Sulfur vacancy-enhanced In2S3-x hollow microtubes for photocatalytic Cr (VI) and tetracycline removal.

Morphological regulation and defect engineering are efficient methods for photocatalytic technology by improving photon absorption and electron dissociation. Herein, In2S3-x hollow microtubes with S-vacancies (MIS) were fabricated via a simple solvothermal reaction using In-based metal-organic frameworks (In-MOFs) as a precursor. Experimental results demonstrate that the hollow structure and optimal S-vacancies can jointly accelerate the photocatalytic reaction, attributed to a larger specific surface area, more active sites, and faster electron transfer efficiency. The champion MIS(2) displayed significantly better photocatalytic activity for Cr(VI) reduction and tetracycline (TC) degradation. The Cr(VI) reduction rate by MIS(2) is 3.67 and 2.82 times higher than those of optimal In2S3 template-free (HIS(2)) and MIS(1) with poor S-vacancies, respectively. The removal efficiency of TC by MIS(2) is 1.37 and 1.15 times higher than those of HIS(2) and MIS(1). Further integration of MIS(2) with aerogel simplifies the recovery process significantly.

N-Doped Carbon/CeO2 Composite as a Biomimetic Catalyst for Antibacterial Application.

Exploring new and high efficiency mimic enzymes is a vital and novel strategy for antibacterial application. Haloperoxidase-like enzymes have attracted wide attention thanks to their amazing catalytic property for hypohalous acid generation from hydrogen peroxide and halides. However, few materials have displayed halogenating catalytic performance until now. Herein, we synthesized N-doped C/CeO2 (N-C/CeO2) composite materials by a combination of the liquid and solid-state method. N-C/CeO2 can possess haloperoxidase-like catalytic activity by catalyzing the bromination of organic signaling compounds (phenol red) with H2O2 at a wide range of temperatures (20 °C to 55 °C), with a solution color changing from yellow to blue. Meanwhile, it exhibits high catalytic stability/recyclability in the catalytic reaction. The synthesized N-C/CeO2 composite can effectively catalyze the oxidation of Br- with H2O2 to produce HBrO without the presence of phenol red. The produced HBrO can resist typical marine bacteria like Pseudomonas aeruginosa. This study provides an efficient biomimetic haloperoxidase and a novel sustainable method for antibacterial application.

Extracellular Polymeric Substances and Biocorrosion/Biofouling: Recent Advances and Future Perspectives.

Microbial cells secrete extracellular polymeric substances (EPS) to adhere to material surfaces, if they get in contact with solid materials such as metals. After phase equilibrium, microorganisms can adhere firmly to the metal surfaces causing metal dissolution and corrosion. Attachment and adhesion of microorganisms via EPS increase the possibility and the rate of metal corrosion. Many components of EPS are electrochemical and redox active, making them closely related to metal corrosion. Functional groups in EPS have specific adsorption ability, causing them to play a key role in biocorrosion. This review emphasizes EPS properties related to metal corrosion and protection and the underlying microbially influenced corrosion (MIC) mechanisms. Future perspectives regarding a comprehensive study of MIC mechanisms and green methodologies for corrosion protection are provided.

AgInS2 and graphene co-sensitized TiO2 photoanodes for photocathodic protection of Q235 carbon steel under visible light.

AgInS2 nanoparticle and graphene nanosheet co-sensitized anatase TiO2 nanotube array films were fabricated by a combination of hydrothermal reaction and electrochemical anodization on titanium sheets. The results showed that the co-sensitization of AgInS2 nanoparticles and graphene nanosheets extended the photoresponse of TiO2 nanotubes into the visible-light region, and improved the photogenerated charge separation and transfer capability. The photocurrent density of the AgInS2/graphene/TiO2 composites (about 4.0 mA cm-2) was 20 times that of bare TiO2 (only 0.2 mA cm-2) under visible-light illumination. The potential negative shift value of AgInS2/graphene/TiO2 composites was up to 0.68 V versus saturated calomel electrode. The AgInS2/graphene/TiO2 composites can provide Q235 carbon steel with highly efficient photocathodic protection under visible-light illumination.

Microbiologically influenced corrosion of marine steels within the interaction between steel and biofilms: a brief view.

Marine is the harshest corrosive environment where almost all marine underwater equipment and facilities undergo corrosion caused by marine microorganisms. With the development of marine resources globally, the marine engineering and relevant infrastructures have increased exponentially. Microbiologically influenced corrosion (MIC) leads to severe safety accidents and great economic losses. The specific aggregation of corrosive microbial communities and their interactions with materials conform to a typical ecological adaptation mechanism. On the one hand, corrosive biofilms in the marine environment selectively colonize on a specific steel substrate by utilizing their complex community composition and various extracellular polymeric substances; on the other hand, the elemental composition and surface microstructure of different engineering steels affect the microbial community and corrosive process. MIC in the marine environment is a dynamic process evolving with the formation of corrosive biofilms and corrosion products. In this mini-review, the interactions between corrosive biofilm and steel substrates are explored and discussed, especially those conducted in situ in the marine environment. Herein, the important role of iron in the dynamic process of marine corrosion is highlighted.

Preparation of ZnWO4/TiO2 composite film and its photocathodic protection for 304 stainless steel under visible light.

ZnWO4/TiO2 composite films were fabricated on TiO2 substrate by hydrothermal method. The ZnWO4 nanorods-sensitized TiO2 coupled with 304 stainless steel was served as photoelectrode to study its anticorrosion effect for metal. Under visible light, the photocathodic protection ability of TiO2 and ZnWO4/TiO2 composite film was measured by photoelectrochemical program on potentiostat. Open circuit potential variation result showed that sanmartinite ZnWO4 nanorods could enhance the photoelectrochemical activity of TiO2, and the ZnWO4/TiO2 composite films could absorb energy and store electrons to play a role in corrosion protection for metal.

Analysis of marine microbial communities colonizing various metallic materials and rust layers.

High-throughput sequencing was used to visualize microbial biocoenoses on different metallic surfaces and rust layers of highly corroded steels after immersion in coastal marine water for 30 months at Sanya, China. Distinct microbial community compositions were observed on these metallic surfaces. The dominant genus was the copper-tolerant, acid-producing Lactobacillus on copper alloys, the common aerobic surface colonizers Bacillus and Ruegeria on aluminum alloys, and aerobic biofilm-forming Pseudomonas on carbon steel. Most of these are copiotrophic microbes compared to planktonic microbes, which are oligotrophic. Additionally, sulfate-reducing prokaryotes (SRP) were detected in the rust layer, but the dominant genera changed from the outer layer to the inner part. The dominant genera detected in the outer, middle and inner rusts layers were Desulfotomaculum, Desulfonatronum (obligate anaerobe) and Desulfovibiro (electroactive), respectively. Further, the coexistence of methanogens with SRP suggests interspecies interactions.

The effective photocatalysis and antibacterial properties of AgBr/Ag2MoO4@ZnO composites under visible light irradiation.

A novel Z-scheme AgBr/Ag2MoO4@ZnO photocatalyst was fabricated via a hydrothermal process and in situ growth method. X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy were used to determine the structure of the photocatalyst. The results showed that the composites were tightly connected by the (101) lattice plane of ZnO, the (222) plane of Ag2MoO4 and the (200) lattice plane of AgBr. Because of the strong redox activity and good separability of photoelectrons and holes induced by the Z-scheme structure, the photodegradation rate for ciprofloxacin (CIP) solution was 80.5% by the photocatalysis of 0.5 AgBr/Ag2MoO4@ZnO. In addition, more than 99.999% of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa cells were killed within 60 min. These results demonstrate that AgBr/Ag2MoO4@ZnO is a promising photocatalyst, which can be used in organic pollutant degradation and the photocatalytic antibacterial area.

Microbial Corrosion Resistance and Antibacterial Property of Electrodeposited Zn-Ni-Chitosan Coatings.

Microbial corrosion is a universal phenomenon in salt water media such as seawater and wastewater environments. As a kind of efficient protective metal coating for steel, the damage of the Zn-Ni alloy coating was found to be accelerated under microbial corrosive conditions. To solve this problem, chitosan, which is considered a natural product with high antibacterial efficiency, was added to Zn-Ni electrolytes as a functional ingredient of electrodeposited Zn-Ni-chitosan coatings. It was found that the addition of chitosan significantly and negatively shifted the electrodeposition potentials and influenced the Ni contents, the phase composition, and the surface morphologies. By exposing the coatings in a sulfate-reducing bacteria medium, the microbial corrosion resistance was investigated. The results showed that compared to the Zn-Ni alloy coating, Zn-Ni-chitosan coatings showed obvious inhibiting effects on sulfate-reducing bacteria (SRB) and the corrosion rates of these coatings were mitigated to some degree. Further research on the coatings immersed in an Escherichia coli-suspended phosphate buffer saline medium showed that the bacteria attachment on the coating surface was effectively reduced, which indicated enhanced antibacterial properties. As a result, the Zn-Ni-chitosan coatings showed remarkably enhanced anticorrosive and antibacterial properties.

Preparation and photocathodic protection property of ZnIn2S4/RGO/TiO2 composites for Q235 carbon steel under visible light.

For improving the photocathodic protection performance of TiO2 photoanode, ZnIn2S4/reduced graphene oxide (RGO)/TiO2 nanotubes (NTs) composite was synthesized by electrochemical anodizing combined with hydrothermal method. The photoelectrochemical and photocathodic protection properties of the ZnIn2S4/RGO/TiO2 composite were investigated in detail. Compared with pure TiO2 NTs, the ZnIn2S4/RGO/TiO2 composite showed a significant improvement in photocathodic protection performances. The photogenerated open circuit potential drop of ZnIn2S4/RGO/TiO2 coupled with Q235 carbon steel in 3.5 wt% NaCl solution under visible light could reach 420 mV versus saturated calomel electrode, which was more than twice as much as that of pure TiO2. The photogenerated current density of ZnIn2S4/RGO/TiO2 could reach 5.6 mA cm-2, which was twice as much as that of pure TiO2. The appearance of the adsorbed oxygen (OA) enabled the ZnIn2S4/RGO/TiO2 to have better photo-carrier separation efficiency and better photogenerated cathodic protection than pure TiO2. The present work demonstrated ZnIn2S4/RGO/TiO2 could be a potential material for photoanodes because of its better visible-light response, higher electrical conductivity and smaller charge transfer resistance.

A 3-dimensional C/CeO2 hollow nanostructure framework as a peroxidase mimetic, and its application to the colorimetric determination of hydrogen peroxide.

Various 3-dimensional C/CeO2 hollow nanostructure frameworks (3D C/CeO2 HNFs) were synthesized by using a polymer blowing process that is accelerated by adding a certain amount of cerium nitrate. Polyvinylpyrrolidone was used as the polymer. The resulting HNFs were characterized by scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. The HNFs possess a large specific surface area, and the CeO2 nanocrystals consist of a single phase. The HNFs display intrinsic peroxidase-like activity and can catalyze the oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine in the presence of H2O2 to produce a blue product. The method was applied to the quantification of H2O2 with a 5.2 nM detection limit. The analytical range is from 10 nM to 1 µM. Graphical abstract Schematic of the preparation of a 3-dimensional C/CeO2 hollow nanostructure framework by a polyvinylpyrrolidone-blowing process accelerated by Ce(NO3)3. They were applied to H2O2 detection by catalyzing the oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) to the oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB) to produce blue-color reaction.

Enhanced photocathodic protection performance of Ag/graphene/TiO2 composite for 304SS under visible light.

Ag and graphene co-sensitized TiO2 composites were successfully fabricated and used as photoanodes for photogenerated cathodic protection of 304 stainless steel (304SS) under visible light. Graphene films was firstly deposited onto the TiO2 nanotube (NT) films via cyclic voltammetric electrodeposition. Ag/graphene/TiO2 films were then fabricated via dipping and photoreduction method. The morphology, composition and optical response of the Ag/graphene/TiO2 NT composites were characterized by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, UV-vis diffusion reflectance spectroscopy, respectively. The photocathodic protection performance of the Ag/graphene/TiO2 composites were systematically studied through open-circuit potential and potentiodynamic polarization measurements in 3.5 wt% NaCl solution under visible light (λ > 400 nm). The composites exhibited enhanced photogenerated cathodic protection performance for 304SS under visible light irradiation compared to pure TiO2. Graphene and Ag have a synergistic effect on the enhancement of photocathodic protection performance of TiO2. The composites prepared with 30-cycle graphene film and 15 mM AgNO3 solution showed the optimal corrosion protection performance.

CdTe and graphene co-sensitized TiO2 nanotube array photoanodes for protection of 304SS under visible light.

CdTe/graphene/TiO2 films that served as photoanodes for cathodic protection application were prepared by an electrochemical deposition method. The deposition of graphene and CdTe nanoparticles (NPs) on the surface of the TiO2 nanotubes was confirmed by scanning electron microscope and transmission electron microscopy. The composites exhibited high light absorption in both the UV and visible light region. The results indicated that TiO2 nanotube photoelectrodes sensitized by 20-cycle graphene and 30-cycle CdTe NPs exhibited effective photocathodic protection properties for 304 stainless steel (304SS) under the visible-light illumination, with an photopotential of -750 mV versus saturated calomel electrode and a current density of 560 µA cm(-2). Due to the efficient photogenerated charge separation, the three-component CdTe/graphene/TiO2 showed stronger photoresponse than pure TiO2 under visible-light illumination. In summary, the CdTe/graphene could improve the photocathodic protection properties of TiO2 films.

Studies on nano-additive for the substitution of hazardous chemical substances in antifouling coatings for the protection of ship hulls.

Adhesion and growth of biofouling organisms have severe influence on the reliability, service life and environmental adaptability of marine ships. Based on the bactericidal capacity of cuprous oxide and photochemical effect of nano-additive, environment-friendly and efficient marine antifouling paints were prepared in this study. The evaluation of the antifouling paints was carried out by the laboratory method using bacteria and phytoplanktonic microorganisms as target organisms, as well as measurements with panels in shallow submergence in natural seawater. Results showed good agreement of all the tests, indicating the remarkable antifouling performance of the paints. To our knowledge, this was one of the first systematic studies on effects of nano-additive for the substitution of hazardous chemical substances in antifouling coatings for the protection of ship hulls by measurements on bacterial inhibition, algal adhesion and growth of large organisms.

Transparent Superhydrophobic and Self-Cleaning Coating.

Surface roughness and low surface energy are key elements for the artificial preparation of biomimetic superhydrophobic materials. However, the presence of micro-/nanostructures and the corresponding increase in roughness can increase light scattering, thereby reducing the surface transparency. Therefore, designing and constructing superhydrophobic surfaces that combine superhydrophobicity with high transparency has been a continuous research focus for researchers and engineers. In this study, a transparent superhydrophobic coating was constructed on glass substrates using hydrophobic fumed silica (HF-SiO2) and waterborne polyurethane (WPU) as raw materials, combined with a simple spray-coating technique, resulting in a water contact angle (WCA) of 158.7 ± 1.5° and a sliding angle (SA) of 6.2 ± 1.8°. Characterization tests including SEM, EDS, LSCM, FTIR, and XPS revealed the presence of micron-scale protrusions and a nano-scale porous network composite structure on the surface. The presence of HF-SiO2 not only provided a certain roughness but also effectively reduced surface energy. More importantly, the coating exhibited excellent water-repellent properties, extremely low interfacial adhesion, self-cleaning ability, and high transparency, with the light transmittance of the coated glass substrate reaching 96.1% of that of the bare glass substrate. The series of functional characteristics demonstrated by the transparent superhydrophobic HF-SiO2@WPU coating designed and constructed in this study will play an important role in various applications such as underwater observation windows, building glass facades, automotive glass, and goggles.

Effects of marine eutrophication environment on microbial corrosion: A review.

Metal materials undergo severe corrosion in eutrophic environments. The effect of DO decay stimulated by high concentrations of nitrogen and phosphorus pollutants on microorganisms leads to the coupling of electrochemical and microbial corrosion processes. However, there are few studies on microbial corrosion mechanisms in eutrophic environments. This article discusses the corrosive factors of marine eutrophication, summarizes the impact of marine eutrophication on microbial corrosion and the potential mechanisms, including aerobic biofilm corrosion, aerobic & anaerobic mixed biofilm corrosion, and anaerobic microbial electron transfer corrosion, and expounds on the research methods for microbial corrosion of materials serving in estuarine areas prone to pollution. Microbial prevention and control, such as nutrient restriction and microbial interspecies competition, are of research value in the field of green protection. Microbial corrosion mechanisms studies in marine eutrophication environments are significant for environment monitor development, water intake and algae control technologies, and corrosion protection in polluted environments.

Turning Waste into Treasure: Invasive Plant Ambrosia trifida L Leaves as a High-Efficiency Inhibitor for Steel in Simulated Pickling Solutions.

High toxicity is the main reason for the limited application of traditional corrosion inhibitors. Herein, it is critical to find a green, efficient, and long-term stable alternative substitute for the hazardous and conventional corrosion inhibitor. Ambrosia trifida L is widely distributed in fields and riverside wetlands as an invasive plant in China. According to the concept of turning waste into treasure, the extract of Ambrosia trifida L leaves (ATL) has the potential to address this issue due to its natural origin and abundant presence of heterocyclic organics. Therefore, ATL, as a green corrosion inhibitor, is prepared for the first time via a simple water-based extraction method. FT-IR (Fourier transform infrared spectroscopy) and UV-Vis (UV-visible) indicate that ATL extract contains abundant heterocyclic organics with conjugated structures, which exhibit the potential to become a high-efficiency inhibitor. Notably, the active sites of ATL molecules and their interaction with Q235 steel at the molecular/atomic level are revealed via theoretical calculations. The highest Ebinding value observed for the major components in the ATL extract is 259.66 kcal/mol, implying a significant adsorption capacity. The electrochemical results verify that microdose ATL extract can prominently inhibit steel corrosion, and the highest inhibition efficiency (η) is 97.5% (1000 mg/L). Following immersion for 24 h, the η value is enhanced to 99.0%, indicating a reliable and long-term ATL extract protection film is formed on the steel surface in harsh acidic solutions. The results of the weight loss, SEM (scanning electron microscope), and LSCM (laser scanning confocal microscopy) are consistent with the above conclusions. Finally, this study anticipates providing theoretical support for developing novel green plant extract inhibitors and aiding in their application in industrial pickling environments.

Microbial corrosion of metallic biomaterials in the oral environment.

A wide variety of microorganisms have been closely linked to metal corrosion in the form of adherent surface biofilms. Biofilms allow the development and maintenance of locally corrosive environments and/or permit direct corrosion including pitting corrosion. The presence of numerous genetically distinct microorganisms in the oral environment poses a threat to the integrity and durability of the surface of metallic prostheses and implants used in routine dentistry. However, the association between oral microorganisms and specific corrosion mechanisms is not clear. It is of practical importance to understand how microbial corrosion occurs and the associated risks to metallic materials in the oral environment. This knowledge is also important for researchers and clinicians who are increasingly concerned about the biological activity of the released corrosion products. Accordingly, the main goal was to comprehensively review the current literature regarding oral microbiologically influenced corrosion (MIC) including characteristics of biofilms and of the oral environment, MIC mechanisms, corrosion behavior in the presence of oral microorganisms and potentially mitigating technologies. Findings included that oral MIC has been ascribed mostly to aggressive metabolites secreted during microbial metabolism (metabolite-mediated MIC). However, from a thermodynamic point of view, extracellular electron transfer mechanisms (EET-MIC) through pili or electron transfer compounds cannot be ruled out. Various MIC mitigating methods have been demonstrated to be effective in short term, but long term evaluations are necessary before clinical applications can be considered. Currently most in-vitro studies fail to simulate the complexity of intraoral physiological conditions which may either reduce or exacerbate corrosion risk, which must be addressed in future studies. STATEMENT OF SIGNIFICANCE: A thorough analysis on literature regarding oral MIC (microbiologically influenced corrosion) of biomedical metallic materials has been carried out, including characteristics of oral environment, MIC mechanisms, corrosion behaviors in the presence of typical oral microorganisms and potential mitigating methods (materials design and surface design). There is currently a lack of mechanistic understanding of oral MIC which is very important not only to corrosion researchers but also to dentists and clinicians. This paper discusses the significance of biofilms from a biocorrosion perspective and summarizes several aspects of MIC mechanisms which could be caused by oral microorganisms. Oral MIC has been closely associated with not only the materials research but also the dental/clinical research fields in this work.

Desulfovibrio-induced gauzy FeS for efficient hexavalent chromium removal: The influence of SRB metabolism regulated by carbon source and electron carriers.

Biosynthetic metal sulfides showed great application prospects in the environmental treatment against high-valence metal pollutants. However, the efficiency of biosynthesis, agglomeration during the reaction process, and the formation of the passivation layer during the reduction process were always the important factors restricting its development. This study explored the composition of the culture medium to promote the growth of highly corrosive sulfate-reducing bacteria (SRB) and its metabolism to produce FeS nanoparticles (NPs). The results showed that reducing the carbon source (CS) and adding electron carriers in the culture medium effectively promoted the production of small, dispersed, and loose FeS NPs in cells. At pH = 7, 24 °C and 10 min reaction time, 0.1 g/L FeS NPs produced by SRB under the conditions of 10 % CS with 10 ppm cytochrome c medium could achieve 100 % removal efficiency of 1 mM hexavalent chromium (Cr(VI)). Under this condition, FeS NPs could be produced by intracellular metabolism in SRB cells, and environmental factors such as pH, metal cations, and Cl- had little effect on the removal of Cr(VI) by this FeS NPs. The surface proteins of FeS NPs significantly enhanced their antioxidant properties. After 7 days of natural environment exposure, the Cr(VI) removal efficiency of FeS NPs was only reduced by 16 % compared with the initial sample. This work provided an in-depth understanding of Cr(VI) removal by SRB biosynthesis of FeS and contributes to the widespread application of FeS in the future.

Effect of yeast extract on microbiologically influenced corrosion of X70 pipeline steel by Desulfovibrio bizertensis SY-1.

Microbiologically influenced corrosion (MIC) is a complicated process that happens ubiquitously and quietly in many fields. As a useful nutritional ingredient in microbial culture media, yeast extract (YE) is a routinely added in the MIC field. However, how the YE participated in MIC is not fully clarified. In the present work, the effect of YE on the growth of sulfate reducing prokaryotes (SRP) Desulfovibrio bizertensis SY-1 and corrosion behavior of X70 pipeline steel were studied. It was found that the weight loss of steel coupons in sterile media was doubled when YE was removed from culture media. However, in the SRP assays without YE the number of planktonic cells decreased, but the attachment of bacteria on steel surfaces was enhanced significantly. Besides, the corrosion rate of steel in SRP assays increased fourfold after removing YE from culture media. MIC was not determined for assays with planktonic SRP but only for biofilm assays. The results confirm the effect of YE on D. bizertensis SY-1 growth and also the inhibitory role of YE on MIC.