Light-induced Electron Transfer Research Articles

A light-triggered molecular switch for an efficient OFET-based organic memory device

An efficient OFET-based memory is designed using spiropyran molecular switch operating via two complementary mechanisms: reversible photoisomerization and light-induced electron transfer involving [Cr(C2O4)3]3− counterion.

Effects of Active-Center Reduction of Plant-Type Ferredoxin on Its Structure and Dynamics: Computational Analysis Using Molecular Dynamics Simulations.

"Plant-type" ferredoxins (Fds) in the thylakoid membranes of plants, algae, and cyanobacteria possess a single [2Fe-2S] cluster in active sites and mediate light-induced electron transfer from Photosystem I reaction centers to various Fd-dependent enzymes. Structural knowledge of plant-type Fds is relatively limited to static structures, and the detailed behavior of oxidized and reduced Fds has not been fully elucidated. It is important that the investigations of the effects of active-center reduction on the structures and dynamics for elucidating electron-transfer mechanisms. In this study, model systems of oxidized and reduced Fds were constructed from the high-resolution crystal structure of Chlamydomonas reinhardtii Fd1, and three 200 ns molecular dynamics simulations were performed for each system. The force field parameters of the oxidized and reduced active centers were independently obtained using quantum chemical calculations. There were no substantial differences in the global conformations of the oxidized and reduced forms. In contrast, active-center reduction affected the hydrogen-bond network and compactness of the surrounding residues, leading to the increased flexibility of the side chain of Phe61, which is essential for the interaction between Fd and the target protein. These computational results will provide insight into the electron-transfer mechanisms in the Fds.

Light-induced energy and electron transfer occurring in tandem in tetra (bis(4′-tert-butylbiphenyl-4-yl)aniline)-zinc(II) porphyrin-fullerene supramolecular conjugates

[Formula: see text]-bis (4′-tert-butylbiphenyl-4-yl)aniline) tethered zinc porphyrins, (BBA)4- ZnP, (BBA- Ph)4- ZnP, and (BBA- OEtOPh)4- ZnP with varied spacer distances have been synthesized and photosynthetic antenna-reaction center models were constructed via axial co-ordination with fulleropyrrolidines, C60Im and C70Im. Selective excitation of the BBA moiety in the porphyrins at 355 nm resulted in the quenching of the emission intensity of the BBA followed by the concomitant appearance of the ZnP emission at 600–640 nm indicating the occurrence of the photoinduced energy transfer from 1BBA* to ZnP. When the zinc porphyrins are titrated with C60Im and C70Im, supramolecular complexes of the type, (BBA)4-ZnP:[Formula: see text]Im/[Formula: see text]Im are formed and the complex formation was monitored by UV-visible spectroscopic studies. Steady-state fluorescence studies involving the excitation of the ZnP at 550 nm displayed the diminished fluorescence intensity of the ZnP emission indicating the photoinduced electron transfer from 1ZnP* to fullerenes. More interestingly, when the BBA moiety is excited in the supramolecular complexes, the emission of both the BBA and ZnP were decreased gradually indicating the occurrence of PEnT from 1BBA* to ZnP followed by a sequential electron transfer from 1ZnP* to C60Im or C70Im indicating the formation of a charge-separated state in these complexes.

Phenothiazine functionalized fulleropyrrolidines: synthesis, charge transport and applications to organic solar cells.

A series of phenothiazine-C60/70 dyads containing fulleropyrrolidine tethered to C-3 position (C60-PTZ and C70-PTZ) or to the heteroatom N-position via either phenyl (C60-Ph-PTZ and C70-Ph-PTZ) or phenoxyethyl linkers (C60-PhOEt-PTZ and C70-PhOEt-PTZ) of the phenothiazine were synthesized and light-induced electron transfer events were explored. Optimized studies suggested that the highest molecular orbital (HOMO) resides on donor phenothiazine moiety while lowest molecular orbital (LUMO) on the acceptor fulleropyrrolidine moiety of the dyads. Optical and electrochemical properties suggested no electronic communication between the donor and acceptor moieties in the ground state. However, steady-state emission studies in solvents of varied polarity, involving selective excitation of C60/C70, disclosed that the emission intensity of C60/C70 was quenched in the dyads in the increasing order, C60/70-PTZ > C60/70-Ph-PTZ > C60/70-PhOEt-PTZ as a consequence of the donor-acceptor distance resulted due to spacer lengths. Also, the emission quenching is more pronounced in polar solvents such as DMF compared to a non-polar solvent, toluene. With the support of parallel electrochemical studies, the emission quenching is attributed to intramolecular photo-induced electron transfer occurring from PTZ to (C60/C70)* generating a radical ion pair, PTZ+⋅-C60-⋅/PTZ+⋅-C70-⋅. Finally, bulk heterojunction (BHJ) solar cells devices inverted fashion prepared by employing the dyads as acceptors, and PTB7 as donor, suggested that the devices prepared from C70 derivatives i.e., PTB7:C70-PTZ and PTB7:C70-PhOEt-PTZ exhibited better power conversion efficiency of 2.66% and 2.15%, respectively over C60 derivatives i.e., PTB7:C60-PTZ and PTB7:C60-PhOEt-PTZ with the efficiencies of 1.80 and 1.72%, respectively. AFM studies revealed that the poor performance of PTB7:C60-PTZ- and PTB7:C60-PhOEt-PTZ-based devices can be ascribed to the lower solubility of the dyads in 1,2-DCB solvent leading to rough morphology.

Effects of abiotic stress on photosystem II proteins

Photosystem II (PSII) represents the most vulnerable component of the photosynthetic machinery and its response in plants subjected to abiotic stress has been widely studied over many years. PSII is a thylakoid membrane-located multiprotein pigment complex that catalyses the light-induced electron transfer from water to plastoquinone with the concomitant production of oxygen. PSII is rich in intrinsic (PsbA and PsbD, namely D1 and D2, CP47 or PsbB and CP43 or PsbC) but also extrinsic proteins. The first ones are more largely conserved from cyanobacteria to higher plants while the extrinsic proteins are different among species. It has been found that extrinsic proteins involved in oxygen evolution change dramatically the PSII efficiency and PSII repair systems. However, little information is available on the effects of abiotic stress on their function and structure.

Heterogeneous Cu2O–Au nanocatalyst anchored on wood and its insight for synergistic photodegradation of organic pollutants

In this study, a Cu2O–Au nanoparticles (NPs) heterojunction catalyst anchored on wood was developed by in situ reduction and hydrothermal treatment, and the properties of the catalyst were systematically characterized. The catalyst exhibited prominent photocatalysis of methyl orange (MO, 0.169 min− 1), and tetracycline (TC, 0.122 min−1) which were degraded completely within 20 min. Even after four recyclings, the efficiency of MO degradation by the catalyst remained at 80%. The natural wood with three-dimensional porous structures acted as a reducing agent and a stabilizer for Au NPs and Cu2O, which helped to maintain high performance and reusability. The presence of Au NPs mediated the light-induced electron transfer and enhanced the absorption of visible light for promoting photocatalytic activity. The intermediates of contaminants within the degradation process were characterized by liquid chromatography-mass spectrometry. Additionally, the photogenerated superoxide radicals and holes were identified by electron spin resonance. Thus, the potential degradation mechanism catalyzed by the Cu2O–Au NPs-wood was proposed. This findings of this study valorizes biomass as a photocatalyst for wastewater remediation.

Microbial biofilms as living photoconductors due to ultrafast electron transfer in cytochrome OmcS nanowires

Light-induced microbial electron transfer has potential for efficient production of value-added chemicals, biofuels and biodegradable materials owing to diversified metabolic pathways. However, most microbes lack photoactive proteins and require synthetic photosensitizers that suffer from photocorrosion, photodegradation, cytotoxicity, and generation of photoexcited radicals that are harmful to cells, thus severely limiting the catalytic performance. Therefore, there is a pressing need for biocompatible photoconductive materials for efficient electronic interface between microbes and electrodes. Here we show that living biofilms of Geobacter sulfurreducens use nanowires of cytochrome OmcS as intrinsic photoconductors. Photoconductive atomic force microscopy shows up to 100-fold increase in photocurrent in purified individual nanowires. Photocurrents respond rapidly (<100 ms) to the excitation and persist reversibly for hours. Femtosecond transient absorption spectroscopy and quantum dynamics simulations reveal ultrafast (~200 fs) electron transfer between nanowire hemes upon photoexcitation, enhancing carrier density and mobility. Our work reveals a new class of natural photoconductors for whole-cell catalysis.

Investigation of Photosystem II Functional Size in Higher Plants under Physiological and Stress Conditions Using Radiation Target Analysis and Sucrose Gradient Ultracentrifugation.

The photosystem II (PSII) reaction centre is the critical supramolecular pigment–protein complex in the chloroplast which catalyses the light-induced transfer of electrons from water to plastoquinone. Structural studies have demonstrated the existence of an oligomeric PSII. We carried out radiation inactivation target analysis (RTA), together with sucrose gradient ultracentrifugation (SGU) of PSII, to study the functional size of PSII in diverse plant species under physiological and stress conditions. Two PSII populations, made of dimeric and monomeric core particles, were revealed in Pisum sativum, Spinacea oleracea, Phaseulus vulgaris, Medicago sativa, Zea mais and Triticum durum. However, this core pattern was not ubiquitous in the higher plants since we found one monomeric core population in Vicia faba and a dimeric core in the Triticum durum yellow-green strain, respectively. The PSII functional sizes measured in the plant seedlings in vivo, as a decay of the maximum quantum yield of PSII for primary photochemistry, were in the range of 75–101 ± 18 kDa, 2 to 3 times lower than those determined in vitro. Two abiotic stresses, heat and drought, imposed individually on Pisum sativum, increased the content of the dimeric core in SGU and the minimum functional size determined by RTA in vivo. These data suggest that PSII can also function as a monomer in vivo, while under heat and drought stress conditions, the dimeric PSII structure is predominant.

Special Section on “Next Generation Solar Cells”

Molecular photovoltaic devices, in a broad sense, are devices made by using molecules or molecular materials that are capable of converting sunlight into electrical current and voltage. Since the use of low molecular weight organic molecules by Tang,[1] the sensitization of TiO2 with dyes coupled to the use of iodine/iodide red/ox couple by Grätzel and O'Regan,[2] the fabrication of bulk-heterojunction polymer/fullerene-based films by Sariciftci et al.,[3] to the latest breakthrough using hybrid lead based perovskite semiconductor materials by Miyasaka and collaborators,[4] there has been an amazing journey harnessing solar power. The dream for cheap, globally available solar energy is closer than ever with a great deal of excellent research being done in laboratories worldwide. This special collection of research articles in Solar RRL presents a flavor of the research done recently in hot research topics from dye sensitized solar cells, organic solar cells, and perovskite solar cells and serves as an example about how proactive the research in molecular photovoltaic devices is. Photochromic thin films based on Grätzel solar cells represent the ultimate frontier in the application of transparent devices that hold the promise for efficient translucid solar cells for applications in building photovoltaics. The dye design still holds the key for the optimization of the solar cell efficiency, when the primary role of the solar cell is not just the efficiency but also its transparency and its operational stability. In organic solar cells, the design of molecules and organic materials with alike goal, transparency, is also key. Moreover, taking into account the general low open circuit voltage in organic solar cells, it is also crucial to understand and reduce the possible pathways for voltage losses, which leads to better solar cell efficiencies. In fact, the efficiency of organic solar cells has exponentially increased during the last few years due to the synthesis and use of non-fullerene electron acceptor molecules and molecular materials. Further research on non-fullerene electron acceptors, as well as organic doping of semiconductors, will remain a hot topic in the near future with the challenge to match the current efficiency of their perovskite-based counterparts. Perovskite semiconductor materials for photovoltaic applications have been, without doubt, a major achievement in recent research. Applications ranging from energy conversion devices, artificial lighting, sensors and photonic applications, have rapidly appeared in the scientific literature since 2009. Indeed, scientific challenges remain, such as the passivation of defects to boost the solar cell efficiencies and the replacement of lead by a less harmful element, but the gap between laboratory and industrial deployment is closing rapidly. For their industrial application, better materials for grids, low-cost manufacture contacts, and treatments to increase the device stability are goals that will be the focus of present and future intense research. Emilio Palomares studied Biology at the UVEG. After graduating, he joined Prof. Hermenegildo García's group at the UPV where he got his PhD. In 2009, he was awarded an ERC Starting Grant to work on quantum dots for energy conversion devices and an ERC PoC in 2015. In 2019, he was awarded Energy & Environmental Solutions International Chair (E2S) by the Université de Pau et des Pays de l'Adour (UPPA). Later in 2020, he was elected ICIQ Director for the next 5 years. His research is focused on several aspects of light induced electron transfer reactions in supramolecular structures and nanostructured inorganic materials, which has evolved towards the control and improvement of the reactions that govern the efficiency on devices such as molecular solar cells, the creation of new hybrid nanomaterials for hydrogen production, and molecular based sensing devices to detect toxic substance in the environment. He is also involved in promoting science and education in society through chemistry workshops for primary and secondary schools.

Ultrafast Charge-Transfer in Panchromatic, Push-Pull Porphyrin-Tetracyanobuta-1,3-Diene-Donor 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 molecular 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. As part of our continued effort in this field of research,1-3 using a combination of cycloaddition-retroelectrocyclization reaction, free-base and zinc porphyrins (H2P and ZnP) are decorated at their b-pyrrole positions with strong charge-transfer complexes, viz., tetracyanobuta-1,3-diene (TCBD)-DONOR as a novel class of push-pull systems.4 The physicochemical properties of these compounds have been investigated using a range of electrochemical, spectroelectrochemical, DFT as well as steady-state and time-resolved spectroscopic techniques. Charge transfer interactions between the porphyrin and the electron-withdrawing TCBD directly attached to the porphyrin p-system extended the absorption well into the near-infrared region. The occurrence of photoinduced charge transfer and separation has been established by complementary transient absorption spectral studies followed by global and target data analyses. The role of central metal in the porphyrin cavity and the nature of the donor in governing these photo events will be discussed. Khan, Y. Jang, Y. Patil, R. Misra, and F. D’Souza, Photoinduced Charge Separation Prompted Intervalence Charge Transfer in a Bis(thienyl)diketopyrrolopyrrole Bridged Donor-TCBD Push-Pull System (hot article), Angew. Chem. Int. Ed. 2021, 60, 20518–20527.S. Yadav, A. Z. Alsaleh,R. Misra and F. D’Souza, ‘Excited State Charge Transfer Leading to Charge Stabilization via an Electron Exchange Mechanism in Symmetric, Central Triphenylamine Derived, Dimethylaminophenyl-Tetracyanobutadiene Donor-Acceptor Conjugates, Chem. Sci. 2021, 12, 1109-1120.Pinjari, A. Z. Alsaleh,Y. Patil, R. Misra and F. D’Souza, Interfacing High-Energy Charge Transfer States to a Near-IR Sensitizer for Efficient Electron Transfer upon Near-IR Irradiation’ Angew. Chem. Int. Ed. 2020, 59, 23697-23705.Sekaran, A. Dawson, Y. Jang, K. V. MohanSingh, R. Misra and F. D’Souza, Charge-Transfer in Panchromatic Porphyrin-Tetracyanobuta-1,3-diene-Donor Conjugates: Switching the Role of Porphyrin in the Charge Separation Process, Chem. Eur. J. 2021, 27, 14335-14344 Figure 1

Pushing the limits of flash photolysis to unravel the secrets of biological electron and proton transfer

Time-resolved absorption spectroscopy is a powerful tool to unravel biological functions and has been a key technology for elucidating the working of electron transfer chains in photosynthesis or photorepair of UV-damaged DNA. Both of these areas have seen important contributions from laboratories all over the world, not the least of them stemming from the ingenious technical advances described by Klaus Brettel, first at the Technical University of Berlin (Germany), and later at the Atomic Energy Agency in Saclay (France). Now, after more than forty years of tireless scientific activity, Klaus is approaching retirement and this collection gathers together tributes in the form of scientific contributions from colleagues along the way, covering a spectrum of topics as diverse as photosynthesis,light-induced DNA repair, electron and proton transfer in light signalling, flavin based photo-enzymology, fluorescent marker photophysics,synthetic models and modelisation, delicate sample transient absorption spectroscopy. In an era where science is increasingly changing context from "fundamental" to "applied", Klaus' curiosity and tenacity worked hand in hand in a most effective manner to further both technical possibilities and basic understanding.

Zinc oxide hollow spheres decorated with cerium dioxide. The role of morphology in the photoactivity of semiconducting oxides

The photochemical activity of the recently proposed CeO2–ZnO photocatalytic material active under visible light has been improved by means of significant modifications of its morphology. A polymeric templating agent (Pluronic) has been used in the synthesis obtaining a particle morphology based on hollow spheres that is better defined in the case of high template concentration. The charge separation ability and the light-induced surface electron transfer under irradiation with visible polychromatic light in various ranges of wavelengths has been investigated by electron paramagnetic resonance. The reactivity of the photogenerated holes has been monitored by the spin trapping technique in the presence of DMPO. The hollow spheres morphology achieved through the synthesis here reported leads to systems with a higher photoactivity under visible irradiation than the same system displaying the classic platelets morphology. A parallel increase of the photocatalytic activity of this novel system in pollution remediation reactions is therefore predictable.

Redox properties and regulatory mechanism of the iron-quinone electron acceptor in photosystem II as revealed by FTIR spectroelectrochemistry.

Photosystem II (PSII) performs oxidation of water and reduction of plastoquinone through light-induced electron transfer. Electron transfer reactions at individual redox cofactors are controlled by their redox potentials, and the forward and backward electron flows in PSII are regulated by tuning them. It is, thus, crucial to accurately estimate the redox potentials of the cofactors and their shifts by environmental changes to understand the regulatory mechanisms in PSII. Fourier-transform infrared (FTIR) spectroelectrochemistry combined with a light-induced difference technique is a powerful method to investigate the mechanisms of the redox reactions in PSII. In this review, we introduce the methodology and the application of this method in the studies of the iron-quinone complex, which consists of two plastoquinone molecules, QA and QB, and the non-heme iron, on the electron-acceptor side of PSII. It is shown that FTIR spectroelectrochemistry is a useful method not only for estimating the redox potentials but also for detecting the reactions of nearby amino-acid residues coupled with the redox reactions.

Proton-controlled Action of an Imidazole as Electron Relay in a Photoredox Triad.

Electron relays play a crucial role for efficient light-induced activation by a photo-redox moiety of catalysts for multi-electronic transformations. Their insertion between the two units reduces detrimental energy transfer quenching while establishing at the same time unidirectional electron flow. This rectifying function allows charge accumulation necessary for catalysis. Mapping these events in photophysical studies is an important step towards the development of efficient molecular photocatalysts. Three modular complexes comprised of a Ru-chromophore, an imidazole electron relay function, and a terpyridine unit as coordination site for a metal ion were synthesized and the light-induced electron transfer events studied by laser flash photolysis. In all cases, formation of an imidazole radical by internal electron transfer to the oxidized chromophore was observed. The effect of added base evidenced that the reaction sequence depends strongly on the possibility for deprotonation of the imidazole function in a proton-coupled electron transfer process. In the complex with MnII present as a proxy for a catalytic site, a strongly accelerated decay of the imidazole radical together with a decreased rate of back electron transfer from the external electron acceptor to the oxidized complex was observed. This transient formation of an imidazolyl radical is clear evidence for the function of the imidazole group as an electron relay. The implication of the imidazole proton and the external base for the kinetics and energetics of the electron trafficking is discussed.

Structure, Function, and Variations of the Photosystem I-Antenna Supercomplex from Different Photosynthetic Organisms.

Photosystem I (PSI) is a protein complex functioning in light-induced charge separation, electron transfer, and reduction reactions of ferredoxin in photosynthesis, which finally results in the reduction of NAD(P)- to NAD(P)H required for the fixation of carbon dioxide. In eukaryotic algae, PSI is associated with light-harvesting complex I (LHCI) subunits, forming a PSI-LHCI supercomplex. LHCI harvests and transfers light energy to the PSI core, where charge separation and electron transfer reactions occur. During the course of evolution, the number and sequences of protein subunits and the pigments they bind in LHCI change dramatically depending on the species of organisms, which is a result of adaptation of organisms to various light environments. In this chapter, I will describe the structure of various PSI-LHCI supercomplexes from different organisms solved so far either by X-ray crystallography or by cryo-electron microscopy, with emphasis on the differences in the number, structures, and association patterns of LHCI subunits associated with the PSI core found in different organisms.

The electronic structure of the metal-organic interface of isolated ligand coated gold nanoparticles.

Light induced electron transfer reactions of molecules on the surface of noble metal nanoparticles (NPs) depend significantly on the electronic properties of the metal–organic interface. Hybridized metal–molecule states and dipoles at the interface alter the work function and facilitate or hinder electron transfer between the NPs and ligand. X-ray photoelectron spectroscopy (XPS) measurements of isolated AuNPs coated with thiolated ligands in a vacuum have been performed as a function of photon energy, and the depth dependent information of the metal–organic interface has been obtained. The role of surface dipoles in the XPS measurements of isolated ligand coated NPs is discussed and the binding energy of the Au 4f states is shifted by around 0.8 eV in the outer atomic layers of 4-nitrothiophenol coated AuNPs, facilitating electron transport towards the molecules. Moreover, the influence of the interface dipole depends significantly on the adsorbed ligand molecules. The present study paves the way towards the engineering of the electronic properties of the nanoparticle surface, which is of utmost importance for the application of plasmonic nanoparticles in the fields of heterogeneous catalysis and solar energy conversion.

Visible light-induced enhancement in the Seebeck coefficient of PEDOT:PSS composites with two-dimensional potassium poly-(heptazine imide)

The Seebeck coefficient of the composites of PEDOT:PSS and two-dimensional poly-(heptazine imide) (KPHI) can be greatly enhanced after exposure to visible light. It is attributed to the light-induced electron transfer from KPHI to PEDOT:PSS.

Cover Feature: Tailoring Quantum Dot Sizes for Optimal Photoinduced Catalytic Activation of Nitrogenase (ChemSusChem 24/2021)

The Cover Feature shows how nanomaterial sizes affect the light-induced electron transfer process with the nitrogenase enzyme. When 2.3 nm CdSe quantum dots are utilized for the photocatalytic hydrogen generation process, an 8-fold increase can be gained as compared with larger-sized quantum dots. Additionally, cysteine-mutated nitrogenase at the electron acceptor side (P-cluster) does not lead to enhanced catalytic performance. More information can be found in the Communication by M. M. Meirovich et al.

D‐Band EPR and ENDOR Spectroscopy of 15N‐Labeled Photosystem I

For billions of years, nature has optimized the photosynthetic machinery that converts light energy into chemical energy. Key primary reactions of photosynthesis occur in large membrane protein–cofactor complexes. The light-induced sequential electron transfer reactions occur through a chain of donor/acceptor cofactors embedded in the protein matrix resulting in a long-lived transmembrane charge-separated state. EPR is the method of choice to study electron transfer and the interaction of protein environment with redox-active cofactors. However, the spectra of organic cofactor radicals typically are not fully resolved and severely overlap at conventional X-band EPR. Even at Q-band EPR, this overlap is present and often a serious problem. As a result, there is a large variation of the reported EPR data and limited understanding of electronic structures of several redox-active cofactors. These serious problems can often be overcome by the excellent spectral resolution provided by high-frequency EPR (HF EPR). Here, we study the electronic structure of the primary electron donor P700 and the secondary electron acceptor A1 of Photosystem I (PSI) using 130 GHz (D-band) EPR and Electron–Nuclear-Double-Resonance (ENDOR) spectroscopy. PSI was isotopically labeled with 15N (I = ½) to avoid quadrupolar interactions in the most abundant nitrogen isotope 14N (I = 1) and simplify the ENDOR spectra. ENDOR spectroscopy is central for determining the hyperfine coupling of nitrogen atoms of the two chlorophyll molecules comprising oxidized P700 and the involvement of protein nitrogen atoms with reduced A1. While HF ENDOR of A1− allows identification of two nitrogen atoms, HF ENDOR of P700+ still does not permit unique assignment of the recorded hyperfine couplings.

Design and Implementation of Environmental Monitoring System Using Photoelectric Wireless Sensor Network

Photoelectrochemical (PEC) sensing is a light-induced electron transfer sensing method based on photoelectric signal conversion to represent the electrode/solution interface. The analysis method is easily disturbed by environmental factors such as light intensity, which reduces the detection accuracy. PEC biosensor with sunlight as the light source is designed. CC2530 RF hardware module and Zstack software protocol stack produced by TI company are adopted to establish PEC wireless sensor network (WSN) for farmland environment detection. 5G-DTU module is selected to realize the remote data transmission between the PEC WSN and remote server. The data exchange is carried out through a 5G mobile communication network. The farmland environment monitoring adopts B/S architecture. The types of all PEC sensors need to be selected and the hardware circuit module is designed. The corresponding interface adopts a unified standard 485 bus communication interface to facilitate the data reading of the sensor. In the experiment, the designed PEC sensor can distinguish between carbon nitride nanosheets (CNNS) and nitrogen fossil graphene loaded silver/TiO2 (Ag/TiO2/D3NGH) by changing the bias potential, and the sensor can work in unstable sunlight. The photocurrent of anode and cathode of the PEC sensor increases with the increase of sunlight intensity, and the photocurrent ratio remains constant with the further increase of the concentration of double electrodes (CNNS, Ag/TiO2/D3NGH). In the field mold test, the designed PEC sensor shows good selectivity for aflatoxin B1 (AFB1), and the AFB1 is recovered from bean products in the field, with a recovery rate of more than 95%, which proves that the photoelectric monitoring system can accurately measure and analyze the field mold.