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Molecular perovskite materials have recently attracted extraordinary interest from the academic community owing to their excellent multifunctional properties. Nevertheless, although massive efforts have been made, molecular ferroelastics with three-dimensional (3D) perovskite structures are still rare. Herein, we report two 3D organic-inorganic hybrid perovskites [(2-hydroxy-propyl)-tripropyl-ammonium][Mn(dca)3] (1) and [(2-hydroxy-1-methyl-ethyl)-tripropyl-ammonium] [Mn(dca)3] (2) [dca = dicyanamide, N(CN)2]. The different position of the chiral center results in a tremendous difference in the properties. Compound 1 displays only one phase transition; however, intriguingly, 2 has three phase transitions and represents ferroelastic behavior with exceptional two-step switching of quadratic nonlinear optical (NLO) properties. To the best of our knowledge, this is the first molecular ferroelastic with two-step switching of quadratic NLO properties. The results demonstrate that the molecular chiral design works, and this finding opens up a new avenue to designing multifunctional molecular perovskite materials.

Increased expression and activity of cardiac and circulating cathepsin D and soluble fms‐like tyrosine kinase‐1 (sFlt‐1) have been demonstrated to induce and promote peripartum cardiomyopathy (PPCM) via promoting cleavage of 23‐kD prolactin (PRL) to 16‐kD PRL and neutralizing vascular endothelial growth factor (VEGF), respectively. We hypothesized that activation of Hes1 is proposed to suppress cathepsin D via activating Stat3, leading to alleviated development of PPCM. In the present study, we aimed to investigate the role of Notch1/Hes1 pathway in PPCM. Pregnant mice between prenatal 3 days and postpartum 3 weeks were fed with LY‐411575 (a notch inhibitor, 10 mg/kg/d). Ventricular function and pathology were evaluated by echocardiography and histological analysis. Western blotting analysis was used to examine the expression at the protein level. The results found that inhibition of Notch1 significantly promoted postpartum ventricular dilatation, myocardial hypertrophy and myocardial interstitial fibrosis and suppressed myocardial angiogenesis. Western blotting analysis showed that inhibition of Notch1 markedly increased cathepsin D and sFlt‐1, reduced Hes1, phosphorylated Stat3 (p‐Stat3), VEGFA and PDGFB, and promoted cleavage of 23k‐D PRL to 16‐kD PRL. Collectively, inhibition of Notch1/Hes1 pathway induced and promoted PPCM via increasing the expressions of cathepsin D and sFlt‐1. Notch1/Hes1 was a promising target for prevention and therapeutic regimen of PPCM.

Nuclear receptor binding SET domain 2 (NSD2)-mediated metabolic reprogramming has been demonstrated to regulate oncogenesis via catalyzing the methylation of histones. The present study aimed to investigate the role of NSD2-mediated metabolic abnormality in pulmonary arterial hypertension (PAH). Monocrotaline (MCT)-induced PAH rat model was established and infected with adeno-associated virus carrying short hairpin RNA (shRNA) targeting NSD2. Hemodynamic parameters, ventricular function, and pathology were evaluated by microcatheter, echocardiography, and histological analysis. Metabolomics changes in lung tissue were analyzed by LC–MS. The results showed that silencing of NSD2 effectively ameliorated MCT-induced PAH and right ventricle dysfunction, and partially reversed pathological remodeling of pulmonary artery and right ventricular hypertrophy. In addition, the silencing of NSD2 markedly reduced the di-methylation level of H3K36 (H3K36me2 level) and inhibited autophagy in pulmonary artery. Non-targeted LC–MS based metabolomics analysis indicated that trehalose showed the most significant change in lung tissue. NSD2-regulated trehalose mainly affected ABC transporters, mineral absorption, protein digestion and absorption, metabolic pathways, and aminoacyl-tRNA biosynthesis. In conclusion, we reveal a new role of NSD2 in the pathogenesis of PAH related to the regulation of trehalose metabolism and autophagy via increasing the H3K36me2 level. NSD2 is a promising target for PAH therapy.

Achieving multifunctional van der Waals nanoelectronic devices on one structure is essential for the integration of 2D materials; however, it involves complex architectural designs and manufacturing processes. Herein, a facile, fast, and versatile laser direct write micro/nanoprocessing to fabricate diode, NPN (PNP) bipolar junction transistor (BJT) simultaneously based on a pre-fabricated black phosphorus/molybdenum disulfide heterostructure is demonstrated. The PN junctions exhibit good diode rectification behavior. Due to different carrier concentrations of BP and MoS2 , the NPN BJT, with a narrower base width, renders better performance than the PNP BJT. Furthermore, the current gain can be modulated efficiently through laser writing tunable base width WB , which is consistent with the theoretical results. The maximum gain for NPN and PNP is found to be ≈41 (@WB ≈600 nm) and ≈12 (@WB ≈600 nm), respectively. In addition, this laser write processing technique also can be utilized to realize multifunctional WSe2 /MoS2 heterostructure device. The current work demonstrates a novel, cost-effective, and universal method to fabricate multifunctional nanoelectronic devices. The proposed approach exhibits promise for large-scale integrated circuits based on 2D heterostructures.

Reduced graphene oxide (RGO) has prospective applications in many fields, including energy storage, printable electronics, and sensing. RGO can simply be obtained at low-cost by reducing graphene oxide (GO). However, how to entirely remove the oxygen-containing groups to yield high-quality graphene is still a great challenge. Here, we report that high-quality intrinsic graphene can be prepared by a simple triggered microwave reduction method under air conditions. The induced spectrum and diffusion processes of GO reduction indicated that high-quality graphene could be produced by strong arc discharge caused by aggregation of electrons at the junction between graphene and GO under microwave irradiation. During the reduction process, the oxygen atoms were removed and carbon atoms were rearranged simultaneously in the graphene lattice structures. In addition, other triggered sources, such as iron wires and paper clips, could also be used to prepare high-quality graphene using the same method. Overall, the triggered microwave reduction of GO provides a simple and low-cost route for large-scale production of high-quality graphene.

Due to its low chemical stability, the surface of black phosphorus (Bp) easily oxidizes to form an oxide layer, which can be used to realize effective electronic tunneling devices. Here, we reported a controllable graphene/Bp van der Waals heterostructure tunneling device by controlling the oxidation etching time. We developed a method for fabricating oxide layers with controllable thickness and realized different thickness oxide layers in different regions of the sample. Through comparative experiments, it was found that as the etching time increased, the tunneling effect was gradually enhanced, and a rectification effect was revealed that also tended to increase. The controllable Bp tunneling effect could help in the design of novel optoelectronic devices.

A sensitive and selective optical biosensor based on reduced graphene oxide (RGO), which uses the polarization-dependent absorption effect of graphene under total internal reflection, is reported for determination of rabbit IgG. RGO sheets with the thickness of about 8.1 nm are fabricated by high temperature reduction and used as a sensing film, because of its strong polarization dependent absorption. This RGO-based optical sensor shows a satisfactory response to rabbit IgG with a minimum concentration of 0.0625 μg/ml. As a contrast, commercial SPR apparatus is used to investigate rabbit IgG with a minimum concentration of 0.3125 μg/ml. Moreover, with antigen–antibody binding, this sensor can also achieve label-free and real-time detection. Taking into account these factors, the RGO-based optical sensor may be a potential candidate for biosensing.

It is known that CH3NH3PbI3 is particularly promising for next-generation solar devices; therefore, molecular perovskite structures have recently received extraordinary attention from the academic community because of their potential in producing unique physical properties. However, although great efforts have been made, molecular ferroelectrics with three-dimensional (3D) perovskite structures are still rare. So far, reported perovskite-like molecular ferroelectrics are basically one- or two-dimensional, significantly deviating from the inorganic perovskite ferroelectrics. Thus, their ferroelectric properties have to be greatly improved to meet the requirements of practical applications. Here, we report a 3D molecular perovskite ferroelectric: (3-ammoniopyrrolidinium)RbBr3 [(AP)RbBr3], with a high Curie temperature (Tc = 440 K) beyond that of BaTiO3. To the best of our knowledge, such above-room-temperature ferroelectricity in the 3D molecular perovskite compound is unprecedented. Furthermore, (AP)RbBr3 ...

An ultra-high sensitivity, multi-parameter monitoring system was established based on a 1.8 mm 3 , high-temperature-reduced graphene oxide microcavity. The gas refractive index, pressure, velocity and flux can be detected in real time based on polarization-sensitive absorption of graphene, and the detection limits are 1.1 × 10 −8 RIU (refractive index units), 3.5 Pa, 3.5 mm/s, and 0.1 ml/min respectively, with an experimental response time less than 0.5 s. These results are a great improvement over those measured previously with single-parameter sensors. Furthermore, the system can also recognize gas flow direction accurately, and enable applications for extreme conditions and for precision instruments with microcavity integrated.

Vertically stacked devices of two-dimensional layered materials (2DLMs) based on van der Waals heterostructures (vdWHs) have recently attracted considerable attention due to their good properties. A tunneling structure is presented in this paper that, unlike other tunneling structures, has no specific insulating two-dimensional materials, such as boron nitride. The tunneling structure is comprised of graphene and black phosphorus. Black phosphorus is chemically active, and can be easily oxidized in the air to form an insulating layer. A tunneling device was produced based on this characteristic of black phosphorus. The insulation layer was an oxide layer formed by the oxidation of black phosphorus. The structure takes advantage of the easy oxidation ability of black phosphorus. The presence of a black phosphorus oxide layer was determined by XPS analysis. The tunneling characteristics of the overlay structure were determined by measuring the current-voltage (Id-V) curve of the device. Simulation studies showed that the oxidation layer was responsible for the tunneling effect. Compared with other black phosphorus devices, the photoelectric properties of the proposed device were greatly improved.

This paper reports a controlled breakdown (CBD) method to fabricate multiple nanopores in a silicon nitride (SiNx) membrane with control over both nanopore count and nanopore diameter. Despite the stochastic process of the breakdown, we found that the nanopores created via CBD, tend to be of the same diameter. We propose a membrane resistance model to explain and control the multiple nanopores forming in the membrane. We prove that the membrane resistance can reflect the number of nanopores in the membrane and that the diameter of the nanopores is controlled by the exposure time and strength of the electric field. This controllable multiple nanopore formation via CBD avoids the utilization of complicated instruments and time-intensive manufacturing. We anticipate CBD has the potential to become a nanopore fabrication technique which, integrated into an optical setup, could be used as a high-throughput and multichannel characterization technique.

Stable porphyrin-oxygenated carbon nanomaterial dispersions were prepared by blending porphyrin solutions with hydroxyl groups modified multi-walled carbon nanotubes (MWNTs-OH) and graphene oxide (GO) dispersions, respectively. Optical nonlinearity and optical limiting (OL) property of these blends are investigated in nanosecond regime. Results show that the OL performance of the blends can be tuned by changing the concentrations ratio of porphyrin and oxygenated carbon nanomaterials. The high concentration of oxygenated carbon nanomaterial leads to the poor OL performance. However, with the moderate concentration, the blends exhibit the low threshold value of OL and the enhanced OL performance at high fluence region. The superior OL performance can be attributed to complementary mechanisms and possible photoinduced electron or energy transfer between porphyrin moiety and oxygenated carbon nanomaterials.

Graphene oxide-MnO2 (GO-MnO2) was successfully synthesized by microwave-assisted method with the substrate of GO covered by MnO2. MnO2 contained disordered pore structure and aggregate of random shape. GO exhibited layer-like shape and had a large numbers of functional groups on its surface. The electrochemical measurements were employed by cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD), the results showed that the GO-MnO2 composite had good capacitive performance, the maximum of specific capacitance was 127 F g-1 at the current density of 100 mA g-1.

We have demonstrated a passively synchronized Q-switched erbium- and ytterbium-doped fibre laser by a common graphene saturable absorber (GSA), which generates optical pulses centered at 1530 nm and 1060 nm. The dynamics of the synchronisation of this laser have been studied. In this passively synchronized Q-switched laser, 1530 nm laser pulses affect the transmittance of 1060 nm light through the GSA and induce synchronisation of the two laser pulses. These experimental results have been explained by a simplified theoretical model of the dual-wavelength cross absorption modulation effect of a GSA. With the increase in the pump power, the repetition rate of synchronized pulses varies from 24. 51–39. 85 kHz, and the pulse widths of 1530 nm and 1060 nm vary from 6. 02–2. 41 μs and from 18. 79–3. 29 μs, respectively.

Hydroxyl groups modified multi-walled carbon nanotubes (MWNTs-OH) were dispersed in N, N-dimethylformamide (DMF), water and chloroform, respectively. Each kind of dispersions were poured in 1-mm, 2-mm and 5-mm quartz cuvettes, respectively. The nonlinear optical (NLO) and optical limiting properties of the dispersions were studied using open-aperture Z-scan technique at 532 nm in nanosecond regime. Results show that thick cuvette or solvents with excellent thermodynamic parameters allows efficient replenishment of MWNTs-OH in the intensely irradiated volume, leading to excellent optical limiting properties arising from the well known nonlinear scattering, while thin cuvette or solvents with poor thermodynamic parameters allows inefficient replenishment of MWNTs-OH, which even leads to false appearance of 'saturable absorption-like' or 'nonlinear refraction-like' behavior due to the depletion of the sample. The different replenishment efficiency of the dispersions with the same solvent in cuvettes of different thickness can be attributed to the different influence of viscous force near the cuvette sidewalls. This influence should also be noted in other nanomaterials sharing similar NLO mechanism to carbon nanotubes dispersions during Z-scan experiments.

An efficient and convenient method is applied to introduce varieties of simple functionalities onto the graphene surface for the bulk preparation, which begins with pristine graphite that does not require initial oxidative damage of the graphene basal planes. Diazonium compounds functionalized reaction is demonstrated and it successfully prevented the aggregation of graphene for which providing solubility in high polar organic media or even in volatile solvents such as ethanol and acetone. This approach is complemented by the phenyl carboxylic diazonium salt functionalized graphene (PCFG) attachment of a symmetrically substituted zinc phthalocyanine (PCFG-Pc) using the amide reaction, which is used for the covalent introduction of a complex phthalocyanine molecule.

Nonlinear optical and optical limiting properties of three graphene materials (pure graphene, graphene oxide, reduced graphene oxide) covalently functionalized by zinc phthalocyanine were studied in nanosecond and femtosecond regimes. In nanosecond regime, reduced graphene oxide–phthalocyanine hybrid shows better optical limiting effect than the other two hybrids. In femtosecond regime, graphene oxide–phthalocyanine shows the best nonlinear optical properties among the three hybrid materials. Based on Z-scan and transient absorption measurements, the mechanisms for nonlinear optical property were analyzed for these materials. Compared with the other two hybrids, reduced graphene oxide–phthalocyanine hybrid is a better candidate in the application of optical limiter.

We used a two-layer structure consisting of polyethylene terephthalate (PET) and silicone to transfer graphene grown by chemical vapor deposition onto various rigid and flexible substrates through dispersive adhesion. It only takes a few seconds to transfer graphene from PET/silicone to the target substrates at ambient conditions. And the recycling of the PET/silicone decreases the production cost greatly. The transferred graphene films were characterized by optical and atomic force microscopy, Raman spectroscopy, electrical analyses, and optical transmittance measurements, and the results show that the graphenes transferred by PET/silicone have a cleaner and more continuous surface, lower doping level, and higher optical transmittance and conductivity than those transferred by thermal release tape. Considering its high efficiency, low cost, large area and high quality, the PET/silicone transfer method would be particularly useful for graphene’s electronic applications such as field-effect transistors and transparent conducting electrodes.

Multi-walled carbon nanotubes covalently functionalized with tetraphenylporphyrin (MWCNT–TPP) with diameter ranges of

Various graphene-based gas sensors that operate based on the electrical properties of graphene have been developed for accurate detection of gas components. However, electronic graphene-based gas sensors are unsafe under explosive atmospheres and sensitive to electromagnetic interference. Here, a novel optical graphene-based gas sensor for NO2 detection is established based on surface chemical modification of high-temperature-reduced graphene oxide (h-rGO) films with sulfo groups. Sulfo group-modified h-rGO (S-h-rGO) films with a thickness of several nanometers exhibit excellent performance in NO2 detection at room temperature and atmospheric pressure based on the polarization absorption effect of graphene. Initial slope analysis of the S-h-rGO sensor indicates that it has a limit of detection of 0.28 ppm and a response time of 300 s for NO2 gas sensing. Furthermore, the S-h-rGO sensor also possesses the advantages of good linearity, reversibility, selectivity, non-contact operation, low cost and safety. This novel optical gas sensor has the potential to serve as a general platform for the selective detection of a variety of gases with high performance.

Graphene, a two-dimensional carbon atom sheet, has attracted tremendous attention and research interest because of its exceptional physical properties. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. The main focus so far has been on fundamental physics and electronic devices. However, because the linear dispersion of the Dirac electrons enables ultrawideband tunability, we believe its true potential lies in photonics and optoelectronics. In this review, we introduce recent advances in the nonlinear optical properties of graphene-based materials. The rise of graphene in nonlinear optics is shown by several recent results, ranging from saturable absorbers and the four-wave mixing effect to giant two-photon absorption, reverse saturable absorption and optical limiting. The relevant forms of the graphene-based materials include pure graphene, graphene oxide and graphene hybrids.

The nonlinear absorption properties of tetraphenylporphyrins (TPP) in different solvents and excitation intensities are investigated with nanosecond pulses by the Z-scan technique. The nonlinear absorption behaviour observed presents a distinct difference between in solvent mixtures and in pure solvents. A crossover from reverse saturable absorption (RSA) to saturable absorption (SA) and then again to RSA is observed with the increases of excitation intensity in chloroform and pyridine mixed solvents. However, porphyrin molecules in pure solvents show good RSA behaviour under the studied intensity range, no saturation absorption is observed with nanosecond excitation. Excited state absorption parameters and two-photon absorption coefficients are obtained by theoretical fit using rate equations for population densities in a seven-level energy scheme.

Graphene with zero-band gap can be easily saturated under strong excitation due to Pauli blocking. In this work, the graphene oxide membrane is reduced on the surface of microfiber by use of high temperature heating. Such reduced graphene oxide can interact with the strong evanescent field of the microfiber and enable saturable absorption in passively mode-locked fiber laser. The system can be effectively utilized to directly generate ultra-wide-band doublet pulses for high-capacity wireless communication applications.

Nonlinear optical properties of hydroxyl groups modified multi-walled carbon nanotubes (MWNTs-OH) with diameter of 20–30 nm (MWNTs 2030 -OH) dispersed in water, N , N -dimethylformamide (DMF) and chloroform were studied by using Open-aperture Z-scan technique with nanosecond pulse at 532 nm. The influences of solvent, laser pulse-width, on-axis fluence at focus and concentration on nonlinear optical properties of MWNTs 2030 -OH were analyzed in detail to obtain the optimal nonlinear optical response for applications in optical limiters. Nonlinear optical properties of MWNTs-OH with different diameter in DMF were also studied and compared with multi-walled carbon nanotubes in DMF and C 60 in toluene.

An organic solution-processable functionalized graphene hybrid material with oligothiophene (6THIOP-NH-SPFGraphene) has been synthesized. The thermogravimetry analysis data shows that the hybrid is more stable than its parent graphene oxide as observed with an increased onset temperature. Ultraviolet–visible absorption and fluorescence emission data show that the attachment of the electron-acceptor group (graphene oxide sheet) onto the oligothiophene molecules results in an improved absorption than its parent compound in the whole spectral region and an efficient quenching of photoluminescence. The optical limiting properties were studied by using the open-aperture Z-scan measures at 532 nm, and the results show that 6THIOP-NH-SPFGraphene demonstrated a superior optical limiting effect, better than that of the benchmark optical limiting material C60.

The graphene-C60 hybrid has been synthesized and characterized. Its nonlinear optical property was investigated. Raman spectroscopy suggested a strong interaction between C60 and graphene. Based on UV and elemental analysis measurement, it is estimated that one C60 molecule is covalently attached for every approximately 110 carbon atoms in graphene. The nonlinear optical performance of this hybrid material was studied using the Z-scan measurement and a much enhanced nonlinear optical performance was observed compared with that of the benchmark material-C60 and graphene. This may be partially attributed to the photoinduced electron transfer mechanism between graphene and C60.

The nonlinear optical properties of two novel graphene nanohybrid materials covalently functionalized with porphyrin and fullerene were investigated by using the Z-scan technique at 532 nm in the nanosecond and picosecond time scale. Results show that covalently functionalizing graphene with the reverse saturable absorption chromospheres porphyrin and fullerene can enhance the nonlinear optical performance in the nanosecond regime. The covalently linked graphene nanohybrids offer performance superior to that of the individual graphene, porphyrin, and fullerene by combination of a nonlinear mechanism and the photoinduced electron or energy transfer between porphyrin or fullerene moiety and graphene.

Optical limiters are employed to protect sensitive optical components or eyes from laser-induced damage. [1,2] They have lower transmittance for high-intensity or fluence laser input while they keep a high linear transmittance. Many works have concentrated on creating ideal optical limiting devices by exploiting passive limiting mechanisms such as nonlinear absorption (multiphoton absorption, reverse saturable absorption (RSA)), nonlinear refraction (electronics or thermal effects), and nonlinear light scattering. Both single-walled carbon nanotube (SWNT) and multiwalled carbon nanotube (MWNT) suspensions have been reported to have strong optical limiting effects in the nanosecond regime, which arise from strong nonlinear light scatterings due to the creation of new scattering centers consisting of ionized carbon microplasmas and solvent microbubbles. [3–9] To promote their optical limiting effects, the optical nonlinear media with other optical nonlinear processes (e.g., two-photon absorption or RSA) have been blended with carbon nanotubes. [10,11] The association of SWNTs with organic chromophores having multiphoton absorption processes was recently shown to be a promising approach to achieve optical limiting systems with broad temporal and spectral responses. [10] Carroll et al. [11] also reported an enhanced nonlinear transmittance obtained by a RSA dye blended with carbon nanotubes. Recently, Blau et al. [12] presented a study on nonlinear optical characterization of stable porphyrin/SWNT composite solutions obtained by non-covalent bonding between the carbon nanotubes and conjugated tetraphenylporphyrin molecules. However, little research has been carried out on optical limiting effects of covalently functionalized SWNTs with reverse saturable absorbents. Vivien et al. [5] predicted that further optimizations of the optical limiting performances of carbon nanotubes may be achieved by the cumulative influences of different nonlinear effects arising from functionalized carbon nanotubes with reverse saturable absorbents. Porphyrins are often used as visible chromophores to decorate the surfaces of semiconductor and metal nanoparticles, and they are also promising candidates for applications in optical limiters owing to their large RSA in the visible even near-infrared wavelength range. [13–15] Furthermore, an effective energy or electron transfer may exist in the functionalized SWNTs with porphyrins. [16] The photoinduced electron transfer can result in a large optical limiting effect, which has been observed in the PVK-modified SWNTs system. [17,18] We also reported that a

A series of novel 21,23-dithiaporphyrins have been synthesized and determination of their optical nonlinearities demonstrated that they have much larger nonlinear refractive cross section than normal porphyrins and exhibit reverse saturable absorption.

Novel covalently porphyrin-functionalized single-walled carbon nanotubes (SWNTs) have been synthesized by the reaction of SWNTs with in situ generated porphyrin diazonium compounds. The resulting nanohybrid was characterized by spectroscopic (UV-Vis-NIR, FTIR and Raman) and microscopic (TEM and AFM) methods. The Raman and absorption spectroscopy data showed that the electronic properties of the modified tubes were mostly retained, without damaging their one-dimensional electronic properties. The fluorescence from the porphyrin moiety was almost completely quenched by SWNTs, indicating that the unique direct linkage mode facilitated the effective energy and electron transfer between the excited porphyrin moiety and the extended π-system of SWNTs. This novel nanohybrid material also exhibited excellent optical limiting properties.

Protein-protein interactions play an important role in the investigation of biomolecules. In this paper, we reported on the use of a reduced graphene oxide microshell (RGOM)-based optical biosensor for the determination of goat anti-rabbit IgG. The biosensor was prepared through a self-assembly of monolayers of monodisperse polystyrene microspheres, combined with a high-temperature reduction, in order to decorate the RGOM with rabbit IgG. The periodic microshells allowed a simpler functionalization and modification of RGOM with bioreceptor units, than reduced graphene oxide (RGO). With additional antibody-antigen binding, the RGOM-based biosensor achieved better real-time and label-free detection. The RGOM-based biosensor presented a more satisfactory response to goat anti-rabbit IgG than the RGO-based biosensor. This method is promising for immobilizing biomolecules on graphene surfaces and for the fabrication of biosensors with enhanced sensitivity.

Graphene has been extensively investigated for its use in flexible electronics, especially graphene synthesized by chemical vapor deposition (CVD). To enhance the flexibility of CVD graphene, wrinkles are often introduced. However, reports on the flexibility of reduced graphene oxide (RGO) films are few, because of their weak conductivity and, in particular, poor flexibility. To improve the flexibility of RGO, reduced graphene oxide nanoshells are fabricated, which combine self-assembled polystyrene nanosphere arrays and high-temperature thermal annealing processes. The resulting RGO films with nanoshells present a better resistance stabilization after stretching and bending the devices than RGO without nanoshells. The sustainability and performance advances demonstrated here are promising for the adoption of flexible electronics in a wide variety of future applications.

We studied nonlinear absorption of three kinds of porphyrin covalently functionalized SWNTs using Z-scan technique with nanosecond pulses at 440 nm, 460nm, 480nm, 500nm, and 532nm. The large enhancement of nonlinear absorption in porphyrin covalently functionalized SWNTs were found at 532 nm. This nonlinear behavior of SWNTs has been shown to arise from strong nonlinear scattering, and porphyrin exhibits strong reverse saturable absorption at 532 nm. The porphyrins covalently functionalized SWNTs offer superior performance to the individual SWNTs and porphyrins by combination of nonlinear mechanism and the photoinduced electron or energy transfer between porphyrin moiety and SWNTs.

The nonlinear absorption of two porphyrin diacids (H4TPP2+ and H2DSP2+), the diprotonated forms of free base tetraphenylporphyrin (H2TPP) and dithiaporphyrin (DSP), were studied in the wavelength range of 500-650 nm. The two porphyrin diacids exhibited perturbed static and dynamic characteristics and enhanced nonlinear absorption properties relative to their parent neutral complexes in solution. Furthermore, for the dithiaporphyrin diacid, the introduction of S-atoms into the porphyrin core makes it a better candidate for optical limiting relative to the simple porphyrin. Their photophysical parameters such as ground and excited states absorption cross-sections, together with fluorescence lifetime and intersystem crossing time, were determined.

Nonlinear refraction and nonlinear absorption of self-assembled porphyrins in the nanosecond and picosecond regimes were studied at 532 nm by the Z-scan technique. First, a marked difference in nonlinear refraction was observed between self-assembled zinc porphyrins and free base porphyrins; however, the effects of self-assembly and metallization on nonlinear absorption are small. Second, an enhancement of nonlinear absorption was observed for the monomeric components of self-assembled structures by adding pyridine, while their nonlinear refractions remained almost unchanged as pyridine was added. It is expected that the metallization and addition of ligand can provide more convenient routes to alter the optical nonlinearities of porphyrins than the modifications of molecular structures of traditional covalent-bond organic materials.

Nonlinear optical properties (NLO) and optical limiting effect of fullerene (C60), multi-walled carbon nanotubes (MWNTs), reduced graphene oxide (RGO) and their oxygenated derivatives were investigated by open-aperture Z-scan technique with nanosecond pulses at 532 nm. C60 functionalized by oxygen-containing functional groups exhibits weaker NLO properties than that of pristine C60. Graphene oxide (GO) with many oxygen-containing functional groups also shows weaker NLO properties than that of RGO. That can be attributed to the disruption of conjugative structures of C60 and graphene by oxygen-containing functional groups. However, MWNTs and their oxygenated derivatives exhibit comparable NLO properties due to the small weight ratio of these oxygen-containing groups. To investigate the correlation between structures and NLO response for these carbon nanomaterials with different dimensions, nonlinear scattered signal spectra versus input fluence were also measured.

Nonlinear optical properties of water-soluble porphyrin 5,10,15,20-Tetrakis (1-methyl-4-pyridinio) porphyrin tetra (p-toluenesulfonate) (TMPyP), protonated TMPyP (), TMPyP film with the gelatin matrix (TMPyP/Gelatin) were investigated by the open-aperture Z-scan technique in the nanosecond regime. Results show that exhibits a larger ratio of excited state absorption cross-section to that of the ground state and enhanced reverse saturable absorption properties compared with TMPyP and TMPyP/Gelatin. also shows the superior optical limiting performance, even better than the benchmark material C60 and the multi-walled carbon nanotubes (MWNTs) dispersion.

Micro- and nanostructures were fabricated directly on graphene nanosheets by controlling the conditions of femtosecond laser pulse etching. High quality graphene micro- and nanostructures with a minimum width of 492 nm were obtained as the graphene nanosheets used in our experiments were large-scale, uniform and highly conductive. Various complex patterns were successfully created through femtosecond laser etching. Furthermore, by managing the laser energy, the graphene under the Au electrodes could be completely or partly removed. This technology of direct patterning of micro- and nanostructures on graphene through femtosecond laser technology might pave the way for the integration of graphene-based electronic microdevices.

The nonlinear optical (NLO) and optical limiting properties of a graphene oxide hybrid material coordinated with Fe3O4 nanoparticles (GO–Fe3O4) were studied by using the Z-scan technique at 532 nm in the nanosecond and picosecond regimes. Results show that GO–Fe3O4 exhibits enhanced NLO and optical limiting properties in comparison with the pristine GO in the nanosecond regime. Compared with fullerene (C60) in toluene at different concentrations, GO–Fe3O4 exhibits a weaker optical limiting effect than C60 at high concentration, but shows a stronger optical limiting effect than C60 at low concentration in the high input fluence region.

Ultrafast carrier dynamics and saturable absorption of few-layered graphene oxide, well-dispersed in organic solvent, are studied using femtosecond pump-probe and Z-scan techniques. The results demonstrate that few-layered graphene oxide has a fast energy relaxation of hot carriers and strong saturable absorption, which is comparable with that of reduced graphene oxide. Fast carrier relaxation combined with well solution processing capability arises from the large fraction of sp2 carbon atom inside the few-layered graphene oxide sheet together with oxidation mainly existing at the edge areas. This superiority of few-layered graphene oxide will facilitate potential applications of graphene for ultrafast photonics.

Cadmium sulfide (CdS) nanocrystals were in situ grown in a polyvinylpyrrolidone (PVP) matrix at room temperature using cadmium nitrate and thioacetamide as the cadmium and sulfur sources, respectively. It was found that the growth of CdS nanocrystals in the PVP matrix was well controlled and the mass concentration of CdS could be up to 18.2 wt% without the formation of large precipitates. The third-order nonlinear optical properties of the composite films were studied at 532 nm in the nanosecond regime by using the Z-scan technique. The results showed that the CdS/PVP nanocomposite film has a promising optical property exhibited by a nonlinear optical refractive index and an absorption coefficient of −1.65 × 10−11 cm2 W−1 and −4.25 × 10−7 cm W−1, respectively. The flexible processing technique allows the production of optical devices with various shapes.

We report on an active tuning of nonlinear absorption from reverse saturable absorption to saturable absorption in supramolecular zinc diphenylporphyrins by the combination of molecular and supramolecular levels at 532, 542 and 552 nm. Firstly, the modifications of molecular structures with bromination result in a discrete but regular change in magnitude and sign of nonlinear absorption (NLA). Furthermore, a fine tuning of NLA was obtained by the intermolecular weak interaction of pyridine and zinc porphyrins. Using an association model, we theoretically simulate the change of NLA. Compared with modifying molecular structures of conventional organic materials, the weak intermolecular interaction of supramolecular porphyrins has another advantage that it can be realized more easily and flexibly to change NLA.

The type of donor used is found to influence greatly the optical nonlinearities of iodine charge-transfer (CT) complexes in solutions for several solvents. The magnitude and sign changes of nonlinear absorption of iodine CT complexes for different solvents as donors are observed, which implies the transition from saturable absorption to reverse saturable absorption. Compared with C60 in toluene, iodine CT complexes with toluene and benzene demonstrate larger reverse saturable absorption. Meanwhile, flexible alteration of optical nonlinearities is easily obtained by adjusting the mixture ratio of different solvents, yielding a prospective means of constructing a nonlinear medium with a large nonlinear coefficient.