This study develops a high-performance room-temperature (RT) hydrazine (N2H4) gas sensing material based on sustainable algal biomass. A porous carbon material (US-1.5) was fabricated from Undaria pinnatifida and sodium alginate via ice-templating and freeze-drying, yielding a hierarchical meso/macroporous structure that facilitates gas diffusion. Natural heteroatoms enable in situ self-doping, modulating electronic structure and surface reactivity. First-principles calculations confirm S-doping enhances adsorption energy and promotes charge transfer, creating more active sites for gas-surface interactions. The resulting US-1.5 sensing material demonstrates a high response of 22.53k% to 500 ppm N2H4, rapid response/recovery times (21.3 s/2.5 s), a low detection limit of 0.138 ppm, excellent selectivity, and cycling stability. It also shows humidity-dependent dual-mode sensing. This work pioneers algal aerogel-derived sensing materials, demonstrating marine waste upcycling for green, cost-effective gas sensing in environmental and industrial safety applications.

Exploiting the natural heteroatom composition of alfalfa, we synthesized a series of biochar from leaves and stems through controlled pyrolysis (300-600 degrees C). Gas-sensing tests indicated that the leaf-derived material prepared at 300 degrees C (ALFLs-3) shows the highest response value to H2O2 vapor among all eight materials. The enhanced gas-sensing performance is attributed to its unique wrinkled microstructure combined with heteroatoms (Ca, K, P), where ALFLs-3 generates substantial structural defects that facilitate the adsorption and activation of both O2 and H2O2. The prepared material operates at room temperature and achieves a response of 154.99 (Delta I/Iair) to 500 ppm H2O2 with rapid 21 s detection cycles, indicating certain competitiveness among room-temperature operable sensing materials. DFT calculations reveal that the co-doped system achieves wellbalanced adsorption energies. The H2O2 adsorption energy of-0.998 eV represents an optimal balance between high sensitivity and satisfactory reversibility, significantly stronger than those in single-element doped systems (e.g.,-0.151 eV for Ca,-0.542 eV for K, and-0.081 eV for P). Meanwhile, the O2 adsorption energy of-2.266 eV, the strongest among all configurations, facilitates efficient oxygen activation by promoting the formation of surface oxygen species. These findings clarify the origin of the improved sensing behavior. This work highlights the potential of plant organ-specific selection and low-temperature conversion strategies for transforming agricultural residues into functional gas sensing materials.

High-entropy carbon materials, a new class of functional materials, leverage multi-component synergy to precisely tune electronic structures and surface reactivity. Inspired by this concept, we developed biostructure-inspired high-entropy-like carbon materials derived from Undaria pinnatifida and applied them to room-temperature gas sensing. Freeze-drying followed by gradient carbonization produced a hierarchical turbinate-like porosity that mimics canine olfaction, while intrinsic multi-element (C/O/Na/Ca/P/S) coordination activated strong gas-surface interactions. DFT calculations confirmed that Ca doping increases hydrazine (N2H4) adsorption energy from -0.412 eV to -1.532 eV and charge transfer from 0.039e to 0.070e, and elevates O-2 adsorption energy from -0.160 eV to -1.524 eV with charge transfer rising from 0.181e to 0.790e, validating the dopant's role in boosting surface reactivity. Strategic defect and morphology engineering, coupled with multi-element self-doping, further enriched active sites, enabling the UD-500 to achieve a 14.12k% response to 500 ppm N2H4 at room temperature with a theoretical detection limit of 1.63 ppm, while exhibiting excellent repeatability, long-term stability (<3.5 % drift over 80 days), and humidity tolerance (11-94 % RH). This work establishes a marine-biomass route to high-performance gas sensors and advances the valorization of waste biomass.

Developing high-performance gas sensors for room-temperature (RT) operation remains a significant challenge in the field of gas detection. This study addresses this issue by designing and synthesizing a series of rare-earth (RE) oxide modified ZnO heterojunctions (RE2O3/ZnO, RE = Nd, Y, Yb) via a co-precipitation method. Systematic characterization combined with density functional theory (DFT) calculations reveals that the Yb2O3/ZnO heterostructure exhibits optimal morphology, abundant oxygen vacancies, and favorable band alignment. The resultant sensor demonstrates exceptional performance for trimethylamine (TMA) detection at RT, featuring a high response (6.84k% to 500 ppm), ultra-fast response/recovery kinetics (8/14 s), excellent selectivity, and a low theoretical detection limit (0.926 ppm). The enhanced sensing mechanism is attributed to the strong Lewis acidity and high polarizability of Yb3+, which optimizes charge transfer and promotes TMA adsorption. Furthermore, the practical utility of the Yb2O3/ZnO sensor is successfully demonstrated through real-time monitoring of fish spoilage, showing a strong linear correlation with storage time. This work not only presents a superior RT gas sensor but also provides deep insights into the role of RE cations in modulating heterojunction properties, offering a valuable strategy for designing advanced sensing materials.

The integration of carbon materials with metal oxide semiconductor (MOS) to engineer heterojunction composites is a proven strategy for enhancing gas-sensing performance. However, the interfacial chemistry and charge transfer mechanisms governing the carbon/MOS interface remain largely elusive. Herein, an n-n heterojunction composite of P-doped biochar/SnO2 was constructed using cotton stalks and wool as dual-biomass precursors. This system achieves highly efficient detection of ethylene glycol (EG) at room temperature, exhibiting a high response of 32.9k%, a limit of detection of 0.53 ppm, and excellent long-term stability over half a year. Mechanistic studies reveal that the preferentially exposed (110) facets of SnO2 exhibit a remarkably strong adsorption energy of −2.829 eV for EG, which dictates the gas selectivity of the composite system. More importantly, based on the one-dimensional Poisson's equation, an electrical amplification model coupling heavy-doping and light-doping regions was established. This model clarifies that the biochar side with lower carrier concentration dominates the variation in the depletion layer width. Arrhenius fitting confirms that the introduction of P elements expands the modulation range of the interfacial potential barrier height from 0.03 eV to 0.39 eV. These results define the specific roles of MOS, which govern adsorption selectivity, and biochar, which govern gas-sensing signal amplification, at the physical level. This dual-precursor strategy enables the simultaneous formation of a tubular carbon scaffold and in situ P doping in a single step. The established quantitative physical model demonstrates that the depletion layer is dominated by the lightly doped biochar side. This work provides a mechanistic framework for understanding interfacial engineering in carbon/MOS composites, enabling rational design of advanced heterojunctions through precise control of interface properties and charge transfer kinetics.

A MgO/biochar composite (MBC) with a wide range of pore sizes was prepared by a MgCl2-NaOH co-impregnation method using lavender stalks as the biochar source, which can effectively remove Pb(II) and Cd(II) from wastewater. The co-impregnation treatment resulted in a specific surface area of the MBC that was approximately 54 times greater than that of the biochar derived from untreated stalks. The ion-exchange capacity of MBC was increased by the incorporation of MgO nanoparticles, which increased the alkali metal ion (Mg2+) content. These specific structures and compositions gave the MBC a high adsorption capacity for Pb(II) and Cd(II). The adsorption data followed a quasi second-order kinetic model. For Cd(II) and Pb(II), the maximum adsorption capacities of MBC-700 (treated at 700 degrees C for 2 h) reached 520 mg/g and 808 mg/g, respectively. The primary adsorption mechanisms were ion exchange, precipitation, electrostatic attraction and surface complexation. Furthermore, metallic lead was recovered by using the reducing properties of the biochar at high temperatures. This study provides a reference for developing inexpensive and efficient heavy metal adsorbents and the low-carbonization utilization of biomass waste.

This study presents a N2H4 sensing material based on a Ni-MOF@BC heterostructure fabricated via a solvothermal route. The composite shows room-temperature sensing properties with a broad linear detection range and low detection limit. The performance mechanism is governed by a synergistic effect that combines the conductive network of BC for accelerated charge transfer, the catalytic activity of Ni-MOF, a built-in electric field for efficient charge separation, and hierarchically porous channels for enhanced gas permeation. A key structural feature, ligand competition-induced lattice distortion forming eta-NiO6 octahedra, is identified as crucial for the high selectivity toward N2H4. This unique distortion optimizes the adsorption energy and facilitates orbital hybridization between the sensor and N2H4 molecules, leading to a stronger and more specific interaction. Furthermore, the material features intelligent humidity-responsive mode-switching, enabling dual-purpose detection across varying ambient conditions. By utilizing Lyocell-derived carbon, this work exemplifies a sustainable design strategy for multifunctional sensing materials, offering a promising route toward low-power, adaptive gas monitoring technologies.

The detection of hydrazine (N2H4), a highly toxic and explosive compound, is of paramount importance for ensuring environmental and industrial safety. However, research on chemoresistive gas sensors for N2H4 detection, particularly the underlying mechanisms, remains limited. To address this gap, we have prepared carbon materials with a unique morphology and trace K doping through a simple carbonization process, utilizing raw cotton straw (RCS) as the starting material. The CS-400 sensor obtained under calcination at 400 degrees C exhibited high sensitivity and selectivity for N2H4, with a response of 30.6 k% and a detection limit of 0.55 ppm for 500 ppm N2H4 at room temperature. Subsequently, the gas sensing mechanism of the straw-based biochar material was focused on, and the roles of cellulose, hemicellulose and lignin in the RCS were analyzed. The interaction between defects and carrier concentration during pyrolysis was elucidated. First-principles calculations confirmed that trace K doping and surface adsorbed oxygen enhance the adsorption of target gases, thereby improving the sensor performance.

This study presents an eco-friendly fabrication method for high-performance room-temperature (RT, 25 degrees C) gas sensors by integrating biomass-derived N-doped carbon quantum dots (N-CQDs) with biochar (BC). The N-CQDs were hydrothermally synthesized from waste milk and the BC substrate was devrived from carbonized Lyocell fiber mask waste. The constructed N-CQDs@BC heterostructure through simple mechanical mixing and milling exhibited better trimethylamine (TMA) sensing capabilities, achieving a remarkable response magnitude of 21k% to 500 ppm TMA gas at RT with a moderate response/recovery time of 82.24 s/10.71 s. The sensor demonstrated outstanding stability by maintaining 21k% response after 45 days of ambient storage and achieved a low detection limit of 1.07 ppm. Density functional theory calculations revealed that N-doping significantly enhanced the material's adsorption capabilities for both O2 and TMA. This improvement in adsorption energy, combined with increased charge transfer, underscores the effectiveness of N-doping in optimizing the material's electronic structure and reactivity. By exclusively utilizing biomass waste resources, this work establishes a simple solution for developing eco-friendly semiconductor gas sensors that combine high sensitivity cost-effectiveness, and environmental sustainability with promising applications.

The development of a green and non-polluting gas-sensitive material for N2H4 detection at room temperature (RT) remains a challenge. Guided by the concept of green and sustainable development, we have prepared a novel porous carbon material (LSC) for high-performance N2H4 detection at RT. This was achieved through a green and environmentally friendly one-step carbonization method, using Laetiporus sulphureus (LS), a tree pathogen abundant in amino acids and proteins, as a precursor for nitrogen self-doping. Through optimization of the carbonization temperature, the LSC-600 sensor achieves highly sensitive and selective detection of N2H4 at RT, with a response of 32.11k%-500 ppm N2H4 and exhibits a faster response (similar to 20.1 s) and recovery (similar to 1.5 s). The LSC-600 sensor shows good long-term stability, with a response to N2H4 varying less than 8.4 % after 30 days. Moreover, its gas-sensitive mechanism is discussed in detail. This research not only presents a green and sustainable approach for the valuable utilization of biomass waste but also furnishes a valuable reference for the development of high-performance sensors. In addition, it expands the scope of bio-manufacturing and opens up new avenues for research and development in materials science.

Ethylene glycol (C2H6O2) is an organic compound widely used in industry and daily life. However, it is toxic to animals and humans and can cause serious health problems when ingested. It is important to explore new sensing materials to achieve effective detection of C2H6O2. In this work, pumpkin shaped aspergillus niger with submicron scale has been cultured, aspergillus niger-derived carbon (ANDC) was prepared by simple carbonization, and then novel ANDC/ZIF-8 composite was prepared using a solvothermal method. ANDC/ZIF-8 exhibits considerable selectivity for C2H6O2 at room temperature, and the detection limit was 0.84 ppm and the response/ recovery time was 13.9/10.6 s, respectively. Compared to ANDC, the gas sensitive performance of ANDC/ZIF-8 composite is greatly improved. This enhancement should be mainly attributed to the formation of heterogeneous junctions and hydrogen bonding interaction between ZIF-8 and C2H6O2. In this way, the mould with regular shapes produced by biomanufacturing was prepared into biochar, which in turn created a new type of gas sensing material and pioneered the introduction of biomanufacturing into the preparation process of gas sensing materials.

In this study, spinel structured manganese nickel oxide (NiMn2O4) nanoparticles were successfully synthesized using a simple and reproducible two-step pyrolysis method. Comprehensive characterization techniques, including XRD, SEM, TEM, EDX, FT-IR, Raman, EPR, XPS, and BET, are used to characterize the morphology, structure, elemental composition, and evaluate their gas sensing performance at room temperature. The results confirmed the successful synthesis of pure-phase cubic spinel structures with abundant oxygen vacancies and mesoporous morphology. In gas sensing tests, the NiMn2O4 sensor exhibited excellent sensitivity (Response = 40 to 500 ppm trimethylamine), fast response/recovery times (6 s/1 s), and superior selectivity toward 13 interfering volatile organic compounds at room temperature. The outstanding linear detection range (20-500 ppm, R2 = 0.998), robust repeatability, and long-term stability (1 month with a drift of +/- 1.52) further validated its practical applicability. This study investigates the plausible gas-sensing mechanism and, by combining simulation calculations and modeling, elucidates the reason for the sensor's excellent selectivity toward trimethylamine. Compared with existing trimethylamine sensors requiring high temperatures, this work provides a breakthrough strategy for designing energy-efficient and high-performance gas sensors, holding potential applications in seafood freshness monitoring and medical diagnostics.

N-methylpyrrolidone (NMP) is an excellent advanced solvent that can be easily absorbed by the human body and has the characteristics of flammability and explosion. To reduce the risk, the environmental concentrations of NMP need to be measured. A series of covalent organic frameworks (COF) connected by an imine bond have been successfully prepared at room temperature by changing the synthesis time catalyzed by scandium(III) trifluoromethanesulfonate (Sc(OTf)3). The effect of the synthesis time on the sample properties was compared by XRD, FT-IR, XPS, SEM, TEM, and BET. The results showed that synthesis time had almost no effect on the morphology, specific surface area, and functional groups of the COF samples but had a significant impact on the pore size distribution, residual bonds, and other defects, which in turn affected the gas sensing performance. The sensor results showed that all samples had good sensing performance for NMP, among which the sample synthesized for 48 h had the best sensing performance, with a limit of detection of 692 ppb and good stability and repeatability. The excellent performance of the COF samples benefits from the large specific surface area, hydrogen bonding interactions, electrostatic attraction, and high defects. This study provides an effective method for NMP detection and expands the application range of the COF materials.

Tetrahedral basic building units are important for the design of new nonlinear optical materials. In this paper, two alkali metal silicates have been reported to have differentiated symmetry and optical properties. LiKSi2O5 crystallizes in the monoclinic system of P21 with the ultraviolet cutoff of 255 nm; LiRbSi2O5 crystallizes in the orthorhombic system of Pca21 with the ultraviolet cutoff of 240 nm. The calculation results show that the second harmonic generation coefficients and the wavelengths of phase matching for LiKSi2O5 are d16 = 0.30 pm/V and 585 nm, while that for LiRbSi2O5 are d24 = 0.38 pm/V and 446 nm, respectively. Hence, the different radii of cations lead to different coordination environments, which will affect the connection styles further influences the symmetries and optical properties of the compounds. It is confirmed that simple ion substitution can change the optical properties, which provides a feasible way for the modulation of nonlinear optical property.

In this study, biomass-derived carbon material obtained from Lyocell fibers was first utilized as a gas sensor. The impacts of varying pyrolytic carbonization temperatures and pregrinding treatments on the structure, surface morphology, elemental composition, and gas sensitivity of the samples were thoroughly examined. The CL-500 sensor can realize rapid detection of trimethylamine with a high response (12.79k%, 500 ppm) and high selectivity at room temperature; the response/recovery times are 10 s and 2 s, respectively, and the theoretical detection limit is 3.96 ppm. Moreover, after four months, the response of the CL-500 sensor to trimethylamine fluctuated by less than 9.7 % compared with that of the fresh sensor, indicating good stability. It also shows good recovery after seven consecutive response-recovery cycles. Additionally, the CL-500 sensor has promising applications in real-life fish freshness monitoring. Theoretical calculations indicate that the introduction of trace amounts of Na enhances the sensing performance of this sensor for target gases. This study serves as a guide for developing cost-effective, high-performance gas sensors, promoting the efficient and high-value utilization of biomass waste.

Inspired by the ordered tubular structure inside the dog nose and its olfactory receptors, this paper reports a biochar/SnO2 composite based on waste disposable bamboo chopsticks (DBC) combined with tin dioxide (SnO2) nanoparticles. The response of optimized biochar/SnO2 composite reaches 4513 to 500 ppm NH3, and the response/recovery times are 50.4 s and 3.7 s, respectively. The biochar/SnO2 composite displays the dog-nose-like ultra-fast response (1 s response up to 1100) to 500 ppm NH3 at room temperature (25 & DEG;C), which makes the biochar/SnO2 composite with the application promising for rapid detection of NH3. The optimized biochar/SnO2 sensor also exhibits good selectivity and linear response with a theoretical detection limit as low as 34 ppb NH3. In addition, the biochar/SnO2 sensor has reliable humidity immunity and long-term stability. Within a period of up to six months, the response fluctuation of biochar/SnO2 sensor to 500 ppm NH3 at 25 & DEG;C is less than 3.7%. However, the susceptibility of biochar/SnO2 composite to the operating temperature need to be overcome. The biochar/SnO2 composite was prepared by low-temperature pyrolytic carbonization (300 & DEG;C) with the advantages of abundant raw materials, low cost and green environmental protection, providing a new outlet for solid waste.

In this study, chitin fibers (CFs) were combined with molybdenum sulfide (MoS2) to develop high-performance sensors, and chitin carbon materials were innovatively introduced into the application of gas sensing. MoS2/CFs composites were synthesized via a one-step hydrothermal method. The surface properties of the composites were greatly improved, and the fire resistance effect was remarkable compared with that of the chitin monomer. In the gas-sensitive performance test, the overall performance of the MoS2/CFs composite was more than three times better than that of the MoS2 monomer and showed excellent long-term stability, with less than 10% performance degradation in three months. Extending to the field of strain sensing, MoS2/CFs composites can realize real-time signal conversion in tensile and motion performance tests, which can help inspectors make analytical judgments in response to the analysis results. The extensive application of sensing materials in more fields is expected to be further developed. Based on the recycling of waste chitin textile materials, this paper expands the potential applications of chitin materials in the fields of gas monitoring, biomedicine, behavioral discrimination and intelligent monitoring.

Tens of billions of pairs of waste disposable bamboo chopsticks (DBC) are produced every year, and it is extremely important to utilize this resource effectively. Inspired by the structural similarity between the dog turbinate and bamboo, DBC were successfully carbonized into carbon materials with a similar structure to that of dog turbinate at different temperatures. The carbon materials derived from DBC were used gas sensors for the first time and the effect of carbonization temperature on the structures, carbon yield and gas sensing performance was studied. By optimizing the carbonization temperature, the biomimetic sensor realized the detection of ammonia (NH3) with high sensitivity and selectivity, exhibited the high response (71.82 k%) to 500 ppm NH3 at room temperature, and had a theoretical detection limit of 0.12 ppm. Furthermore, the biomimetic sensor showed excellent immunity to formaldehyde, acetone, relative humidity (RH) and other interference factors, and its response to 95% RH was less than one thousandth of that to 500 ppm NH3. Compared with the fresh sensor, after 50 days the fluctuation of the sensor's response to NH3 was less than 4.2%, and it still had excellent recovery capability in 10 consecutive response-recovery cycles. What’s more, the biomimetic sensor has been successfully used to monitor the freshness of mutton in the actual environment. This study provides a reference for the development of low-cost and high-performance gas sensors and the effective utilization of biomass waste.

Green and economical self-doped nitrogen-containing fluorescent carbon quantum dots (N-CQDs) were synthesized using a one-pot hydrothermal treatment method. The optical and structural properties of the N-CQDs were investigated in detail by UV-vis and fluorescence spectroscopy, X-ray diffraction (XRD) techniques, transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) spectroscopy, and elemental analysis illustrate the surface function and composition of N-CQDs. N-CQDs emit a broad fluorescence between365 ̴ 465 nm and fluoresce most strongly at the excitation wavelength of 415 nm. Meanwhile, Cr (VI) could significantly burst the fluorescence intensity of N-CQDs. N-CQDs showed an excellent sensitivity and selectivity to Cr (VI), which exhibited good linearity in the range of 0 ̴ 40 µmol/L with a detection limit of 0.16 µmol/L. In addition, the mechanism of Fluorescence quenching of N-CQDs by Cr (VI) was investigated. This work well provides a research idea for the preparation of green carbon quantum dots from biomass and their use for the detection of metal ions.

Structures and performances from nature provide ideasfor humansto deal with energy and environmental crisis. Inspired from naturalstructures, bacterial cellulose nanofibers with a fine-meshed networkwere selected as the raw materials to design acetone gas sensors.Here, Fe2O3 nanorods were successfully introducedon the surface of carbon nanofibers by a feasible hydrothermal catalyticcarbonization at 120 degrees C. Lots of heterojunctions between thebacterial cellulose carbon nanofiber and the Fe2O3 nanorod were constructed, resulting in high gas-sensing propertiesto acetone vapor. At room temperature, the response of Fe2O3/bacterial cellulose carbon nanofiber composite (BCCF-Fe2O3) to 5 ppm of acetone reached 2060% within 10s. BCCF-Fe2O3 showed high sensitivityand selectivity, ppb-level detection limit (100.7 ppb), nice long-termstability (30 days), low energy consumption (1.4 mu W), and goodanti-humidity performance in acetone detection. To our surprise, BCCF-Fe2O3 had realized ultrasensitive exhaled acetonedetection within 16 s, proving an effective and inexpensive strategyfor diabetic noninvasive diagnosis.