tailor the characteristics of supraparticles.

Herein, we present the imbibition-induced, spontaneous, and selective wetting characteristics of gallium-based liquid metal alloys on a metallized surface with micro-scale topographical features. Gallium-based liquid metal alloys are fascinating materials that have enormous surface tension; therefore, they are difficult to pattern into films. The complete wetting of eutectic alloy of gallium and indium is realized on microstructured copper surfaces in the presence of HCl vapor, which removes the native oxide from the liquid metal alloy. This wetting is numerically explained based on the Wenzel’s model and imbibition process, revealing that the dimensions of the microstructures are critical for effective imbibition-driven wetting of the liquid metal. Further, we demonstrate that the spontaneous wetting of the liquid metal can be directed selectively along the microstructured region on the metallic surface to create patterns. This simple process enables the uniform coating and patterning of the liquid metal over large areas without an external force or complex processing. We demonstrate that the liquid metal-patterned substrates maintain electrical connection even in a stretched state and after repetitive stretching cycles.

Polydimethylsiloxane (PDMS) can be linked to the surface of metal-oxide photocatalysts by immersion and UV illumination. The surfaces become hydrophobic and keep their hydrophobicity even under extended UV exposure. Titanium dioxide (TiO2) is a prominent example of a metal-oxide photocatalyst. Here, we studied the influence of a grafted PDMS layer on the photocatalytic activity and wetting properties of TiO2. By varying the molecular weight of PDMS, we controlled the thickness of the polymer layer from 0.6 to 5.5 nm. We recommend a PDMS molecular weight of 6.0 kDa. It leads to a grafted PDMS layer thickness of 2.2 nm, a receding contact angle of 94°, a low contact angle hysteresis of 9°, and the layer is still photocatalytically active.

Superparamagnetism exists only in nanocrystals, and to endow micro/macro-materials with superparamagnetism, superparamagnetic nanoparticles have to be assembled into complex materials. Most techniques currently used to produce such assemblies are inefficient in terms of time and material. Herein, we used evaporation-guided assembly to produce superparamagnetic supraparticles by drying ferrofluid droplets on a superamphiphobic substrate in the presence of an external magnetic field. By tuning the concentration of ferrofluid droplets and controlling the magnetic field, barrel-like, cone-like, and two-tower-like supraparticles were obtained. These assembled supraparticles preserved the superparamagnetism of the original nanoparticles. Moreover, other colloids can easily be integrated into the ferrofluid suspension to produce, by co-assembly, anisotropic binary supraparticles with additional functions. Additionally, the magnetic and anisotropic nature of the resulting supraparticles was harnessed to prepare magnetically actuable microswimmers.

Surface-templated evaporation driven (STED) method is a promising method to fabricate supraparticles with various sizes, porosities, and shapes by drying colloidal dispersion drops on liquid repellent surfaces. Until now, for the method, only spherical shaped colloidal particles have been used as primary colloids. Here, we introduce six different shapes of nano-colloidal dispersions for the STED method: nanocubics, nanoplates, nanosheets, coffin-shaped nanoparticles (NPs), spherical NPs, and aggregates of NPs. It is confirmed that the shape and size of the primary colloids have little effect for drying the dispersion drop when a single component colloidal dispersion is dried. For heterogeneous supraparticles with composite material assembly, still the shape of the colloids has no influences, while the size and dispersity play roles for tuning the morphology of the supraparticles. From the results, we propose a way to fabricate homogeneous mixture, core/shell, and Janus core/shell structures of the supraparticles depending on the size and dispersity of the mixture colloidal dispersion. Indeed, knowledge on the effects of types of colloids would be of great importance for tailoring supraparticles.

Surface-templated evaporation-driven supraparticle synthesis is a versatile method for supraparticle fabrication. A supraparticle is formed by drying droplet of a colloidal dispersion on liquid repellent surfaces, allowing precise control of the size and mean composition of the supraparticles. The crucial factor determining the morphology is the motion of the contact line of the dispersion droplet on the liquid repellent surface. Here, we study effects of (i) the apparent contact angle and (ii) the contact line friction of a droplet on the shape of the supraparticle. In order to change the initial apparent contact angle of the dispersion droplet a surfactant was added to decrease surface tension. In addition, two different liquid repellent surfaces were used: a polydimethysiloxane (PDMS) grafted surface and a lubricated surface. Both surfaces exhibited distinctly different contact line friction during evaporation. As the initial contact angle of a droplet decreases and friction of a contact line increases, flatter supraparticles are fabricated. By using this simple manipulation principle, eventually, various shapes of supraparticles can be obtained, such as mushroom, hemispherical, convex lens, and disk shapes. This study presents fundamental and critical information that allow us to manipulate the shape of a supraparticle via surface-templated evaporation-driven synthesis that increases the scalability of supraparticles for use in a wide range of applications.

Lubricant impregnated surfaces (LISs) exhibit sliding angles below 5°. A LIS is presented that possesses photocatalytic activity as well as improved liquid repellency. In a single-step reaction, the surface of photocatalytic mesoporous TiO2 substrate is modified by grafting polydimethylsiloxane (PDMS) brush and the residual non-bound PDMS serves as lubricant. Since the lubricant and the hydrophobic layer are chemically identical, the grafting PDMS layer is stably swollen by the lubricant PDMS, which inhibits direct contact of liquid drops to the solid substrate. Liquid drops such as water, methanol, and even low-surface-tension fluorocarbons, slide on the surface with tilt angles below 1°. The surface exhibits long-term stable photocatalytic activity while retaining its liquid repellency. This photocatalytic activity allows photocatalytic chemistry, for example, decomposition of organics, on LIS to be carried out.

Corrosion protection coatings have been required for long-term uses of metallic materials applied in various environments incorporating liquid and/or vapor phase corrosion reactants. In this study, we introduce a fluorocarbon lubricant impregnated nanoporous oxide (FLINO) coating on stainless steel for realizing effective resistances against corrosive media in both liquid and vapor phases. The FLINO layer on stainless steel significantly enhances corrosion resistances with superior durability and self-healing capability. The combination of nanoporous structure and fluorocarbon lubricant layer provides an outstanding atmospheric corrosion resistance, which has been a serious issue to be overcome on corrosion-resistant coatings. Therefore, the FLINO coating exhibiting stable and remarkable corrosion resistance against both liquid and vaporized corrosive media, called omnicorrosion-resistance, gives a new route for the versatile protection of metallic materials in various environments encompassing both underwater and atmospheric applications.

Cracks observed in brittle materials are mostly regarded as defects or failures. However, they can be a valuable tool when implemented in a controlled way. Here, we introduce a strategy to control the crack propagation of mesoporous micropatterns (prisms and pyramids), which leads to the isolation of well-defined microstructures. Mesoporous micropatterns were fabricated by the soft imprinting technique with wet TiO2 nanoparticle (NP) pastes, followed by sintering to remove organic components. Since the volume of the paste significantly shrinks during the sintering step, stress is localized at the edge of micropatterns, in good agreement with finite element method simulations, creating well-defined cracks and their propagation. It was demonstrated that the degree of stress localization is determined by the thickness of residual layers, NP size, and heating rate. After controlled crack propagation and delamination of microparticles from the substrates, mesoporous microwires and microparticles were successfu...

Oil-impregnation into a hydrophobized porous surface structure effectively enhances corrosion resistance of metallic materials. In this study, an anti-corrosive silicone oil-impregnated porous oxide layer without hydrophobic coating (i.e., low surface energy materials) was created on metal surfaces. Various surface porous oxide layers were fabricated using magnesium alloy, stainless steel, aluminum alloy, and copper. Their corrosion resistances were compared after silicone oil-impregnation. The impregnation of silicone oil into a hydrophilic porous oxide layer followed by heat treatment lead to the formation of a polydimethylsiloxane (PDMS) brush on oxide surfaces, which enhanced the affinity with the impregnated oil and repellency to water. The silicone oil-impregnated porous oxide surfaces with PDMS brushes showed a high repellency to water, indicating inhibition of a direct contact with corrosive aqueous liquids. Hence, the corrosion resistances of the surface-treated magnesium alloy, stainless steel, aluminum alloy, and copper were significantly enhanced. In the presence of local damages, the silicone oil naturally permeated into the damaged region and the PDMS brush, which was formed by a simple heat treatment, showed the capability to repair anti-corrosion. It is believed that the results of this fundamental and practical study will provide a new approach for anti-corrosive surface finishing for metals.

Anti-biofouling has been improved by passive or active ways. Passive antifouling strategies aim to prevent the initial adsorption of foulants, while active strategies aim to eliminate proliferative fouling by destruction of the chemical structure and inactivation of the cells. However, neither passive antifouling strategies nor active antifouling strategies can solely resist biofouling due to their inherent limitations. Herein, we successfully developed multimodal antibacterial surfaces for waterborne and airborne bacteria with the benefit of a combination of antiadhesion (passive) and bactericidal (active) properties of the surfaces. We elaborated multifunctionalizable porous amine-reactive (PAR) polymer films from poly(pentafluorophenyl acrylate) (PPFPA). Pentafluorophenyl ester groups in the PAR films facilitate creation of multiple functionalities through a simple postmodification under mild condition, based on their high reactivity toward various primary amines. We introduced amine-containing poly(dimethylsiloxane) (amine-PDMS) and dopamine into the PAR films, resulting in infusion of antifouling silicone oil lubricants and formation of bactericidal silver nanoparticles (AgNPs), respectively. As a result, the PAR film-based lubricant-infused AgNPs-incorporated surfaces demonstrate outstanding antibacterial effects toward both waterborne and airborne Escherichia coli, suggesting a new door for development of an effective multimodal anti-biofouling surface.

Metal oxide photocatalysts (MOPCs) decompose organic molecules under illumination. However, the application of MOPCs in industry and research is currently limited by their intrinsic hydrophilicity because MOPCs can be wetted by most liquids. To achieve liquid repellency, the surface needs to possess a low surface energy, but most organic molecules with low surface energy are degraded by photocatalytic activity. Herein, current methods to achieve liquid repellency on MOPCs, while preventing degradation of hydrophobic coatings, are reviewed. Classically, composite materials containing MOPCs and hydrophobic organic compounds possess good liquid repellency. However, composites normally form irregular coatings and are hard to prepare on surfaces such as those that are mesoporous or nanostructured. In addition, the adhesion of composites to substrates is often weak, resulting in delamination. Recent studies have shown that the direct grafting reaction of polydimethylsiloxane (PDMS) from silicone oil (methyl-terminated PDMS) under illumination results in a stable polymer brush. This easy and simple grafting method allows us to create stable liquid-repellent surfaces on MOPCs of various types, structures, and sizes. In particular, super-liquid-repellent drops with an underlying air layer can be created on PDMS-grafted nano-/microstructured MOPCs. Potential applications of surfaces combining liquid repellency and photocatalytic activity are also discussed; thus offering new ways of using MOPCs in a wider range of applications.

Here, we propose a simple mechanoresponsive system on patterned soft surfaces to manipulate both anisotropy and orientation of liquid wetting. On the poly(dimethylsiloxane) embedding line patterned structures, additional topographies, such as wrinkles and cracks, can be provided by applying compressive and tensile stress, respectively. This tunable hierarchy of structures with the different scales and directions of lines, wrinkles, and cracks allow the mechanoresponsive control of anisotropic wetting in a single platform. In addition, the wetting behavior on those surfaces is precisely investigated based on the concept of critical contact angle to overcome the ridges in a step flow.

Dye aggregation and electron recombination in TiO2 photoanodes are the two major phenomena lowering the energy conversion efficiency of dye-sensitized solar cells (DSCs). Herein, we introduce a novel surface modification strategy of TiO2 photoanodes by the fluorinated self-assembled monolayer (F-SAM) formation with 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFTS), blocking the vacant sites of the TiO2 surface after dye adsorption. The F-SAM helps to efficiently lower the surface tension, resulting in efficient repelling ions, e.g., I3(-), in the electrolyte to decrease the electron recombination rate, and the role of F-SAM is characterized in detail by impedance spectroscopy using a diffusion-recombination model. In addition, the dye aggregates on the TiO2 surface are relaxed by the F-SAM with large conformational perturbation (i.e., helix structure) seemingly because of steric hindrance developed during the SAM formation. Such multifunctional effects suppress the electron recombination as well as the intermolecular interactions of dye aggregates without the loss of adsorbed dyes, enhancing both the photocurrent density (11.9 → 13.5 mA cm(-2)) and open-circuit voltage (0.67 → 0.72 V). Moreover, the combined surface modification with the F-SAM and the classical coadsorbent further improves the photovoltaic performance in DSCs.

Oligomeric, hydrophobic coadsorbents based on polystyrene (o-PS, Mn = 2600) terminated by a carboxylic acid exhibit dual functions in dye-sensitized solar cells (DSCs): suppression of electron recombination at the TiO2 surface, and enhanced concentration of the strongly-anchored dye, N719, which has two carboxylic acid groups. Engineering the TiO2 surface via o-PS results in the concurrent and significant enhancement of photovoltage and photocurrent, consequently increasing the energy conversion efficiency of DSCs by as much as 28.7%. The electron recombination rate was largely reduced via the blockage of vacant sites with o-PS chains on the TiO2 surface due to the physical hindrance to I3−s in electrolyte. In addition, the formation of the o-PS:I2 charge transfer complex at the photoanode/electrolyte interface lessened the effective concentrations of free I3− and/or I2 for electron recombination. Upon sequential o-PS coadsorption, the concentration of the strongly-anchored dyes on the TiO2 surface was increased via deprotonation of the weakly-anchored dyes, giving rise to an increase in the electron injection efficiency and, subsequently, the overall power conversion efficiency. The dual functions of the o-PS coadsorbent have been therefore demonstrated to increase the overall efficiency of DSCs.

Supraballs of various sizes and compositions can be fabricated via drying of drops of aqueous colloidal dispersions on super-liquid-repellent surfaces with no chemical waste and energy consumption. A "supraball" is a particle composed of colloids. Many properties, such as mechanical strength and porosity, are determined by the ordering of a colloidal assembly. To tune such properties, a colloidal assembly needs to be controlled when supraballs are formed during drying. Here, we introduce a method to control a colloidal assembly of supraballs by adjusting the dispersity of the colloids. Supraballs are fabricated on superamphiphobic surfaces from colloidal aqueous dispersions of polystyrene microparticles carrying pH-responsive poly[2-(diethylamino)ethyl methacrylate]. Drying of dispersion drops at pH 3 on superamphiphobic surfaces leads to the formation of spherical supraballs with densely packed colloids. The pH 10 supraballs are more oblate and consist of more disordered colloids than the pH 3 supraballs, caused by particle aggregates with random sizes and shapes in the pH 10 dispersion. Thus, the shape, crystallinity, porosity, and mechanical properties could be controlled by pH, which allows broader uses of supraballs.

We report transparent Al:LiF composite/molybdenum oxides (MoO3) as interconnecting layers for tandem white organic light emitting diodes (WOLEDs) consisting of blue and red phosphorescent unit devices. The Al:LiF (3 nm)/MoO3 (10 nm) interconnecting layers show a high transmittance, good carrier generation and injection capability for tandem WOLEDs. The performance of tandem WOLEDs is sensitive to the LiF doping concentration, which is mainly attributed to the difference in efficiency of carrier injection into the adjoining electroluminescent units. For 10~20% LiF concentration, the external quantum efficiency of tandem device is almost equal to the sum of the efficiencies of blue and red OLEDs at high current density; furthermore, a small variation of Commission Internationale de l'Eclairage (CIE) coordinates with the current density is obtained.

Water-repelling surfaces inspired by lotus leaves have been developed for their commercial needs in superhydrophobic and self-cleaning coatings on glasses and windows. The extraordinary properties originate from their multiscale structures with waxy materials. To obtain high transparency as well as superhydrophobicity, microhair arrays are designed with large spacing to reduce optical scattering effects caused by microstructures, but with a trilevel hierarchical structure to compensate for the loss of superhydrophobicity. In this study, a soft molding technique on wet pastes consisting of nanoparticles (NPs) is proposed to create a multilevel hierarchical structure of sub-100 nm nanoparticles, which demonstrates excellent water repellency. Additionally, full advantage is taken of the TiO2 NP mesoporous structure for UV protection and for its ability to attach to various kinds of functional (for example, photoresponsive) dyes. Furthermore, the stability of fluorinated surfaces against UV light is enhanced by the passivation of the TiO2 surface with a thin silica coating.

Stable push-pull substituted heteroleptic bis(tridentate) ruthenium(II) polypyridine complexes with COOH or 2,2′-bipyridine anchor groups have been prepared and characterized by 1H, 13C and 15N NMR 1D and 2D spectroscopy, infrared spectroscopy, elemental analysis, high-resolution ESI mass spectrometry, electrochemistry, UV/Vis absorption spectroscopy, luminescence spectroscopy, and density functional calculations. The complexes feature a pronounced electronic directionality and high absorption wavelengths up to λmax = 544 nm extending to 720 nm as a result of favorable push-pull substitutions. A remarkable photostability in the presence of water and coordinating ions (I–) was discovered for the tridentate complexes when compared with the standard ruthenium sensitizer N719 and tris(bidentate) [Ru(bpy)3](PF6)2, which are highly photolabile under the same conditions (photodissociation/photosubstitution). The complexes were studied as photosensitizers in dye-sensitized solar cells. The incident photon-to-current conversion efficiency follows the absorption spectra into the NIR region. However, the high positive charge of the complexes (2+) favors the recombination of the injected electrons with I3– of the redox electrolyte, which is evidenced by high dark currents and short electron recombination lifetimes, leading to low cell performances compared with cells with the negatively charged N719 dye.

We investigate orientation and lateral ordering of poly(styrene-block-methyl methacrylate) (PS-b-PMMA) diblock copolymer (diBCP) thin films placed on ordered nanoparticle (NP) monolayers. The densely packed NP monolayers were prepared on silicon substrates with the Langmuir–Blodgett (LB) deposition technique. The perpendicular domain orientation of BCP thin films is obtained on the ordered NP monolayers due to the nanoscale regular roughness which exerts the elastic deformation on the BCP nanodomains and suppresses the substrate-induced parallel orientation. The effect of BCP film thickness as well as the NP size on the orientation of BCP nanodomains was systematically investigated. We also demonstrate the defect-tolerant ordering of the perpendicular orientation of BCP thin films on the NP-vacant sites.

3D TiO2 photoanodes in dye-sensitized solar cells (DSCs) are fabricated by the soft lithographic technique for efficient light trapping. An extended strategy to the construction of randomized pyramid structure is developed by the conventional wet-etching of a silicon wafer for low-cost fabrication. Moreover, the futher enhancement of light absorption resulting in photocurrent increase is achieved by combining the 3D photoanode with a conventional scattering layer.

The contact between liquid drops and hot solid surfaces is of practical importance for industrial processes, such as thermal spraying and spray cooling. The contact and bouncing of solid spheres is also an important event encountered in ball milling, powder processing, and everyday activities, such as ball sports. Using high speed video microscopy, we demonstrate that hydrogel drops, initially at rest on a surface, spontaneously jump upon rapid heating and continue to bounce with increasing amplitudes. Jumping is governed by the surface wettability, surface temperature, hydrogel elasticity, and adhesion. A combination of low-adhesion impact behavior and fast water vapor formation supports continuous bouncing and trampolining. Our results illustrate how the interplay between solid and liquid characteristics of hydrogels results in intriguing dynamics, as reflected by spontaneous jumping, bouncing, trampolining, and extremely short contact times., Drops of liquid on a hot surface can exhibit fascinating behaviour such as the Leidenfrost effect in which drops hover on a vapour layer. Here Pham et al. show that when hydrogel drops are placed on a rapidly heated plate they bounce to increasing heights even if they were initially at rest.

Losing contact: Omniphobic surfaces can be readily produced by acid-catalyzed graft polycondensation of dimethyldimethoxysilane (PDMS). Droplets show a very small contact angle hysteresis as well as a low sliding angle of only a few degrees. The nm-thick PDMS layer is neither easily washed away nor depleted. This method offers a novel approach towards the preparation of super-liquid-repelling surfaces.

We studied the condensation of water drops on a micro-structured lubricant-infused surfaces. Hierarchical micro-prism surfaces were fabricated by soft imprinting with wet TiO2 nanoparticle paste. After hydrophobization, the patterned surfaces were infused with silicone oil as a lubricant. When cooling at high humidity (over 80%), water drops nucleate and start growing on the surface. Once they have reached a certain size, the drops at neighboring channels of the micro-prisms attract each other and spontaneously form cylindrical chains. These chains of drops align perpendicular to the prism array. The morphology and the length-to-width ratio of the chains of drops depend on the thickness of the lubricant layer. This new concept of water drop alignment on lubricant-infused surfaces offers a new route for pattern formation with condensed drops.

We report transparent Al:LiF composite/molybdenum oxides (MoO3) as interconnecting layers for tandem white organic light emitting diodes (WOLEDs) consisting of blue and red phosphorescent unit devices. The Al:LiF (3 nm)/MoO3 (10 nm) interconnecting layers show a high transmittance, good carrier generation and injection capability for tandem WOLEDs. The performance of tandem WOLEDs is sensitive to the LiF doping concentration, which is mainly attributed to the difference in efficiency of carrier injection into the adjoining electroluminescent units. For 10~20% LiF concentration, the external quantum efficiency of tandem device is almost equal to the sum of the efficiencies of blue and red OLEDs at high current density; furthermore, a small variation of Commission Internationale de l'Eclairage (CIE) coordinates with the current density is obtained.

A method for mesoporous supraparticle synthesis on superamphiphobic surfaces is designed. Therefore, supraparticles assembled with nanoparticles are synthesized by the evaporation of nanoparticle dispersion drops on the superamphiphobic surface. For synthesis, no further purification is required and no organic solvents are wasted. Moreover, by changing the conditions such as drop size and concentration, supraparticles of different sizes, compositions, and architectures are fabricated.

Polydimethylsiloxane (PDMS) can be grafted to metal-oxide photocatalysts such as titanium oxide by simple UV irradiation in solution or melt. The PDMS graft metal oxides are still photocatalytically active. They are hydrophobic, liquid repellent, self-cleaning, prevent biofouling and are long-term stable even in UV light.

Direct evidence of the effects of the localized surface plasmon resonance (LSPR) of gold nanoparticles (Au NPs) in TiO2 photoanodes on the performance enhancement in quasi-solid-state dye-sensitized solar cells (DSCs) is reported by comparing gold/silica core–shell nanoparticles (Au@SiO2 NPs) and hollow silica nanoparticles with the same shell size of the core–shell nanoparticles. The Au nanoparticles were shelled by a thin SiO2 layer to produce the core–shell structure, and the SiO2 hollow spheres were made by dissolving the Au cores of the gold/silica core–shell nanoparticles. Therefore, the size and morphology of the SiO2 hollow spheres were the same as the Au@SiO2 NPs. The energy conversion efficiency was improved nearly 36% upon incorporating the Au nanoparticles, mostly due to the increase in Jsc, while Voc and FF were unchanged. The improvement was mostly contributed by the LSPR of the Au@SiO2 NPs, whereas the other parameters, such as the electron lifetime and electron diffusion coefficient, were nearly unchanged. Therefore, LSPR is an effective tool in improving the photocurrent and consequently the performance of DSCs.

A novel poly(ethylene glycol) (PEG) based oligomeric coadsorbent was employed to passivate TiO2 photoanodes resulting in the large increase in both open-circuit voltage (Voc) and short-circuit current density (Jsc) primarily because of the reduced electron recombination by the effective coverage of vacant sites as well as the negative band-edge shift of TiO2. The effective suppression of electron recombination was evidenced by electrochemical impedance spectroscopy (EIS) and by stepped light-induced transient measurements of photocurrent and voltage (SLIM-PCV). The work function measurements also showed that the existence of coadsorbents on TiO2 interfaces is capable of shifting the band-edge of TiO2 photoanodes upwardly resulting in the increase in photovoltage. In addition, the coadsorbent was proven to be effective even in the presence of common additives such as LiI, 4-tert-butylpyridine, and guanidinium thiocyanate. The effect of Li+ cation trapping by ethylene oxide units of the coadsorbent was part...