Narrow-gap Semiconductors Research Articles

Photocatalytic performance and mechanism insights of an S-scheme ZnMn2O4/ZIF-67 heterostructure in photocatalytic CO2 reduction under visible light irradiation

Improved separation among photoelectrons and holes (e−, h+) and regulated electron transport routes are essential to improve photocatalytic performance. This work adopts a convenient but more efficient method to prepare an S-scheme composite photocatalyst integrating narrow band gap semiconductor ZnMn2O4 (ZMO) and zeolitic imidazole framework ZIF-67(Z67) for improved photocatalytic CO2 reduction. The designed photocatalyst ZMO(X)/Z67 showed more visible light harvesting capacity compared to individual ZMO and Z67. The ZMO/Z67 nanocomposite containing 3 % ZMO nanosphere produced 1.91 times higher methanol (48.64 μmolg−1) compared to pure Z67 (25.36 μmolg−1) and 1.42 times higher ethanol (30.32 μmolg−1) compared to pure Z67 (21.28 μmolg−1) after 8 h visible light illumination. The composites' increased photocatalytic performance might be attributed primarily to excellent photogenerated charge separation and transfer via the linked S-scheme heterojunction between ZMO nanospheres and Z67. Various characterization methods are used to explore the structural, morphological, optical, and electrochemical features of produced photocatalysts, and a thorough photocatalytic mechanism is provided. After four recycling, the composite photocatalyst demonstrated good stability and recyclability. This study attributed to a viable method for constructing a direct S-scheme heterojunction for photocatalytic CO2 reduction.

Defect induced Raman shifts and bandgap engineering in layered SnSe2+δ bulks

In the context of the extensive application prospect of two-dimensional (2D) chalcogenides, we synthesized layered SnSe2+δ bulks with defects employing a hybrid chemical vapor transport-melt approach. Both the Eg and A1g Raman characteristic peaks in SnSe2+δ are dominated by cubic anharmonicity, coupled with nonlinear temperature dependencies below 140 K. Notably, the reduction in phonon energy observed in these vibrational modes can be ascribed to defect-mediated Raman scattering, irrespective of deficient or excess Se defects. However, the lower consistency in the Raman shifts of the in-plane Eg vibrations compared to the out-of-plane A1g modes suggests that the defects predominantly entail the absence of Se atoms and the substitutions of Sn by Se, delineating a continuum of Se-deficient and Se-enriched compositions. Furthermore, Se defects induce the contraction of the indirect bandgaps, facilitating a transition from medium to narrow bandgap semiconductors in SnSe2+δ, which underscores the tunable nature of the bandgaps through the incorporation of Se defects. These discoveries present an avenue for bandgap engineering and foster a deeper comprehension of the phonon and thermal properties of layered chalcogenides for further advanced technologies.

Current Oscillations and Resonances in Nanocrystals of Narrow-gap Semiconductors

In single colloidal nanocrystals of narrow-gap semiconductors PbS and InSb, current instability in the form of quasi-periodic spikes and current resonance peaks was studied by measuring on a scanning probe microscope and analyzing Current-Voltage Characteristics (CVC). The observed phenomena are explained in models of the wave de Broglie process and Bloch oscillations. Statistically, the percentages of such samples and the parameters of oscillations on the current-voltage characteristic are higher, the larger the size quantization parameter, determined by the de Broglie wavelength. A possible practical use is the generation and recording of terahertz radiation modulated by ultrashort pulses.

Non-Equilibrium Long-Wave Infrared HgCdTe Photodiodes: How the Exclusion and Extraction Junctions Work Separately.

The cooling requirement for long-wave infrared detectors still creates significant limitations to their functionality. The phenomenon of minority-carrier exclusion and extraction in narrow-gap semiconductors has been intensively studied for over three decades and used to increase the operating temperatures of devices. Decreasing free carrier concentrations below equilibrium values by a stationary non-equilibrium depletion of the device absorber leads to a suppression of Auger generation. In this paper, we focus on analyzing exclusion and extraction effects separately, based on experimental and theoretical results for a HgCdTe photodiode. To carry out an experiment, the n+-P+-π-N+ heterostructure was grown by metal organic chemical vapor deposition on CdTe-buffered GaAs substrate. In order to separate the extraction and exclusive junctions, three different devices were evaluated: (1) a detector etched through the entire n+-P+-π-N+ heterostructure, (2) a detector made of the P+-π photoconductive junction and (3) a detector made of the π-N+ photodiode junction. For each device, the dark current density-voltage characteristics were measured at a high-temperature range, from 195 K to 300 K. Next, the carrier concentration distribution across the entire heterostructure and individual junctions was calculated using the APSYS simulation program. It was shown that when the n+-P+-π-N+ photodiode is reverse biased, the electron concentration in the π absorber drops below its thermal equilibrium value, due to the exclusion effect at the P+-π junction and the extraction effect at the π-N+ junction. To maintain the charge neutrality, the hole concentration is also reduced below the equilibrium value and reaches the absorber doping level (NA), leading to the Auger generation rate's reduction by a factor of 2ni/NA, where ni is the intrinsic carrier concentration. Our experiment conducted for three separate detectors showed that the exclusion P+-π photoconductive junction has the most significant effect on the Auger suppression-the majority of the hole concentration drops to the doping level not only at the P+-π interface but also deep inside the π absorber.

Are Selenides the Same as Sulfides? Structure, Spectroscopy, and Properties of Narrow-Gap Rare-Earth Semiconductors RE2Sn(S1-xSex)5 (RE = La, Ce; x = 0-0.8).

The ternary rare-earth sulfides RE2SnS5 (RE = La-Nd) and the partial solid solutions RE2Sn(S1-xSex)5 (RE = La, Ce; x = 0-0.8) were prepared in the form of polycrystalline samples by reaction of the elements at 900 °C and as single crystals in the presence of KBr flux. They adopt the La2SnS5-type structure (orthorhombic, space group Pbam, Z = 2) consisting of chains of edge-sharing SnCh6 octahedra separated by RE atoms. Although the cell parameters evolve smoothly in RE2Sn(S1-xSex)5, detailed structural analysis by single-crystal X-ray diffraction revealed a pronounced preference for the Se atoms to occupy two out of the three chalcogen sites, which offers a rationalization for why the all-selenide end-members RE2SnSe5 do not form. Solid-state 119Sn NMR spectra confirmed the nonrandom distribution of SnS6-nSen local environments, which could be resolved into individual resonances. The Raman spectra of RE2SnS5 compounds show an intense peak at 307-320 cm-1 assigned to a symmetric A1g mode, which is dominated by Sn-S bonds; the Raman peak intensities varied with Se substitution in La2Sn(S1-xSex)5. Optical diffuse reflectance spectra, band structure calculations, and electrochemical impedance spectra indicated that these compounds are narrow band gap semiconductors; the optical band gaps are insensitive to RE substitution in RE2SnS5 (0.7 eV) but they gradually decrease with greater Se substitution in RE2Sn(S1-xSex)5 (0.7-0.4 eV).

Tuning the electronic and magnetic properties of MoS2 bilayers by transition-metal intercalation

Two dimensional (2D) transition-metal dichalcogenides and their heterostructures are important materials for future electronic device applications. By using the first-principles calculations we investigate how the electronic and magnetic properties of MoS2 bilayer is modified by intercalating transition-metals (Fe, Co, and Ni). The Fe-intercalated MoS2 bilayer is found to be a non-magnetic gapless semimetal. Without spin–orbit coupling it has the Dirac state on the Γ-M line in k space at the Fermi level. The spin degeneracy of the Dirac state is removed by spin–orbit coupling. However, the bottom of the conduction band and the top of the valence band are in contact with the Fermi level making the system a non-magnetic gapless semimetal. The Dirac state is also observed in both Co-intercalated and Ni-intercalated MoS2 bilayers because they have the same symmetry in crystal structure as the Fe-intercalated MoS2 bilayer. The difference in the number of valence electrons in the intercalated atoms drastically change the electronic and magnetic properties. The Co-intercalated MoS2 bilayer is a ferromagnetic metal, where the Dirac state is below the Fermi level. The Ni-intercalated MoS2 bilayer is a non-magnetic narrow gap semiconductor, where the Dirac state is far below the Fermi level. The results revealed the electronic and magnetic properties of the transition-metal-intercalated MoS2 bilayers and will be useful for designing a variety of 2D materials.

Single crystal growth and transport properties of narrow-bandgap semiconductor RhP2

Abstract We report the growth of high-quality single crystals of RhP2, and systematically study its structure and physical properties by transport, magnetism, and heat capacity measurements. Single-crystal x-ray diffraction reveals that RhP2 adopts a monoclinic structure with the cell parameters a = 5.7347(10) Å, b = 5.7804(11) Å, and c = 5.8222(11) Å, space group P21/c (No. 14). The electrical resistivity ρ(T) measurements indicate that RhP2 exhibits narrow-bandgap behavior with the activation energies of 223.1 meV and 27.4 meV for two distinct regions, respectively. The temperature-dependent Hall effect measurements show electron domain transport behavior with a low charge carrier concentration. We find that RhP2 has a high mobility μ e ∼ 210 cm2⋅V−1⋅s−1 with carrier concentrations n e ∼ 3.3 × 1018 cm−3 at 300 K with a narrow-bandgap feature. The high mobility μ e reaches the maximum of approximately 340 cm2⋅V−1⋅s−1 with carrier concentrations n e ∼ 2 × 1018 cm−3 at 100 K. No magnetic phase transitions are observed from the susceptibility χ(T) and specific heat C p(T) measurements of RhP2. Our results not only provide effective potential as a material platform for studying exotic physical properties and electron band structures but also motivate further exploration of their potential photovoltaic and optoelectronic applications.

In situ constructed ferroelectric-nanonet-supported heterostructure thin film for high-performance photovoltaics

Heterostructure, which combines robust ferroelectrics and narrow-bandgap semiconductors together, is promising for acquiring both intensive photocurrent and large photovoltage output in photovoltaics; therefore, manipulation of the properties by engineering heterostructure has driven significant research activity. Herein, well-known Aurivillius-type ferroelectric Bi2WO6 and mullite-type Bi2Fe4O9 are chosen, and an excellent platform to investigate the role of ferroelectric-semiconductor heterostructure in tuning the photovoltaic effect is constructed by in situ depositing p-type nanoscale Bi2Fe4O9 onto n-type Bi2WO6 nanonet matrix. The nanonet-supported two-dimensional planar-like heterostructure and its ferroelectric domain switchability are confirmed by atomic force microscopy techniques. Significantly, the desired Bi2WO6/Bi2Fe4O9 film optimizes the key steps from light to electricity, and exhibits a large and stable photovoltaic effect, achieving four/three orders of magnitude enhancement of short-circuit photocurrent density/open-circuit voltage under laser irradiation. Furthermore, electric-field-controlled switchable asymmetric photoresponse and device stability were clearly observed, due to, in particular, Bi2WO6/Bi2Fe4O9 interfacial Schottky barrier formation and its modulation by poling-modified ferroelectric polarization. These findings highlight an important insight to construct diversified heterostructures with multi-functioning performances.

Dual‐Polarity Response in Self‐Powered Infrared SnTe Photodetector with Double Symmetric Schottky Junctions

AbstractSelf‐powered photodetectors with dual‐polarity response have great advantages in processing complex light information that is proven to be applied in switchable light imaging, optical communication, and spectral band distinction. Here, a novel strategy for designing self‐powered photodetectors by introducing the double symmetric Schottky junctions at the semiconductor‐metal interfaces is proposed, which guarantees the linear response characteristic and dominates the transfer of photogenerated carriers without external bias. Narrow bandgap semiconductor SnTe is employed as the photosensitive material. The bandgap is characterized to be 126 meV, showing great potential for wide spectrum response. As the consequence of selective excitation of unilateral Schottky junction and switching of electric field polarity, the device obtains a dual‐polarity photoresponse, which can be tuned from −14.8 to 13.5 µV. Moreover, an ultra‐broadband photoresponse from near‐infrared 808 nm to far infrared 10.6 µm is achieved with deep exploration of the working mechanism. The synergistic effect of photo thermoelectricity and photoconductivity created a high photoresponsivity of 0.35 mV W−1 excited by 10.6 µm at room temperature. This work provides a novel design strategy for self‐powered photodetectors with a dual‐polarity powered principle, which can take full advantage of the directivity of the photoresponse to identify optical information.

Wenzhou TE: A First-Principle-Calculated Thermoelectric Materials Database.

Since the implementation of the Materials Genome Project by the Obama administration in the United States, the development of various computational materials' databases has fundamentally expanded the choice of industries such as materials and energy. In the field of thermoelectric materials, the thermoelectric figure of merit (ZT) quantifies the performance of the material. From the viewpoint of calculations for vast materials, the ZT values are not easily obtained due to their computational complexity. Here, we show how to build a database of thermoelectric materials based on first-principle calculations for the electronic and heat transport of materials. Firstly, the initial structures are classified according to the values of bandgap and other basic properties using the clustering algorithm K-means in machine learning, and high-throughput first principle calculations are carried out for narrow-bandgap semiconductors which exhibit a potential thermoelectric application. The present framework of calculations mainly includes a deformation potential module, an electrical transport performance module, a mechanical and a thermodynamic properties module. We have also set up a search webpage for the calculated database of thermoelectric materials, providing search facilities and the ability to view the related physical properties of materials. Our work may inspire the construction of more computational databases of first-principle thermoelectric materials and accelerate research progress in the field of thermoelectrics.

KMg4Bi3: A Narrow Band Gap Semiconductor with a Channel Structure.

The creation of new families of intermetallic or Zintl-phase compounds with high-spin orbit elements has attracted a considerable amount of interest due to the presence of unique electronic, magnetic, and topological phenomena in these materials. Here, we establish the synthesis and structural and electronic characterization of KMg4Bi3 single crystals having a new structure type. KMg4Bi3 crystallizes in space group Cmcm having unit cell parameters a = 4.7654(11) Å, b = 15.694(4) Å, and c = 13.4200(30) Å and features an edge-sharing MgBi4 tetrahedral framework that forms cage-like one-dimensional channels around K+ ions. Diffuse reflectance absorption measurements indicate that this material has a narrow band gap of 0.27 eV, which is in close agreement with the electronic structure calculations that predict it to be a trivial insulator. Electronic transport measurements from 80 to 380 K indicate this material behaves like a narrow band gap semiconductor doped to ∼1018 holes/cm-3, with thermopowers of ∼100 μV/K and appreciable magnetoresistance. Electronic structure calculations indicate this material is close to a topological phase transition and becomes a topological insulator when the lattice is uniformly expanded by 3.5%. Overall, this unique structure type expands the landscape of potential quantum materials.

Fluorescent porous hybrid silsesquioxane-based semiconductor polymer for sunlight-driven gold recovery with high efficiency and selectivity

As an important precious metal, the recovery of gold can not only relieve the shortage of resources, but also has a high economic value. In this work, a novel silsesquioxane-based fluorescent porous hybrid polymer (PTSC) was prepared successfully by Heck coupling reaction of octavinylsilsesquioxane with a dibromated distyry-bithiophenes containing cyano groups. The structure of PTSC was fully investigated, which featured a high surface area of 455 m2 g−1, wide light adsorption band, narrow optical band gap (1.73 eV) and excellent semiconductor performance. As Au(III) adsorbent, the adsorption capacity of PTSC reached 3080 mg g−1 under light irradiation for 4 h at pH = 5, and the purity of the recovered gold in e-waste could reach 23.92 K. The adsorption mechanism showed that photoelectrons produced by PTSC could reduce all Au(III) adsorbed to Au(I) and Au(0). Moreover, a hybrid aerogel device based on PTSC and chitosan was fabricated to realize the enrichment and recovery of gold ions in wastewater. Besides, PTSC could also act as a probe to detect Au(III) with high selectivity and specificity. This study provided a new strategy for efficient recovery and detection of Au(III).

Thiazole-functionalized conjugated microporous polymers enable efficient gold recovery from e-waste

From the perspectives of environmental protection and efficiency, the use of clean and efficient photocatalytic reduction technology to recover gold from e-waste not only has a high economic value, but also reduces environmental pollution. However, it remains a challenge to construct adsorbents with simultaneously high photocatalytic activity, high stability, high capacity and high selectivity. Here, we demonstrate the application of D-π-A type thiazole-functionalized conjugated microporous polymer (termed BTD-TEA) for adsorption-photocatalytic recovery of gold from e-waste. The synthesized BTD-TEA not only have a narrow optical bandgap (1.75 eV) and excellent semiconductor properties, but also have ultra-high acid stability (stable in aqua regia). Surprisingly, BTD-TEA exhibits breakthrough gold adsorption capacity (4052.83 mg g−1), ultrafast adsorption kinetics, excellent selectivity and outstanding reusability under light conditions. This work provides a promising new adsorption-photocatalytic strategy for gold recovery from e-waste.

Modifying electronic and optical properties of violet phosphorus through variable fluorine coverage.

We present a comprehensive investigation of the electronic properties of fluorinated monolayer violet phosphorus using first-principles calculations. Our results reveal a strong dependence of the electronic properties on the different fluorine coverages of fluorination. As the fluorine coverage increases, monolayer violet phosphorus undergoes a significant transition from a wide direct bandgap semiconductor to a narrow indirect bandgap semiconductor. Moreover, both semi-fluorinated and fully fluorinated monolayer violet phosphorus exhibit advantageous semiconducting characteristics, with a tunable bandgap of 0.50 ~ 1.04 eV under biaxial strain ranging from -6% to 6%. Notably, the fully fluorinated monolayer violet phosphorus demonstrates a higher coefficient of light absorption within the visible range. Therefore, our findings highlight the tunability of monolayer violet phosphorus properties through the absorption of various fluorine coverages, providing valuable insights for the design and development of novel semiconductor devices based on this material.

Fabricating S-scheme Sb2S3@CdSexS1–x quasi-one-dimensional heterojunction photoanodes by in-situ growth strategy towards photoelectrochemical water splitting

Nowadays, energy and environmental problems are becoming increasingly prominent in society, the development of clean and environmentally friendly energy is in line with the construction of ecological civilization and energy, which have attracted the attention of many researchers over the past decades. Narrow band gap semiconductor Sb2S3 is widely used in the area of solar cells because of its high light absorption coefficient and suitable bandgap width. However, numerous deep-level defects provide plentiful photogenerated carrier recombination sites, which restricts the improvement of photoelectrochemical properties seriously. In this work, S-scheme Sb2S3@CdSexS1–x core-shell quasi-one-dimensional heterojunction photoanodes were prepared on the FTO substrate by a two-step vapor transport deposition (VTD) method, chemical bath deposition (CBD) and in-situ selenization method. The results showed that CdSexS1–x nanoparticles (NPs) were tightly coated on the Sb2S3 nanorods (NRs). The photocurrent density of the Sb2S3@CdSexS1–x photoanodes was 1.61 mA cm–2 under 1.23 VRHE. Compared with the Sb2S3 photoanodes (0.61 mA cm–2), Sb2S3@CdSexS1–x photoanodes obtained a 2.64-fold improvement, and the dark current was effectively reduced. It showed excellent stability and fast photocurrent response in a 600 s optical stability test. It was concluded that: (1) The charge transfer mechanism of the S-scheme can avoid the problem of high recombination rate of photogenerated charge carriers due to the defects of Sb2S3 effectively, and realized spatial separation of photogenerated carriers. (2) The [hk1] oriented Sb2S3 NRs and the formed quasi-one-dimensional heterostructures promote efficient carrier transport. (3) The introduction of Se effectively regulated the band structure of CdS, slowed down the photocorrosion of S, and improved the stability of the photoelectrodes significantly.

Constructing stable type-II NaLiTi3O7/La2S3 heterojunctions for efficient photocatalytic charge separation and hydrogen production

Designing titanium-based oxides with efficient photogenerated carrier separation is an essential approach to enhance their photocatalytic hydrogen production performance. ALiTi3O7 possesses excellent stability, corrosion resistance, and non-toxicity. More importantly, its stoichiometry can be changed along with the variations in A-site elements and Li content, leading to tunable redox potentials of the conduction band minimum (CBM) and valence band maximum (VBM). Exploring the possible application of such materials in the field of photocatalysis is crucial for developing novel and efficient titanium-based photocatalysts. As a member of the family, NaLiTi3O7 (NLT) has a large bandgap, limiting its application as visible light photocatalyst. To address this issue, non-toxic La2S3 (LS) narrow-bandgap semiconductor was incorporated to form a heterojunction. The characterization techniques have revealed the structural and interfacial characteristics of the NLT-LS heterojunction, while the Infrared, Raman, UV–Vis diffuse reflectance spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), and work-function tests elucidated the influence of the interface interaction on charge carrier separation mechanism. The test results further demonstrated that the formation of a type II heterojunction facilitated the transfer of photogenerated electrons from the conduction band of LS to the conduction band of NLT under light radiation. Simultaneously, the induced holes were confined to the valence band of LS. This charge transfer characteristic significantly improved the separation efficiency of the photogenerated carriers in the heterojunction, ultimately resulting in a photocatalytic hydrogen production rate of 102.4 μmol h−1 g−1 for the NLT-LS2 sample, which is ∼8 times higher than that of pure NLT and almost no decay after four cycles.

Photovoltaic properties of alkali metal X (X=Li, Na, K, Rb, Cs) doped defective molybdenum diselenide structures: First principles study

The electronic structure, work function, complex dielectric function, absorption coefficient and reflectivity of defective MoSe2 models containing point defects as well as alkali metal doping have been calculated based on the first principles of density flood theory. The effect of alkali metal doping on the optoelectronic properties of MoSe2 under defect conditions is investigated. Alkali metal elements were doped separately on the basis of a single Se atom defect, and the results show that the doped systems can all be stable. The introduction of the defect decreases the band gap of MoSe2 from 1.498 eV to 0.816 eV. The alkali-metal-doped defective MoSe2 systems have semiconductor-metal transitions with collisions between the bottom of the conduction band and the top of the valence band for each of the systems, except for the K doping. The K-doped defective MoSe2 is a narrow band gap semiconductor with a band gap of 0.202 eV. Overall, alkali metal doping under defective conditions improves the electrical conductivity of MoSe2, resulting in enhanced conductivity of the crystal. The work function analysis reveals that the work function of the alkali metal doped defective MoSe2, except for K doping, decreases gradually with the increase of its atomic radius, while the electrical conductivity of each system is enhanced. Optical property analyses revealed that the absorption coefficient of alkali-metal doped defective MoSe2 was significantly higher than that of intrinsic MoSe2 in the infrared light region, which compensated for the lack of zero absorption of the intrinsic material in the infrared light region, and enhanced its light-absorbing ability in the infrared light region and part of the visible light region. The reflectivity of each defective MoSe2 system doped by alkali metals is much smaller than that of the intrinsic, and the reflection peaks are red-shifted in the direction of the low-energy region. Overall, the doping of alkali metal atoms reduces the average reflectivity of the defective MoSe2 materials, which is conducive to the enhancement of light absorption and photoelectron emission from the materials. It is hoped that the research results in this paper will contribute to expanding the potential applications of MoSe2 materials in solar cells, photovoltaic devices, and photodetectors.

Revealing the Structural, Elastic, Electronic, and Optical Properties of K2ScCuCl6 and K2YCuCl6: An In-Depth Exploration Using Density Functional Theory.

The optoelectronic, structural, and elastic properties of K2ScCuCl6 and K2YCuCl6 double perovskite compounds were thoroughly investigated in this study using density functional theory. It is observed that both compounds exhibit exceptional structural and mechanical stability. The structural stability is assessed using Goldsmith's tolerance factor (tG), with values approaching unity indicating a reliable cubic perovskite structure. Phonon stability was ensured by the absence of negative energy formations and only real frequencies in the phonon calculations. Applying the finite displacement method also provided further evidence of the compounds' thermodynamic stability. The electronic properties analysis revealed that K2ScCuCl6 and K2YCuCl6 are narrow band gap semiconductors, with band gap values of 1.8 and 2.5 eV, respectively. This was confirmed by analyzing the density of states. Furthermore, the optical properties exhibited transparency at lower photon energies and significant absorption at higher energies. These exciting findings suggest that K2ScCuCl6 and K2YCuCl6 have promising applications in high-frequency UV devices.

Z-scheme heterojunction photocatalyst formed by MOF-derived C-TiO2 and Bi2WO6 for enhancing degradation of oxytetracycline: Mechanistic insights and toxicity evaluation in the presence of a single active species

In the work, Bi2WO6/C-TiO2 photocatalyst was successfully synthesized for the first time by loading narrow bandgap semiconductor Bi2WO6 on MOF-derived carboxyl modified TiO2. The phase structure, morphology, photoelectric properties, surface chemical states and photocatalytic performance of the prepared photocatalysts were systematically investigated using various characterization tools. The degradation efficiency of oxytetracycline by 6BT Z-scheme heterojunction photocatalyst under visible light could reach 93.6 % within 100 min, which was related to the high light harvesting and effective separation and transfer of photo-generated carriers. Furthermore, the effects of various environmental factors in actual wastewater were further investigated, and the results showed that 6BT exhibited good adaptability, durability and resistance to interference. Unlike most works, the degradation system with a different single active species were designed and constructed based on their formation mechanism. In addition, for the first time, a positive study was conducted on the priority attack sites, intermediate products, and degradation pathways for the photocatalytic degradation of oxytetracycline by a single active species through HPLC-MS and Fukui index calculations. The toxicity changes of intermediate products produced in three different single active species oxidation systems were evaluated using toxicity assessment software tools (T.E.S.T.), Escherichia coli growth experiments, and wheat growth experiments. Among them, the intermediate products formed through O2– oxidation had the lowest toxicity and the main active sites it attacked were the 20C, 38O, 18C, 41O, and 55O atoms with high f+ values in the oxytetracycline molecular structure. This work provided the insight into the role of each active species in the degradation of antibiotics and offered new ideas for the design and synthesis of efficient and eco-friendly photocatalysts.

Tuning the electro-optical properties of germanene nanoribbons by boron atom substitution for application in information transmission

Germanene nanoribbons, a one-dimensional material, have great potential for future technological applications. This research aims to investigate the electro-optical properties of boron-doped germanene nanoribbons with a width of five atoms. The theory used in this study is density functional theory (DFT). The original system is a narrow band gap semiconductor, with a gap size of 0.06[Formula: see text]eV. The doped configurations, which retain the honeycomb hexagonal structure, are stable and metallic in nature. The introduction of B atoms flattens the configuration, leading to a partial charge shift from Ge to B. The absorption peaks in the 3B and 5B configurations occur in the frequency range less than 500[Formula: see text]nm, indicating good absorption of visible light, and suggesting possible applications in light-sensitive components. Notably, the real part of the dielectric function’s 0z component is negative, offering immense potential for optical, microwave and communication applications.