Photoactive Structures Research Articles

Construction of Donor-Acceptor-Type Conjugated Microporous Polymers by Oxidative Coupling of Boranil-Carbazole Mixed Monomers for Enhanced Photocatalytic Oxidation.

Conjugated microporous polymers (CMPs), featuring photoactive structures, a high surface area, robust thermal stability, and facile modulation, provide a versatile platform for fabricating diverse heterogeneous photocatalysts. The incorporation of donor-acceptor (D-A) structures into CMPs to increase their charge separation potential and enhance the photocatalytic efficacy is a viable strategy. In this work, we designed and synthesized a unique set of D-A monomers, incorporating boranil dyes as electron-deficient moieties and carbazoles as electron-rich subunits. Subsequently, D-A CMPs were prepared via an economical and environmentally friendly oxidation coupling reaction, and their potential in photocatalytic oxidation reactions was investigated. Modulation of the polymer's photoelectronic properties and photocatalytic performance can be achieved by adjusting the boranil content in the monomer. The polymer pCZFB-3, with the highest content of boranil units, exhibited an optimal photocatalytic activity. This finding confirms that strengthening the D-A effect can significantly enhance a catalyst's photoelectronic properties and catalytic efficacy. This study presents insights into designing innovative heterogeneous photocatalysts based on boron-containing dyes.

Unravelling superior photodegradation ability and key photoactive structures of hydrochar particle to typical emerging contaminant than corresponding bulk hydrochar from food waste

Hydrochar from waste biomass is a promising material for removing emerging contaminants (e.g., antibiotics) in water/soil environment. Abundant small-sized hydrochar particles (HPs) with a high content of reactive functional groups and high mobility are easily released into ecosystems through hydrochar applications. However, the photodegradation ability and corresponding structures of HPs are largely unknown, which hinder accurate estimation of the remediation effect of hydrochar in ecosystems. Herein, photodegradation performance of HP towards targeted norfloxacin (NOR, a typical antibiotic) under light irradiation (visible and UV light) were investigated after adsorption processes upon release into soil/water, and its reactive species and photoactive structures were clarified and compared with those of residual bulk hydrochar (BH) comprehensively. The results showed that: (1) photodegradation percentages of HPs were 4.02 and 4.48 times higher than those of BHs under UV and visible light, in which reactive species of both HPs and BHs were ·OH and ·O2−; (2) density functional theory (DFT) results identified that the main photoactive structure of graphitic-N decreased the energy gap (Eg) of HPs, and C=O, COOH groups improved electron donating ability of BHs; (3) well-developed graphitization structure of HP resulted from higher polymerization reaction was an significant photoactive structure involving its superior photodegradation ability relative to that of BH. The distinct heterogeneities of photodegradation ability in HP and BH and underlying photoactive structures provide an in-depth understanding of hydrochar application for removing emerging contaminants in soil/water environment. Identifying photoactive structures is helpful to predict photodegradation ability of hydrochar according to their abundance.Graphical

Universal photoelectrochemical aptasensing platform for antibiotic based on CuInS2/rGO and triplex DNA

In this work, a universal and convenient photoelectrochemical (PEC) biosensor was proposed to detect antibiotic on the basis of CuInS2/rGO and triplex DNA molecular switch. High performance photoactive structure was formed via p-type CuInS2 nanosphere complexed with rGO, which was employed to enhance the cathode photocurrent. Capture probe (CP) was conjugated onto the photoactive interface through covalent bonding. In the absence of target, the triplex DNA (THMS) was in a closed state. After introducing a target, the interaction between the target and the specific ring part DNA fragment leaded to the dissociation of the THMS and thereby liberated the single strand DNA (SP). The above identification process was completed in the homogeneous solution. Then, SP was captured to the electrode by CP and hybridized to form dsDNA. The steric effect of dsDNA hindered the interfacial charge transfer, resulting in signal-off photocurrent output. By only altering the specific loop section sequence of THMS, different targets can release the same SP, and can be detected on the same sensing platform under the same testing conditions. As proof of principle, three kinds of antibiotics amoxicillin (AMOX), ampicillin (AMP) and tobramycin (TOB) was detected, achieving limit of detection values of 3.17 pM, 0.63 nM and 2.81 fM, respectively. This approach was also used to detect antibiotic residues in food and environmental samples, which provides a promising paradigm for developing universal, high-performance and convenient PEC biosensing platform.

Self-Powering Sensory Device with Multi-Spectrum Image Realization for Smart Indoor Environments.

The development of organic-based optoelectronic technologies for the indoor Internet of Things market, which relies on ambient energy sources, has increased, with organic photovoltaics (OPVs) and photodetectors (OPDs) considered promising candidates for sustainable indoor electronic devices. However, the manufacturing processes of standalone OPVs and OPDs can be complex and costly, resulting in high production costs and limited scalability, thus limiting their use in a wide range of indoor applications. This study uses a multi-component photoactive structure to develop a self-powering dual-functional sensory device with effective energy harvesting and sensing capabilities. The optimized device demonstrates improved free-charge generation yield by quantifying charge carrier dynamics, with a high output power density of over 81 and 76 µW cm-2 for rigid and flexible OPVs under indoor conditions (LED 1000lx (5200 K)). Furthermore, a single-pixel image sensor is demonstrated as a feasible prototype for practical indoor operating in commercial settings by leveraging the excellent OPD performance with a linear dynamic range of over 130dB in photovoltaic mode (no external bias). This apparatus with high-performance OPV-OPD characteristics provides a roadmap for further exploration of the potential, which can lead to synergistic effects for practical multifunctional applications in the real world by their mutual relevance.

Oxidation of Zinc Microparticles by Microwave Plasma to Form Effective Solar-Sensitive Photocatalysts

The presented work studies the processes of synthesis of ZnO microstructures using atmospheric-pressure microwave nitrogen plasma and investigates their photocatalytic activity in the processes of degradation of 2,4-dinitrophenol and the antibiotic ciprofloxacin when irradiated with sunlight. The work proposes an effective method for formation of photosensitive ZnO powders. Due to the features of plasma treatment in the open atmosphere of zinc metal microparticles, ZnO structures are formed with sizes from hundreds of nanometers to several micrometers with various micromorphologies. The lattice parameters of ZnO structures are characteristic of a hexagonal unit with a = 3.258 Å and c = 5.21 Å, volume 47.95 Å3. The size of the crystallites is 48 nm. The plasma treatment was performed by means of a 2.45-GHz plasmatron at a power input of 1 kW in nitrogen flow at a rate of 1–10 L/min. Zn microparticles were injected into the microwave plasma at a mass rate of 20 g/min. High photoactivity was demonstrated (rate constants 0.036 min−1 and 0.051 min−1) of synthesized ZnO structures during photo-degradation of 2,4-dinitrophenol and ciprofloxacin, respectively, when exposed to solar radiation. Photo-active structures of ZnO synthesized using microwave plasma can find application in processes of mineralization of toxic organic compounds. Structures of ZnO synthesized using microwave plasma can find application in processes of mineralization of toxic organic compounds, and also in scintillation detectors, phosphors.

Nuclease-propelled target dual-recycling amplification strategy integrated with cascaded sensitization effect of ZnO/CuInS2/Ag2Se photoactive structures for lab-on-paper photoelectrochemical microRNA bioassay

Herein, a new paper-based photoelectrochemical (PEC) biosensor was proposed for microRNA determination based on the cascaded sensitization effect of ZnO/CuInS2/Ag2Se photoactive structures and nuclease-propelled target dual-recycling amplification strategy. Concretely, the paper-based ZnO sensitized with CuInS2 were served as a signal generator and a substrate for immobilizing hairpin DNA (H2). Ag2Se quantum dots (QDs), labeling at the terminal of probe DNA (pDNA), served as the sensitization agents. When target microRNA existed, duplex-specific nuclease activated the first recycling amplification procedure, resulting in the release of numerous converted DNA sequences (cDNA). Afterward, the second target recycling amplification procedure was initiated upon the H2-immobilized electrode was incubated with cDNA and lambda exonuclease, which made massive short DNA fragments free from H2. Consequently, a small quantity of target miRNA-141 was converted into abundant short DNA fragments, which could further hybridize with Ag2Se QDs labelled pDNA, activating the cascaded sensitization effect of ZnO/CuInS2/Ag2Se photoactive structures and giving great signal enhancement. Benefiting from the considerable signal amplification enabled by nuclease-assisted target dual-recycling amplification strategy and cascaded photosensitive structures, the proposed biosensor realized the ultrasensitive detection of miRNA-141 with great accuracy and selectivity, which rendered a prospective paradigm to develop high-performance microfluidic paper analytical devices.

UV-curable low dielectric siloxane-benzocyclobutene resins via introducing carbosilane groups

• New UV-curable low dielectric siloxane-benzocyclobutene oligomers ( SBCOs ) on the basis of carbosilane groups were prepared. • The oligomeric SBCOs have a UV/thermally dual crosslinked structure. • Cured siloxane-benzocyclobutene resins exhibited high thermostability, mechanical strength, and low dielectric properties. Low dielectric UV-curable resins are compatible with photolithography and 3D printing technique, and have great potential for use in inter-layered packaging and antenna. However, it is still a challenge to construct photoactive structure which combines low dielectric properties. In the present work, we propose a new type of low dielectric UV-curable resins by employing photoactive silacyclobutene groups. This low dielectric resins were prepared by UV/thermally curing of siloxane-benzocyclobutene oligomers (SBCOs). Oligomeric SBCOs were prepared by the simple hydrolysis-polycondensation of 1,1-dichlorosilacyclobutane followed by termination of the benzocyclobutene groups. In this way, silaycyclobutene and benzocyclobutene groups were simultaneously introduced into the resins to enable UV and thermally curing of SBCOs. The molecular weight of SBCOs were tuned by the ratio of 1,1-dichlorosilacyclobutane and benzocyclobutene-containing monomer. The cured siloxane-benzocyclobutene resins were thermostable, mechanically strong, and had low dielectric properties.

Overcoming the Challenge of High Surface Recombination in Thin‐Film Photovoltaic Cells Based on Subwavelength Arrays for Elevated Light Trapping

Surface arrays of subwavelength photoactive structures have been demonstrated for photovoltaic (PV) applications with elevated omnidirectional and broadband absorption. However, this approach suffers from an increase in surface recombination and loss of photovoltage. Herein, surface decoration with subwavelength dielectric (SiO2) arrays that provide enhanced light trapping without compromising the photovoltage performance is proposed. An increase of ≈ 50% in broadband absorption is shown in an ultrathin film of 200 nm due to the presence of a top surface SiO2 nanopillar array in comparison with the same film decorated with an optimized antireflective coating of 50 nm of Si3N4. Interestingly, the broadband enhancement is not due to lower reflection, but rather the presence of the arrays forces a considerable lower transmission. The distribution of the optical power flux density suggests that the low transmission is due to appreciable refraction, which is induced by the presence of the dielectric arrays. Finally, the photovoltaic performance is examined for various array geometries and absorber acceptor concentrations and an overall increase of >60% in PV efficiency is calculated for a decorated photovoltaic cell in comparison with a PV cell with an antireflection coating of 50 nm Si3N4.

Cathode Photoelectrochemical Paper Device for microRNA Detection Based on Cascaded Photoactive Structures and Hemin/Pt Nanoparticle-Decorated DNA Dendrimers.

In this work, a lab-on-paper cathode photoelectrochemical (PEC) sensing platform was constructed for ultrasensitive microRNA-141 (miRNA-141) assay using cascaded multiple photo-active structures as signal generators and hemin/Pt nanoparticle (Pt NP) trunk-branching-decorated DNA dendrimers as signal reinforcers. Specifically, pyramid-like Cu2O was first in situ grown on the Au nanoparticle-functionalized tangled cellulose fibers network, followed by the sensitization of trepang-like BiVO4-Bi2S3 heterostructures, forming the cascaded sensitization structures. Then, the DNA dendrimer was introduced into the photocathode sensing interface by coupling the duplex-specific-nuclease (DSN)-induced target recycling reaction with multiple-branched hybridization chain reaction (MHCR). The programmed target recycling procedures propelled using DSN guaranteed the highly amplified transduction of miRNA-141 to the exposed initiator strand, which triggered the cascaded MHCR accompanied by the formation of the DNA dendrimer with unique trunk-branching structures. Finally, the hemin/Pt NP trunk-branching-decorated DNA dendrimer (HPTD) was acquired by the assembly of Pt NPs and hemin on the trunk and branch, respectively. The resulting HPTD with the synergy catalysis of Pt NPs and hemin could efficiently catalyze the decomposition of H2O2 for in situ generation of O2 as the electron acceptor, leading to an enhanced photocurrent response. Based on the target-dependent photocurrent enhancement, ultrasensitive determination of miRNA-141 was realized with persuasive selectivity, high stability, and excellent reproducibility. Thus, the proposed paper-based cathode PEC sensing platform possessed promising application prospect in clinical miRNA diagnosis.

3D-Printed Photoactive Semiconducting Nanowire–Polymer Composites for Light Sensors

We demonstrated 3D-printed photoactive composites for light sensors. The composites consist of semiconducting polymer nanowires dispersed in an insulating polymer matrix through a thermo- or photocuring process. The nanowires formed percolated networks for charge-carrier collection at a very low nanowire volume concentration. Photodetectors had been fabricated with such composites and obtained a low leakage current density of 25 nA cm–2, a large conductivity change of 18025 times upon light irradiation (1 sun), and a high specific detectivity of 4.5 × 1010 Jones. The composite precursors before curing had been used as paints on different surfaces including wood, cardboard, and glass fiber cloth to create photoactive coatings on these surfaces. The precursors had also been used for 3D printing to create photoactive structures with a mechanical modulus of 4 GPa and an ultimate strength of 36 MPa.

Photoelectrochemical biosensor of HIV-1 based on cascaded photoactive materials and triple-helix molecular switch

In this work, an ultrasensitive photoelectrochemical (PEC) biosensor was proposed to detect nucleic acids on the basis of cascaded photoactive materials and triple-helix molecular switch. DNA sequence of human immunodeficiency virus type 1 (HIV-1) was chosen as the target DNA (T-DNA). Cascaded photoactive structure was formed via different sizes of CdTe quantum dots (QDs) sensitized ZnO nanorods (ZnO NRs), which was employed as a cascaded photoactive interface to amplify the photocurrent signal. A hairpin structure DNA (H-DNA) as capture probe was conjugated onto the photoactive interface through amide bond, and then a single-stranded DNA modified with gold nanoparticles labeled alkaline phosphatase (ALP-Au NPs-DNA) at each end was introduced to hybridize with the H-DNA to form a triple-helix conformation. The T-DNA detection was based on the photocurrent response change resulted from conformation change of the triple-helix molecule after hybridization with T-DNA. In the absence of T-DNA, the triple-helix molecule was in a closed state and the ALP of ALP-Au NPs-DNA could specifically catalyze the ascorbic acid 2-phosphate (AAP) to generate ascorbic acid (AA) as electron donors, which resulted in a significant photocurrent response due to the rapid electron transfer process. However, in the presence of T-DNA, the T-DNA hybridized with the ALP-Au NPs-DNA molecule, which caused triple-helix molecule in an opened state and compelled ALP-Au NPs-DNA away from the electrode surface, resulting in the absence of ALP which could catalyze AAP to generate AA. Subsequently, the photocurrent response significantly decreased. The proposed PEC biosensor not only had a wide detection range of 1fM-1nM and low detection limit (0.65 fM), but also showed excellent reproducibility, specificity and stability, which had great application prospect and opened up a new research method in the early clinical diagnosis and cancer research.

Surfactant modified Bi2(S0.3Se0.7)3 nanoflakes for photo electrochemical cell application

The development of new photoactive structures by combining the lower and higher band gap materials with a controlled morphology can result in the efficiency improvement of the photo electrochemical cell. In this work, optimal change in optical, morphological and electrical properties of bismuth sulphoselenide (Bi2(S0.3Se0.7)3) thin films was observed through different surfactant assisted synthesis procedures. Chemical bath deposition method was implemented to synthesize surfactant assisted nano crystalline Bi2(S0.3Se0.7)3 thin films at room temperature. All these thin films were characterized for their optoelectronic properties by UV–Vis and FTIR spectoscopy, structural properties by X-ray diffraction; and surface and morphological properties by Field emission scanning electron and atomic force microscopy respectively. Photo conversion efficiency of photo electrochemical cell was observed through J–V measurement technique under standard conditions. Among all surfactants, sodium dodecyl sulphate assisted Bi2(S0.3Se0.7)3 thin films exhibited better photo electrochemical conversion efficiency.

Coil-globule structure transition and binding characteristics of DNA molecules induced by isoquinoline-based photoactive ionic liquid surfactant

The photodynamic therapy and gene transportation across cell membrane are closely related with the binding behavior of the photoactive vectors on DNA. Here, the binding characteristics of an isoquinoline-based photoactive ionic liquid surfactant, lauryl isoquinolinium bromide ([C12iQuin]Br), with DNA was investigated for the first time by various analytical techniques. It was found that the DNA molecules are strongly compacted at a low [C12iQuin]Br concentration, and then undergo a complete coil-to-globule structure transition upon further addition of [C12iQuin]Br, which was verified by cryo-TEM. Based on the 1H NMR and 2D NOESY spectra, it can be concluded that the photoactive [C12iQuin]Br is an AT-specific minor groove binder. At a lower [C12iQuin]Br concentration, the isoquinolinium ring of [C12iQuin]Br would be arranged facing to the plane of the minor groove of DNA, and the hydrophobic tails of [C12iQuin]Br would be arranged parallel to the minor groove. The hydrophobic interaction between the hydrocarbon chains of the bound [C12iQuin]Br and DNA bases provides the dominate driving force in the binding process. The unique binding mode of [C12iQuin]Br on DNA causes the formation of the new photoactive structures of [C12iQuin]Br-DNA complexes, which would promise the novel applications in the photodynamic therapy or the gene transportation.

Photoactive Langmuir-Blodgett, Freely Suspended and Free Standing Films of Carboxylate Ligand-Coated ZnO Nanocrystals.

A new possibility for the formation of macroscopic and photoactive structures from zinc oxide nanocrystals is described. Photoactive freely suspended and free-standing films of macroscopic area (up to few square millimeters) and submicrometer thickness (up to several hundreds of nanometers) composed of carboxylate ligand-coated zinc oxide nanocrystallites (RCO2-ZnO NCs) of diameter less than 5 nm are prepared according to a modified Langmuir-Schaefer method. First, the suspension of RCO2-ZnO NCs is applied onto the air/water interface. Upon compression, the films become turbid and elastic. The integrity of such structures is ensured by interdigitation of ligands stabilizing ZnO NCs. Great elasticity allows transfer of the films onto a metal frame as a freely suspended film. Such membranes are afterward extracted from the supporting frame to form free-standing films of macroscopic area. Because the integrity of the films is maintained by ligands, no abolishment of quantum confinement occurs, and films retain spectroscopic properties of initial RCO2-ZnO NCs. The mechanism of formation of thin films of RCO2-ZnO NCs at the air/water interface is discussed in detail.

Self-organized porphyrin arrays on surfaces: the case of hydrophilic side chains and polar surfaces

Energy collection in photosynthetic microorganisms occurs through vectorial energy transfer along organized assemblies of chromophores. This process has inspired many research groups and yielded numerous examples of self-assembled photoactive structures. Dye sensitization of solar cells usually requires covalent anchoring of dyes onto the surface of metal oxides. A new porphyrin derivative that self-assembles upon non-covalent interaction with a surface has been designed and characterized by AFM. Interaction with metal oxide surfaces is further documented by the sensitization of metal oxide surfaces and the generation of photocurrent in non-optimized dye sensitized solar cells.

Using Thin Films of Rutile-Phase TiO2 Nanoparticles as Photoactive Material in Metal-Semiconductor Structures with Low Thermal Processing

Rutile-phase TiO2 nanoparticles are embedded within an organic SiO2 matrix (Spin-On Glass) and the final suspension is deposited by spinning on (a) thin aluminum stripes or (b) in between thin aluminum films and ultra-thin titanium stripes. The maximum processing temperature for both devices is 220 � C. The first device is a “horizontal” TiO2:SiO2/Al/Glass photoactive structure which is then electrically characterized under dark and illuminated conditions (I–V -Light) so that the total resistance of a simple aluminum stripe is measured before/after ultraviolet-visible (UV-Vis) irradiation. Compared to dark conditions, excess carriers are photogenerated within the TiO2 nanoparticles during light exposure and they are transferred to both ends of the aluminum stripe after applying a low potential difference. A large decrease in the resistance of the aluminum stripe (down to 43% of its original value) is obtained when this horizontal structure is irradiated with UV-B light thus acting as a photoresistor. The second device is a “vertical” Ti/TiO2:SiO2/Al/Glass photoactive structure. Here, the path for photogenerated and electrically-driven carriers occurs vertically, or inside a Metal-Insulator-Metal (MIM) capacitor. Because of the ultra-thin titanium layer (100 A in thickness), this gate electrode is highly transparent to most of the UV-Vis irradiation so that when all carriers are being photogenerated, they are almost immediately separated at the top/bottom electrodes by a small applied electric field due to the thin and high-dielectric constant of the photoactive TiO2:SiO2 film. This way, a fast and large increase/decrease in gate current (about 4–7 orders of magnitude) is observed when this device is under illumination/dark conditions. This vertical structure operates as a photocapacitor, where all photogenerated carriers could be efficiently stored within the MIM capacitor itself and thus, enable simultaneous conversion and storage of solar energy in the same device.

Получение фотоактивных структур Si(n+)/Si(p)/Si(p+) методом ионно-лучевой кристаллизации

Получение фотоактивных структур Si(n+)/Si(p)/Si(p+) методом ионно-лучевой кристаллизации

Photosensitive polyimides consisting of simple mixtures of 4‐substituted diazonaphthoquinones and polyamic acids

AbstractPolyimide resists that can be developed with a basic aqueous solution were produced by simple mixtures of conventional polyamic acids and naphthoquinone diazides in which sulfonate groups are substituted at the 4‐position. The diazonaphthoquinones bearing electron‐withdrawing groups gave negative tone resists. On the other hand, those bearing electron‐donating groups gave positive tone resists. The difference in the resist behaviors depending on the photoactive structure was explained by crosslinking caused by photogenerated sulfonic acids. The thermal stability of polyimides prepared from the resists was almost the same as that of conventional polyimides.