Energy Level Difference Research Articles

Multiple Exciton Generation on Doped Wide-Band Semiconductor Photoanode with Hierarchical Quantum Structure.

The multiple exciton generation (MEG) effect, which produces multiple photo-generated charge carriers from a single high-energy photon absorption by a semiconductor with a narrow bandgap, has the potential to revolutionize photovoltaic, photoelectric detection, and other technologies. Here, this work finds that the surface carbon-modified wide-bandgap photoanode with hierarchical quantum structure can drive a photoelectrochemical reaction with a quantum efficiency exceeding 145% by the first time. More studies reveal that the presence of the MEG effect in the MEG-CdS photoanode is attributed to the formation of high-quality surface C-modified CdS quantum nanosheets on CdS bulk film by in situ, this hierarchical quantum structure leads to quantum confinement effects that increase effective Coulomb interaction for driving MEG and decrease competition for thermal exciton cooling. The acceptor level introduced by carbon reduces the MEG threshold (approximately twice the energy level difference) and collaborates with the built-in electric field of the C-CdS/bulk-CdS homojunction to enable the effective generation and separation of photo-generated charge carriers. The internal quantum efficiency of the MEG-CdS photoanode reaches up to a recording value of 145%, providing a novel perspective on the contribution of surface-modified wide-band semiconductors and their quantum effects in the application of MEG.

Oriented Molecular Dipole-Enabled Modulation of NiOx/Perovskite Interface for Pb-Sn Mixed Inorganic Perovskite Solar Cells.

Nickel oxide (NiOx) is considered as a potential hole transport material in the fabrication of lead-tin (Pb-Sn) perovskite solar cells (PSCs) for tandem applications. However, the energy level mismatch and unfavorable redox reactions between Ni≥3+ species and Sn2+ at the NiOx/perovskite interface pose challenges. Herein, high-performance Pb-Sn-based inorganic PSCs are demonstrated by modulating the NiOx/perovskite interface with a multifunctional 4-aminobenzenesulfonic acid (4-ABSA) interlayer. The 4-ABSA interlayer induces the formation of an oriented dipole moment directed from NiOx to perovskite, effectively elevating the valance band maximum of the NiOx film, thus balancing the energy level difference and promoting charge carrier extraction of the device. Moreover, the 4-ABSA molecules interact with both NiOx and perovskite, suppressing the reaction of highly active Ni≥3+ species with perovskites while regulating perovskite crystallization. This results in perovskite films with reduced defect density and enlarged grains. Consequently, a remarkable device efficiency of 17.4% is obtained, representing the highest reported value for Pb-Sn-based inorganic PSCs thus far. Furthermore, the 4-ABSA interlayer enhances the UV-radiation and operational stability of the resulting devices, maintaining over 80% and 90% of the initial efficiency after 240h of UV-light exposure and 480h of 1 sun illumination, respectively.

P-type surface charge transfer doping of diamond via low-dimensional transition metal oxides

Device applications of ultra-wide-bandgap diamond rely on the precise control of both carrier type and concentration. However, due to the strong covalent bonds in bulk diamond, conventional doping methods have struggled to achieve large-scale tuning of its properties. Surface charge transfer doping (SCTD) is seen as a simple and effective solution, leveraging energy-level differences between surface dopant and the semiconductor to regulate carrier properties efficiently. Here, we conducted a comprehensive theoretical study on p-type SCTD of hydrogen-terminated diamond (100) surface [diamond(100):H] using low-dimensional transition metal oxides. The doping effects of the molecular MoO3 and monolayer MoO3 were first explored. The areal hole density for molecular-MoO3-doped diamond(100):H sharply rises and then slightly decreases with increasing MoO3 density, reaching a peak of 7.55 × 1013 cm−2—surpassing the maximum value achieved with a MoO3 monolayer. For identical MoO3 densities, a stronger interaction with diamond(100):H results in a greater areal hole density. We also studied one-dimensional chain-like CrO3 and two-dimensional layered V2O5. However, a V2O5 monolayer cannot achieve the saturation areal hole density due to the large energy separation between the conduction band minimum (CBM) of V2O5 and the valence band maximum (VBM) of diamond(100):H. Increasing the number of V2O5 monolayers will enhance the doping effect. Overall, optimal doping can be achieved with smaller dimensions, higher density and thickness of the transition metal oxides, stronger interactions with diamond(100):H, and a larger energy separation between the dopant's CBM and diamond(100):H's VBM. This study provides theoretical guidance to develop superior diamond-based electronic and optoelectronic devices.

Quantifying Uncertainty in Laser-Induced Damage Threshold for Cylindrical Gratings.

The laser-induced damage threshold (LIDT) is a key measure of an optical component's resistance to laser damage, making its accurate determination crucial. Following the ISO 21254 standards, we studied the measurement strategy and uncertainty fitting method for laser damage, establishing a calculation model for uncertainty. Research indicates that precise LIDT measurement can be achieved by using a small energy level difference and conducting multiple measurements. The LIDT values for the cylindrical grating are 15.34 ± 0.00052 J/cm2 (95% confidence) and 15.34 ± 0.00078 J/cm2 (99% confidence), demonstrating low uncertainty and reliable results. This strategy effectively measures the LIDT and uncertainty of various grating surface shapes, offering reliable data for assessing their anti-laser-damage performance.

Conduction Band and Defect Engineering for the Prominent Visible-Light Responsive Photocatalysts.

Controlling trap depth is crucial to improve photocatalytic activity, but designing such crystal structures has been challenging. In this study, we discovered that in 2D materials like BiOCl and Bi4NbO8Cl, composed of interleaved [Bi2O2]2+ and Cl- slabs, the trap depth can be controlled by manipulating the slab stacking structure. In BiOCl, oxygen vacancies (VO) create deep electron traps, while chlorine vacancies (VCl) produce shallow traps. The depth is determined by the coordination around anion vacancies: VO forms strong σ bonds with Bi-6p dangling bonds below the conduction band minimum (CBM), while those around Cl are parallel, forming weak π-bonding. The strong re-hybridization makes the trap depth deeper. In Bi4NbO8Cl, VCl also creates shallow traps, but VO does not produce deep traps although Bi-6p orbitals are also forming strong σ bonding. This difference is attributed to the difference of energy level of CBM. In both cases, CBM consists of Bi-6p orbitals extending into the Cl layers. However, these orbitals are isolated in BiOCl, but those in Bi4NbO8Cl are bonded with each other between neighboring [Bi2O2]2+ layers. This unique bonding-based CBM prevents the formation of deep electron traps, and significantly enhances H2 evolution activity by prolonging lifetime of highly reactive free electrons.

Disentangling Structural Domains in Solution‐Processed 2D Lead Halide Perovskite by Transient Absorption Spectroscopy

Abstract2D lead halide perovskites (LHPs) exhibit outstanding optoelectronic properties, making them utilized in various emerging applications. Understanding their fundamental properties is urgent for improving device performance. Here, the structural domains in 2D PEA2MAn‐1PbnI3n+1 films are studied by temperature‐dependent transient absorption (TA) measurements. For <n> = 1 film at low temperatures, the ground state bleach (GSB) shows obvious splitting when the high‐energy state is resonantly excited, whereas only one GSB exists under low‐energy resonant excitation, indicating that the two split energy states correspond to different structural domains. For <n> = 2 film, similar phenomena are observed, but the energy level difference between the two domains is decreased. With further increase of the inorganic layers number, the two domains can no longer be distinguished. In addition, by changing the organic cations, it is demonstrated that the two structural domains originate from distortions in the inorganic PbI6 octahedral frames. Finally, the possibility that the two energy states are from the formation of polaron states is ruled out by TA measurement on CsPbBr3 QDs. The results provide new insights into the structural domain properties of 2D LHPs, which directly influence the suitability of these materials for future optoelectronic devices.

Achieving pure-fluorescent color-tunable WOLED through long-range coupling of spatially separated electron–hole pairs

Abstract Color-tunable white organic light-emitting diode (CT-WOLED) with a wide correlated color temperature (CCT) offers numerous advantages in meeting human daily needs related to circadian rhythm. The study of CCT variation trends and the rules governing the expansion of the CCT range will help further improve the performance of such devices. This research proposes an effective strategy for achieving high-efficiency fluorescent CT-WOLEDs through long-range radiative coupling of spatially separated electron–hole pairs. After inserting a 5 nm thick DMAC-DPS layer between the donor (TAPC) and the acceptor (PO-T2T), the charge transfer excitons between TAPC and PO-T2T still exist. As the voltage increases, holes selectively undergo different photophysical processes, resulting in a wide CCT range. This demonstrates the extraordinary potential of spatially separated electron–hole pairs in regulating luminescent properties. By further introducing a bulk exciplex and the conventional red fluorescent dye DCJTB, the device’s efficiency, brightness, and CCT range have been further optimized. Additionally, significant highest occupied molecular orbital energy level difference between the hole transport layer TAPC and the spacer layer facilitates hole accumulation at the TAPC/spacer interface, thereby enhancing the long-range coupling effect. In device E, we achieved a wide CCT range of 2774 K along with a high external quantum efficiency of 9.2%. The results indicate that our proposed long-range coupling strategy not only enables a wide CCT range but also ensures broad spectral emission and high electroluminescence efficiency, providing new possibilities for the field of intelligent lighting.

(Invited) Organic Floating-Gate Transistors for Printable Nonvolatile Memory and Optoelectronic Device Applications

There has been considerable interest in the development of nonvolatile memories using organic materials owing to their potential use in flexible and printed electronic devices. In recent years, organic field-effect transistors (OFETs) having floating-gate structures as the charge storage layer have attracted increasing interest because they allow achieving large threshold voltage (Vth ) shifts and a relatively long retention time with a simple device configuration. However, the fabrication of floating-gate OFET memories by solution processes is generally difficult because it often suffers from the mixing of soluble organic materials at their interfaces. In previous studies, we have developed solution-processable floating-gate OFET memories by using top-gate/bottom-contact OFETs based on polymer semiconductors and the vertical phase separation behavior in the solution-processed composite film of a polymer insulator (PMMA or polystyrene) and a soluble small-molecule semiconductor (TIPS-pentacene) [1-3]. Here, I report the memory characteristics of solution-processed floating-gate OFET memories using a typical p-type polymer semiconductor of polythiophenes (P3HT and PBTTT) and an ambipolar polymer semiconductor based on diketopyrrolopyrrole (DPP) and their usefulness for the development of printable nonvolatile memories and image sensing devices with high functionality.Figure 1(a) shows the typical structure of our memory devices. Since a variety of orthogonal solvents are available for polymer semiconductors, the organic charge storage layer composed of PMMA and TIPS-pentacene molecules can be deposited onto the semiconductor layer by spin coating using butyl acetate. During thermal annealing at 100 ºC, TIPS-pentacene molecules segregate to the upper side of the composite film through vertical phase separation, and floating-gate electrodes consisting of TIPS-pentacene and organic tunneling layers are simultaneously formed by solution processes.Figure 1(b) shows the energy band diagram of the P3HT-based organic FET memory during the programming process. Because P3HT has a shallow LUMO level compared to the work function of the Au source-drain electrodes, the P3HT FET memory shows only a negligible Vth shift when programmed in the dark. Under light illumination, the device exhibits a large Vth shift of over 30 V by storing photogenerated electrons into TIPS-pentacene floating gates. To investigate the applicability of the OFET memories to large-area image sensors, the imaging of a black and white pattern using the recorded drain currents of the memory array under light illumination has been demonstrated [Fig. 1(c)]. We also found that P3HT FET memories with organic semiconductor floating gates exhibit light-intensity dependent synaptic characteristics when programmed under red light, enabling the enhancement of the functionality of organic image sensors.In contrast to OFET memories based on polythiophenes, DPP-DTT FET memories can be programmed in the dark because of the deep LUMO level and good electron transport property of DPP-DTT. It was also found that the electrical characteristics of DPP-DTT TFT memory devices depend on the difference of work function of source-drain and gate electrodes and tuning the energy level difference enables ambipolar carrier trapping and good retention characteristics [Fig. 1(d)]. The DPP-DTT FET memories having hole trapping characteristics also achieve NAND-like memory operations as memory devices are connected in series.

Dynamic Rare-Earth Metal-Organic Frameworks Based on Molecular Rotor Linkers with Efficient Emissions and Ultrasensitive Optical Sensing Performance.

4,4',4″-Triphenylamine tricarboxylate (TPA-COOH) with a distinct molecular rotor structure was reacted with rare-earth (RE) metal ions to obtain seven dynamic RE-based luminescent MOFs (RE-LMOFs) (i.e., emission colors in the blue, yellow-green, red, and near-infrared regions and emission peak wavelengths between 400 and 1600 nm) via the effective transfer of absorbed energy from TPA-COOH to the RE metal ions through the antenna effect. Due to the large energy level difference between RE ions, it was rare in the early days to use the same ligand to construct energy-level matching RE-LMOF homologues with multiple RE metal centers. The uncoordinated oxygen atoms on the molecular rotor linkers in RE-LMOFs provide active sites that can specifically capture highly toxic metal ions and strong oxidative pollutants. The limit of detection (LOD) of RE-LMOF for Al(III) ions is far below the maximum concentration of Al(III) ions in drinking water stipulated by the U.S. Environmental Protection Agency (USEPA) and that for H2O2 is much lower than the H2O2 content in cancer cells, showing excellent application potential for diagnosing early cell cancelation.

Decorating nitrogen-deficient crystalline g-C3N4 with Ti3C2(OH)2 for photocatalytic CO2 reduction and RhB degradation enhancement

Visible light responding photocatalytic technology has shown great potential to mitigate the greenhouse effect and global pollution issues in recent years. Herein, alkalized titanium carbide Ti3C2Tx (TCOH) is combined with nitrogen-deficient g-C3N4 (CN-Nx) by simply mixing for photocatalytic CO2 reduction and RhB degradation. TCOH replaces noble metals as a co-catalyst for CN-Nx due to its full-spectrum absorption properties and excellent conductivity, which effectively enhances the overall light absorption capacity of CN-Nx. Additionally, a large Fermi energy level difference between TCOH and CN-Nx leads to a built-in electric field forming at their interface when combined. This built-in electric field can enhance the photogenerated electron-hole pair separation and reduce the recombination rate. So the visible light utilization ranges of optimized 2TCOH-30 %/CN-N0.02 expanded from 477 nm (CN-N0.02) to 481 nm, and the average lifetimes of the photogenerated carriers is 4.37 ns, which is 2.64 times longer than CN-N0.02. Moreover, the CO yield reaches 67.55 μmol/g during photocatalytic CO2 reduction of 2TCOH-30 %/CN-N0.02, which is 4.06 and 2.54 times than 2TCOH and CN-N0.02. During the RhB degradation, 2TCOH-30 %/CN-N0.02 can remove approximately 98.3 % of RhB in 15 min, which is1.6 and 1.4 times of 2TCOH and CN-N0.02. Also, 2TCOH-30 %/CN-N0.02 shows excellent stability, the photocatalytic capacity for CO2 reduction and RhB degradation has no significant degradation after six times circles.

Energy Level Tuning in CsPbBr3 Perovskite Solar Cells through In Situ-Polymerized PEDOT Hole Transport Layer.

The all-inorganic CsPbBr3 perovskite solar cells exhibit excellent stability against humidity and thermal conditions as well as relatively low production cost, rendering them a gradually emerging research hot spot in the field of photovoltaics. However, the absence of a hole transport layer (HTL) in its common structure and the substantial energy level difference of up to 0.6 eV between the highest occupied molecular orbital (HOMO) level of CsPbBr3 and the work function of the carbon electrode have emerged as the primary factor limiting the improvement of its power conversion efficiency (PCE). In this work, the monomer 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) is spin-coated onto the surface of the CsPbBr3 film directly and then subjected to annealing; DBEDOT undergoes in situ polymerization to form poly(3,4-ethylenedioxythiophene) (PEDOT), which aims to ameliorate the issue of excessive energy level difference between CsPbBr3 and the carbon electrode, and to facilitate the extraction and transport efficiency of holes between the CsPbBr3 perovskite and the carbon electrode. Compared to the pristine device, the PCE of the device based on in situ polymerization is enhanced and achieves a maximum efficiency of 9.81%. Furthermore, the unencapsulated devices based on in situ polymerization maintain 95.9% of their original efficiency after 40 days of stability testing.

Lateral Electronic Junction of a Single Ultrathin Silicon Induced by Interfacial Dipole of Self-Assembled Monolayer.

Interface engineering is pivotal for enhancing the performance and stability of devices with layered structures, including solar cells, electronic devices, and electrochemical systems. Incorporating the interfacial dipole between the bulk layers effectively modulates the energy level difference at the interface and does not significantly influence adjacent layers overall. However, interfaces can drastically affect adjoining layers in ultrathin devices, which are essential for next-generation electronics with high integrity, excellent performance, and low power consumption. In particular, the interfacial effect is pronounced in ultrathin semiconductors, which have a weak electric field screening effect. Herein, the substantial interfacial impact on the ultrathin silicon is shown, the p- to n-type inversion of the semiconductor solely through the deposition of a self-assembled monolayer (SAM) without external bias. The effects of SAMs with different interfacial dipoles are investigated by using Hall measurement and surface analytic techniques, such as UPS, XPS, and KPFM. Furthermore, the lateral electronic junction of the ultrathin silicon is engineered by the regioselective deposition of SAMs with opposite dipoles, and the device exhibits rectification behavior. When the interfacial dipole of SAM is manipulated, the rectification ratio changes sensitively, and thus the fabricated diode shows potential to be developed as a sensing platform.

Preparation and Properties of 3D Spherical Bi2S3/Bi2O2CO3 Photocatalytic Materials Self‐Assembled by 2D Nanosheets

ABSTRACTThe micro‐morphology of photocatalytic materials has a great influence on their photocatalytic performance. Quantum dots can provide the plasmon resonance effect and broaden the wavelength range of light absorption. In this study, a kind of 3D spherical flower‐like structure was constructed by self‐assembly of 2D nanosheets, the Bi2S3 particles with 5 ± 1 nm diameter were modified on the surfaces of Bi2O2CO3 nanosheets to prepare the Bi2S3/Bi2O2CO3 composite. The energy level difference (0.45 eV) between the conduction bands (CB) of Bi2S3 and Bi2O2CO3 led to which the e− was transferred to CB of Bi2O2CO3. The energy level difference (0.83 eV) between the CB of Bi2O2CO3 and the valence band (VB) of Bi2S3 was much smaller than the band gap (1.28 eV) of Bi2S3, and it led to which the electrons on the CB of Bi2O2CO3 were recombined with the holes on the VB of Bi2S3. A kind of innovative type heterojunction was constructed between Bi2S3 and Bi2O2CO3, which encouraged the photogenerated h+ and ·OH to be located on the VB of Bi2O2CO3 with the strongest oxidation potential, the prepared material showed excellent performance for the photodegradation of RhB, and the active groups were also controlled in the photocatalysis process.

Ir(III)‐Based Photosensitizer‐Loaded M1 Macrophage Exosomes for Synergistic Photodynamic Therapy

AbstractThe synthesis of organic photosensitizers with effective reactive oxygen species (ROS) generation remains one of the urgent needs for cancer therapy. In this study, a simple strategy is developed to endow the intrinsic non‐photosensitizer fluorophores with profound ROS‐generating ability upon light irradiation. This strategy is featured by introducing donor–acceptor (D‐A) structured fluorophores as auxiliary ligands into the Ir(III) metal complex, which provides the Ir(III) metal center‐based triplet state (T1) as an energy level springboard to efficiently enhance the energy transition to the D‐A ligand‐based triplet state (T1'). The energy level difference between T1 and T1' can be regulated through altering the cyclometalated ligands of Ir(III), facilitating the energy transfer from T1 to T1' for augmented ROS generation. To improve the pharmacological properties of the obtained D‐A coordinated Ir(III) complex, it is incorporated with the exosomes extracted from M1 phenotype macrophages (M1‐Exos). The generated nanocomplexes are able to trigger synergistic photodynamic therapy, facilitating the reprogramming of tumor‐associated macrophages and eradicating the tumors in mice. This study provides a general strategy to transform non‐photosensitizer fluorophores into effective photosensitizers for biomedical applications.

Self-powered multifunctional platform based on dual-photoelectrode for dual-mode detection and inactivation of Salmonella enteritidis

Self-powered photoelectrochemical (PEC) sensing is a novel sensing modality. The introduction of dual-mode sensing and photoelectrocatalysis in a self-powered system enables both detection and sterilization purposes. To this end, herein, a self-powered multifunctional platform for the photoelectrochemical-fluorescence (PEC-FL) detection and in-situ inactivation of Salmonella enteritidis (SE) was constructed. The platform utilized Bi4NbO8Cl/V2CTx/FTO as a photoanode and CuInS2/FTO as a photocathode and incubated quantum dot (QDs) signaling probes on the surface of the photocathode. During detection, the system drives the transfer of photogenerated electrons between the dual photoelectrodes through the Fermi energy level difference. The photoanode amplifies the photoelectric signal, while the photocathode is solely dedicated to the immune recognition process. QDs provide an additional fluorescence signal to the system. Under optimal experimental conditions, the multifunctional platform achieves detection limits of 3.2 and 5.3 CFU/mL in PEC and FL modes respectively, with a detection range of 2.91 × 102 to 2.91 × 108 CFU/mL. With the application of an external bias voltage, it further promotes electron transfer between the dual photoelectrodes, inhibits the recombination of photogenerated electrons and holes. It generates a significant amount of superoxide radicals (·O2−) in the cathodic region, resulting in strong sterilization efficiency (99%). The constructed self-powered multifunctional platform exhibits high sensitivity and sterilization efficiency, it provides a feasible and effective strategy to enhance the comprehensive capability of self-powered sensors.

Molecular-level regulating intersystem crossing of polyphenols: Engineering high-efficiency phytochemical photosensitizer for MRSA elimination

Natural polyphenols-mediated green photosterilization is promising but remains challenging in practical applications due to their unsatisfactory performance with insufficient intrinsic energy level and ROS generation. In this work, the molecular-level engineering strategy of natural polyphenols (quercetin, QC) by p-Methoxybezaldehyde (MB)-induced nucleophilic substitution is constructed for enhanced photodynamic MRSA therapy. Both the experimental and theoretical results disclose that the unprecedented H-aggregates of QC-MB supramolecular realized accelerated ISC with minimizing the energy level difference (ΔEst), achieving enhanced photodynamic performance with 2.2-fold enhancement on 1O2 quantum yield (75 %) compared to free quercetin (33 %). The well-designed photosensitizer realizes efficient MRSA elimination: with enhanced killing efficacy from 30.44 % to 99.95 % in vitro and effective eradication of mature biofilms. Mechanism study and gene transcription analysis reveal that the combined therapy of optical stimuli with QC-MB achieves the dual mechanism of ROS attack and virulence regulation against MRSA infection during the whole infection process. Moreover, the excellent biocompatibility and anti-infectious in vivo demonstrate the engineered QC-MB as a promising strategy for MRSA therapy.

Impurity and valence-dependent solid/solid triboelectric and solid/liquid tribovoltaic effect of CuxO submicron rods for AC and DC generation

CuxO is a promising p-type semiconductor, but its triboelectric properties are unexplored. This study investigates both the triboelectric properties of CuxO and the solid–liquid tribovoltaic effects between CuxO and various liquids. CuxO submicron rods are synthesized on Cu foams, doped with Li, and subjected to oxidant reactions. Li doping and valence changes increase CuxO’s work function, as shown by Kelvin probe force microscopy. Solid-solid triboelectric measurements reveal systematic changes in triboelectric voltage and current, with CuxO negatively shifting in the triboelectric series. On the other hand, the CuxO/liquid tribovoltaic effect conducted in an immersion-type device generates a stable direct current. The magnitudes of the tribovoltaic current and voltage systematically vary with the energy level differences between CuxO and the liquids. From the direction of tribovoltaic current and magnitude of tribovoltaic voltage, the relative positions of fermi levels for several liquids are determined. Among all, the best CuxO/NaCl(aq) tribovoltaic nanogenerators exhibit a high-power density of 4900 nW/cm2, and the generated DC is applied for novel rectifier/capacitor-free self-powered electroplating. This work demonstrates a viable method to adjust the triboelectric properties of CuxO and proposes a method to determine the relative energy levels of liquids for the first time.

Comparing the biological effectiveness of low energy 100 kV and high energy 5 MeV X-rays against Oriental fruit fly (Diptera: Tephritidae).

Radioisotope irradiators (using cesium-137 or cobalt-60) are used as sources of ionizing radiation to control quarantine or phytosanitary insect pests in internationally traded fresh commodities and to sterilize insects used in sterile insect release programs. There are institutional initiatives to replace isotopic irradiators (producing γ-rays) with lower-energy X-ray machines due to concerns about radiological terrorism and increasingly stringent regulations on the movement of radioisotopes. Questions remain about whether the biological effects of low-energy X-rays are comparable to those of γ-rays since differences in energy levels and dose rates of X-rays may have different efficacies. We compared adult emergence, flight ability, and adult survival in the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritdae), after irradiation of third instar larvae with 100 kV or 5 MeV (5,000 kV) X-rays at 20 and 40 Gy in replicated studies. At 20 Gy, the adult emergence rate was significantly lower after irradiation with 100 kV compared to 5 MeV X-rays, suggesting higher efficacy at the lower energy level. In a follow-up study using 100 kV X-rays, applying 20 Gy using a slow dose rate (0.24 Gy min-1) resulted in significantly higher adult emergence than did a fast dose rate (3.3 Gy min-1), suggesting lower efficacy. Although our study suggests higher efficacy of low energy 100 kV X-rays, there is uncertainty in measuring the dose from an X-ray tube operating at 100 kV using an ionization chamber; we discuss how this uncertainty may change the interpretation of the results. Using a 100 kV X-ray irradiator to develop a phytosanitary treatment may underestimate the dose required for insect control using commercial high-energy γ-ray or X-ray systems.

Study on the regulation of ε-CL-20 by an external electric field.

To explore the influence of the external electric field (EEF) on ε-CL-20. The molecular structure, frontier molecular orbitals (FMOs), global reactivity parameters (GRP), surface electrostatic potential, nitro charge, and UV-Vis spectra of ε-CL-20 under EEF were studied using density functional theory (DFT). The calculation results show that the electric field applied along N16-N24 has a significant effect on the structure of ε-CL-20. With an increase in the positive EEF, the bond length of the initiating bond decreases, and the bond order and bond dissociation energy increase, which increases the thermal stability of ε-CL-20 to a certain extent. In addition, with an increase in the positive EEF intensity, the LUMO migrates from both sides of the positive electric field to one side of the nitro group, and the HOMO migrates from the skeleton to the nitro group. It is worth noting that in the negative EEF, when the electric field strength changed from 0 to 0.016 a.u., the negative charge of the total nitro group gradually decreased. When the electric field strength becomes 0.02 a.u., the negative charge of the total nitro group suddenly increases, and ε-CL-20 is significantly polarized. When the electric field strength is sufficiently strong, the occupied and unoccupied orbitals of the ε-CL-20 molecule change, resulting in a change in the energy level difference between the occupied and unoccupied orbitals, which further excites the corresponding excited state, resulting in a new UV-Vis absorption peak. Based on the density functional theory (DFT), the structural optimization and energy calculation were carried out by using B3LYP/6-311 + G(d, p) and B3LYP/def2-TZVPP methods, respectively. After optimization convergence, vibration analysis was performed without imaginary frequencies to obtain stable configurations. Then the molecular structure, frontier molecular orbitals (FMOs), global reactivity parameters (GRP), surface electrostatic potential, nitro charge, and UV-Vis spectra were analyzed.

Substituent effects in 2-hydroxybenzophenone-based ultraviolet absorbers

2-Hydroxybenzophenone is the simplest molecule among benzophenone-based UV absorbers. Changing the position and type of substituents affects the strength of intramolecular hydrogen bonding and thus modulates the UV absorption properties. In this work, 132 2-hydroxybenzophenone-based UV absorbers with different substituent positions and species were designed to investigate the substituent effect in their UV absorption properties. The results show that when the substituent positions are the same, the characteristic peaks of the compounds containing substituents of the same group of atoms or homologous groups correspond to similar wavelengths. When the substituent groups are the same, the wavelength redshift of the characteristic peaks of the UV absorption spectra of the compounds of the NX and NZ classes is more pronounced than that of the remaining species, and the substituent group containing N atoms causes the molecule to have a more pronounced wavelength redshift. The redshift of the characteristic absorption peaks corresponding to the wavelengths decreases with the increase of the energy level difference. Atoms-in-molecules (AIM) analysis showed that the electron-absorbing group in the compound enhances the hydrogen bond strength to a lesser extent than the electron-donating group. Natural Bond Orbital (NBO) analysis further revealed that the type and position of the substituent groups in the molecular structure influenced the strength of the intramolecular hydrogen bonding by affecting the distribution of the charges among individual atoms in the 2-hydroxybenzophenone molecules. This work aims to reveal the effect of substituents on the UV absorption properties of 2-hydroxybenzophenone-based molecules and to provide theoretical guidance for the design of such UV absorber molecules absorbing UV light at specific wavelengths.