Film Formation Research Articles

Enhancing Carrier Behavior via Controlled Molecular Film Formation Engineering Leads to Significant Improvement in Electroluminescence

The quality of organic thin films critically influences carrier dynamics in organic semiconductors. In neat/doped films, even tiny voids can be penetrated by water or oxygen molecules to create charge‐trap states called water/oxygen‐induced traps that significantly hinder carrier mobility. While the water/oxygen‐induced traps in non‐doped films and crystalline states have been investigated comprehensively, there is a lack of thorough examination regarding their properties in the doped state. Therefore, there is a high demand for a molecular design strategy that effectively modulates the molecular stacking behavior in doped films and practical devices and enhances the quality of these films. Herein, we proposed a versatile molecular design principle that enables the formation of "nano‐cluster" structures on both the surface and interior of doped films in target molecule 10‐(4‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)phenyl)‐1'‐(4‐fluorophenyl)‐10H‐spiro[acridine‐9,9'‐xanthene] (DspiroO‐F‐TRZ), which is modified with a fluorophenyl group. These "nano‐cluster" structures exhibit more uniform shapes within doped films and effectively reduce defective state densities while enhancing carrier injection and transport properties, ultimately improving device performance. Notably, TADF‐OLED based on DspiroO‐F‐TRZ demonstrates nearly twice as much efficiency as its control counterpart due to contributions from 'nano‐cluster' structure enhancements toward improved electroluminescence performance.

Enhancing Carrier Behavior via Controlled Molecular Film Formation Engineering Leads to Significant Improvement in Electroluminescence.

The quality of organic thin films critically influences carrier dynamics in organic semiconductors. In neat/doped films, even tiny voids can be penetrated by water or oxygen molecules to create charge-trap states called water/oxygen-induced traps that significantly hinder carrier mobility. While the water/oxygen-induced traps in non-doped films and crystalline states have been investigated comprehensively, there is a lack of thorough examination regarding their properties in the doped state. Therefore, there is a high demand for a molecular design strategy that effectively modulates the molecular stacking behavior in doped films and practical devices and enhances the quality of these films. Herein, we proposed a versatile molecular design principle that enables the formation of "nano-cluster" structures on both the surface and interior of doped films in target molecule 10-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-1'-(4-fluorophenyl)-10H-spiro[acridine-9,9'-xanthene] (DspiroO-F-TRZ), which is modified with a fluorophenyl group. These "nano-cluster" structures exhibit more uniform shapes within doped films and effectively reduce defective state densities while enhancing carrier injection and transport properties, ultimately improving device performance. Notably, TADF-OLED based on DspiroO-F-TRZ demonstrates nearly twice as much efficiency as its control counterpart due to contributions from 'nano-cluster' structure enhancements toward improved electroluminescence performance.

Investigations of Crucial Factors for the Non-Covalent Functionalization of Black Phosphorus (BP) using Perylene Diimide Derivatives for the Passivation of BP Nanosheets.

The non-covalent functionalization of black phosphorus (BP) was studied with a scope of ten tailor-made perylene diimides (PDIs). A combination of UV/Vis-, fluorescence-, as well as Raman spectroscopy and atomic force microscopy was used to investigate the structural factors, which contribute to a pronounced PDI-BP interaction and thus support the protection of BP nanosheets against oxidative degradation. We were able to show, that water-soluble, amphiphilic PDIs with highly charged head groups can be used for the non-covalent functionalization of BP in aqueous media. Here, based on the hydrophobic effect, an efficient adsorption of the respective PDI molecules takes place and leads to the formation of a passivating film, yielding a considerable stabilization of the BP flakes under ambient conditions exceeding 30 days.

Enhancement on the thermal and tribological behaviors of polyurethane/epoxy-based interpenetrating network composites by orientationally aligned CNF/MXene/WPU aerogels

Tribological behaviour of polyurethane/epoxy interpenetrating polymer network (PU/EP IPN) as friction materials was investigated. This was a combination of the good flexibility of PU and high hardness of EP to realize polymer synergistic effect of interpenetrating network structure, aiming to broaden and develop the application of polymer-based composites in friction engineering materials. A novel CNF/MXene/WPU aerogel (CMW) was prepared by employing flexible NCO-terminated waterborne polyurethane prepolymer (WPU) as the supporting skeleton of aerogel, and synchronously combining the reinforcing-phase carbon nanofibers (CNF) and lubricating-phase MXene. Subsequently, the prepared ultralight porous yet mechanically robust CMW aerogels were encapsulated with IPN by vacuum impregnation. As expected, the addition of aerogel imparted IPN matrix with enhanced thermal and tribological properties due to the thermal dispersion and enhancement effects conferred on the matrix by the highly aligned and ordered three-dimensional interconnected structure of aerogel. Meanwhile, CMW reinforced IPN composites were explored for the formation of a high-quality transfer film on the contact surface during friction. The transfer film prevented direct contact between the friction couples, which facilitated the improvement of wear resistance of composites, thus giving this material great potential for tribological applications.

The effect of alkyl chain on the corrosion inhibition of benzyldimethylammonium chloride in acidic environments

Incorporating quaternary ammonium salts (QAS) during pickling is an efficient and eco-friendly approach to mitigating metal corrosion. This study investigated the effectiveness of Benzyldimethylhexadecylammonium chloride (HDBAC) and Benzyldimethyltetradecylammonium chloride (TDBAC) in inhibiting the corrosion of Q235 steel in H2SO4, utilizing electrochemical methods, atomic force microscopy (AFM), scanning electron microscopy (SEM), and theoretical calculations. The electrochemical results demonstrated that compared with the blank impedance value of 40.68Ω cm2, HDBAC and TDBAC at 5 mM concentration showed impedance values of 997.69Ω cm2 and 676.17 Ω cm2 at 298 K, indicating that they can effectively prevent the corrosion of Q235. SEM and AFM further showed the formation of a protective barrier film by HDBAC and TDBAC on the steel surface, effectively isolating it from the corrosive medium. Theoretical calculations further elucidated the mechanism by which these inhibitors create this protective barrier. The experiment also verified the hypothesis that the length of the hydrophobic chain of surfactants affects the adsorption behavior and the inhibition efficiency. When comparing their inhibitory effects at 5 mM concentrations, HDBAC exhibited superior performance (95.92 %) against Q235 in 0.5 M H2SO4, compared to TDBAC (94.09 %). These findings provide valuable insights for developing more effective and sustainable corrosion inhibitors for industrial applications.

Formamidinium lead iodide perovskite photovoltaics with MoS2 quantum dots

We present the formation of a composite film made out of formamidinium lead iodide (FAPI) and molybdenum disulphide quantum dots (MoS2 QDs) and propose a corresponding photovoltaic device architecture based on a ‘type-I’ alignment of the two materials’ electronic energy levels. The introduction of the MoS2 QDs has not compromised the overall crystallinity of the FAPI film and the composite absorber has shown improved stability. We report on the benefits of this composite film and energy band arrangement as the photogenerated carriers in MoS2 QDs, both positive and negative, are injected into the FAPI host matrix, resulting in an increased current density of 24.19 mA cm−2 compared to a current density of 19.83 mA cm−2 for the control device with FAPI only. The corresponding photoconversion efficiency increases from 12.6 to 15.0%. We also show that inclusion of MoS2 QDs in FAPI films resulted in a notable improvement in the fill factor and open-circuit voltage of the solar cells. Most importantly, MoS2 QDs enhanced the film stability by reducing defect formation and acting as passivating agents that minimize recombination losses and improve charge carrier transport. Our results suggest that a composite film in a type-I device architecture can introduce benefits for both future developments in perovskite solar cells and effectively tackling the longstanding challenges of carrier transport in QDs solar cells.

Ablation behaviour and mechanism of in-situ NbC composite coating under plasma jet

NbC composite coatings of Nb2O5-Al-SiC system (in-situ) and NbC-SiC-Al2O3 system (ex-situ) were successfully prepared on graphite substrate by plasma spraying, respectively. The ablation resistance of two systems of NbC composite coatings was evaluated by plasma jet, and the ablation mechanism of the Nb2O5-Al-SiC system coating prepared in-situ was revealed. The results showed that the NbC-SiC-Al2O3 system composite coating has completely failed after ablation for 10 s, and the Nb2O5-Al-SiC system coating only has a small amount of spalling at the edge of the coating surface after ablation for 20 s. The excellent ablation resistance of Nb2O5-Al-SiC system coating was attributed to the formation of a Nb2O5 liquid-phase film on the surface of the coating during the ablation process, which can effectively block the penetration of heat and oxygen into the coating. Moreover, the reaction between Nb2O5 and Al2O3 at high temperatures generated the high-temperature stable phase AlNbO4, which can further improve the structural stability of the Nb2O5 film, and then improve the ablation resistance of the Nb2O5-Al-SiC system coatings.

Research on the corrosion mechanism of Q345R steel under water-oil two-phase flow with the HCl and NH4Cl corrosive medium in low-temperature system of petrochemical plants

The serious corrosion failure phenomenon of HCl and NH4Cl in the water-oil two-phase flow are usually occurred in the low-temperature system of petroleum refinery facilities. In this paper, the corrosion mechanism of these corrosive medium in two-phase flow environment was investigated in detail by using corrosion weight loss, electrochemical measurement methods, surface analysis techniques, and numerical research methods. The results indicate that the corrosion rate of Q345R steel in an HCl-NH4Cl coupling medium falls between the rates observed with each medium alone. The stirring of the corrosive fluid creates an unstable oil-in-water emulsion. The formation of an oil film on the surface of Q345R steel slows down the corrosion process and alters the surface corrosion morphology when the oil phase was not originally present. Increasing the proportion of the water phase accelerates the corrosion rate, and the stronger wettability of the oil phase makes the loose γ-FeOOH products easier to cover the surface, which can effectively prevent the mass transfer and corrosion reaction process.

Regulating Intermolecular Interactions and Film Formation Kinetics for Record Efficiency in Difluorobenzothiadizole-based Organic Solar Cells.

The difluorobenzothiadizole (ffBT) unit is one of the most classic electron-accepting building blocks used to construct D-A copolymers for applications in organic solar cells (OSCs). Historically, ffBT-based polymers have achieved record power conversion efficiencies (PCEs) in fullerene-based OSCs owing to their strong temperature-dependent aggregation (TDA) characteristics. However, their excessive miscibility and rapid aggregation kinetics during film formation have hindered their performance with state-of-the-art non-fullerene acceptors (NFAs). Herein, we synthesized two ffBT-based copolymers, PffBT-2T and PffBT-4T, incorporating different π-bridges to modulate intermolecular interactions and aggregation tendencies. Experimental and theoretical studies revealed that PffBT-4T exhibits reduced electrostatic potential differences and miscibility with L8-BO compared to PffBT-2T. This facilitates improved phase separation in the active layer, leading to enhanced molecular packing and optimized morphology. Moreover, PffBT-4T demonstrated a prolonged nucleation and crystal growth process, leading to enhanced molecular packing and optimized morphology. Consequently, PffBT-4T-based devices achieved a remarkable PCE of 17.5%, setting a new record for ffBT-based photovoltaic polymers. Our findings underscore the importance of conjugate backbone modulation in controlling aggregation behavior and film formation kinetics, providing valuable insights for the design of high-performance polymer donors in organic photovoltaics.

A New Mechanism for the Inhibition of SA106 Gr.B Carbon Steel Corrosion by Nitrite in Alkaline Water.

The purpose of this study was to investigate the composition of oxide films formed on SA106 Gr.B carbon steel in nitrite solutions at 35 °C for 1000 h. The product of the reduction of nitrite during the corrosion inhibition process was also examined. The X-ray photoelectron spectroscopy results revealed that a thin Fe3O4 film was formed and ammonium ions were adsorbed on the outermost surface of the oxide film. The presence of ammonium ions was also demonstrated by ion chromatography. These results indicate that nitrites are reduced to ammonium ions, which in turn promotes the formation of the protective Fe3O4 film.

Investigation on Be, Mg, Ca, B, Ga, C, Si, and Ge atoms doped on Al (111) surface and their effect on oxygen adsorption: A first-principle calculation

Oxygen corrosion of the aluminum alloy has a substantial impact on the durability of engineering materials and equipment. To better understand how various alloy elements affect oxygen corrosion, we used first-principle DFT method to study the role of each given dopant atom (Be, Mg, Ca, B, Ga, C, Si, and Ge) in the formation of surface oxide film on the Al (111) surface, in the case replacing a surface Al atom. Our calculations show that the electron gain or loss abilities of these alloy elements differ from that of Al metal, with Be, B, C, and Si atoms tending to penetrate into the surface, Mg, Ca, and Ga atoms protruding, and Ge atom just embedded into the Al (111) surfaces. Additionally, the type of doping element at the Al (111) surface can greatly affect the O2 absorption, predicting that Ca-doped surface absorb the least amount of oxygen, followed by Si-doped surface, with Be-, Mg-, B-, Ga-, C-, and Ge-doped surfaces showing higher O2 absorption. Based on adsorption energy (Eads) and partial density of states (PDOS) analysis, we conclude that the doped Al (111) surfaces can make O2 adsorption different owing to the difference in electronic properties of the doping atoms. These insights draw a greater knowledge of the role of alloy elements in the oxygen corrosion of Al alloys, enabling guidance for designing more corrosion-resistant materials.

Water Vapor Adsorption-Desorption Hysteresis Due to Clustering of Water on Nonporous Surfaces.

Water vapor is continuously adsorbed onto and desorbed from all kinds of surfaces depending on changes in relative humidity. Adsorption-desorption hysteresis of water that occurs on various nonporous surfaces and extends down to low relative humidities has been reported for decades, but remains unexplained. Here we show experimentally that such hysteresis is a common phenomenon on metal oxide and mineral surfaces and can be divided into two distinct categories based on the wettability of the adsorbent surface. Type I hysteresis occurs on more hydrophobic surfaces and is associated with adsorption isotherms that behave rather linearly as water saturation is approached, whereas type II hysteresis occurs on more hydrophilic surfaces and is associated with adsorption isotherms that curve steeply upward close to saturation. Our model calculations strongly indicate that adsorption in both types occurs cluster-wise, and the type I hysteresis is caused by contact angle hysteresis, while type II hysteresis is associated with film formation close to saturation. The understanding of water vapor adsorption and desorption mechanisms may be key for explaining and quantifying physical and chemical interfacial phenomena in atmospheric and industrial environments.

Click-Chemistry-Enabled Functionalization of Cellulose Nanocrystals with Single-Stranded DNA for Directed Assembly.

Controlling the self-assembly of cellulose nanocrystals (CNCs) requires precise control over their surface chemistry for the directed assembly of advanced nanocomposites with tailored mechanical, thermal, and optical properties. In this work, in contrast to traditional chemistries, we conducted highly selective click-chemistry functionalization of cellulose nanocrystals with complementary DNA strands via a three-step hybridization-guided process. By grafting terminally functionalized oligonucleotides through copper-free click chemistry, we successfully facilitated the assembly of brushlike DNA-modified CNCs into bundled nanostructures with distinct chiral optical dichroism in thin films. The complexation behavior of grafted DNA chains during the evaporation-driven formation of ultrathin films demonstrates the potential for mediating chiral interactions between the DNA-branched nanocrystals and their assembly into chiral bundles. Furthermore, we discuss the future directions and challenges that include new avenues for the development of functional, responsive, and bioderived nanostructures capable of dynamic reconfiguration via selective complexation, further surface modification strategies, mitigating diverse CNC aggregation, and exploring environmental conditions for the CNC-DNA assembly.

An electrochemical and theoretical approach towards the efficient microwave synthesis of imidazolium-based ionic liquids for unprecedented mild steel corrosion inhibition in 0.5 M H2SO4 solution

The inhibition potential of newly synthesized imidazolium-based ionic liquids (IL-1 and IL-2) on mild steel corrosion in a 0.5 M H2SO4 solution has been comprehensively investigated using gravimetric analysis, potentiodynamic polarization, and electrochemical impedance spectroscopy across various temperatures. Gravimetric analysis indicated that the adsorption of these inhibitors adhered to the Langmuir adsorption isotherm. Significantly, IL-2, featuring a longer alkyl chain, demonstrated superior inhibition efficiency (92.51 % at 303 K) compared to IL-1 (88.71 % at 303 K). Potentiodynamic polarization studies revealed a mixed-type inhibitory behavior, impacting both anodic and cathodic reactions. Surface morphological analyses via SEM and EDX confirmed the formation of a protective film on the mild steel surfaces, substantiating the corrosion inhibition capabilities of IL-1 and IL-2. The novelty of this research lies in the application of density functional theory (DFT) using the B3LYP method, which elucidated that the alkyl chain length at the N-3 position in imidazolium cation-based ionic liquids significantly enhances their inhibition potential. This mechanistic insight suggests that these ionic liquids effectively obstruct both anodic and cathodic sites, providing robust corrosion protection in a 0.5 M H2SO4 solution.

Film-forming modifications and mechanistic studies of soybean protein isolate by glycerol plasticization and thermal denaturation: A molecular interaction perspective

Plasticizer and thermal denaturation are indeed important factors for soybean protein film formation. The objective of the study was to investigate the effects of glycerol and thermal denaturation on the film-forming performances of soybean protein isolate (SPI) and elucidate the underlying mechanisms. From the results, glycerol had almost no effect on the protein’s secondary and tertiary structures. Indeed, the dispersion of glycerol diminished the intra- or intermolecular hydrogen bonding of SPI and interacted with the amino acids of subunits through hydrogen bonding and van der Waals forces. By interfering with protein network interactions, the glycerol molecule achieved a plasticizing effect on SPI films. The effects of heat treatment on SPI film properties were mainly realized through the changes in molecular conformation caused by protein denaturation, which manifested in the enhancement of light barrier and mechanical capabilities, and markedly altered the distribution of water states within the film network. This study provided valuable insights to clarify the mechanism of protein film formation.

Zr-based conversion film fabricated on cold rolled steel by separately providing zirconium and fluorine ions: Performance and mechanism study

Controlling the concentrations of Zr4+ and F− in traditional Zirconium (Zr)-based film-formation solution is challenging due to their dependence on the hydrolytic equilibrium of H2ZrF6. In this study, Zr-based films were prepared on cold rolled steel surface through the film-formation solution prepared by mixing Zr(NO3)4 and different amount of HF. The electrochemical results demonstrated that the Zr-based film prepared by Zr(NO3)4 and HF exhibited superior corrosion resistance compared to H2ZrF6. Under optimal film formation conditions, the protective efficiency of the prepared film reached 74.4 % which was higher than that of film fabricated in H2ZrF6. The electrochemical results concurrently demonstrated the self-reinforcing anti-corrosion performance of the prepared films. Scanning electron microscopy revealed that the Zr film, prepared in Zr(NO3)4 and HF, exhibited excellent corrosion resistance attributed to its high film density. The X-ray photoelectron spectroscopy and energy dispersive spectroscopic results indicated the presence of a fluoride layer on the surface of the Zr film. The F− ions can chelate with the corrosion products and selectively deposit onto the damaged areas of the film, thereby effectively contributing to the repair of the film layer. The results of density functional theory calculations demonstrated that Zr4+ readily forms Zr(OH)4 rather than ZrF62−. The present study offers an enhanced approach for regulating the properties of films prepared via H2ZrF6 by separately providing zirconium and fluorine ions.

A Study on the Influence of Functionalized Graphene on the Mechanical and Biocompatibility Performance of Electrospun Polyvinyl Alcohol Nanocomposites

Polyvinyl alcohol (PVA), a synthetic polymer produced by polymerizing vinyl acetate and subjecting it to alkaline hydrolysis, exhibits properties such as film formation, emulsification, and adhesion. However, pure PVA’s biocompatibility and mechanical properties are limited. Its hydrophilicity also causes it to dissolve in water and blood, rendering it less suitable for drug delivery applications. To address these limitations, PVA was crosslinked with glutaraldehyde (GA) to enhance toughness and resistance to water and blood dissolution. Additionally, carboxyl (COOH) and hydroxyl (OH) functionalized graphene were incorporated into electrospun PVA nanocomposites to further improve their mechanical properties. The results show that adding COOH- and OH-functionalized graphene in four different concentrations (0.5, 1.0, 1.5, and 2.0 wt.%) significantly enhanced the mechanical characteristics of PVA nanocomposites. Tensile strength and Young's modulus increased substantially, with OH-functionalized graphene increasing tensile strength and Young's modulus by 224% and 338.3%, respectively, and COOH-functionalized graphene increasing these properties by 245.6% and 371.4%. Morphological characterization using FT-IR and FESEM confirmed the successful incorporation of graphene into the PVA matrix. Biocompatibility testing through APTT and PT assays showed both nanocomposites are biocompatible, suggesting their potential for biomedical applications. The optimal filler concentration for both graphene types was 1.5 wt.%. This research demonstrates the promising potential of innovative materials for healthcare and biomedical engineering applications.

Electrochemical, thermodynamic and DFT studies of Fomitopsis pinicola as green corrosion inhibitor for carbon steel in sulfuric acid

In this work, the methanolic extract of Fomitopsis pinicola has been evaluated as a green corrosion inhibitor for the dissolution of 1018 carbon steel in 0.5 M sulfuric acid. For this, gravimetric tests and electrochemical methods such as potentiodynamic polarization curves, linear polarization resistance (LPR) and Electrochemical Impedance Spectroscopy (EIS) techniques were used. These tests were aided with Infrared and GC–MS analytical techniques. In addition to this, theoretical calculation with the use of the density functional theory (DFT) technique has been used to correlate the electronic extract properties and its inhibitory capacity. Weight loss results have shown an inhibitor efficiency of 85 % with the addition of 400 ppm. Thermodynamic parameters have shown that Fomitopsis pinicola extract is physically adsorbed onto the steel following a Langmuir adsorption isotherm. Potentiodynamic polarization curves showed that the extract behaves as a mixed type of corrosion inhibitor inducing the formation of a protective film onto the steel surface. In the presence of the Fomitopsis pinicola extract, a more resistive film obtained the highest polarization resistance value when 400 ppm of extract was used. In addition to this, as the concentration of the extract increased the charge transfer resistance and the double electrochemical layer capacitance decreased. GC–MS results indicated that main compounds contained in the Fomitopsis pinicola extract were Dehydrergosterol, Hydrazino-acetic acid ethyl ester, and Phthalic acid, di (2-propylpentyl) ester, whereas theoretical calculations showed that the highest EHOMO and lowest ELUMO values correspond to Dehydrergosterol and the Phthalic acid, which are the responsible for the extract inhibitory properties.

Colloidal Stabilizer‐Mediated Crystal Growth Regulation and Defect Healing for High‐Quality Perovskite Solar Cells

AbstractHigh‐quality perovskite (PVK) films is essential for the fabrication of efficient and stable perovskite solar cells (PSCs). However, unstable colloidal particles in PVK suspensions often hinder the formation of crystalline films with low defect densities. Herein, ethylenediaminetetraacetic acid (EDTA) as a colloidal stabilizer into lead iodide (PbI2) is introduced colloidal solutions. EDTA forms chelated complexes with Pb2+, enhancing the electrostatic repulsion and steric hindrance between colloidal particles. This stabilizes the particles and inhibits disordered motion (Brownian motion) and excessive aggregation. As a result, PbI2 films with a uniform hole distribution are formed, providing ample pathways for subsequent PVK film growth and sufficient space. During the film formation process, the replacement of molecules by formamidinium iodide (FAI) and EDTA slows down crystallization, ultimately leading to PVK films with large grain sizes and low defect density. By using this approach, champion power conversion efficiencies (PCEs) of 24.05% for FA0.97Cs0.03PbI3 PSC, 11.08% for CsPbBr3 PSC, and 25.19% for FA0.945MA0.025Cs0.03Pb(I0.975Br0.025)3 PSC are achieved. Moreover, the EDTA‐based FA0.97Cs0.03PbI3 device retains over 90% of its initial PCE after 1000 h at the maximum power point (MPP) under continuous illumination.

Mechanism of Improving Etching Selectivity for E-Beam Resist AR-N 7520 in the Formation of Photonic Silicon Structures

The selectivity of the reactive ion etching of silicon using a negative electron resist AR-N 7520 mask was investigated. The selectivity dependencies on the fraction of SF6 in the feeding gas and bias voltage were obtained. To understand the kinetics of passivation film formation and etching, the type and concentration of neutral particles were evaluated and identified using plasma optical emission spectroscopy. Electron temperature and electron density were measured by the Langmuir probe method to interpret the optical emission spectroscopy data. A high etching selectivity of 8.0 ± 1.8 was obtained for the etching process. The optimum electron beam exposure dose for defining the mask was 8200 pC/m at 30 keV.