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The oxygen evolution reaction (OER) underpins many aspects of energy storage and conversion in modern industry and technology, but which still be suffering from the dilemma of sluggish reaction kinetics and poor electrochemical performance. Different from the viewpoint of nanostructuring, this work focuses on an intriguing dynamic orbital hybridization approach to renormalize the disordering spin configuration in porous noble-metal–free metal–organic frameworks (MOFs) to accelerate the spin-dependent reaction kinetics in OER. Herein, we propose an extraordinary super-exchange interaction to reconfigure the domain direction of spin nets at porous MOFs through temporarily bonding with dynamic magnetic ions in electrolytes under alternating electromagnetic field stimulation, in which the spin renormalization from disordering low-spin state to high-spin state facilitates rapid water dissociation and optimal carrier migration, leading to a spin-dependent reaction pathway. Therefore, the spin-renormalized MOFs demonstrate a mass activity of 2,095.1 A g metal −1 at an overpotential of 0.33 V, which is about 5.9 time of pristine ones. Our findings provide a insight into reconfiguring spin-related catalysts with ordering domain directions to accelerate the oxygen reaction kinetics.

Accompanied by internal defect evolution in the perovskite lattice, the naturally formed “hollow” defects and obviously blue-shifted emission of CsEuCl3 nanocrystals were observed.

Mn4+-activated phosphors have become a hotspot in the development of inorganic red phosphors due to the fascinating photoluminescent properties. Herein, the synergetic manipulation of the flux effect and charge compensation was employed to improve the performance of Mn4+-activated CaAl12O19 red phosphors. The crystallinity was improved by appropriate Zn2+-doping, while nonradiative transition between Mn4+ ions is reduced by charge compensation of the formation of Mn4+–Mg2+ pairs with Mg2+ dopants. Thus, the emission of Mn4+-activated CaAl12O19 red phosphors has been remarkably enhanced. The low probability of nonradiative transition between Mn4+ ions was demonstrated by the thermal stability analysis. To depict the luminescent process, the crystal-field strength (Dq), and Racah parameters (B and C) were calculated to determine the sequence of the energy levels. Meanwhile, the warm WLEDs with high CRI and low CCT were obtained using the prepared phosphors as red-emitting composition. Our results clearly suggested that the synergetic strategy by combining the flux effect and charge compensation is an effective method to enhance the luminescence of CaAl12O19:Mn4+, and CaAl12O19:Mn4+/Zn2+/Mg2+ red-emitting phosphors, which have potential application value in warm WLEDs.

In this work, a dual p-n heterojunction of Cu2O/Ni(OH)2/TiO2 with type-II band alignment and matched build-in electric field was fabricated. This dual p-n heterojunction promoted the separation and transfer of charge carriers, which is much more efficient than individual p-n heterojunction. Photocatalytic hydrogen evolution under the simulated sunlight shows a high rate of 6145 μmol g−1 h−1 for Cu2O/Ni(OH)2/TiO2, which is 1.9 and 2.7 times that of Ni(OH)2/TiO2 and Cu2O/TiO2, respectively. The apparent quantum yield of Cu2O/Ni(OH)2/TiO2 is about 20.2% under the irradiation of monochromatic light (λ = 420 nm). The recycling test of hydrogen evolution also verified a high stability for this dual heterojunction. The type-II band alignment and matched build-in electric field was confirmed, which accelerate the migration of charge carriers. The width of space-charge layer was calculated and proved that the p-n junctions in Cu2O/Ni(OH)2/TiO2 are fully-depleted, which largely reduced the bulk recombination of charge carriers. The synergistic effect of the improved visible-light response, type-II band alignment, matched build-in electric field, and fully-depleted space-charge layer contributes to the enhanced photocatalytic hydrogen evolution.

To research and develop the potential red emission phosphors for warm white-light-emitting diodes (WLED), we systematically investigated double alkaline rare-earth molybdates KGd1−xEux(MoO4)2 (0.05 ≤ x ≤ 1) phosphors. The crystal structure, morphology, chemical composition, and photoluminescence properties of the phosphors with different Eu3+ doping concentrations were investigated in detail. The results indicate that Eu3+ doping concentration can affect the crystal structure and morphology of KGd1−xEux(MoO4)2 phosphors. The luminescence performance reveals that KGd1−xEux(MoO4)2 phosphor could emit intense red emission under multiplexed excitations at 362, 382, 394, 465, and 535 nm, which are matched well with the commercial UV, blue and green LED chips. An abnormal quenching behavior was observed in the KGd1−xEux(MoO4)2 phosphors. And the quenching behavior at the excitation of Eu3+–O2− Charge-Transfer band and Eu3+ ions 4f–4f transitions is quite different. Finally, we fabricated a WLED lamp by coating the InGaN blue chip with a mixture of YAG: Ce3+ yellow phosphors and KEu(MoO4)2 red phosphors. The obtained WLED lamps showed warm white light with a lower CCT value (~ 5142 K) than that fabricated without the red phosphors (CCT = 5892 K). These results proved that the KGd1−xEux(MoO4)2 could be a very promising red-emitting phosphor for WLED.

Lead-free Bi4Ti3O12/NiFe2O4 nanocomposite films have been prepared via sol-gel spin-coating route. The successful phase formation of orthorhombic Bi4Ti3O12 and cubic NiFe2O4 has been confirmed using x-ray diffraction without any detectable extra phase. The scanning electron microscopy with EDS measurement reveals homogeneous and dense growth of both phases accompanied by clear interface between the two layers. The loop of magnetization versus magnetic field indicates the ferromagnetic properties at room temperature with saturation magnetization of ~257.48 emu/cm3, coercive field of ~121 Oe and remnant magnetization of ~57.03 emu/cm3. Room-temperature ferroelectric behavior is also obtained along with the good fatigue endurance properties and low leakage current density. The frequency dependence of dielectric constant displays the monotonous decreasing tendency with low dielectric loss. Moreover, evident magnetodielectric behavior is achieved in the nanocomposite films at room temperature. The coexistence of ferromagnetic and ferroelectric behavior including the appearance of magnetodielectric effect proves the room-temperature multiferroic properties in Bi4Ti3O12/NiFe2O4 nanocomposite films, which makes the films meaningful as the lead-free multiferroic systems for device applications at room temperature.

Intergrowth ceramic series Bi4Ti3O12/Bi4.5Na0.5Ti4O15 have been prepared through solid state reaction. X-ray diffraction analysis shows the coexistence of Bi4Ti3O12 and Bi4.5Na0.5Ti4O15 phases with slight lattice distortion. Scanning electron micrographs present the growth of grains and grain boundaries with different contents of Bi4.5Na0.5Ti4O15. The relaxation dielectric properties of the ceramics have been observed. The room-temperature dielectric constant at 100 Hz is initially increased and then decreased with the increase of Bi4.5Na0.5Ti4O15. The impedance spectroscopy and the electrical modulus are also measured for explaining the dielectric behavior. The Nyquist plots display different semicircle arcs at 300 and 600 K. The imaginary part of electrical modulus has two peaks in the range of the measuring temperature. They prove the common influence of grains and grain boundaries on the dielectric properties. For further fitting the experimental data by Arrhenius theory, activation energy is obtained for grains and grain boundaries. Finally, the relaxor dielectric properties are attributed to the competition mechanism from the different growth situation of grains and grain boundaries with increasing Bi4.5Na0.5Ti4O15. Therefore, this kind of ceramics ought to be promising candidates for multifunctional device applications.

Synergistic the modulation of photon absorption capability and interfacial charge transfer of the photocatalyst are highly required for developing high-performance heterojunction photocatalysts. The ternary CdS-graphene quantum dots-titanate nanotubes (CdS-GQDs-TNTs) nanocomposite have been prepared by an in situ growth method. The physicochemical characterization reveals that the GQDs are firmly decorated on both inner and outer surface of TNT through the formation of Ti–O–C chemical bonding, and CdS QDs are loaded on the outer surface of TNTs through strong interfacial interaction. The intimate integrated CdS-GQDs-TNTs nanocomposite exhibits much superior photocatalytic performance toward H2 production compared with binary GQDs-TNTs and pure TNTs photocatalyst, which can be attributed to the combined interaction of the stronger visible light harvesting, the longer lifetime of photogenerated electron−hole pairs, faster interfacial charge transfer rate, fast and long-distance electron transport pass. The interfacial charge transfer mechanism of CdS-GQDs-TNTs ternary composite are proposed based on photoelectrochemical measurements.

Black-phase formamide lead iodide (α-FAPbI3), considered one of the most important materials for a solar cell application, is generally poorly stable in air, which leads to not only the inability of photovoltaic devices but also the lack of its fundamental optics research. In this paper, we synthesized a stable α-FAPbI3 film by modifying a previously reported method and investigated its temperature- and excitation intensity-dependent photoluminescences (PLs). It is found that at low temperatures, the crystal phase competition process is unusually complicated and out of order. The temperature range of the biphasic coexistence is at least 30 K, and during this process, the PL intensity of either the high-temperature phase (cubic) or low-temperature phase (tetragonal) changes chaotically. After the complete transition to the tetragonal phase, compared with the cubic monophase, PL resulting from the crystal defects is obviously enhanced. Our findings provide a deeper understanding of the complex structural phase transition of halide perovskite and valuable insights into the fundamental optics of α-FAPbI3.

Crystal structure, morphology, magnetic, and dielectric properties of (1 − x)Bi2Fe4O9–xMgFe2O4 bicomponent ceramics are investigated in detail. The material has been synthesized via sol–gel method. Analysis of X-ray diffraction data of the bicomponent ceramics shows the coexistence of orthorhombic Bi2Fe4O9 and spinel MgFe2O4 phases with no third phase. Microstructural and surface morphology displays the homogeneous grain distribution with different grain sizes of Bi2Fe4O9 and MgFe2O4. The magnetic measurement shows decreasing coercivity and increasing values of remnant and saturation magnetization with the increase in MgFe2O4. Temperature-dependent dielectric properties and electrical modulus are conducted in the temperature range of 27–527 °C with the frequency ranging from 1 to 30 kHz. Two abnormal peaks are, respectively, observed at low and high temperature ranges. The variation of electric properties is closely related to the composition of MgFe2O4. The results of dielectric and electrical modulus indicate the appearance of dielectric relaxation in (1 − x)Bi2Fe4O9–xMgFe2O4. Combined with the study of activation energy, the dielectric relaxation is mainly induced by different electric responses of various charge carriers intrinsically dominating in a thermally activated process with the incorporation of MgFe2O4. The combination of Bi2Fe4O9 and MgFe2O4 enhances the coexistence of magnetic and electric properties in the present composites. It is quite promising from application point of view.

Exchange bias behaviors up to room temperature have been observed in NiCo2O4/NiO nanoparticle system. The field-cooled magnetic hysteresis loops exhibit shifts both in the field and magnetization axes simultaneously. The variation of exchange bias field and magnetization shift depends strongly on the measuring temperature. In addition, the dependence of exchange bias effect on measuring temperature is not monotonous, which is reflected in the different tendency during the decrease process of magnetization shift and exchange bias field. The exchange bias field is decreased firstly at the range of 10–50 K followed by an increase of 50–200 K and decreased again of 200–320 K. By analyzing various magnetic measurements, the special exchange bias effect in NiCo2O4/NiO can be owing to the spin glass state and the ferrimagnetic/antiferromagnetic coupling during different temperature ranges.

Epitaxial PbTiO3 films with a smooth and dense surface were fabricated by a promising hydrothermal synthesis on an Nb:SrTiO3(100) substrate. The resulting coated substrate was used to fabricate a Pt/PbTiO3/Nb:SrTiO3 heterostructure device. The device exhibited a multilevel storage capacity with an appropriate R OFF / R ON ratio and excellent endurance and retention. An electric conduction analysis indicated that the resistive switching behavior of the device was attributed to the trap controlled space-charge-limited current conduction that was caused by the oxygen vacancies in the PbTiO3 hydrothermal films. The modulation of the Pt/PbTiO3 Schottky-like junction depletion under an applied electric field is thought to be responsible for the resistive switching behavior of the device in the carrier injection-trapped/detrapped process.

The polycrystalline xBi0.5Na0.5TiO3-(1-x)NiFe2O4 solid solutions with different ratios have been synthesized by sol-gel method. The samples are respectively annealed with nonmagnetic and magnetic field annealing processes. X-ray diffraction patterns present the pure formation with coexistence of Bi0.5Na0.5TiO3 and NiFe2O4 phases. Micrographs measured with scanning electron microscope show the dense surface morphology. Evident enhancement in electric polarization and magnetoelectric coupling coefficient is observed with magnetic field annealing. As the content of Bi0.5Na0.5TiO3 increases, magnetoelectric effect is most prominent at the ratio of x = 0.7 with magnetic field annealing. These results indicate the successful influence on room-temperature magnetoelectric coupling effect by magnetic field annealing.

The large number of energy levels available to lanthanide ions makes the emission mechanism of lanthanide-doped luminescent materials extremely complicated. Herein, we focus on the discussion and analysis of luminescence manipulation in Gd2O3:Yb3+/Er3+ nanocrystals and systematically investigate ion-ion interaction–induced energy transfer in up- and downconversion processes to shed light on the manipulation mechanism, showing that the luminescence of the above nanocrystals can be controlled by varying the content of Yb3+. Based on Dexter's energy transfer theory and the fact that excitation of Er3+ ions results in the appearance of emission attributed to the 2F5/2→2F7/2 transition of Yb3+ in the near-infrared region (950–1100 nm), this behavior is ascribed to the occurrence of energy transfer from Er3+ to Yb3+.

The 0.7(Bi 0.5 Na 0.5 ) 1- x Ba x TiO 3 -0.3NiFe 2 O 4 samples ( x = 0.02–0.12) have been synthesized through sol-gel method. Structure, micromorphology and the room-temperature multiferroic properties have been investigated, respectively. The characterization of structure and micromorphology reveals the coexistence of two different phases. In addition, lattice deformation and morphology variation can be clearly confirmed with doping Ba ions. Dielectric properties are improved evidently from x = 0.02–0.08 and then weakened from x = 0.08–0.12 with enough low values of dielectric loss for all the samples. The ferroelectric polarization demonstrates that room-temperature ferroelectric properties are monotonously enhanced with increasing content of Ba. The change tendency of magnetic properties is firstly decreasing and then increasing with the special content value of x = 0.08. Room-temperature magnetoelectric coupling effect is verified by the measurement of magnetoelectric coupling coefficient. The variation trend of magnetoelectric coupling coefficient with doping of Ba is similar to that of magnetic properties. The room-temperature multiferroic properties of 0.7(Bi 0.5 Na 0.5 ) 1- x Ba x TiO 3 -0.3NiFe 2 O 4 samples are related to the larger ionic radius of Ba. Furthermore, the special multiferroic behavior with x = 0.08 can be attributed to the morphotropic phase boundary effect with doping Ba.

Tailoring the band gap and understanding the underlying mechanism are important for extending the applications of graphene quantum dots in optoelectronics. In this work, we synthesize fluorinated graphene oxide quantum dots (F-GOQDs) through a photochemical method, and study their optical properties. The obtained F-GOQDs exhibit a maximal blue-shift of photoluminescence (PL) emission of ca. 77 nm compared to that of the graphene oxide quantum dots (GOQDs). The PL shift results from the substitution of the hydroxyls and carbonyls groups with fluorine during the fluorination process, which can tune the band gap of the GOQDs. Density functional theory (DFT) calculations support our proposed mechanism for band gap tuning in the GOQDs through the use of fluorination.

Light-modulated lead-free perovskites-based memristors, combining photoresponse and memory, are promising as multifunctional devices. In this work, lead-free double perovskite Cs2AgBiBr6 films with dense surfaces and uniform grains were prepared by the low-temperature sol-gel method on indium tin oxide (ITO) substrates. A memory device based on a lead-free double perovskite Cs2AgBiBr6 film, Pt/Cs2AgBiBr6/ITO/glass, presents obvious bipolar resistive switching behavior. The ROFF/RON ratio under 445 nm wavelength light illumination is ~100 times greater than that in darkness. A long retention capability (&gt, 2400 s) and cycle-to-cycle consistency (&gt, 500 times) were observed in this device under light illumination. The resistive switching behavior is primarily attributed to the trap-controlled space-charge-limited current mechanism caused by bromine vacancies in the Cs2AgBiBr6 medium layer. Light modulates resistive states by regulating the condition of photo-generated carriers and changing the Schottky-like barrier of the Pt/Cs2AgBiBr6 interface under bias voltage sweeping.

High-quality CH3NH3PbI 3−xClx (MAPIC) films were prepared using potassium chloride (KCl) as an additive on indium tin oxide (ITO)-coated glass substrates using a simple one-step and low-temperature solution reaction. The Au/KCl-MAPIC/ITO/glass devices exhibited obvious multilevel resistive switching behavior, moderate endurance, and good retention performance. Electrical conduction analysis indicated that the resistive switching behavior of the KCl-doped MAPIC films was primarily attributed to the trap-controlled space-charge-limited current conduction that was caused by the iodine vacancies in the films. Moreover, the modulations of the barrier in the Au/KCl-MAPIC interface under bias voltages were thought to be responsible for the resistive switching in the carrier injection trapping/detrapping process.

Additional file 1 Supporting Information.

Correction for ‘Enhanced photoluminescence stability and internal defect evolution of the all-inorganic lead-free CsEuCl3 perovskite nanocrystals’ by Yalei Gao et al., Phys. Chem. Chem. Phys., 2022, 24, 18860–18867, https://doi.org/10.1039/D2CP01374F.

Materials with tunable photoluminescence (PL) are highly desirable. It can lead to important applications such as photodetectors, bio-imaging, and broadband modulators. In this work, nitrogen-doped graphene oxide quantum dots (NGOQDs) were synthesized by hydrothermal method. The microstructures as well as optical properties of NGOQDs were studied. The as-prepared NGOQDs present tunable PL and exhibit a maximal PL blue-shift of ca. 88 nm compared to that of the graphene oxide quantum dots (GOQDs). The observed PL blue-shift of the NGOQDs is attributed to the high content of pyridine-like and pyrrolic-like nitrogen atoms doping in the NGOQDs. Our proposed mechanism for the PL blue-shift of the NGOQDs is supported by density functional theory (DFT) calculations.

To research and develop potential multifunctional nanoprobes for biological application, lanthanide-doped MCM-41 (Ln-MCM-41, Ln = Gd/Eu) silica nanoparticles with excellent pore structure and optical–magnetic properties were synthesized via a facile and economical sol–gel method. The microstructure and pore distribution of Ln-MCM-41 nanoparticles were obviously affected by the Ln-doping. As the Ln/Si mole ratio increased, the specific surface area and total pore volume of Ln-MCM-41 nanoparticles rapidly decreased. However, the Ln-MCM-41 nanoparticles still retained the typical well-ordered mesoporous structure, and exhibited excellent drug release behavior. Moreover, the drug release rate of Ln-MCM-41 was remarkably pH-dependent and increased gradually upon decreasing pH. Additionally, these nanoparticles also exhibit considerable photoluminescence properties, living cells photoluminescence imaging in vitro, and paramagnetism behavior at room temperature due to the Ln3+-ions doping. Our research shows the possibility of our Ln-MCM-41 nanoparticles as multifunctional nanoprobes for application in bioseparation, bioimaging, and drug delivery.

As an ultrathin transport layer, graphene-based materials play an increasingly important role in perovskite optoelectronics. Full comprehension of the carrier transfer process between them is of great significance, however, seldom attention has been paid to how the carrier transfer, from graphene derivative to perovskite, affects the physical property of perovskite. Here, we report that CsPbBr3 and CsPbI3 QDs produce a Burstein-Moss type photoluminescence (PL) blueshift arisen from the electron transfer from graphene oxide (GO), and in CsPbI3 QDs this effect is highly notable, ~50 meV. Such results indicate that perovskite QDs is highly optically sensitive to the electron injection, and quite promising in optoelectronic modulator applications.

Single phase NiCr2O4 has been successfully prepared by sol–gel technique. Characterization of crystal and morphology exhibits the tetragonal structure and homogeneous growth with regular crystalline shape. Large dielectric constant of ~2447 is observed at room temperature. The relaxation behavior below room temperature is confirmed through measurements of dielectric constant, dielectric loss, electric modulus and impedance depended on frequency or temperature. The analysis through equivalent circuit simulation demonstrates the influence of grains at low temperature and the common contribution of grains and grain boundaries at high temperature. Moreover, the change in dielectric response indicates the presence of magnetodielectric coupling effect. Two different mechanisms are considered to control the magnetodielectric coupling, yielding the positive and negative coupling coefficient at different temperature ranges. The intrinsic magnetoelectric coupling gives rise to the frequency independent magnetodielectric behavior at low temperature. As temperature increases above 150 K, the large magnetodielectric coupling coefficient depended on frequency is contributed by the Maxwell-Wagner effect. The negative value of magnetodielectric coupling coefficient is attributed to the leakage current. Therefore, both mechanisms of Maxwell-Wagner and leakage are competing as a function of frequency, which results in the coefficient crossover at room temperature. Such features bring NiCr2O4 a step closer to potential applications in areas such as magnetic field sensors, actuators and others.

Highly efficient H2 production from water splitting has been achieved by N-doped titanate nanotubes (N-TNTs) decorated with graphene quantum dots (GQDs) in this work. In order to promote charge carrier transmission at the interface, a facile and environmentally friendly in situ growth method was employed to construct a strongly coupled N-TNT/GQD composite photocatalyst. The results revealed that N atoms were effectively doped into the crystal lattice of the TNTs in the form of both interstitial N and substitutional N, and the GQDs were decorated onto both the inner and outer surfaces of the N-TNTs through the formation of Ti-O-C chemical bonds. Photoelectrochemical measurements proved that, in N-TNT/GQD composite, N-doping can extend light response to the visible-light range, and the coupling with GQDs not only enhanced visible-light absorption, but also promoted interfacial charge carrier transfer. Due to the synergistic effect between N-doping and GQD coupling, the closely integrated N-TNT/GQD composite exhibits a much superior photocatalytic H2 production performance under UV-vis irradiation, being 2.1 times higher than that of pure TNTs.

The adsorption and diffusion of F2 molecules on pristine graphene have been studied using first-principles calculations. For the diffusion of F2 from molecular state in gas phase to the dissociative adsorption state on graphene surface, a kinetic barrier is identified, which explains the inertness of graphene in molecular F2 at room temperature, and its reactivity with F2 at higher temperatures. Studies on the diffusion of F2 molecules on graphene surface determine the energy barriers along the optimal diffusion pathways, which help to understand the high stability of fluorographene., 15 pages, 5 figures, 2 tables

N-doped graphene oxide (NGO) thin film is synthesized by irradiation of graphene oxide (GO) thin film in NH 3 atmosphere. NGO thin film obtained by irradiation of GO thin film for 60 min has a high N-doping level of 12.69 at.%, and the amino-like N dominates the doping with the level of 7.90 at.%. The photoconductivity properties of NGO thin film under white-light illumination have been systematically examined. The results show that compared to reduced graphene oxide (rGO) thin film, NGO thin film exhibits significant photoconductivity enhancement with a high ratio of 2000%, and shows a faster photoresponse. The current responsivity and external quantum efficiency values for the NGO film reach ∼31 mA W −1 and ∼87% at 2 V, respectively. It may attribute to the high doping level of amino-like N on the basal plane and the pyridine-like N at the vacancy-site of graphene sheets, which can offer substantial photocarriers and the effective transfer to the electrodes.

Density functional theory calculations were used to study the structural, electronic, and magnetic properties of double-side partially fluorinated graphene. Both even and uneven fluorinated structures examined. It is found that midgap states and magnetic moments only appear in the uneven double-side fluorinated graphene. The magnetic moments mainly come from the carbon atoms at the edge of the fluorinated region in unevenly double-side fluorinated graphene. The dependence of magnetic moments on external tensile strain was also examined, which shows that the induced magnetic moments can be significantly increased by increasing the tensile strain.

A gram-scale approach has been developed to prepare highly pure graphene quantum dots (GQDs) from Vulcan XC-72 carbon black refluxed with concentrated nitric acid using a home-built experimental system. The weight of the GQDs is high, up to 1.2 g in each run with a yield of 75 wt%, and the purity is 99.96 wt%. The results show that the GQDs exhibit multicolor photoluminescence from green to light red under different excitation wavelengths.

Reduced graphene oxide–carbon nanotube (RGO–CNT) hybrid materials were prepared by a simple catalyst-free route. The thermostability, photoluminescence (PL) and electrical properties of RGO–CNTs were investigated systematically. The results revealed that compared to RGO, RGO–CNTs showed multicolor PL, and higher thermostability and conductivity. The RGO–CNTs therefore have important potential applications in the fields of photonic and electrical devices.

Inducing magnetic moments in graphene is very important for its potential application in spintronics. Introducing sp3-defects on the graphene basal plane is deemed as the most promising approach to produce magnetic graphene. However, its universal validity has not been very well verified experimentally. By functionalization of approximately pure amino groups on graphene basal plane, a spin-generalization efficiency of ~1 μB/100 NH2 was obtained for the first time, thus providing substantial evidence for the validity of inducing magnetic moments by sp3-defects. As well, amino groups provide another potential sp3-type candidate to prepare magnetic graphene.

N-doped graphene (NG) has been prepared by annealing reduced graphene oxide (RGO) in ammonia. The magnetic properties of RGO and NG have been studied. The results showed that doping RGO with N at a relatively low temperature (⩽600 °C) can increase its magnetization, and which can be increased by 64.1% at the annealing temperature of 500 °C.

Inducing robust magnetic moments on the basal plane of the graphene sheet is very difficult and is one of the greatest challenges in the study of physical chemistry of graphene materials. Theoretical studies predicted that introduction of a kind of sp3-type defects formed by OH groups is an effective pathway to achieve this goal [Boukhvalov, D. W. & Katsnelson, M. I. ACS Nano 5, 2440–2446 (2011)]. Here we demonstrate that OH groups can efficiently induce robust magnetic moments on the basal plane of the graphene sheet. We show that the inducing efficiency can reach as high as 217 μB per 1000 OH groups. More interestingly, the magnetic moments are robust and can survive even at 900°C. Our findings highlight the importance of OH group as an effective sp3-type candidate for inducing robust magnetic moments on the basal plane of the graphene sheet.

The long spin diffusion length makes graphene very attractive for novel spintronic devices and thus has triggered a quest for integrating the charge and spin degrees of freedom. However, ideal graphene is intrinsic non-magnetic, due to a delocalized π bonding network. Therefore, synthesis of ferromagnetic graphene or its derivatives with high magnetization is urgent due to both fundamental and technological importance. Here we report that N-doping can be an effective route to obtain a very high magnetization of ca. 1.66 emu/g and can make graphene oxide (GO) to be ferromagnetism with a Curie-temperature of 100.2 K. Clearly, our findings can offer the easy realization of ferromagnetic GO with high magnetization, therefore, push the way for potential applications in spintronic devices.

Fluorination was confirmed to be the most effective route to introduce localized spins in graphene. However, adatoms clustering in perfect graphene lead to a low efficiency. In this study, we report experimental evidence of the generation of localized spin magnetic moments on defective graphene (reduced graphene oxide) through fluorination. More interstingly, the result shows that defects help increase the efficiency of the fluorination with regard to the density of magnetic moments created. Fluorinated reduced graphene oxide can have a high magnetic moment of 3.187 × 10(-3) μB per carbon atom and a high efficiency of 8.68 × 10(-3) μB per F atom. It may be attributed to the many vacancies, which hinder the clustering of F atoms, and introduce many magnetic edge adatoms.

Reduced graphene oxide quantum dots (rGOQDs) were synthesized by annealing GOQDs in H2 atmosphere. The photoluminescence (PL) properties of GOQDs and the rGOQDs samples were investigated. The results showed that compared to GOQDs, a blue to purple tunable PL of rGOQDs can be obtained by regulating the annealing temperature. The increase fraction of the newly formed isolated sp2 clusters may be responsible for the observed tunable PL.

Highly oxidative debris (OD) was obtained by aqueous ammonia wash of as-prepared graphene oxide (GO) which composed of OD and lightly oxidative GO sheets. The magnetic properties of OD and GO were studied. The results showed that OD has a low magnetization of 0.16 emu/g, and the magnetization of GO can be increased from 0.38 to 0.42 emu/g by discarding low-magnetization OD. Thus, this study provided a reliable method to increase the magnetization of GO. Hydroxyl groups were proposed to be the magnetic source.