Recent developments in polydopamine-based photocatalytic nanocomposites for energy production: Physico-chemical properties and perspectives

Preparation of polyphenol-structural colored silk fabrics with bright colors

Conventional textile dyeing relies on the use of dyes and pigments, which can cause severe environmental contamination and waste a large amount of water. Structural coloring is one of the effective ways to achieve environmentally friendly coloring of textiles. In this work, three plant polyphenols with the same o-benzenetriol structure (tannic acid (TA), gallic acid (GA), and tea polyphenol (TP)) were selected as raw materials. Three plant polyphenols can quickly form nanofilms at the gas-liquid interface through a Schiff base reaction with polyethyleneimine (PEI) under mildly alkaline conditions, which were deposited to the surface of silk fabric, allowing precise control over the thickness of film by adjusting the time, resulting in various structurally colored silk fabric. This method for creating structural colors is not substrate-specific and enables the quick production of structural colors on various textile substrates. Furthermore, the structural color silk fabric based on plant polyphenol has antibacterial performance. This textile coloring method is simple, cost-effective and environmentally friendly, providing a new approach to eco-friendly textile dyeing.

Ultrasensitive molecular imprinted electrochemical sensor for in vivo determination of glycine betaine in plants

Glycine betaine (GB) is a bioactive molecule protecting plants from abiotic stress. This study fabricated an ultrasensitive molecular imprinted polymer (MIP) electrochemical sensor to perform in vivo measurements of GB. Polydopamine (PDA) was formed on the carboxylated multi-walled carbon nanotubes (COOH-MWCNTs) by spontaneous polymerisation of dopamine (DA). Then MIP-coated MWCNTs were fabricated on a Au nanoparticles (NP) and thionine (Thi) modified screen-printed electrode (SPE). The MIP-COOH-MWCNTs/pThi/AuNPs/SPE exhibited an ultrasensitive GB detection response between 1 fmol/L and 10 mmol/L (R2 = 0.996) with a low detection limit (0.707 fmol/L, S/N = 3). In vivo measurement of GB in cucumber seedling leaves under different salinity stress conditions confirmed the practical applicability of the MIP sensor. Thus, this study proposed a novel and promising fabrication method for an electrochemical MIP sensor that has broad application prospects in precision agriculture.

TiO2/PDA Multilayer Nanocomposites with Exceptionally Sharp Large-Scale Interfaces and Nitrogen Doping Gradient

The evolving field of photocatalysis requires the development of new functional materials, particularly those suitable for large-scale commercial systems. One particularly promising approach is the creation of hybrid organic/inorganic materials. Despite being extensively studied, materials such as polydopamine (PDA) and titanium oxide continue to show significant promise for use in such applications. Nitrogen-doped titanium oxide and free-standing PDA films obtained at the air/water interface are particularly interesting. This study introduces a straightforward and reproducible approach for synthesizing a novel class of large-scale multilayer nanocomposites. The method involves the alternate layering of high-quality materials at the air/water interface combined with precise atomic layer deposition techniques, resulting in a gradient nitrogen doping of titanium oxide layers with exceptionally sharp oxide/polymer interfaces. The analysis confirmed the presence of nitrogen in the interstitial and substitutional sites of the TiO2 lattice while maintaining the 2D-like structure of the PDA films. These chemical and structural characteristics translate into a reduction of the band gap by over 0.63 eV and an increase in the photogenerated current by over 60% compared with pure amorphous TiO2. Furthermore, the nanocomposites demonstrate excellent stability during the 1 h continuous photocurrent generation test.

Biomimetic theranostic nanoparticles for effective anticancer therapy and MRI imaging

Cancer remains a leading cause of mortality worldwide, necessitating the development of innovative therapeutic approaches. Nanoparticle-based drug delivery systems have garnered significant interest due to their multifunctionality, offering the potential to enhance cancer treatment efficacy and improve patient tolerability. Membrane-coated drug delivery systems hold great potential for enhancing the therapeutic outcome of nanoparticle-based anticancer therapies. In this study, we report the synthesis of multifunctional iron-functionalized mesoporous polydopamine nanoparticles (MPDAFe NPs). These nanoformulations demonstrate substantial potential for combining efficient drug delivery and magnetic resonance imaging (MRI) and showcase the advantages of biomimetic coating with tumor cell-derived membranes. This coating confers prolonged circulation and improved the targeting capabilities of the nanoparticles. Furthermore, comprehensive biosafety evaluations reveal negligible toxicity to normal cells, while the combined chemo- and phototherapy exhibited significant cytotoxicity towards cancer cells. Additionally, the photothermal effect evaluation highlights the enhanced cytotoxicity achieved through laser irradiation, showcasing the synergistic effects of the nanomaterials and photothermal therapy. Importantly, our chemotherapeutic effect evaluation demonstrates the superior efficacy of doxorubicin-loaded MPDAFe@Mem NPs (cancer cell membrane-coated MPDAFe NPs) in inhibiting cancer cell viability and proliferation, surpassing the potency of free doxorubicin. This study comprehensively investigates theranostic, membrane-coated drug delivery systems, underlining their potential to increase the efficacy of cancer treatment strategies. The multifunctional nature of the iron-functionalized polydopamine nanoparticles allows for efficient drug delivery and imaging capabilities, while the biomimetic coating enhances their biocompatibility and targeting ability. These findings contribute valuable insights towards the development of advanced nanomedicine for improved cancer therapeutics.

Laser-Induced Graphitization of Polydopamine on Titania Nanotubes

Since the discovery of laser-induced graphite/graphene, there has been a notable surge of scientific interest in advancing diverse methodologies for their synthesis and applications. This study focuses on the utilization of a pulsed Nd:YAG laser to achieve graphitization of polydopamine (PDA) deposited on the surface of titania nanotubes. The partial graphitization is corroborated through Raman and XPS spectroscopies and supported by water contact angle, nanomechanical, and electrochemical measurements. Reactive molecular dynamics simulations confirm the possibility of graphitization in the nanosecond time scale with the evolution of NH3, H2O, and CO2 gases. A thorough exploration of the lasing parameter space (wavelength, pulse energy, and number of pulses) was conducted with the aim of improving either electrochemical activity or photocurrent generation. Whereas the 532 nm laser pulses interacted mostly with the PDA coating, the 365 nm pulses were absorbed by both PDA and the substrate nanotubes, leading to a higher graphitization degree. The majority of the photocurrent and quantum efficiency enhancement is observed in the visible light between 400 and 550 nm. The proposed composite is applied as a photoelectrochemical (PEC) sensor of serotonin in nanomolar concentrations. Because of the suppressed recombination and facilitated charge transfer caused by the laser graphitization, the proposed composite exhibits significantly enhanced PEC performance. In the sensing application, it showed superior sensitivity and a limit of detection competitive with nonprecious metal materials.

Graphene Oxide-Magnetic Nanoparticles Loaded Polystyrene-Polydopamine Electrospun Nanofibers Based Nanocomposites for Immunosensing Application of C-Reactive Protein

The large surface area/volume ratio and controllable surface conformation of electrospun nanofibers (ENFs) make them highly attractive in applications where a large surface area is desired, such as sensors and affinity membranes. In this study, nanocomposite-based ENFs were produced and immobilization of Anti-CRP was carried out for the non-invasive detection of C-reactive protein (CRP). Initially, the synthesis of graphene oxide (GO) was carried out and it was modified with magnetic nanoparticles (MNP, Fe₃O₄) and polydopamine (PDA). Catechol-containing and quinone-containing functional groups were created on the nanocomposite surface for the immobilization of Anti-CRP. Polystyrene (PS) solution was mixed with rGO-MNP-PDA nanocomposite and PS/rGO-MNP-PDA ENFs were produced with bead-free, smooth, and uniform. The surface of the screen-printed carbon electrode (SPCE) was covered with PS/rGO-MNP-PDA ENFs by using the electrospinning technique under the determined optimum conditions. Next, Anti-CRP immobilization was carried out and the biofunctional surface was created on the PS/rGO-MNP-PDA ENFs coated SPCE. Moreover, PS/rGO-PDA/Anti-CRP and PS/MNP-PDA/Anti-CRP immunosensors were also prepared and the effect of each component in the nanocomposite-based electrospun nanofiber (MNP, rGO) on the sensor response was investigated. The analytic performance of the developed PS/rGO-MNP-PDA/Anti-CRP, PS/rGO-PDA/Anti-CRP, and PS/MNP-PDA/Anti-CRP immunosensors were examined by performing electrochemical measurements in the presence of CRP. The linear detection range of PS/rGO-MNP-PDA/Anti-CRP immunosensor was found to be from 0.5 to 60 ng/mL and the limit of detection (LOD) was calculated as 0.33 ng/mL for CRP. The PS/rGO-MNP-PDA/Anti-CRP immunosensor also exhibited good repeatability with a low coefficient of variation.

Dopamine Photochemical Behaviour under UV Irradiation

To understand the photochemical behaviour of the polydopamine polymer in detail, one would also need to know the behaviour of its building blocks. The electronic absorption, as well as the fluorescence emission and excitation spectra of the dopamine were experimentally and theoretically investigated considering time-resolved fluorescence spectroscopy and first-principles quantum theory methods. The shape of the experimental absorption spectra obtained for different dopamine species with standard, zwitterionic, protonated, and deprotonated geometries was interpreted by considering the advanced equation-of-motion coupled-cluster theory of DLPNO-STEOM. Dynamical properties such as fluorescence lifetimes or quantum yield were also experimentally investigated and compared with theoretically predicted transition rates based on Fermi's Golden Rule-like equation. The results show that the photochemical behaviour of dopamine is strongly dependent on the concentration of dopamine, whereas in the case of a high concentration, the zwitterionic form significantly affects the shape of the spectrum. On the other hand, the solvent pH is also a determining factor for the absorption, but especially for the fluorescence spectrum, where at lower pH (5.5), the protonated and, at higher pH (8.0), the deprotonated forms influence the shape of the spectra. Quantum yield measurements showed that, besides the radiative deactivation mechanism characterized by a relatively small QY value, non-radiative deactivation channels are very important in the relaxation process of the electronic excited states of different dopamine species.

Replacing amine by azide: Dopamine azide polymerization triggered by sodium periodate

Polydopamine (PDA) have been widely described for a range of biomedical and surface engineering applications. However the structure of PDA remains elusive due to the insoluble nature of the polymer....

Rhodium-Complex-Functionalized and Polydopamine-Coated CdSe@CdS Nanorods for Photocatalytic NAD+ Reduction

We report on a photocatalytic system consisting of CdSe@CdS nanorods coated with a polydopamine (PDA) shell functionalized with molecular rhodium catalysts. The PDA shell was implemented to enhance the photostability of the photosensitizer, to act as a charge-transfer mediator between the nanorods and the catalyst, and to offer multiple options for stable covalent functionalization. This allows for spatial proximity and efficient shuttling of charges between the sensitizer and the reaction center. The activity of the photocatalytic system was demonstrated by light-driven reduction of nicotinamide adenine dinucleotide (NAD⁺) to its reduced form NADH. This work shows that PDA-coated nanostructures present an attractive platform for covalent attachment of reduction and oxidation reaction centers for photocatalytic applications.