Photoactive Materials Research Articles

All-small-molecule organic solar cells based on cyclometalated tris-Ir(III) complexes as donor materials

Cyclometalated tris-Ir(III) complexes with six-coordinated octahedral configuration are beneficial to reduce aggregation for improved film morphology in organic solar cells (OSCs). Herein, two homoleptic tris-Ir complexes of eBz3Ir and eTBz3Ir showing majority absorption from UV to light-blue range are designed as electron donor materials. Owing to the extended π-conjugation by an extra thiophene ring in each ligand, eTBz3Ir exhibits red-shifted and stronger absorption as well as better charge transport property than eBz3Ir. Therefore, when employing the fused-ring non-fullerene acceptor Y6 or L8-BO to fabricate all-small-molecule OSCs (ASMOSCs), eTBz3Ir blended devices demonstrate higher efficiency than eBz3Ir, with maximum power conversion efficiency (PCE) achieving at 9.48/7.55% for Y6 and 10.48/6.46% for L8-BO devices, respectively. To our knowledge, over 10% PCE is among the highest values for binary ASMOSCs based on organometallic Ir complexes as photovoltaic materials. Such uncompetitive solar-light absorption but relatively high PCE indicates homoleptic Ir complexes with octahedral configurations are expected as promising photoactive materials for high-efficiency ASMOSCs.

Synthesis of ruthenium-based metallo-covalent organic frameworks for efficient photocatalytic ring opening of α-ketoepoxides under visible light

Two-dimensional (2D) metallo-covalent organic frameworks (MCOFs) have been regarded as an interesting new class of photoactive materials due to their superior thermal and chemical stability. Herein, we reported a heterogeneous metallaphotocatalyst Ru-COF which was prepared by using an sp2 carbon-conjugated covalent organic framework containing bipyridine as the support for a RuII complex. Under visible-light irradiation, the Ru-COF was used as the photocatalyst that catalyzed the ring-opening reaction of α-ketoepoxides to give various target products with good functional group tolerance in moderate to high yields at room temperature. Importantly, compared with Ru(bpy)3Cl2, Ru-COF shows admirable reusability and higher catalytic activity. Furthermore, radical ions captured by the control experiments provided direct evidence for the mechanism of the visible light photoredox reaction.

A Flexible Broadband Visible Light Plasmon‐Absorber Based on a 2D Monolayer of Au‐Nanoparticle/TiO2‐Nanowire Core–Shell Heterostructures

AbstractPlasmon‐induced hot carrier transfer is a promising approach for photoelectric applications, but its practical application is often hindered by its relatively narrow absorption bandwidth and low light harvesting at visible wavelengths. This work reports a broadband visible light plasmon‐absorber based on a dandelion‐like hierarchical metal‐semiconductor Au‐TiO2 core–shell nanostructure where each Au nanoparticle (AuNP) core is covered by an optically transparent mesh‐shell composed of TiO2 nanowires (TNWs) (denoted as AuTNW‐dCS). These AuTNW‐dCSs are assembled to form a 2D arrayed plasmonic monolayer by connecting adjacent AuNPs with cross‐linked TiO2 NWs, which can induce a remarkable broadband absorption in the visible spectrum of 500–700 nm. Driven by a wide light adsorption range, improved hot‐electron carriers, and excellent analyst's immobilization capability, the AuTNW‐dCS based photoelectric immunosensor owns excellent performance for alpha‐fetoprotein detection in human serum, with a practical linear range of 0.1–1000 ng mL−1, a low detection limit of 0.1 ng mL−1, and satisfying selectivity under visible light‐emitting diode light irradiation. This work enlightens the prospective research on the use of metal/semiconductor core–shell heterostructures as photoactive materials for sensing applications. Additionally, it gives an impetus for developing flexible nanofilms based on plasmonic metal/semiconductor nanohybrids, beneficial for building wearable point‐of‐need platform.

Photoluminescence of Mn2+ in the Borosulfate Zn[B2(SO4)4]:Mn2+ - A Tool to Detect Weak Coordination Behavior of Ligands.

The impact of the surrounding ligand field is successfully exploited in the case of Eu2+ to tune the emission characteristics of inorganic photoactive materials with potential application in e.g., phosphor-converted white light-emitting diodes (pc-wLEDs). However, the photoluminescence of Mn2+ related to intraconfigurational 3d5-3d5 transitions is also strongly dependent on local ligand field effects and has been underestimated in this regard so far. In this work, we want to revive the idea how to electronically tune the emission color of a transition metal ion in inorganic hosts by unusual electronic effects in the metal-ligand bond. The concept is explicitly demonstrated for the weakly coordinating layer-like borosulfate ligand in the Mn(II)-containing solid solutions Zn1-xMnx[B2(SO4)4] (x = 0, 0.03, 0.04, 0.05, 0.10). Zn[B2(SO4)4]:Mn2+ shows orange narrow-band luminescence at 590 nm, which is an unusually short wavelength for octahedrally coordinated Mn2+ and indicates an uncommonly weak ligand field. On the other hand, the analysis of the interelectronic Racah repulsion parameters reveals ionic Mn-O bonds with values close to the Racah parameters of the free Mn2+ ion. Overall, this strategy demonstrates that electronic control of the metal-ligand bond can be a tool to make Mn2+ a potent alternative emitter to Eu2+ for inorganic phosphors.

Photolumineszenz von Mn2+ in dem Borosulfat Zn[B2(SO4)4] : Mn2+ – Eine Möglichkeit zum Nachweis schwach koordinierender Liganden

AbstractDer Einfluss des umgebenden Ligandenfelds wird im Fall von Eu2+ erfolgreich genutzt, um die Emission anorganischer photoaktiver Materialien durchzustimmen, die z. B. in phosphor‐konvertierten Weißlicht‐emittierenden Dioden (pc‐wLEDs) Anwendung finden. Allerdings ist auch die Photolumineszenz von Mn2+, die auf intrakonfiguralen 3d5–3d5‐Übergängen basiert, stark von lokalen Ligandenfeldeffekten abhängig. Dieser Aspekt wurde bislang eher vernachlässigt. In der vorliegenden Arbeit wollen wir daher die Idee wieder aufleben lassen, die Emissionsfarbe eines Übergangsmetall‐Ions in anorganischen Wirtsverbindungen durch ungewöhnliche elektronische Effekte in der Metall‐Ligand‐Bindung einzustellen. Das Konzept wird explizit für das schwach koordinierende, schichtartigen Borosulfat‐Anion in den Mn2+‐haltigen festen Lösungen Zn1‐xMnx[B2(SO4)4] (x=0; 0.03; 0.04; 0.05; 0.10) demonstriert. Zn[B2(SO4)4] : Mn2+ zeigt orange Schmalbandlumineszenz bei 590 nm, was eine ungewöhnlich kurze Wellenlänge für oktaedrisch koordiniertes Mn2+ darstellt und auf ein besonders schwaches Ligandenfeld hinweist. Eine Analyse der interelektronischen Racah‐Abstoßungsparameter deutet stark ionische Mn−O‐Bindungen mit Werten nahe der Racah‐Parameter des freien Mn2+‐Ions an. Insgesamt demonstriert diese Strategie, dass elektronische Anpassungen der Metall−Ligand‐Bindung als Instrument genutzt werden können, um Mn2+ zu einem potenten alternativen Emitter anstelle von Eu2+ für anorganische Leuchtstoffe zu machen.

One‐dimensional molecular co‐crystal alloys capable of full‐color emission for low‐loss optical waveguide and optical logic gate

AbstractThe luminescence color of molecule‐based photoactive materials is the key to the applications in lighting and optical communication. Realizing continuous regulation of emission color in molecular systems is highly desirable but still remains a challenge due to the individual emission band of purely organic molecules. Herein, a novel alloy strategy based on molecular co‐crystals is reported. By adjusting the molar ratio of pyrene (Py) and fluorathene (Flu), three types of molecular co‐crystal alloys (MCAs) assemblies are prepared involving Py‐Flu‐OFN‐x%, Py‐Flu‐TFP‐x%, Py‐Flu‐TCNB‐x%. Multiple energy level structure and Förster resonance energy transfer (FRET) process endow materials with tunable full‐spectra emission color in visible region. Impressively, these MCAs and co‐crystals can be successfully applied to low optical loss waveguide and optical logic gate by virtue of all‐color luminescence from blue across green to red, together with smooth surface of one‐dimensional microrods, which show promising applications as continuous light emitters for advance photonics applications.

Stabilizing α-FAPbI3 at FAPbI3/SnO2-X Interface By Reducing Oxygen Vacancies in SnO2-X

CH3NH3PbI3 (CH3NH3 + is denoted MA hereinafter) was selected as the photoactive material in the early stage of perovskite solar cell (PSC) research. However, MAPbI3 shows poor thermal stability due to high volatility of the MA organic cation. Replacing the MA organic cation with a CH(NH2)2 + (CH(NH2)2 + is denoted FA hereinafter) organic cation was suggested to resolve the thermal stability issue. Additionally, FAPbI3 holds higher potential for high-efficiency solar cells with a broader photoresponse range in the solar spectrum than MAPbI3. However, fabricating FAPbI3 thin films is more challenging than MAPbI3. FA exhibits a larger ionic size (2.56 Å) than MA (2.17 Å), making incorporation of FA into PbI6 octahedra difficult. Incorporating FA induces tilting of PbI6 octahedra, which causes reversible deformation of perovskite-phase FAPbI3 (α-phase) into unfavorable phases (δ-phase and PbI2) at room temperature. Several reports on stabilizing the α-phase of FAPbI3, such as through heterogeneous cation or anion mixing, have been presented. For example, mixing smaller ions such as MA, Cs, and Br reduces the unit cell volume of FAPbI3, enhancing hydrogen bonding between FA and the PbI6 octahedron. This hydrogen bonding prevents reversible deformation of and stabilizes the α-phase of FAPbI3 in ambient atmosphere. In conventional PSCs, the perovskite layer usually forms an interface with an electron or hole transport layer (ETL or HTL). The compatibility of materials forming the interface is significant for separating charges from the perovskite with minimal loss. Nevertheless, although stabilizing FAPbI3 in a bulk manner is widely studied, stabilizing FAPbI3 at the interface is relatively overlooked. Stabilizing FAPbI3 at the interface is more important since the interface contains a high portion of structural defects compared to the bulk, almost 100-fold. Unfavorable phases, such as δ-phase FAPbI3 and PbI2, formed at the interface will hinder the charge extraction process from FAPbI3 to the transport layer, similar to defects. Especially, in the n-i-p structure, the perovskite is epitaxially deposited over the ETL, and tuning the interface after deposition is nearly impossible, which stresses the importance of the surface structure of the ETL. In the case of FAPbI3/SnO2-x, Sn and O are the key atoms for stabilizing the PbI6 octahedron and organic cation, respectively, which affects the growth of the perovskite at the interface. Oxygen vacancies in the surface of SnO2-x can cause distortion of the perovskite structure at the interface, inducing unfavorable phases, such as the δ-phase, PbI2, or other unknown phases. Furthermore, oxygen vacancies are more prevalent issue in SnO2-x than TiO2-x due to the stronger multivalency of Sn, which further emphasizes control of oxygen vacancies in SnO2-x. Since the open-circuit voltage (Voc) and fill factor (FF) show greater potential for improvement than the short-circuit current density (Jsc), stabilizing α-FAPbI3 at the interface may be a necessary step for researchers to further increase the power conversion efficiency (PCE) and stability of PSCs. In this work, we systematically studied the formation of δ-phase FAPbI3 and PbI2 induced by oxygen vacancies of the SnO2-x surface at the FAPbI3/SnO2-x interface. Using X-ray diffraction (XRD) and transmission electron microscopy (TEM), we observed PbI2 segregation and δ-phase FAPbI3 formation adjacent to SnO2-x. The generation of iodine interstitials at the interface was revealed as the driving force of the unfavorable phase transition. The absence of oxygen atoms interacting with tin atoms lowered the energy barrier for iodine interstitial generation almost by half, and the iodine interstitials accelerated the unfavorable phase transition of FAPbI3. For the first time, organic cation loss at the FAPbI3/SnO2-x interface was also observed as a severe drawback to forming an ideal heterojunction. Oxygen vacancies in the SnO2-x surface, which act as hydrogen bonding sites for FA cations, induced withdrawal of FA cations, which was revealed by X-ray photoelectron spectroscopy (XPS) measurements. Inspired by this phenomenon, we fabricated a SnO2-x layer with reduced oxygen vacancies by using oxidized black phosphorus quantum dots (O-BPs). The multiple P=O bonds of O-BPs effectively assisted the formation of a SnO2-x layer with minimal oxygen vacancies. After P=O passivation, most of the detrimental effects were mitigated, showing highly stable α-FAPbI3 crystal structures. Consequently, we achieved a maximum PCE of 23.43% with enhanced thermal and operational stability.

Covalent Organic Frameworks As Functional Support Materials

Covalent Organic Frameworks are photoactive materials that could play a future role in photophysical devicesor as photocatalyst anchoring sites. Despite challenges associated with processing them into usable formsthere is reason to be optimistic about the possibilities they could hold for functional support materials. Onereason for optimism is the simplicity with which their topological symmetry can be altered to enhancephotogenerated charge separation which may open the door for their use as functional support materials withnovel properties that may open new doors for device engineers. Figure 1

(Nanocarbons Division Robert C. Haddon Research Award) Nano Carbons in Mimicking the Early Events of Photosynthetic Reaction Center: ‘Simple’ and ‘Not-so-Simple’ Donor-Acceptor Conjugates

Light-induced electron transfer is a key step in solar energy conversion, and a process with myriad relevance in the fields of artificial photosynthesis, photocatalysis, photoconductivity, and photovoltaics. In a donor-acceptor, D-A system, light absorption by a chromophore results in the formation of an excited state species, followed by a charge transfer between an electron donor (D) and an electron acceptor (A) leading to a charge-separated D .+ -A .- species.The optimization of these processes and comprehending their mutual interplay to ultimately achieve charge-separated species is of paramount importance for the development of efficient systems in solar light conversion schemes.The present talk summarizes our research over the years focused on utilizing nano carbons, viz., fullerenes, endohedral fullerenes, carbon nanotubes, and graphene in the construction of donor-acceptor systems capable of undergoing photoinduced energy and electron transfer events. Both, covalently linked with rigid, semi-rigid, flexible, or conjugated spacers, and self-assembled via metal-ligand axial coordination, ion-pairing, ion-dipole, or hydrogen bonding strategies were utilized in the construction of donor-acceptor conjugates. Multi-modular donor-acceptor constructs were designed, synthesized, and studied to probe sequential energy and electron transfer events, finally resulting in long-lived charge-separated states. In some instances, these molecular systems were also used as photocatalytic energy conversion schemes. The pros and cons of utilizing nanocarbon materials as photo-active functional materials will be highlighted. D’Souza, F.; Sandanayaka, A. S. D.; Ito, O. ‘SWNT-Based Supramolecular Nanoarchitectures with Photosensitizing Donor and Acceptor Molecules’ Phys. Chem. Letts. 2010, 1. 2586-2593.D’Souza, and O. Ito ‘Photosensitized electron transfer processes of nano carbons applicable to solar cells,’ Chem. Soc. Rev. 2012, 41, 86-96.B. KC, F. D’Souza, ‘Design and photochemical study of supramolecular donor-acceptor systems assembled via metal-ligand axial coordination Coord. Chem. Rev. 2016, 322, 104-141.Bottari, M. A. Herranz, L. Wibmer, M. Vollard, L. Rodriguez-Perez, D. M. Guldi, A. Hirsch, N. Martin, F. D’Souza, T. Torres, Chemical functionalization and characterization of graphene-based materials, Chem. Soc. Rev. 2017, 46, 4464-4500.Barrejon, L. M. Arellano, F. D’Souza, F. Langa, ‘Bidirectional charge transfer in carbon-based hybrid nanomaterials’ Nanoscale, 2019, 11, 14978-14992.Kazemi, Y. Jang, A. Liyanage, P. A. Karr, and F. D’Souza, ‘A Carbon Nanotube Binding Bis(pyrenylstyryl)BODIPY-C60 Nano Tweezer: Charge Stabilization through Sequential Electron Transfer’, Angew. Chem. Int. Ed. 2022, in press

Integration of Photoelectrochemical Signal Transduction with RNA-Cleaving Dnazymes for Culture-Free Detection of Bacteria

There is a growing interest in developing ultrasensitive biological sensors that can be used for rapid testing at the point-of-need.1 A major hurdle in developing such sensors for detecting pathogens such as bacteria is that they require target enrichment or amplification to deliver the required limit-of-detection.2 Among signal transduction strategies, photoelectrochemical (PEC) signal readout, built on the use of light for enhancing electrochemical reactions, is emerging as an ultrasensitive signal transduction mechanism.3 However, the existing PEC platforms fail to deliver single step testing due to the existence of multiple manual steps, including the addition of biological materials labelled with inorganic photoactive nanoparticles, for signal transduction.3 RNA-cleaving DNAzymes (RCDs), a class of synthetic nucleic acids, have been selected for precisely identifying specific bacterial species without the need for sample processing.4 RCDs are molecular switches that cleave a segment of themselves in response to a particular bacterial target, combining biological recognition with signal transduction.4 We developed photoactive RCDs by tagging them with TiO2 nanomaterials for combining these molecular switches with PEC signal readout. We designed these molecular switches to make and then break semiconductive heterostructures in response to bacterial targets. These photoactive RCDs were the foundational basis for the design novel and highly sensitive PEC bacterial sensor.We developed two photoactive materials for use in the PEC bacterial assay: TiO2 nanorod clusters (rutile) that form high surface area photoelectrodes and sub-nanometer sized TiO2-nanoparticles (anatase) that link to RCDs to create photoactive reporter probes. Combining TiO2-assemblies and TiO2-nanoparticles gives rise to a semiconductor heterostructure that massively improves the photoexcitation efficiency of the combined material system and improves photocurrent generation. Our PEC bacterial sensor makes use of this phenomenon for bacterial detection by utilizing photoactive RCDs to modulate photocurrent by breaking and then rebuilding the TiO2 heterostructures, as a signaling mechanism. The assay consists of a release electrode – modified with photoactive RCDs and a capture electrode – modified with single-stranded DNA probes. Upon target interaction, RCDs release photoactive reporters which are captured by the probes, decreasing the release electrode signal while raising the capture electrode signal.The resulting biosensor can detect E. coli bacterial contamination with high specificity and has achieved a very low limit of detection of 21 CFU/mL in buffer and 18 CFU/mL in lake water samples. These results have set a new record for amplification-free detection of bacteria, that does not rely on target enrichment, reagent addition, or sample processing. This presents a new tool for rapid and in-field water testing.References Nat. Microbiol., 1, 16089 (2016).L. Castillo-Henríquez et al., Sensors, 20, 6926 (2020).A. Victorious, S. Saha, R. Pandey, T. F. Didar, and L. Soleymani, Front. Chem., 7, 617 (2019).I. Cozma, E. M. McConnell, J. D. Brennan, and Y. Li, Biosens. Bioelectron., 177, 112972 (2021).

Modern Applications of Porphyrin-Based MOFs in Agriculture

Nanosized metal-porphyrinic frameworks are an interesting class of porous electro- and photoactive materials finding applications in medicine (photodymanic therapy, photothermal therapy, drug delivery and chemotherapy, immunotherapy), [1], sanitary and antimicrobial devices [2], waste water purification [3], photocatalytic organic transformations [4], production of solar fuels [5], and more recently, in agriculture [6]. The fact that porphyrin derivatives are colored, they are prone for the photosensitization of singlet oxygen (1O2(g); a reactive oxygen species of type II) either at the solid state/air interfaces or in solution leading to applications listed above using visible light. In fact, they even do this efficiently. Reactive oxygen species of type I (for examples, H-O radical, HO-OH, superoxide radical, perhydroxyl radical, etc) are also photo-produced when given metals inside the porphyrins and metallic nodes in the frameworks are used, or when the metal-porphyrinic frameworks form a composite with another semiconductor. Moreover, the size of the nanoparticles can be tailored. All of these properties are cleverly exploited in the field of agriculture and include the following applications: controlled delivery of pesticides and agro-chemicals, detection of pesticides and pathogenic metals, elimination of pesticides and toxic metals, and photodynamic antimicrobial activity, and the nanosized metal-porphyrinic frameworks also have an important implication in food safety. This presentation will describe these features along with new experimental results.

Solid-state spiro-rhodamines: rational design of photoactive materials

Solid-state spiro-rhodamines: rational design of photoactive materials

Numerical study of MoSe2-based dual-heterojunction with In2Te3 BSF layer toward high-efficiency photovoltaics

In this study, molybdenum diselenide (MoSe2)-based dual-heterojunction with Indium Telluride (In2Te3) as an absorber and a back surface field (BSF) layers with Al/ITO/CdS/MoSe2/In2Te3/Ni heterostructure has been studied by SCAPS-1D simulator. To explore the potentiality of layered materials in photovoltaic devices, a detailed investigation has been executed on the CdS window, MoSe2 absorber, and In2Te3 BSF layers at varied layer thicknesses, carrier concentrations, interface and defect densities, resistances, and operating temperatures. The photoconversion efficiency (PCE) of 24.78% with short circuit current J sc of 30.55 mA cm−2, open circuit voltage V oc of 0.95 V, and fill factor FF of 85.5% were obtained in the reference cell (without the In2Te3 BSF layer), while a notably improved PCE of 29.94% (5.16% higher) with J sc of 31.06 mA cm−2, V oc of 1.10 V, and FF of 87.28% was achieved by inserting the In2Te3 BSF layer. With a favorable band alignment and almost similar chemical and physical properties as transitional metal dichalcogenides (TMDCs) materials, the proposed dual heterostructure with CdS, MoSe2, and In2Te3 exhibits huge potential as a photoactive material and paves a pathway for the fabrication of uniquely layered material-based thin, flexible high-efficiency solar cells.

Self-assembled p-n Ag2O@Bi2O2S nanoflower heterojunctions for sensitive photoelectrochemical immunoassay

A new photoelectrochemical immunoassay based on self-assembled p-n Ag2O@Bi2O2S nanoflower heterojunction was designed and developed for quantitative monitoring of prostate-specific antigen (PSA) in biological fluids. Primarily, self-assembled p-n Ag2O@Bi2O2S nanoflower heterojunctions were served as the photoactive materials and coated onto the surface of electrodes. Subsequently, the glucose oxidase (GOx) was bound to the detection antibody (mAb2) labeled gold nanoparticles (Au NPs) and then were employed to accomplish a sandwich-like immunoreaction to generate H2O2 on a microplate incubated with monoclonal anti-PSA antibodies. In the presence of PSA, the product (H2O2) was catalyzed by the substrate, which was used as an electron sacrificial agent to improve signal conversion and capture of photogenerated electrons. Under optimum conditions, a wide linear range of 0.01–50 ng mL−1 and a low detection limit of 5.3 pg mL−1 were accomplished with the sensor, exhibiting an excellent photocurrent response. Moreover, the proposed sensor revealed satisfactory reproducibility, high selectivity, and acceptable accuracy for the real sample testing. Importantly, our work provides a novel strategy for high sensitivity detection of disease-associated biomarkers for the early diagnosis of cancers.

A Review of the Improvements in the Performance and Stability of Ternary Semi-Transparent Organic Solar Cells: Material and Architectural Approaches

In the past decade, considerable efforts have been made to develop semi-transparent organic solar cells (ST-OSCs). Different materials and architectures were examined with the aim of commercializing these devices. Among these, the use of ternary active layers demonstrated great promise for the development of efficient semi-transparent organic solar cells with the potential for future applications, including but not limited to self-powered greenhouses and powered windows. Researchers seek alternative solutions to trade-off between the power conversion efficiency (PCE) and average visible transmittance (AVT) of ST-OSCs, with photoactive materials being the key parameters that govern both (PCE) and (AVT), as well as device stability. Several new organic materials, including polymers and small molecules, were synthesized and used in conjunction with a variety of techniques to achieve semi-transparent conditions. In this review paper, we look at the working principle and key parameters of semi-transparent organic solar cells, as well as the methods that have been used to improve the performance and stability of ternary-based semi-transparent organic solar cells. The main approaches were concluded to be spectral enhancement and increments in the transparency of the active layer through band gap tuning, utilizing novel organic semi-conductors, optical engineering, and the design architecture of the active layers.

Fluorination of Covalent Organic Framework Reinforcing the Confinement of Pd Nanoclusters Enhances Hydrogen Peroxide Photosynthesis.

Metal-isolated clusters (MICs) physically confined on photoactive materials are of great interest in the field of photosynthesis of hydrogen peroxide (H2O2). Despite recent important endeavors, weak confinement of MICs in the reported photocatalytic systems leads to their low catalytic activity and stability. Herein, we report a new strategy of fluorinated covalent organic frameworks (COFs) to strongly confine Pd ICs for greatly boosting the photocatalytic activity and stability of H2O2 photosynthesis. Both experimental and theoretical results reveal that strong electronegative fluorine can increase the metal-support interaction and optimize the d-band center of Pd ICs, thus significantly enhancing the stability and activity of photocatalytic H2O2. An optimal TAPT-TFPA COFs@Pd ICs photocatalyst delivers a stable H2O2 yield rate of 2143 μmol h-1 g-1. Most importantly, the as-made TAPT-TFPA COFs@Pd ICs exhibit high catalytic stability over 100 h, which is the best among the reported materials.

Label-free "signal-off" PEC aptasensor for determination of kanamycin based on 3D nanoflower-like FeIn2S4/CdS Z-scheme heterostructures.

Highly photoactive 3D nanoflower-like FeIn2S4/CdS heterostructures were synthesized by hydrothermal treatment and low-temperature cation exchange. The FeIn2S4/CdS displayed 14.5 times signal amplification in contrast to FeIn2S4 alone. It was applied as a photoactive substrate to construct a label-free photoelectrochemical (PEC) aptasensor for ultrasensitive determination of kanamycin (KAN). Under the optimal conditions, the constructed PEC aptasensor displayed a wide linear range (5.0 × 10-4 ~ 5.0 × 101ngmL-1) and a low detection limit (S/N = 3) of 40.01fgmL-1. This study provides some constructive insights for preparation of advanced photoactive materials and exhibits great potential for quantitative determination of antibiotics in foods and environmental samples.

A smartphone-powered photoelectrochemical POCT via Z-scheme Cu2O/Cu3SnS4 for dibutyl phthalate in the environmental and food

As a major hazardous additive released from microplastics and nanoplastics, identifying dibutyl phthalate (DBP) in complex matrices attracts a growing concern in environmental monitoring and food safety. For the first time, Cu2O/Cu3SnS4 nanoflower is prepared and serves as the photoactive material which can be constructed as a smartphone-based photoelectrochemical (PEC) point-of-care test (POCT). Effectively matching energy levels between Cu2O and Cu3SnS4 accelerated the transfer of photogenerated electron-hole pairs, significantly improving the intelligent PEC POCT performance. The novel Cu2O/Cu3SnS4 has proven to be the Z-scheme heterojunction by density functional theory calculation. A competitive immunoassay has been realized on a Cu2O/Cu3SnS4 modified electrode, dramatically decreasing the photocurrent signal and enhancing POCT sensitivity. The smartphone has been used to record and transfer PEC results. Under optimal conditions, the PEC POCT exhibited a satisfying linear range (0.04–400 ng/mL) and a low detection limit of 7.94 pg/mL in real samples, together with excellent stability, repeatability, reproducibility and selectivity. The PEC POCT system provides good performance and practicability in determining DBP in water and edible oil samples. This proposal provides a practical strategy for the intelligent POCT for environment monitoring and food safety.

Ultrasensitive Photocathodic Biosensor Based on the Cu2O/PTB7-Th/PDA+ Composite with Enhanced Photoelectrochemical Performance for the Detection of MicroRNA-375-3p.

Herein, an ultrasensitive photocathodic biosensor was fabricated based on Cu2O/PTB7-Th/PDA+ photoactive materials with high photocarrier separation efficiency for the detection of microRNA-375-3p. Impressively, the photocathodic signal of the Cu2O material was significantly enhanced by using PTB7-Th as an energy level-matching photoactive material to enhance the bulk charge separation and N,N-bis (2-(trimethylammoniumiodide) propylene) perylene-3,4,9,10-tetracarboxydiimide (PDA+) as an interfacial charge transfer mediator to efficiently suppress charge recombination at the photoelectrode/electrolyte interface. Compared with the pristine Cu2O as a photocathode, the obtained Cu2O/PTB7-Th/PDA+ exhibited a 17 times higher photocathodic signal. As a proof of concept, a PEC biosensor was fabricated by using Cu2O/PTB7-Th/PDA+ as a photoactive material and a target-triggered 3D DNA walker integrated with the dumbbell hybridization chain reaction (DHCR) as a signal amplifier to achieve the sensitive detection of microRNA-375-3p with a detection limit of 0.3 fM. This work provided a method to increase the photocurrent signal and the sensitivity of PEC-sensing platforms for the detection of biomarkers and disease diagnosis.

Facile growth of perovskite nanoparticles confined on dimension-controlled Si nanorod arrays for various promising photophysical applications

In this study, a facile growth of hybrid perovskite nanoparticles (NPs) has been demonstrated on mesoporous, high-aspect ratio, morphology-controlled Si nanorod (NR) arrays. A generic method of directly confining perovskite nanocrystallites (average size <7 nm) on a mesoporous substrate without the use of colloidal stabilization was introduced. The perovskite NPs coated on dimension-and position-controlled Si NR arrays were systematically investigated by their various photophysical properties such as optical reflectance, cathodoluminescence (CL), and photoluminescence (PL) behaviors at both room temperature and low temperature. The dimension and position of the Si NR arrays were controlled by e-beam lithography followed by selective metal-assisted chemical etching (MACE). Organic-inorganic perovskite NPs were synthesized on the surface of Si NR array by spin coating of perovskite precursor solution and followed by annealing. The porous and rough sites on the surface of the NR arrays acted as nucleation centers for the formation of perovskite NPs. Due to the excitonic recombination of CH3NH3PbBr3, the NPs confined on the various NR templates exhibited strong PL emission in the 505–510 nm region. Furthermore, due to greater radiative recombination and lesser carrier trapping in the NPs, the PL and CL emission intensities of the perovskite NPs localized on the surface of the NR array were dramatically increased (PL enhancement factor ∼ 7.7, when NR aspect ratio ∼ 17.2) as compared to the bulk perovskite microcrystals. The low-temperature PL study revealed higher exciton binding energy of the NPs as compared to the bulk microcrystalline film. A systematic investigation revealed that the optical absorption, as well as the emission color of the perovskite NPs, can be tuned by the aspect ratio of the Si NR arrays. The results of our studies indicate the application of bandgap engineering of perovskite nanocrystals through confinement in a mesoporous, well-organized, regularly-ordered template as a powerful tool for tuning the emission wavelength in next-generation photonic sources. Furthermore, the important findings on the periodic array of photoactive nanoscale materials introduced in this manuscript may open up huge opportunities in numerous cutting-edge applications such as light emitting diode arrays, photodetector arrays, individually addressable devices, display devices with controlled pixel size and pixel density, etc.