Synthesis of high-performance conjugated microporous polymer/TiO2 photocatalytic antibacterial nanocomposites

UV-Triggered Drug Release from Mesoporous Titanium Nanoparticles Loaded with Berberine Hydrochloride: Enhanced Antibacterial Activity

Mesoporous titanium nanoparticles (MTN) have always been a concern and are considered to have great potential for overcoming antibiotic-resistant bacteria. In our study, MTN modified with functionalized UV-responsive ethylene imine polymer (PEI) was synthesized. The characterization of all products was performed by different analyses, including SEM, TEM, FT-IR, TGA, XRD, XPS, and N2 adsorption-desorption isotherms. The typical antibacterial drug berberine hydrochloride (BH) was encapsulated in MTN-PEI. The process exhibited a high drug loading capacity (22.71 ± 1.12%) and encapsulation rate (46.56 ± 0.52%) due to its high specific surface area of 238.43 m2/g. Moreover, UV-controlled drug release was achieved by utilizing the photocatalytic performance of MTN. The antibacterial effect of BH@MTN-PEI was investigated, which showed that it could be controlled to release BH and achieve a corresponding antibacterial effect by UV illumination for different lengths of time, with bacterial lethality reaching 37.76% after only 8 min of irradiation. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the nanoparticles have also been studied. The MIC of BH@MTN-PEI was confirmed as 1 mg/mL against Escherichia coli (E. coli), at which the growth of bacteria was completely inhibited during 24 h and the concentration of 5 mg/mL for BH@MTN-PEI was regarded as MBC against E. coli. Although this proof-of-concept study is far from a real-life application, it provides a possible route to the discovery and application of antimicrobial drugs.

Erythrosine-Dialdehyde Cellulose Nanocrystal Coatings for Antibacterial Paper Packaging

Though paper is an environmentally friendly alternative to plastic as a packaging material, it lacks antibacterial properties, and some papers have a low resistance to oil or water. In this study, a multifunctional paper-coating material was developed to reduce the use of plastic packaging and enhance paper performance. Natural cellulose nanocrystals (CNCs) with excellent properties were used as the base material for the coating. The CNCs were functionalized into dialdehyde CNCs (DACNCs) through periodate oxidation. The DACNCs were subsequently complexed using erythrosine as a photosensitizer to form an erythrosine-CNC composite (Ery-DACNCs) with photodynamic inactivation. The Ery-DACNCs achieved inactivations above 90% after 30 min of green light irradiation and above 85% after 60 min of white light irradiation (to simulate real-world lighting conditions), indicating photodynamic inactivation effects. The optimal parameters for a layer-by-layer dip coating of kraft paper with Ery-DACNCs were 4.5-wt% Ery-DACNCs and 15 coating layers. Compared to non-coated kraft paper and polyethylene-coated paper, the Ery-DACNC-coated paper exhibited enhanced mechanical properties (an increase of 28% in bursting strength). More than 90% of the bacteria were inactivated after 40 min of green light irradiation, and more than 80% were inactivated after 60 min of white light irradiation.

Enhanced Photocatalytic Properties of All-Organic IDT-COOH/O-CN S-Scheme Heterojunctions Through π-π Interaction and Internal Electric Field

Herein, we present a distinct methodology for the in situ electrostatic assembly method for synthesizing a conjugated (IDT-COOH)/oxygen-doped g-C3N4 (O-CN) S-scheme heterojunction. The electron delocalization effect due to π-π interactions between O-CN and self-assembled IDT-COOH favors interfacial charge separation. The self-assembled IDT-COOH/O-CN exhibits a broadened visible absorption to generate more charge carriers. The internal electric field between the IDT-COOH and the O-CN interface provides a directional charge-transfer channel to increase the utilization of photoinduced charge carriers. Moreover, the active species (•O2-, h+, and 1O2) produced by IDT-COOH/O-CN under visible light play important roles in photocatalytic disinfection. The optimum 40% IDT-COOH/O-CN can kill 7-log of methicillin-resistant Staphylococcus aureus (MRSA) cells in 2 h and remove 88% tetracycline (TC) in 5 h, while O-CN only inactivates 1-log of MRSA cells and degrades 40% TC. This work contributes to a promising method to fabricate all-organic g-C3N4-based S-scheme heterojunction photocatalysts with a wide range of optical responses and enhanced exciton dissociation.

Vitamin B5 copper conjugated triazine dendrimer improved the visible-light photocatalytic activity of TiO2 nanoparticles for aerobic homocoupling reactions

In this work, Cu-vitamin B5 (pantothenic acid) bonded to 2,4,6-trichloro-1,3,5-triazine produced a bioconjugated dendrimer giving rise to the visible-light photocatalytic activity of nanocrystalline TiO2. XPS spectra uncovered the coexistence of Cu(II)/Cu(I) oxidation states with a predominant contribution of Cu(I). The new heterogeneous bio-relevant Cu-photocatalyst (Cu(I) Cu(II) [PTAPA G2-B5] @TiO2) revealed a band gap value [Eg = (2.8 eV)] less than those of Cu free components [PTAPA G1-B5]@TiO2 (3.04) and [PTAPA G2-B5]@TiO2 (3.06) and particularly the bare TiO2 (3.15 eV). The reactions showed to be light-dependent with the best performance under room light bulbs. The photocatalytic efficiency of the as-prepared heterojunction photocatalyst was exploited in the aerobic Csp2-Csp2 homocoupling of phenylboronic acid and Csp-Csp homocoupling of phenyl acetylenes under visible-light irradiation to prepare structurally and electronically different biaryls. A radical pathway relying on the photogenerated e- and h+ and involving the Cu(I)-Cu(II) synergistic cooperation was postulated. The reusability and stability of the catalyst were verified by the recycling test, FT-IR spectra, and ICP-OES analysis.

Red mud accommodated mesoporous black TiO2 framework with enhanced organic pollutant photodegradation

In this work, black TiO2 (BTiO2) loaded on black red mud (BRM) was successfully prepared with the conversion of Fe2O3 into magnetic Fe3O4 in red mud and the reduction of partial Ti4+ to Ti3+ in TiO2 via the facile sol-gel method and H2 reduction treatment. The obtained low-cost BRM/BTiO2 composites exhibit remarkable photocatalytic degradation toward rhodamine B (91.2%) and tetracycline (83.6%) under visible light irradiation, much better than pristine TiO2. This enhancement is attributed to the narrow bandgap with the desired solar-light excitation, the black color with good solar-light absorption, and the heterojunctions with the efficient separation of photogenerated electron-hole pairs. Moreover, the desired magnetic separation of BRM/BTiO2 composites realizes the recycle and recovery of photocatalysts, favoring practical applications in environment. This work provides a cost-efficiency way to prepare RM-supported TiO2 composites for treating organic pollutants in the wastewater, which is of great significance to the comprehensive utilization of RM waste, the cost saving of the photocatalyst, and the visible-light active enhancement of TiO2.

Frustrated Lewis pair boosting photocatalytic antibacterial activity on PDI-bridged bimetallic UiO-66-NH2

Designing frustrated Lewis pair (FLP)-structured photocatalysts is a new challenge in catalysis. In particular, the relationship between the active sites and photocatalytic charge transport mechanism over FLP-structured photocatalysts is still ill-defined. In this study, a novel perylene-3,4,9,10-tetracarboxylic diimide/UiO-66(Ti/Zr)-NH₂ (denoted as PDI/TUZr) photocatalyst is successfully constructed using an ammoniation process. The PDI/TUZr heterojunction is equipped with a unique "Zr/Ti SBUs-ligand-PDI" FLP structure and exhibits remarkable catalytic FLP properties. In this "Zr/Ti SBUs-ligand-PDI" structure, the Zr/Ti bimetal centers and PDI serve as Lewis acid and base sites, respectively, and the C-N chemical bond provides a channel for electron transmission, and a bimetallic system facilitates electron transfer from excited ligand to Zr/Ti-SBUs nodes. These superior microstructural designs cooperate to promote substrate activation for photocatalytic antibacterial reactions. Accordingly, 2.2-fold enhancement is achieved in visible photocatalytic antibacterial activity on Staphylococcus aureus for 4%PDI/0.2TUZr composite compared with unadorned UZr. This study provides insights into the formation and carrier transfer behaviors of solid FLP on MOFs and illustrates a rational strategy for the construction of highly efficient photocatalysts.

A Multifunctional Dental Resin Composite with Sr-N-Doped TiO2 and n-HA Fillers for Antibacterial and Mineralization Effects

Dental caries, particularly secondary caries, which is the main contributor to dental repair failure, has been the subject of extensive research due to its biofilm-mediated, sugar-driven, multifactorial, and dynamic characteristics. The clinical utility of restorations is improved by cleaning bacteria nearby and remineralizing marginal crevices. In this study, a novel multifunctional dental resin composite (DRC) composed of Sr-N-co-doped titanium dioxide (Sr-N-TiO2) nanoparticles and nano-hydroxyapatite (n-HA) reinforcing fillers with improved antibacterial and mineralization properties is proposed. The experimental results showed that the anatase-phase Sr-N-TiO2 nanoparticles were synthesized successfully. After this, the curing depth (CD) of the DRC was measured from 4.36 ± 0.18 mm to 5.10 ± 0.19 mm, which met the clinical treatment needs. The maximum antibacterial rate against Streptococcus mutans (S. mutans) was 98.96%, showing significant inhibition effects (p < 0.0001), which was experimentally verified to be derived from reactive oxygen species (ROS). Meanwhile, the resin exhibited excellent self-remineralization behavior in an SBF solution, and the molar ratio of Ca/P was close to that of HA. Moreover, the relative growth rate (RGR) of mouse fibroblast L929 indicated a high biocompatibility, with the cytotoxicity level being 0 or I. Therefore, our research provides a suitable approach for improving the antibacterial and mineralization properties of DRCs.

A Sensitive Photoelectrochemical Sensor for Levodopa Detection Using Benzothiadiazole-Based Conjugated Microporous Polymer-Coated Graphene Heterostructures

Since the 1960s, levodopa (LDA) has been the standard drug for treating of Parkinson's disease. In this study, a novel benzothiadiazole-based conjugated microporous polymer-coated graphene heterostructure (CMP-rGO) was synthesized and used to construct a sensitive photoelectrochemical (PEC) sensor capable of detecting LDA. Under optimal experimental conditions, the intensity of the photocurrent produced by the sensor was linear from 0.005 to 40 μM, and the limit of detection of the sensor was 0.0027 μM. The sensor showed good repeatability, stability, and selectivity for LDA detection. Finally, the constructed sensor was used to detect LDA in levodopa tablets, human serum samples, and urine samples and satisfactory results were obtained. Therefore, the PEC sensor provides a novel platform for the detection of LDA in real samples and broadens the applications of conjugated microporous polymers in PEC sensing.

Polypropylene Modified with Ag-Based Semiconductors as a Potential Material against SARS-CoV-2 and Other Pathogens

The worldwide outbreak of the coronavirus pandemic (COVID-19) and other emerging infections are difficult and sometimes impossible to treat, making them one of the major public health problems of our time. It is noteworthy that Ag-based semiconductors can help orchestrate several strategies to fight this serious societal issue. In this work, we present the synthesis of α-Ag₂WO₄, β-Ag₂MoO₄, and Ag₂CrO₄ and their immobilization in polypropylene in the amounts of 0.5, 1.0, and 3.0 wt %, respectively. The antimicrobial activity of the composites was investigated against the Gram-negative bacterium Escherichia coli, the Gram-positive bacterium Staphylococcus aureus, and the fungus Candida albicans. The best antimicrobial efficiency was achieved by the composite with α-Ag₂WO₄, which completely eliminated the microorganisms in up to 4 h of exposure. The composites were also tested for the inhibition of SARS-CoV-2 virus, showing antiviral efficiency higher than 98% in just 10 min. Additionally, we evaluated the stability of the antimicrobial activity, resulting in constant inhibition, even after material aging. The antimicrobial activity of the compounds was attributed to the production of reactive oxygen species by the semiconductors, which can induce high local oxidative stress, causing the death of these microorganisms.

Preparation, Antimicrobial Properties under Different Light Sources, Mechanisms and Applications of TiO2: A Review

Traditional antimicrobial methods, such as antibiotics and disinfectants, may cause adverse effects, such as bacterial resistance and allergic reactions. Photocatalysts based on titanium dioxide (TiO₂) have shown great potential in the field of antimicrobials because of their high efficiency, lack of pollution, and lack of side effects. This paper focuses on the antimicrobial activity of TiO₂ under different light sources. To improve the photocatalytic efficiency of TiO₂, we can reduce electron-hole recombination and extend the photocatalytic activity to the visible light region by doping with different ions or compounds and compounding with polymers. We can also improve the surface properties of materials, increase the contact area with microorganisms, and further enhance the resistance to microorganisms. In addition, we also reviewed their main synthesis methods, related mechanisms, and main application fields to provide new ideas for the enhancement of photocatalytic microorganism performance and application popularization in the future.

Designing novel MgFe2O4 coupled V2O5 nanorod for synergetic photodegradation of tetracycline with enhanced visible-light energy harvesting: Photoluminescence, kinetics, intrinsic mechanism and bactericidal effect

The present study focused on the enhancement of degradation of an important pharmaceutical pollutant, tetracycline with the help of nano photocatalyst under visible light irradiation. The study found that the synergetic effect of novel MgFe₂O₄-V₂O₅ enhanced the photocatalytic degradation of tetracycline. Here, the photocatalyst was synthesized by sonochemical technique. Scanning electron microscopy image indicates the coupling of MgFe₂O₄ nanocapsules on the surface of the V₂O₅ nanorod. The bandgap of MgFe₂O₄ (1.8 eV) and V₂O₅ (2.5 eV) was shifted to 2.32 eV in MgFe₂O₄-V₂O₅ to promote visible-light harvesting and it was depicted by the UV-visible DRS. XPS was used to identify the presence of chemical states with the existence of Mg 1s, Fe 2p, V 2p, and O 1s. The electrochemical impedance spectroscopy and photoluminescence spectra indicate the better separation of charge carriers owing to the formation of type II heterojunction formation. The tetracycline (25 mg/L) was degraded with MgFe₂O₄-V₂O₅ (150 mg/L) that exhibited 3.3 and 5 folds enhanced rates than its counterparts (MgFe₂O₄ and V₂O₅) owing to synergism. The possible intermediate formation and degradation pathway was determined based on GC/MS analysis. TOC analysis of end products indicated maximum mineralization of tetracycline. The MgFe₂O₄-V₂O₅ showed excellent recycling ability and reusability. The key photo-degradation of tetracycline was occurred by the generation of hydroxyl radicals. The MgFe₂O₄-V₂O₅ exhibited high antibacterial activity that ensures the dual functionality of the prepared nanocomposites (NCs). Therefore, the present study displays MgFe₂O₄ decorated V₂O₅ nanorod as an ideal candidate for environmental remediation.

Visible-light-induced bactericidal properties of a novel thiophene-based linear conjugated polymer/TiO2 heterojunction

The low utilization of visible light and the fast recombination of photogenerated electron-hole pairs are the two intrinsic defects that have hindered the antibacterial applications of TiO₂. The addition of organic photocatalytic agents to form heterojunctions with TiO₂ powder can effectively address these problems. A novel linear conjugated polymer poly[(thiophene-ethylene-thiophene)-thiophene-3-carboxylic acid decyl ester] (PTCD) was successfully synthesized via Stille coupling polymerization. PTCD and TiO₂ can form a heterojunction photocatalyst (PTCD/TiO₂), and this product was characterized using NMR and XRD. The UV-vis spectra showed that the absorption edge of the PTCD/TiO₂ heterojunction extends to approximately 700 nm, which indicates that the visible-light utilization is greatly improved. Staphylococcus aureus (S. aureus) was selected as the target organism to test the photocatalytic antimicrobial activity of the material. Photogenerated electrons can undergo directional transmission of the PTCD polymer to TiO₂ on the PTCD/TiO₂ heterojunction to realize excellent antibacterial properties. With an optimized PTCD loading ratio of 30%, PTCD/TiO₂ showed an antibacterial rate that was 14.5 times greater than that of pure TiO₂ in 4 h under visible-light irradiation.

Photo-regulated dual-functional zinc oxide nanocomposite for synergistic sterilization and antioxidant treatment

The C-FZnO-RT composite achieved synergistic bactericidal performance against both E. coli and S. aureus under light conditions.

Microwave-Assisted Rapid Synthesis of Eu(OH)3/RGO Nanocomposites and Enhancement of Their Antibacterial Activity against Escherichia coli

Nanomaterials with high antibacterial activity and low cytotoxicity have attracted extensive attention from scientists. In this study, europium (III) hydroxide (Eu(OH)₃)/reduced graphene oxide (RGO) nanocomposites were synthesized using a rapid, one-step method, and their antibacterial activity against Escherichia coli (E. coli) was investigated using the synergistic effect of the antibacterial activity between Eu and graphene oxide (GO). The Eu(OH)₃/RGO nanocomposites were prepared using a microwave-assisted synthesis method and characterized using X-ray diffraction, scanning electron microscopy, photoluminescence spectroscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. Raman sprectroscopy and X-ray diffraction confirmed the pure hexagonal phase structure of the nanocomposites. Further, the antibacterial properties of Eu(OH)₃/RGO were investigated using the minimum inhibitory concentration assay, colony counting method, inhibition zone diameter, and optical density measurements. The results revealed that the Eu(OH)₃/RGO exhibited a superior inhibition effect against E. coli and a larger inhibition zone diameter compared to RGO and Eu(OH)₃. Further, the reusability test revealed that Eu(OH)₃/RGO nanocomposite retained above 98% of its bacterial inhibition effect after seven consecutive applications. The high antibacterial activity of the Eu(OH)₃/RGO nanocomposite could be attributed to the release of Eu³⁺ ions from the nanocomposite and the sharp edge of RGO. These results indicated the potential bactericidal applications of the Eu(OH)₃/RGO nanocomposite.

Antimicrobial Efficacy and Spectrum of Phosphorous-Fluorine Co-Doped TiO2 Nanoparticles on the Foodborne Pathogenic Bacteria Campylobacter jejuni, Salmonella Typhimurium, Enterohaemorrhagic E. coli, Yersinia enterocolitica, Shewanella putrefaciens, Listeria monocytogenes and Staphylococcus aureus

Contamination of meats and meat products with foodborne pathogenic bacteria raises serious safety issues in the food industry. The antibacterial activities of phosphorous-fluorine co-doped TiO₂ nanoparticles (PF-TiO₂) were investigated against seven foodborne pathogenic bacteria: Campylobacter jejuni, Salmonella Typhimurium, Enterohaemorrhagic E. coli, Yersinia enterocolitica, Shewanella putrefaciens, Listeria monocytogenes and Staphylococcus aureus. PF-TiO₂ NPs were synthesized hydrothermally at 250 °C for 1, 3, 6 or 12 h, and then tested at three different concentrations (500 μg/mL, 100 μg/mL, 20 μg/mL) for the inactivation of foodborne bacteria under UVA irradiation, daylight exposure or dark conditions. The antibacterial efficacies were compared after 30 min of exposure to light. Distinct differences in the antibacterial activities of the PF-TiO₂ NPs, and the susceptibilities of tested foodborne pathogenic bacterium species were found. PF-TiO₂/3 h and PF-TiO₂/6 h showed the highest antibacterial activity by decreasing the living bacterial cell number from ~10⁶ by ~5 log (L. monocytogenes), ~4 log (EHEC), ~3 log (Y. enterolcolitca, S. putrefaciens) and ~2.5 log (S. aureus), along with complete eradication of C. jejuni and S. Typhimurium. Efficacy of PF-TiO₂/1 h and PF-TiO₂/12 h NPs was lower, typically causing a ~2–4 log decrease in colony forming units depending on the tested bacterium while the effect of PF-TiO₂/0 h was comparable to P25 TiO₂, a commercial TiO₂ with high photocatalytic activity. Our results show that PF-co-doping of TiO₂ NPs enhanced the antibacterial action against foodborne pathogenic bacteria and are potential candidates for use in the food industry as active surface components, potentially contributing to the production of meats that are safe for consumption.