그래핀 산화물(GO), 폴리에틸렌 글리콜 다이아크릴레이트(PEGDA), 폴리에틸렌 글리콜 메틸 에터 아크릴레이트 (PEGMEA)의 나노복합체를 자외선 광중합을 통해 합성하였다. GO는 가교된 폴리에틸렌 옥사이드(XPEO) 매트릭스 내에 최 대 1.0 wt% 농도까지 균일하게 분산시켰다. 더 높은 농도에서는 GO가 응집되는 경향을 보였다. 잘 분산된 GO는 친수성 PEO 사슬과 추가적인 화학적 가교 네트워크를 형성했다. XPEO-GO 나노복합체는 GO 농도에 따라 기계적 강도 및 염과 가 스에 대한 차단 특성이 향상된 것으로 나타났다. 이 연구는 다양한 GO 농도와 플레이크 크기를 가진 XPEO-GO 하이드로겔 의 제조 및 특성화를 다루고 있다. 이러한 특성은 나노복합 하이드로겔이 강화된 XPEO 기반 바이오소재 및 고급 항균성 한 외여과(UF) 친수성 코팅에서의 잠재적 응용 가능성을 시사한다.

비록 산화 그래핀의 비표면적은 환원된 산화 그래핀에 비해 낮지만, 산화 그래핀의 이산화탄소 흡착량은 기존 그 래핀 또는 환원된 산화 그래핀에 비해 많다. Lerf-Klinowski 모델에 따르면, 산화 그래핀은 가장 자리와 면 내부에 수산화기, 에폭시드, 카보닐, 카복실기 등이 있으며, 이러한 작용기가 이산화탄소 분자와 강하게 결합하여 화학 흡착을 유도한다. 본 연 구에서는 산소 플라즈마/UV 오존 및 열처리를 통해 그래핀 산화물의 산소 함량과 이산화탄소 흡착 친화도 사이의 상관관계 를 탐구하였다. 산소 함량의 변화는 XPS와 FT-IR 분석을 통해 확인하였다. 흥미롭게도 산화 그래핀의 이산화탄소 흡착 경향 은 전체 산소 함량과 정비례하지 않았다. 반면, XPS 분석 결과 산화 그래핀의 카보닐 작용기가 이산화탄소 흡착에 중요한 기 여를 하는 것으로 나타났다. 이러한 연구 결과는 산화 그래핀의 특성 및 이를 활용한 탄소 포집 및 가스 저장 응용 가능성에 대한 통찰을 제공한다.

Transition metal oxide-based materials have mainly been studied as electrodes for energy storage devices designed to meet essential energy demands. Among transition metal oxide-based materials, hydrated vanadium pentoxide (V2O5 ‧ nH2O), a vanadium oxide material, has demonstrated great electrochemical performance in the electrodes of energy storage devices. Graphene oxide (GO), a carbon-based material with high surface area and high electrical conductivity, has been added to V2O5 ‧ nH2O to compensate for its low electrical conductivity and structural instability. Here, V2O5 ‧ nH2O/GO nanobelts are manufactured with water without adding acid to ensure that the GO is uniformly dispersed, using a microwave-assisted hydrothermal synthesis. The resulting V2O5 ‧ nH2O/GO nanobelts exhibited a high specific capacitance of 206 F/g and more stable cycling performance than V2O5 ‧ nH2O without GO. The drying conditions of the carbon paper electrodes also resulted in more stable cycling performance when conducted at high vacuum and high temperature, compared with low vacuum and room temperature conditions. The improvement in electrochemical performance due to the addition of GO and the drying conditions of carbon paper electrodes indicate their great potential value as electrodes in energy storage devices.

Molybdenum, valued for its high melting point and exceptional physical and chemical properties, is studied in diverse fields such as electronics, petrochemicals, and aviation. Among molybdenum oxides, molybdenum dioxide stands out for its higher electrical conductivity than other transition metal oxides due to its structural characteristics, exhibiting metallic properties. It is applied as pellets to gas sensors, semiconductors, and secondary batteries for its properties. Thus, research on molybdenum dioxide compaction and pressureless sintering is necessary, yet research on pressureless sintering is currently insufficient. This study synthesized MoO₃ powder via solution combustion synthesis and reduced it using the 3% hydrogen/argon gas mixture to investigate the effect of reduction temperature on the powder. Additionally, the reduced powder was compacted and subjected to pressureless sintering with temperature as a variable. The density and the microstructure of brown parts were analyzed and discussed.

Copper, silver, and gold-reduced graphene oxide nanocomposite (Cu-rGO, Ag-rGO, and Au-rGO) were fabricated via the hydrothermal method, which shows unique physiochemical properties. Environment friendly electromagnetic radiation was employed to synthesize rGO from GO. The nonlinear optical phenomenon of noble metal decorated rGO is predominantly due to excited state absorption, which arises from surface plasmon resonance and increases in defects at the surface due to Cu, Ag, and Au incorporation. It is found that the third-order nonlinear absorption coefficient was in the order of 10− 10 m/W, with notable enhancements in the third-order properties of Au-rGO compared to other nanocomposites and their respective counterparts. Functionalizing rGO induces defect states ( sp3), increasing NLO response. Cu, Ag, and Au exhibit higher Surface-Enhanced Raman Scattering (SERS) activity due to rGO-induced structural modifications. SERS signals are influenced by dominant signals from Au nanorods. The electronic structures for pure and doped rGO were investigated through Density Functional Theory (DFT). The computed partial density of states (PDOS) confirms the enhancement of the state in Au-doped rGO is due to the charge transference from Au to C 2p orbital. The optical absorption spectra and PDOS reveal the possibility of free carrier absorption enhancement in Au which validates experimentally observed higher two-photon absorption (β) value of Au-doped rGO. The tuning of nonlinear optical and SERS behaviour with variation in the noble metal upon rGO provides an easy way to attain tuneable properties which are exceedingly required in both optoelectronics and photonics applications.

Artificial photosynthesis harnesses clean and sustainable solar power to catalyze the conversion of CO2 and H2O molecules into valuable chemicals and O2. This sustainable approach combines energy conversion with environmental pollution control. Non-oxide photocatalysts with broad visible-light absorption and suitable band structures, hold immense potential for CO2 conversion. Nevertheless, they still face numerous challenges in practical applications, particularly in CO2 conversion with H2O. Surface modification and functionalization play the significant role in improving the activity of non-oxide photocatalysts. Multifarious strategies, such as cocatalyst loading, surface regulation, doping engineering, and heterostructure construction, have been explored to optimize light harvesting, bandgap driving force, electron–hole pairs separation/transfer, CO2 adsorption, activation, and catalysis processes. This review summarizes recent progress in surface modification strategies for non-oxide photocatalysts and discusses their enhancement mechanisms for efficient CO2 conversion. These insights are expected to guide the design of high-performance non-oxide photocatalyst systems.

We report a new route of akaganéite (β-FeOOH) formation and maghemite (γ-Fe2O3) formation. Akaganéite can be produced by stirring Fe2+ at room temperature for a day under mild conditions. We used FeCl2 ·4H2O as the precursor and mixed it with the Na-rich particle from the oxidation debris solution. The role of the concentration ratio between graphene oxide (GO) and NaOH was addressed to generate oxidation debris (OD) on the surface. In particular, the characterization of OD by transmission electron microscope (TEM) imaging provides clear evidence for the crystal formation of Na-rich particle under electron beam irradiation. For the base treatment process, increasing the concentration of a NaOH in Na-rich solution contributed primarily to the formation of γ-Fe2O3. The characterization by scanning electron microscope (SEM) and TEM showed that the morphology was changed from needle-like to small-oval form. In addition, β-FeOOH can be effectively produced directly using GO combined with FeCl2 ·4H2O at room temperature. More specifically, the role of parent material (Hummer's GO and Brodie's GO) was discussed, and the crystal transformation was identified. Our results concluded that β-FeOOH can be formed in basic and acidic conditions.

The structure and magnetic properties of composite powders prepared by ball milling a mixture of Fe2O3 ‧ (0.4-1.0)Fe were investigated. Hysteresis loops and differential scanning calorimetry (DSC) curves are used to characterize the materials and to examine the effect of the solid state reaction induced by ball milling. The results showed that a solid state reaction in Fe2O3 ‧ (0.4-1.0)Fe clearly proceeds after only 1 h of ball milling. The system is characterized by a positive reaction heat of +2.23 kcal/mole. The diffraction lines related to Fe2O3 and Fe disappeared after 1 h of ball milling and, instead, diffraction lines of the intermediate phase of Fe3O4 plus FeO formed. The magnetization and coercivity of the Fe2O3 ‧ 0.8Fe powders were changed by the solid state reaction process of Fe2O3 by Fe during ball milling. The coercivity of the Fe2O3 ‧ 0.8Fe powders increased with increasing milling time and reached a maximum value of 340 Oe after 5 h of ball milling. This indicates the grain size of Fe3O4 was clearly reduced during ball milling. The magnetic properties of the annealed powders depend on the amount of magnetic Fe and Fe3O4 phases.

Despite enormous popularity of graphene oxide (GO) several open questions remain regarding the structure and properties of this material. One of those questions is the role of a graphite precursor on the properties of GO product. In this study, we investigate the oxidation process and the structure of GO products, made from the four different graphite precursors: synthetic graphite, two natural flaky graphites, and expanded graphite. The highest rate of the oxidation reaction was registered for the small particle size synthetic graphite. Thermal expansion of natural flaky graphite did not significantly affect the rate of the reaction. The nature of the graphite precursor does not notably affect the chemical composition of the synthesized GO products. However, it affects stability of respective aqueous dispersions. The solutions of the three GO samples, prepared from the natural graphite sources demonstrate excellent stability due to complete exfoliation of GO to single-atomic-layer sheets. GO from synthetic graphite forms unstable dispersions due to the presence of numerous multi-layered particles. This, in turn, is explained by the presence of not fully graphitized, amorphous inclusions in synthetic graphite. Our observations suggest that synthetic graphite should not be used as GO precursor when the ability to completely exfoliate and the stability of dispersions are critical for intended applications.

In this study, laser-induced graphene oxide (LIGO) was synthesized through a facile liquid-based process involving the introduction of deionized (DI) water onto polyimide (PI) film and subsequent direct laser irradiation using a CO2 laser (λ = 10.6 μm). The synthesized LIGO was then evaluated as a sensing material for monitoring changes in humidity levels. The synthesis conditions were optimized by precisely controlling the laser scribing speed, leading to the synthesis of LIGO with different structural characteristics and varying oxygen contents. The increased number of oxygen-containing functional groups contributed to the hydrophilic properties of LIGO, resulting in a superior humidity sensing capabilities compared with laser-induced graphene (LIG). The LIGO-based sensors outperformed LIG-based sensors, demonstrating approximately tenfold higher sensing responsivity when detecting changes at each humidity level, along with 1.25 to 1.75 times faster response/recovery times, making LIGO-based sensors more promising for humidity-monitoring applications. This study demonstrated laser ablation in a renewable and natural precursor as an eco-friendly and energy-efficient approach to directly synthesize LIGO with controllable oxidation levels.