Thermal Annealing Approach Research Articles

Aluminum Josephson junction microstructure and electrical properties modified by thermal annealing

Reproducibility of Al/AlOx/Al Josephson junctions is a challenge for scaling up superconducting quantum processors. The frequency uncertainty of the transmon qubits arising from the fabrication process is attributed to deviations in the Josephson junction microstructure and electrical properties. Here, we present a solution for this problem using the post-fabrication Josephson junction thermal annealing process. The developed thermal post-exposure method allows not only to increase the junction resistance by 175%, but also to decrease by 60% with a step of 10% in Rn, which opens up new possibilities for tuning the frequency of qubits. The resistance is shown to be strongly temperature dependent, and is weakly dependent on the holding time. The linear dimensions of the electrodes and the sidewalls contribution to the total JJ area also have a significant impact on the final resistance after annealing. Finally, a theoretical model of the structure modification in a tunnel barrier with changes in oxygen concentration gradient is proposed. The proposed thermal annealing approach can be used to form stable and reproducible tunnel barriers and scalable frequency trimming for widely used fixed-frequency transmon qubits.

Gradient Thermal Annealing Assisted Perovskite Film Crystallization Regulation for Efficient and Stable Photovoltaic-Photodetection Bifunctional Device.

Perovskite crystallization regulation is essential to obtain excellent film optoelectronic properties and device performances. However, rapid crystallization during annealing always results in poor perovskite film and easy formation of trap, thereby greatly restricting device performance due to severe non-radiative recombination. Here, an easy and reproducible gradient thermal annealing (GTA) approach is used to regulate the perovskite crystallization. Through a low-temperature initial annealing of GTA, the solvent evaporation is slowed down, thus extending nucleation time and providing a buffer for the rapid crystallization of perovskite grains in the subsequent high-temperature stage. As a result, completely converted and highly crystalline perovskite is obtained with 1.6 times larger grain size, reduced trap density and suppressed non-radiative recombination of photo-generated carriers. The film crystallinity is also enhanced with more advantageous (100) and (111) lattice facets which are favorable for carrier transport. Consequently, the perovskite photodetectors exhibit a large linear dynamic range of 174dB and an excellent response even under ultra-weak light of 303 pW. Meanwhile, perovskite solar cells achieved increased PCE and maintained 85% of original efficiency after heating at 65°C for nearly 1000 h under unencapsulated conditions. To the knowledge, this represents the best performance reported for a perovskite photovoltaic-photodetection bifunctional device.

Oxygen-reduced surface-terminated MXenes as cathodes for enhanced reversible Li–CO2 batteries

Li–CO2 batteries have garnered global attention due to their dual attributes of high energy density and effective CO2 capture. However, they still face a formidable challenge in decomposing the discharge products Li2CO3, resulting in subpar battery performance. MXene has been proposed as a promising candidate owing to its high electrical conductivity and effective CO2 activation performance. Nevertheless, unavoidable surface terminations (such as –O and –OH) during synthesis strongly influence their catalytic properties, posing a significant hurdle for high-performance Li–CO2 batteries. Herein, a thermal annealing approach is proposed to control the surface termination groups of MXene to reduce the generation of lithium hydroxide byproducts, thereby accelerating Li2CO3 decomposition kinetics and enhancing the reversibility of the battery. The systematic annealing of MXene in the range of 500–800 °C confirmed optimal surface terminations at 500 °C (TC500). The TC500, when tested as a catalyst in a Li–CO2 battery, exhibited enhanced performance metrics, such as low voltage gap (1.98 V), high specific capacity (15,740.38 mA h g−1 at 100 mA g−1), and prolonged cycle stability (700 h at 200 mA g−1). The proposed work offers an effective strategy for regulating MXene surface termination groups via simple annealing treatments to achieve high-performance Li–CO2 batteries.

Ruthenium-nickel oxide derived from Ru-coupled Ni metal–organic framework for effective oxygen evolution reaction

Developing Ru-based catalysts with both high activity and stability for the oxygen evolution reaction (OER) is very significant in the water electrolysis technique. Here, a bimetallic metal oxide catalyst (RuO2-NiO) derived from Ru-coupled Ni metal–organic framework (Ni-MOF) by using terephthalic acid as the ligand was successfully synthesized through a facile ultrasonic treatment and subsequent thermal annealing approach; and the effective role of the coupled effect between RuO2 and NiO in stabilizing Ru was found significant in OER catalysis. A relatively small d-band center due to the electronic structure regulation and synergistic effect of the heterostructure was found to cause weakened adsorption of surface oxygen species. Theoretical calculations demonstrated that the electronic modulation between RuO2 and NiO can significantly accelerate the dissociation of water and modulate the chemical adsorption of oxygen intermediates on the catalyst, thereby enhancing the OER activity of the catalyst. The optimized catalyst of RuO2-NiO afforded a current density of 10 mA cm−2 at low overpotentials of 210 mV toward OER, and good catalytic stability, kinetics and efficiency were also discussed. This remarkable catalytic performance can be attributed to the unique sheet-like structure and porous morphology of the catalyst with increased exposure of active sites and the coupling effect between RuO2 and NiO for moderate binding strength to the intermediates. This study showed an effective approach for bimetallic oxide catalyst fabrication and their applications in energy conversion reactions.

Dependence of CZTS thin film properties and photovoltaic performance on heating rate and sulfurization time

In this study, effect of heating rate and sulfurization time on the properties of CZTS thin films and their photovoltaic performances was investigated. CZTS layers were prepared by a two-stage technique comprising deposition of precursor films by sputtering on Mo-foil substrates (Mo-foil/ZnS/CuSn/Cu) and a sulfurization process utilizing Rapid Thermal Annealing (RTA) approach. Heating rates and sulfurization times at 550 °C were changed to determine the best conditions. CZTS films were characterized by several techniques. All samples showed Cu-poor and Zn-rich chemical composition regardless of the heating rate and annealing time of the sulfurization process. XRD diffraction patterns showed that only kesterite CZTS phase was formed in all samples. Although Raman spectroscopy measurements confirmed formation of kesterite CZTS phase in all samples, forming of Cu2SnS3 (CTS) secondary phase was detected in all films except for the sample prepared utilizing a relatively low heating rate of 1 °C/s and 60 s sulfurization time (CZTS-I-60). The largest crystallite size and the less micro strain and dislocation density were also found in this sample. All CZTS thin films displayed dense and compact polycrystalline surface microstructure. Optical characterizations showed that the optical band gaps of the films were in the range of 1.48–1.58 eV. PL emission spectra of the films exhibited transition from conduction band to acceptor/defect levels instead of band-to-band transition. Solar cells were fabricated and the highest Voc and conversion efficiency (4.39%) were achieved employing the film obtained with ramp rate of 1 °C/s and the sulfurization time of 60 s, because of better structural properties and purer crystal structure determined for this sample.

Recent progress in intermetallic nanocrystals for electrocatalysis: From binary to ternary to high‐entropy intermetallics

AbstractDeveloping sustainable and clean energy‐conversion techniques is one of the strategies to simultaneously meet the global energy demand, save fossil fuels and protect the environment, in which nanocatalysts with high activity, selectivity and durability are of great importance. Intermetallic nanocrystals, featuring their ordered atomic arrangements and predictable electronic structures, have been recognized as a type of active and durable catalysts in energy‐related applications. In this minireview, the very recent progress in the syntheses and electrocatalytic applications of noble metal‐based intermetallic nanocrystals is summarized. Various synthetic strategies, including the conventional thermal annealing approach and its diverse modifications, as well as the wet‐chemical synthesis, for the construction of binary, ternary and high‐entropy intermetallic nanocrystals have been discussed with representative examples, highlighting their strengths and limitations. Then, their electrocatalytic applications toward oxygen reduction reaction, small molecule oxidation reactions, hydrogen evolution reaction, CO2/CO reduction reactions, and nitrogen reduction reaction are discussed, with the emphasis on how the ordered intermetallic structures contribute to the enhanced performance. We conclude the minireview by addressing the current challenges and opportunities of intermetallic nanocrystals in terms of syntheses and electrocatalytic applications.

Growth of titania and tin oxide from Ti2SnC via rapid thermal oxidation in air for lithium‐ion battery application

AbstractHerein, we report the synthesis of TiO2–SnO2–C/carbide hybrid electrode materials for Li‐ion batteries (LIBs) via two different methods of controlled oxidation of layered Ti2SnC. The material was partially oxidized in an open‐air furnace (OAF) or using a rapid thermal annealing (RTA) approach to obtain the desired TiO2–SnO2–C/carbide hybrid material; the carbide phase encompassed both residual Ti2SnC and TiC as a reaction product. We tested the oxidized materials as an anode in a half cell to investigate their electrochemical performance in LIBs. Analysis of the various oxidation conditions indicated the highest initial lithiation capacity of 838 mAh/g at 100 mA/g for the sample oxidized in the OAF at 700°C for 1 h. Still, the delithiation capacity dropped to 427 mAh/g and faded over cycling. Long‐term cycling demonstrated that the RTA sample treated at 800°C for 30 s was the most efficient, as it demonstrated a reversible capacity of around 270 mAh/g after 150 cycles, as well as a specific capacity of about 150 mAh/g under high cycling rate (2000 mA/g). Given the materials’ promising performance, this processing method could likely be applied to many other members of the MAX family, with a wide range of energy storage applications.

Highly effective and tunable microwave absorber integrating multiscale attenuation behaviours derived from prussian blue analogue/graphene oxide aerogel

Tunable and efficient absorption of graphene-based microwave absorbers are essential on the realms of electromagnetic compatibility and protection in various application scenarios. However, challenges arise owing to their limited microwave attenuation behaviors. Herein, CoNiFe Prussian blue analogue (PBA)-derived magnetic alloy@carbon nanocubes anchored on N-doped reduced graphene oxide (rGO) aerogels were achieved via CoNiFe-PBA nanocubes assisting assembly of GO and subsequent thermal annealing approach. Such three-dimensional (3D) graphene-based macroscopic architecture integrates multiple attenuation behaviours occurred across multiple length scales. Attributed to the synergy of multiple scattering, conduction loss, multiple heterogeneous interface and dipolar polarizations, and magnetic loss, the optimized CoNiFe-PBA/GO aerogel derivative simultaneously exhibits strong reflection loss and wide effective bandwidth with an ultralow filling content (1.1 wt%) at both X band (−66.01 dB and 5.2 GHz at 3.2 mm) and Ku band (−66.23 dB and 6.6 GHz at 2.6 mm). Multiscale assembly strategy of graphene-based electromagnetic functional materials from molecular level to macroscale proposed and demonstrated by this work shows promise for exploring tunable and efficient microwave absorbers.

Facile Transformation of Waste Biomass into Nitrogen-Doped Graphene for Highly Efficient Metal-Free Electrocatalyst for the Oxygen Reduction Reaction

Key words: Metal-free catalyst, Oxygen reduction reactions, Pyridinic nitrogen, Stability It is of significant interest to produce metal-free electrocatalysts for oxygen reduction reactions (ORR) derived from low-cost and environmentally friendly biomass. This work presents a facile thermal annealing approach for large-scale synthesis of the nitrogen-doped graphene (N-GO) nanoflakes using melamine as the nitrogen source and chestnut shells-based biomass as the carbon source. This approach allows us to achieve a high nitrogen doping level in graphene. Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR) were used to characterize the N-GO. XPS analysis revealed the presence of pyridinic, graphitic, and pyrrolic nitrogen doping in graphene sheets, with pyridinic nitrogen being the most abundant. Electrochemical investigations showed that a higher concentration of pyridinic nitrogen configurations contribute significantly to the superior electrocatalytic activity toward oxygen reduction reactions (ORR) in alkaline electrolytes. The as-synthesized N-GO exhibits high ORR activity with the onset and half-wave potential of 0.90 V and 0.79 V in alkaline medium, respectively; which is among the best reported to the date for metal-free catalysts. Moreover, compared with the commercial Pt/C, optimized N-GO electrocatalyst exhibits more positive onset potential and better long-term stability, making it a promising metal-free catalyst for practical fuel cells. Acknowledgements: The authors are thankful to Campus France and the National Research Foundation of Korea for financing the PHC Star mobility project (45823YC). Figure 1

Realization of specific localized surface plasmon resonance in Au-modified Ni nanoplasmonics for efficient detection

Monometallic nanostructures have gained tremendous research attentions owing to the ability of supporting surface plasmons and improving devices performance. However, the relatively inflexible localized surface plasmon resonance (LSPR) absorption peaks restrict the further development of monometallic plasmonics and relevantapplications. Herein, the bimetallic Au-Ni nanoparticles (NPs) with an ∼ 325 nm LSPR absorption peak were fabricated and decorated on polar GaN microwire (MW) array PDs via thin film thermal annealing approach. Compared with monometallic Au and Ni NPs, the bimetallic Au-Ni NPs can not only modulate LSPR absorption peak but also enhance absorptivity. Moreover, the bimetallic NPs/GaN MW array PDs demonstrated the maximum increase in responsivity than bare GaN under the resonance wavelength of 325 nm. Theimprovement in bimetallic NPs devices is correlated with the stronger light absorption, scattering and hot electron transfer at the GaN interface. This work presents a simply valid method for preparing the bimetallic Au-Ni NPs with tunable LSPR absorption peak, which can be helpful for realizing the energy-efficient optoelectronic device applications in most functional fields.

Bottom‐Up‐Etching‐Mediated Synthesis of Large‐Scale Pure Monolayer Graphene on Cyclic‐Polishing‐Annealed Cu(111) (Adv. Mater. 8/2022)

Single-Crystal Foils In article number 2108608, Bin Wu, Jichen Dong, Yunqi Liu, and co-workers report the development of a cyclic electrochemical polishing and thermal annealing approach to obtain single-crystal Cu(111) foils. Pure monolayer graphene is produced on Cu(111) based on a general “bottom-up etching” method. In particular, the obtained graphene shows high and uniform electronic quality using terahertz time-domain spectroscopy (THz-TDS) measurement.

Identification of Nanoscale Processes Associated with the Disorder-to-Order Transformation of Carbon-Supported Alloy Nanoparticles.

Due to their ordered crystal structures and high structural stabilities, intermetallic nanoparticles often display enhanced catalytic, magnetic, and optical properties compared to their random alloy counterparts. Intermetallic nanoparticles can be achieved by thermal annealing of their disordered (random alloy) counterparts. However, high temperatures and long annealing times needed to achieve the disorder-to-order transition often lead to a loss of sample monodispersity and an increase in the average size of nanoparticles. Here, we performed ex situ powder X-ray diffraction (XRD) and in situ annealing transmission electron microscopy (TEM) experiments to elucidate nanoscale processes that contribute to the ordering of carbon-supported PdCu nanoparticles as a model system. Random alloy PdCu nanoparticles supported on carbon were thermally annealed for various lengths of time at the disorder-to-order phase transition temperature, where changes in nanoparticle size and the crystal phase were monitored. The nanoparticles were only completely transformed to the intermetallic phase by undertaking measures to deliberately increase their size by increasing the number of nanoparticles on the carbon support. In situ annealing TEM experiments reveal nanoscale processes that account for the disorder-to-order phase transformation. Five different processes were observed at 400 °C. Isolated nanoparticles remained in the random alloy phase or underwent a phase transformation to the intermetallic phase. Nanoparticles fused with neighboring nanoparticles resulting in no change in phase or conversion to the intermetallic phase. Evidence of vapor transport was also observed, as some isolated nanoparticles were found to diminish in size upon heating. These variable processes account for the heterogeneity often observed for intermetallic nanoparticle samples achieved through annealing and motivate the development of synthetic routes that suppress particle-particle coalescence, as well as investigating metal-support interactions to facilitate the disorder-to-order phase transformation under mild conditions. Overall, this work furthers our knowledge of the formation of intermetallic nanoparticles by thermal annealing approaches, which could accelerate the development of electrocatalysts and the application of intermetallic nanoparticles in magnetic storage devices.

Removal of oxytetracycline by graphene oxide and Boron-doped reduced graphene oxide: A combined density function Theory, molecular dynamics simulation and experimental study

Graphene-based nanomaterials have demonstrated great potential in the field of environmental applications, especially on water treatment processes. Accordingly, herein, in order to be used as adsorbent in the removal of oxytetracycline (OTC), graphene oxide (GO) and boron doped reduced graphene oxide (B-rGO) was investigated. GO was obtained through the oxidation/exfoliation process using the modified Hummers’ Method and further etched by a thermal annealing approach to obtain B-rGO, utilizing boric acid as boron source for the study. FT-IR, TEM and XRD were used to characterize the morphology properties of GO and B-rGO and confirm the success of these synthesis. To evaluate the degradation potential of OTC by GO and B-rGO, pH of the sample, GO and B-rGO concentration, initial OTC concentration, reaction time and temperature has been selected as effective parameters. Based on the obtained experimental results GO and B-rGO were found to possess favorable adsorption efficiencies reaching 86% and 100% for GO and B-rGO, respectively, rapidly uptake rate with up to 85% of total removal occurring within the initial 10 min. In addition, it is noteworthy that OTC removal from solution was strongly dependent on pH but independent of temperature. The classical isotherm and kinetic adsorption models suggested that the process perfectly conformed to Freundlich and Pseudo-second-order model (R2 ≥ 0.95). Furthermore, density functional theory (DFT) simulation performed at the B3PW91 level of theory as well as a topological analysis were introduced to elucidate theoretically the interfacial interaction at the molecular-scale associated with OTC sorption on both adsorbents.

Low-Fluorine Ba-Deficient Solutions for High-Performance Superconducting YBCO Films

High-performing superconducting YBa2Cu3O7–x (YBCO) films are fabricated by a chemical solution deposition methodology through novel barium-deficient low-fluorine solutions. The precursor solutions, distinguished for being straightforward, inexpensive and eco-friendly, allow us to reduce the growing temperature of YBCO down to 750 °C. We investigated the influence of the growing temperatures on both the microstructure and superconducting properties of YBCO films by using conventional thermal annealing and flash-heating approaches. A clear correlation between the growing temperature (Tg) and the superconducting performance of the films was obtained with improved performances observed at low Tg.

Single magnetic domain Terfenol-D microstructures with passivating oxide layer

Studies on giant magnetostrictive intermetallic compound Tb0.3Dy0.7 Fe1.92 (Terfenol-D) thin films are gaining increasing attention due to the interest in small scale magnetic structures. In this work, polycrystalline Terfenol-D thin films (60 nm) are produced using a Direct Current (DC) magnetron sputtering process and a hybrid thermal annealing approach, i.e. substrate heating and post-annealing. The crystallized Terfenol-D films are micropatterned (3 μm and 20 μm diameters) using a photolithographic method followed by Argon etching. The continuous and micropatterned thin films are characterized with XRD, SQUID and MOKE magnetometers showing properties similar to bulk polycrystalline Terfenol-D. Additional studies are conducted using X-ray absorption spectroscopy and the X-ray magnetic circular dichroism to investigate oxidation. Results show that while the top surface of these Terfenol-D structures are capped with Ta thin films, the side walls of the structures are exposed to ambient atmosphere raising the concern of oxidation issues. This work shows that a passivating oxide layer forms on the side walls of these small-scale Terfenol-D disks which is attributed to both the Ta capping layer as well as residual stresses preventing continued stress corrosion cracking caused by the oxidation process.

PdNi/N-doped graphene aerogel with over wide potential activity for formic acid electrooxidation

Anti-CO poisoning ability is significant in formic acid oxidation in the fuel cell technique. Herein, PdNi alloy supported on N-doped graphene aerogel (PdNi/GA-N) was found to have catalytic ability toward formic acid electrooxidation over a wide potential range because of the improved anti-CO poisoning ability. This catalyst was fabricated by simple freeze-drying of mixture solution of graphene aerogel, polyvinylpyrrolidone, Pd2+ and Ni2+ and the subsequent thermal annealing reduction approach in the N2/H2 atmosphere. Pd–Ni alloy particles anchored over the folding N-doped graphene surface with a porous hierarchical architecture structure in the 3D directions. It showed the catalytic performance of its maximum mass activity of 836 mA mg−1 in a broad potential range (0.2–0.6 V) for formic acid oxidation. The CO stripping experiment demonstrated its largely improved anti-CO poisoning ability with the peak potential of 0.67 V, approximately 60 and 40 mV less compared to those of Pd/GA-N and Pd/C samples. The high anti-CO poisoning ability and strong electronic effect resulting from the interaction between the 3D GA-N support and the Pd–Ni alloy makes it a promising catalyst for application in direct formic acid fuel cells.

Identification and Analysis of Key Parameters for the Ossification on Particle Functionalized Composites Hydrogel Materials.

Developing materials for tissue engineering and studying the mechanisms of cell adhesion is a complex and multifactor process that needs analysis using physical chemistry and biology. The major challenge is the labor-intensive data mining as well as requirements of the number of advanced techniques. For example, hydrogel-based biomaterials with cell-binding sites, tunable mechanical properties, and complex architectures have emerged as a powerful tool to control cell adhesion and proliferation for tissue engineering. Composite hydrogels could be used for bone tissue regeneration, but they exhibit poor ossification properties. In current work, we have designed new osteoinductive gellan gum hydrogels by a thermal annealing approach and consequently functionalized them with Ca/Mg carbonate submicron particles. Determination of key parameters, which influence a successful hydroxyapatite generation, was done via the principal component analysis of 18 parameters (Young's modulus of the hydrogel and particles, particle size, and mass) and cell behavior at various time points (like viability, numbers of the cells, rate of alkaline phosphatase production, and cells area) obtained by characterizing such composite hydrogel. It is determined that the particles size and concentration of calcium ions have a dominant effect on the hydroxyapatite formation, because of providing local areas with a high Young's modulus in a hydrogel, a desirable property for cell adhesion. The detailed analysis presented here allows identifying hydrogels for cell growth applications, while on the other hand, material properties can be predicted, and their overall number can be minimized leading to efficient optimization of bone reconstruction and other cell growth applications.

Anchoring of gold nanoparticles into aligned TiO2 nanotube: Improved supercapacitive performance

Firmly anchored Au nanoparticles onto well-defined architecture of aligned TiO2 nanotube grown on Titanium substrate leads to the improved pseudocapacitive electrochemical performance in aqueous electrolyte. The electrode architecture of Au anchored TiO2 nanotubes have been grown through anodization and thermal annealing approach. Cyclic voltammetry, charge–discharge and electrochemical impedance performed through three electrode configuration proven that the coating of Au nanoparticles onto TiO2 remarkably enhance the supercapacitive performance compared to bare one. The remarkable specific capacitance of 876 Fg−1 at 5 mVs−1 scan rate in 1 M LiClO4 electrolyte for the gold nanoparticles anchored TiO2 composite electrode.

Heterogeneous catalytic degradation of organic pollutants by peroxymonosulfate activated with nitrogen doped graphene oxide loaded CuFe2O4

Nitrogen doped graphene oxide loaded CuFe2O4 nanoparticles (CuFe2O4-NG) catalyst was successfully synthesized by thermal annealing and hydrothermal reaction approaches for degrading organic pollutants by peroxymonosulfate (PMS) activation. CuFe2O4-NG exhibited superior degradation efficiency toward orange II among GO, NG, CuFe2O4 and CuFe2O4-NG. The obtained catalysts were systemically characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Raman spectrum analysis and X-ray photoelectron spectroscopy to understand the relationship between inner structure and catalytic activity. It can recognize the key reactive oxygen species including SO4•–, •OH, O2•– and 1O2 in CuFe2O4-NG/PMS degradation system by electron paramagnetic resonance and free radical quenching studies, indicating the existence of both radical pathway and non-radical pathway. Based on the valence state changes of Cu and Fe in XPS spectra, the redox cycles between Fe(III) and Fe(II), Cu(II) and Cu(I) mediated by HSO5– contributed to the production of SO4•–, •OH and O2•–. Carbonyl groups and ketonic groups on the catalyst could promote the self-decomposition of PMS, leading to the generation of 1O2. The synergistic effect between NG and CuFe2O4 can accelerate the activation of PMS and pose the new insight for organic pollutants removal.

Economic procedure for facile and eco-friendly reduction of graphene oxide by plant extracts; a comparison and property investigation

Hummer’s method which uses concentrated acid and oxidant agents, still is the most productive procedure for production of graphene oxide (GO). However, the reduction of the prepared GO sheets to the reduced graphene oxide (rGO) is the main problem for practical applications. However, the main problem is that prepared GO needs to reduce to graphene for practical applications. Some of the industries where graphene is making an important impact as follows; transport, medicine, electronics, energy, defense and desalination. Conventional methods for reduction of GO, such as thermal annealing or chemical approaches, have been applied frequently. However, they have drawbacks, such as toxic nature of them, their high prices and harmful effects to both environment and human body that make their use undesirable. Here we proposed and tested a green approach including plant extracts for a satisfying reduction of GO to reduced graphene oxide (r-GO) which leads to removing of oxygen containing functional groups. The extracts of Mentha (or Mint) and Tribulus terrestris indicated the moderate antioxidant activities in 2,2-diphenyl-1-picrylhydrazyl (DPPH) test (IC50 = 28 and 33 ppm respectively). After reduction GO by mentioned extracts, the products characterized by XRD, FT-IR, SEM, TEM, Raman and TGA analysis. The obtained results represented that the interaction between GO and Mint extract leads to more efficient reduction of GO in compare to Tribulus terrestris extract. More investigation of Mint extract reduction potential was performed by reducing of GO and Fe3+ ions using Mint extract in the synthesis of rGO/Fe3O4. VSM analysis was a good evidence for suitable reduction of Fe ions and GO, which produced rGO/Fe3O4 nanocomposite with superparamagnetic property.