Drop-coating Method Research Articles

Double Free: A Promising Route toward Moisture-Stable Hypotoxic Hybrid Perovskites

Double Free: A Promising Route toward Moisture-Stable Hypotoxic Hybrid Perovskites

Study on the Ion Substitution Mechanism of CsPbIBr2 Films Prepared by a Drop-Coating Method

In this paper, the ion substitution mechanism of CsPbIBr2 films prepared by a drop-coating method is studied. CsI/CsBr methanol solution is drop-coated on a CsPbIBr2 precursor film to prepare the CsPbIBr2 perovskite film. After drop-coating, it is found that the color of the perovskite film changes with CsI/CsBr methanol solution drop-coated on the perovskite precursor film. When CsBr methanol solution is drop-coated on a CsPbIBr2 precursor film, the color of the obtained CsPbIBr2 film is orange. The color of the obtained CsPbIBr2 film is brown while CsI methanol solution is drop-coated on a CsPbIBr2 precursor film. Then, the hole-free, carbon-based CsPbIBr2 perovskite solar cells (FTO/ZnO/CsPbIBr2/C) are fabricated. For the solar cells fabricated by drop-coating with 30 μL of CsBr, without methanol solution, with 10 μL of CsI, with 50 μL of CsI, and with 90 μL of CsI, the power conversion efficiency (PCE) values are 2.98, 3.99, 6.04, 7.60, and 8.42%, respectively. The short-circuit current density (JSC) also increases with the changing of drop-coating solution. Therefore, we suppose that perhaps there is an ion substitution during the preparation of the CsPbIBr2 films. The ion substitution supposition is verified by the results of X-ray diffraction, ultraviolet–visible spectra, X-ray photoelectron spectroscopy, and secondary ion mass spectroscopy. Specifically, the I element is replaced by the Br element while drop-coating CsBr methanol solution. The Br element is substituted by the I element by drop-coating CsI methanol solution. Also, it is verified that the ion substitution occurs in the entire perovskite film.

Flexible paper-based Ni-MOF composite/AuNPs/CNTs film electrode for HIV DNA detection

It is very important to develop a rapid, simple, low cost point-of-care (POC) method for the early diagnosis of pathogens. In this work, a flexible paper-based electrode based on nickel metal-organic framework (Ni-MOF) composite/Au nanoparticles/carbon nanotubes/polyvinyl alcohol (Ni–Au composite/CNT/PVA) was constructed to detect target human immunodeficiency virus (HIV) DNA by DNA hybridization using methylene blue (MB) as a redox indicator. The CNT/PVA and Ni–Au composite were deposited on the cellulose membrane by vacuum filtration and drop-coating method in turn to obtain Ni–Au composite/CNT/PVA (CCP) film electrode. Compared to the CNT/PVA film electrode, CCP film electrode makes a higher loading of the probe DNA for its large specific surface area and conjugated π-electron system that can provide hydrogen bond sources to achieve interactions between MOF and single-stranded DNA, which improves the sensitivity for detecting target DNA. The variation of peak current for MB molecules adsorbed onto DNA before and after hybridization with HIV DNA was monitored. Electrochemical results proved that the CCP film maintained stable electrochemical property even after bending 200 times or stretching under different strains from 0% to 20%. The flexible paper electrode showed excellent sensing performance with a linear range of 10 nM–1 μM and a low detection limit of 0.13 nM. The target HIV DNA was successfully detected even in complex serum samples using the flexible CCP film electrode. Therefore, the simple and inexpensive flexible paper-based MOF composite film electrode can also be utilized for other pathogens POC diagnosis.

A Highly Efficient and Stable Photocatalyst; N-Doped ZnO/CNT Composite Thin Film Synthesized via Simple Sol-Gel Drop Coating Method.

The thin film of N-doped ZnO/CNT nanocomposite was successfully fabricated on soda lime glass substrate by a simple sol-gel drop-coating method. The structural, morphological, chemical, and optical properties of as prepared samples were characterized by a variety of tools such as X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared spectroscopy (FT-IR), and UV-visible spectroscopy. The hexagonal crystalline structure was confirmed from XRD measurement without any other impurity phase detection in samples. The N-doped ZnO/CNT composite showed excellent photo-catalytic activity towards cationic methylene blue (MB) dye degradation with 100% removal rate under UV light irradiation as compared to N-doped ZnO (65%) and pure ZnO (47.36%). The convincing performance has also been observed for the case of visible light irradiation. The enhancement of that photocatalytic activity might be due to narrowing the band gap as well as the reduction of electron–hole pair recombination in ZnO matrix with the incorporation of dopant nitrogen and CNT. It is assumed from the obtained results that N-doped ZnO/CNT nanocomposite thin film can be employed as an economically achievable and ecofriendly method to degrade dye with UV and visible light irradiation. Additionally, density functional theory (DFT) calculations were applied to explore the effect of N-doping on electronic structure of ZnO. The computational study has supported the experimental results of significant band gap contraction, which leads to the maximum absorption towards higher wavelength and no appreciable change of lattice parameters after doping. A conceivable photocatalytic mechanism of N-doped ZnO/CNT nanocomposite has been proposed as well.

Facile environment-friendly peptide-based humidity sensor for multifunctional applications

Humidity monitoring plays a key role in the human–machine interface (HMI) and health-related devices. Current inorganic sensing materials provide a stable and fast method to monitor relative humidity (RH). However, these materials require complicated preparation processes and even toxic reagents. Organic humidity-sensing materials were considered to be biocompatible, but they face slow response time and cannot be used in real-time systems. There is still a great challenge to seek biocompatible humidity-sensing materials with high performance. Micro-nano structures formed by self-assembled peptides have been proven to have good optical, mechanical, semiconductive properties and intrinsic biocompatibility, which can be used for monitoring human health and activities. Herein, we reported an environmentally friendly humidity sensor based on peptide self-assembled micro-nano fibers. This humidity sensor was fabricated by a drop-coating method, in which the peptide fiber served as the humidity-sensing material and the Au electrode was used as a substrate. Self-assembled fiber networks exhibit excellent absorption of water molecules, which result in an extraordinary humidity sensitivity of more than 30,000 as well as ultrafast response (66 ms). To demonstrate the multifunctional possibilities, peptide humidity sensors were applied to respiration monitoring, non-contact switch, and baby diaper wetting monitoring. Our results provide useful strategies for detecting humidity changes in physiological activities based on peptide self-assembled fibers. These results indicated that peptide could be a promising candidate for human–machine interaction and healthcare humidity monitoring.

WGM lasing in irregular cavities with arbitrary boundaries.

Because of its limited light field mode and high Q value, the whispering-gallery-mode (WGM) cavity has been widely studied. In this study, we propose a simple, rapid, low-cost and no-manufacturing technology method that we call the drip-coating method to obtain an irregular cavity with arbitrary boundaries. By using polyvinyl alcohol (PVA) solution doped with rhodamine 6G, the irregular cavity with arbitrary boundaries was drip-coated on a high-reflection mirror, forming a WGM laser. The sample was pumped with a 532 nm pulsed laser, and the single-mode WGM and multi-WGM lasing were obtained. All WGMs are the vertical oscillation modes, which originate from both the total internal reflection of the PVA/air interface and vertical reflection of the PVA/mirror interface. The other boundaries of the cavity were not involved in the reflection and could have any shape. The mechanism of producing single-mode lasing is due to the action of the loss-gain cavity. Multi-WGM lasing is attributed to at least two groups of different WGMs existing in an irregular cavity. This can be confirmed by using a microsphere model and intensity correlation method. These results may provide an alternative for the design of WGM lasers.

Methane Combustion Using Pd Deposited on CeOx-MnOx/La-Al2O3 Pellistors.

Pd deposited on CeOx-MnOx/La-Al2O3 has been prepared as a sensitive material for methane (CH4) detection. The effect of different amounts (1.25%, 2.5% and 5%) of Pd loading has been investigated. The as prepared materials were deposited on Pt microcoils using a drop-coating method, as a way of developing pellistors operated using a Wheatstone bridge configuration. By spanning the operating temperature range between 300 °C and 550 °C, we established the linearity region as well as the maximum sensitivity towards 4900 ppm of CH4. By making use of the sigmoid dependence of the output voltage signal from the Wheatstone bridge, the gas surface reaction and diffusion phenomena have been decoupled. The pellistor with 5% Pd deposited on CeOx-MnOx/La-Al2O3 exhibited the highest selective-sensitivity in the benefit of CH4 detection against threshold limits of carbon monoxide (CO), sulfur dioxide (SO2) and hydrogen sulfide (H2S). Accordingly, adjusting the percent of Pd makes the preparation strategies of pellistors good candidates towards CH4 detection.

Decoration of γ-graphyne on TiO2 nanotube arrays: Improved photoelectrochemical and photoelectrocatalytic properties

A series of γ-graphyne/TiO2 nanotube array heterostructures are first synthesized by a facile and environmental-friendly drop-coating method. The prepared heterostructures is completely investigated by a collection of characterizations. Interestingly, the unique C-O-Ti linkage between γ-graphyne and TiO2 nanotube arrays is verified by both X-ray photoelectron spectroscopy and Fourier transform infrared analysis. After modification of γ-graphyne, the maximum transient photo-current and photo-potential of TiO2 nanotube arrays are improved by 2.2 and 1.3 folds, respectively. Moreover, a maximum of 3.64 and 1.35 folds enhancements are severally verified for the photoelectrocatalytic degradation of levofloxacin and rhodamine B over the heterostructures compared to that of TiO2 nanotube arrays. Furtherly, the heterostructures also show superior photoelectrocatalytic performance on nitrogen fixation and oxygen evolution than TiO2 nanotube arrays. The crystal, morphological, photoelectrochemical, and photoelectrocatalytic stability of the heterostructures are confirmed. This work sheds light on designing γ-graphyne modified composites for photoelectrochemical and photoelectrocatalytic application.

Robust Superamphiphobic Coatings Based on Raspberry-like Hollow SnO2 Composites.

Good mechanical and chemical stabilities are the key factors for the wide application of superhydrophobic surfaces. In this work, we first prepared raspberry-like hollow structured SnO2 nanoparticles using a simple hydrothermal method, followed by an annealing step. Then, the intrinsic raspberry-like hollow SnO2 nanoparticles were combined with hydrophilic SiO2 nanoparticles to construct rough surfaces with suitable hierarchical structures, and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS-17) was used as a hydrophobic modifier of SnO2, while epoxy resin was used as an adhesive to prepare a superamphiphobic coating with good stability and durability. Such a coating can be applied on various substrates using a simple spray-coating or drop-coating method. The water contact angle and diiodomethane contact angle of the coating could reach up to ∼165 and ∼151°, respectively. After various chemical and mechanical stability tests including hot water treatment, salt water corrosion, strong adhesive tape peeling, and kneading, the coatings still remained amphiphobic. The facile fabrication of the robust superhydrophobic coating has great potential for applications in real life and industrial production.

Synthesis of High-Performance Photonic Crystal Film for SERS Applications via Drop-Coating Method

Silica nanospheres with a well-controlled particle size were prepared via a nucleation-to-growth synthesis process. A facile method is proposed for improving the self-assembly behavior of silica colloidal particles in droplet coatings by the simple controlling of the drying temperature. It is shown that a periodically arranged, opal-structured, photonic crystal film with a large area of approximately 4.0 cm2 can be prepared, even when the particle size is up to 840 nm. When the band gap of the silica photonic crystals falls in the visible-light region, the crystals exhibit distinct structural colors. Moreover, the wavelength of the reflected light increases with an increasing particle size of silica. When the photonic band gap overlaps the wavelength of the laser source, the overall Raman spectrum intensity is significantly enhanced. Accordingly, the proposed nucleation-to-growth process and drop-coating method provides a cheap and simple approach for the manufacture of uniform sized silica and surface-enhanced Raman scattering substrates, respectively.

Influence of precursor concentration on printable mesoscopic perovskite solar cells.

Over the last decade, the power conversion efficiency of hybrid organic-inorganic perovskite solar cells (PSCs) has increased dramatically from 3.8% to 25.2%. This rapid progress has been possible due to the accurate control of the morphology and crystallinity of solution-processed perovskites, which are significantly affected by the concentration of the precursor used. This study explores the influence of precursor concentrations on the performance of printable hole-conductor-free mesoscopic PSCs via a simple one-step drop-coating method. The results reveal that lower concentrations lead to larger grains with inferior pore filling, while higher concentrations result in smaller grains with improved pore filling. Among concentrations ranging from 0.24-1.20 M1), devices based on a moderate strength of 0.70 M were confirmed to exhibit the best efficiency at 16.32%.

Removal of fluoride from water using activated carbon fibres modified with zirconium by a drop-coating method

Metal-modified carbon materials have been widely used for fluoride removal, but the traditional impregnation by soaking method suffers from low loading of metals and substantial use of chemicals. This study proposed a new approach to prepare zirconium modified activated carbon fibres (Zr-ACF) by a drop-coating method. Using the same amount of chemicals, the drop-coating method yielded a 5.5 times higher fluoride adsorption capacity than the soaking method due to more effective loading of Zr(IV) onto ACF. The effects of various preparation conditions, including the addition of a complexing agent (oxalic acid) and Zr/ACF mass ratio (0.2–1), were investigated. Zr-ACF prepared by drop-coating was characterised by SEM and BET, and the functional groups involved in the anchoring of Zr(IV) on ACF and the adsorption of fluoride onto Zr-ACF were identified by FTIR and XPS. Adsorption experiments at pH between 3 and 11 revealed that ion exchange and electrostatic attraction were the main adsorption mechanisms at different pH levels. Co-existing anions such as CO32−, HCO3− and Cl− had an insignificant negative impact (<5%) on fluoride adsorption capacity while SO42− decreased fluoride adsorption capacity by 11.5%. The adsorption kinetics followed the pseudo-second-order model. The adsorption isotherms followed the Langmuir isotherm model with a maximum fluoride adsorption capacity of 28.50 mg/L at 25 °C, which was higher than other carbon-based materials in the literature. The remarkable improvement of adsorption capacity and reduced chemical consumption demonstrate that Zr-ACF prepared by drop-coating is a promising adsorbent for fluoride removal.

Preparation and photo-responsive behavior of reversible photochromic polyurethane cement composites

A smart coating based on a polyurethane cement (PUC) substrate with photochromic behavior and anti-ultraviolet performance was obtained successfully by depositing photochromic sol–gel material on the PUC surface using a simple drop-coating method. The results revealed that the PM concentration considerably affected the photochromic properties. The total color change (ΔE*) was optimum (66) at a PM concentration of 20%. The chromogenic time of the photochromic PUC was 2.4 s, and the fading time was 30 s at room temperature. Furthermore, accelerated aging and abrasion tests suggested that the treated PUC composites had excellent anti-ultraviolet properties and mechanical stability. The results indicate that the proposed photochromic PUC is a promising candidate for many applications, such as road and bridge construction and green buildings.

Fabrication of durable polytetrafluoroethylene superhydrophobic materials with recyclable and self-cleaning properties on various substrates

Most of the artificial superhydrophobic surfaces easily lose their good water repellency once they are chemically or mechanically damaged, which seriously hinders their practical application. Durable superhydrophobic materials with recyclability, low-temperature resistance, and self-cleaning properties were successfully prepared by employing silica particles and polytetrafluoroethylene via a simple drop-coating method. The as-prepared superhydrophobic materials not only show excellent superhydrophobicity but also display fascinating durability and chemical stability after a series of rigorous tests. Importantly, the debris scraped from the superhydrophobic materials can be recycled and easily reused to prepare new superhydrophobic materials. This facile strategy may pave the way for the scalable and recyclable robust superhydrophobic materials in practical applications.

A Facile Fabrication of a Potentiometric Arrayed Glucose Biosensor Based on Nafion-GOx/GO/AZO.

In this study, the potentiometric arrayed glucose biosensors, which were based on zinc oxide (ZnO) or aluminum-doped zinc oxide (AZO) sensing membranes, were fabricated by using screen-printing technology and a sputtering system, and graphene oxide (GO) and Nafion-glucose oxidase (GOx) were used to modify sensing membranes by using the drop-coating method. Next, the material properties were characterized by using a Raman spectrometer, a field-emission scanning electron microscope (FE-SEM), and a scanning probe microscope (SPM). The sensing characteristics of the glucose biosensors were measured by using the voltage–time (V-T) measurement system. Finally, electrochemical impedance spectroscopy (EIS) was conducted to analyze their charge transfer abilities. The results indicated that the average sensitivity of the glucose biosensor based on Nafion-GOx/GO/AZO was apparently higher than that of the glucose biosensor based on Nafion-GOx/GO/ZnO. In addition, the glucose biosensor based on Nafion-GOx/GO/AZO exhibited an excellent average sensitivity of 15.44 mV/mM and linearity of 0.997 over a narrow range of glucose concentration range, a response time of 26 s, a limit of detection (LOD) of 1.89 mM, and good reproducibility. In terms of the reversibility and stability, the hysteresis voltages (VH) were 3.96 mV and 2.42 mV. Additionally, the glucose biosensor also showed good anti-inference ability and reproducibility. According to these results, it is demonstrated that AZO is a promising material, which could be used to develop a reliable, simple, and low-cost potentiometric glucose biosensor.

Reduced Graphene Oxide/TEMPO-Nanocellulose Nanohybrid-Based Electrochemical Biosensor for the Determination ofMycobacterium tuberculosis

A novel peptide nuclide acid (PNA) electrochemical biosensor based on reduced graphene oxide (NH2-rGO)/2,2,6,6-tetramethylpiperidin-1-yl)oxyl nanocrystalline cellulose (TEMPO-NCC) for the detection ofMycobacterium tuberculosis(M. Tuberculosis) is described. In this study, the nanohybrid films NH2-rGO/TEMPO-NCC were immobilized onto screen-printed carbon electrode (SPE) via a simple drop-coating method. The electrochemical characterization of the designed electrode was investigated using cyclic voltammetry (CV) and impedance spectroscopy (EIS). Meanwhile, the sensitivity and selectivity of the designed biosensor againstM. tuberculosiswere measured by the differential pulse voltammetry (DPV). The response of the PNA probe-modified (NH2-rGO)/TEMPO-NCC demonstrated that the fabricated biosensor was able to distinguish between complementary, noncomplementary, and one-base mismatch DNA sequences using methylene blue (MB) as the electrochemical indicator. The developed electrochemical biosensor exhibited a linear calibration curve in the concentration range of1×10−8 Mto1×10−13 Mwith the limit of detection of3.14×10−14 M. The developed electrochemical biosensor has also been tested with a polymerase chain reaction (PCR) product ofM. tuberculosisDNA which has shown successful results in distinguishing between negative and positive samples of M. tuberculosis.

Highly conducting Sc and Y co-doped ZrO2 thin film solid electrolyte on a porous Ni/YSZ electrode prepared via simple drop-coating method

Dense and crack-free thin film solid electrolyte of scandium and yttrium co-doped zirconia (Sc0.08Y0.08Zr0.84O1.92) or 4S4YSZ has been successfully deposited on a NiO-YSZ porous electrode substrate via simple drop-coating deposition method. The 4S4YSZ precursor powder was synthesized using sol-gel method and the NiO-YSZ substrate, with 1:1 wt% composition, was prepared via modified glycine-nitrate combustion method. The NiO-YSZ substrates were pre-sintered at different temperatures, 1000 °C and 1300 °C, to investigate the effect on the thin film deposition and its microstructure. XRD results showed that both 4S4YSZ and NiO-YSZ exhibited a cubic crystal structure with no observable impurity peaks. SEM-EDS revealed a dense morphology of 4S4YSZ thin film with thickness of about 7μm after sintering while maintaining a desirable porous NiO-YSZ microstructure of the electrode substrate for the 1000 °C pre-sintered substrate as compared to a still porous solid electrolyte for the higher substrate pre-sintering temperature at 1300 °C. And from the conductivity measurements using EIS, the 4S4YSZ thin film revealed a notable high total conductivity of about 1.2x10-1 Scm-1 at 700 °C with 0.73 eV activation energy. Reduction of NiO/YSZ to Ni/YSZ further increases the porosity of the electrode substrate while maintaining a dense solid electrolyte thin film.

Surface and morphology analyses, and voltammetry studies for electrochemical determination of cerium(iii) using a graphene nanobud-modified-carbon felt electrode in acidic buffer solution (pH 4.0 ± 0.05).

Trace determination of radioactive waste, especially Ce3+, by electrochemical methods has rarely been attempted. Ce3+ is (i) a fluorescence quencher, (ii) an antiferromagnet, and (iii) a superconductor, and it has been incorporated into fast scintillators, LED phosphors, and fluorescent lamps. Although Ce3+ has been utilized in many industries due to its specific properties, it causes severe health problems to human beings because of its toxicity. Nanomaterials with fascinating electrical properties can play a vital role in the fabrication of a sensor device to detect the analyte of interest. In the present study, surfactant-free 1,8-diaminonaphthalene (DAN)-functionalized graphene quantum dots (DAN-GQDs) with nanobud (NB) morphology were utilized for the determination of Ce3+ through electrochemical studies. The working electrode, graphene nanobud (GNB)-modified-carbon felt (CF), was developed by a simple drop-coating method for the sensitive detection of Ce3+ in acetate buffer solution (ABS, pH 4.0 ± 0.05) at a scan rate of 50 mV s−1 using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. CV and DPV studies validated the existence of distinctive peaks at approximately +0.20 and +0.93 V (vs. SCE), respectively, with a limit of detection of approximately 2.60 μM. Furthermore, electrochemical studies revealed that the GNB-modified-CF electrode was (i) stable even after fifteen cycles, (ii) reproducible, (iii) selective towards Ce3+, (iv) strongly pH-dependent, and (v) favored Ce3+ sensing only at pH 4.0 ± 0.05. Impedance spectroscopy results indicated that the GNB-modified-CF electrode was more conductive (1.38 × 10−4 S m−1) and exhibited more rapid electron transfer than bare CF, which agrees with the attained Randles equivalent circuit. Microscopy (AFM, FE-SEM, and HR-TEM), spectroscopy (XPS and Raman), XRD, and energy-dispersive X-ray (EDX) analyses of the GNB-modified-CF electrode confirmed the adsorption of Ce3+ onto the electrode surface and the size of the electrode material. Ce3+ nanobuds increased from 35–40 to 50–55 nm without changing their morphology. The obtained results provide an insight into the determination of Ce3+ to develop an electrochemical device with low sensitivity.

The design and development of short peptide-based novel smart materials to prevent fouling by the formation of non-toxic and biocompatible coatings.

Biofouling refers to the undesirable process that leads to the accumulation of microorganisms such as bacteria or fungi on substrates. This is one of the major concerns associated with several components of our regular life such as food, health, water and energy. In the healthcare sector, biofouling on medical devices is known to cause infections, which are often resistant to conventional antibiotics and lead to increase in the number of hospital and surgery-related deaths. One of the better ways to tackle the problem of biofouling is the development of smart antifouling materials that can produce a biocompatible, non-toxic, eco-friendly and functional coating and maintain a biological environment without any adverse effect. To this end, in the present study, we have reported the design and synthesis of two simple chemically modified peptides, namely, PA1 (PFB-VVD) and PA2 (PFB-LLE). The design as well as the amino acid sequence of the peptides contains three basic components that enable their ability to (i) self-assemble into functional coatings, (ii) bind with the desired surface via the bi-dentate coordination of dicarboxylate groups and (iii) exhibit antifouling activity and generate a non-toxic biocompatible supramolecular coating on the desired surface. PA1 having aspartic acid as the anchoring moiety exhibits better antifouling activity compared to PA2 that has glutamic acid as the anchoring moiety. This is probably due to the greater adhesive force or binding affinity of aspartic acid to the examined surface compared to that of glutamic acid, as confirmed by force measurement studies using AFM. Most importantly, the simple drop-coating method promises great advantages due to its ease of operation, which leads to a reduction in the production cost and increase in the scope of commercialization. To the best of our knowledge, this is the first attempt to develop an ultra-short peptide-based smart antifouling material with a dicarboxylate group as the surface binding moiety. Furthermore, these findings promise to provide further insights into antifouling mechanisms in the future by the development of a smart material using a dicarboxylate group as an anchoring moiety.

ZnPc/TiO2 composites for photocathodic protection of 304 stainless steel

ZnPc/TiO2 composites were synthesized by a drop-coating method and used as photoanodes for photocathodic protection to slow the corrosion of 304 stainless steel (304SS). TiO2 is a wide-band-gap (3.2 eV) conductor that only absorbs UV light with a wavelength <380 nm, and the recombination rate of photogenerated carriers in TiO2 is high. Zinc phthalocyanine (ZnPc) is a material with strong visible-light absorption. The combination of ZnPc and TiO2 can increase the absorption of visible light. Furthermore, the lowest unoccupied molecular orbital (LUMO) conduction-band level of ZnPc is higher than that of TiO2; thus, the electrons in ZnPc excited by the light can migrate to the conduction band of TiO2, thereby accelerating the separation of electrons and holes. The results show that the visible-light absorption of the ZnPc/TiO2 composite is markedly improved compared with that of TiO2 alone. The open-circuit potential (OCP) of 304SS coupled with the ZnPc/TiO2 composite decreased substantially compared with that of 304SS coupled with pure TiO2, reaching approximately −700 mV. The proposed ZnPc/TiO2 composites offer superior photocathodic protection for 304SS.