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Graphene oxide (GO) laminate membranes for water purification have surged in popularity due to their hydrophilicity, high throughput and excellent separation abilities. However, concerns about swelling and stability in water persist. Herein, we prepared high stability, composite reduced graphene oxide (rGO)/graphene oxide (GO) membranes. The composite membranes (i.e. rGO/GO composite membranes) displayed excellent rejection performance for methylene blue (MB) of up to 99.0%, together with ultrahigh water permeance (201.7 L m−2 h−1 bar−1) compared to pristine GO membranes (54.8 L m−2 h−1 bar−1). This study broadens the applications of graphene-based membranes and enhances their performance in water treatment. [ABSTRACT FROM AUTHOR]

Understanding the final fate of nanomaterials (NMs) in the liver is crucial for their safer application. As a representative two-dimensional (2D) soft nanomaterial, graphene oxide (GO) has shown to have high potential for applications in the biomedical field, including in biosensing, drug delivery, tissue engineering, therapeutics, etc. GO has been shown to accumulate in the liver after entering the body, and thus, understanding the GO–liver interaction will facilitate the development of safer bio-applications. In this study, the hepatic clearance of two types of PEGylated GOs with different lateral sizes (s-GOs: ~70 nm and l-GOs: ~300 nm) was carefully investigated. We found that GO sheets across the hepatic sinusoidal endothelium, which then may be taken up by the hepatocytes via the Disse space. The hepatocytes may degrade GO into dot-like particles, which may be excreted via the hepatobiliary route. In combination with ICP-MS, LA-ICP-MS, and synchrotron radiation FTIR techniques, we found that more s-GO sheets in the liver were prone to be cleared via hepatobiliary excretion than l-GO sheets. A Raman imaging analysis of ID/IG ratios further indicated that both s-GO and l-GO generated more defects in the liver. The liver microsomes may contribute to GO biotransformation into O-containing functional groups, which plays an important role in GO degradation and excretion. In particular, more small-sized GO sheets in the liver were more likely to be cleared via hepatobiliary excretion than l-GO sheets, and a greater clearance of s-GO will mitigate their hepatotoxicity. These results provide a better understanding of the hepatic clearance of soft NMs, which is important in the safer-by-design of GO. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) membranes have attracted a great deal of attention due to their special two-dimensional (2D) structure and excellent ion sieving properties. However, GO membranes for high valence metal ion rejection still suffer from the limitation of low water permeance and low stability in wastewater treatment. In this study, we reported a kind of 2,4-diamino-6-(4-fluorophenyl)pyrimidine cross-linking graphene oxide (F-GO) membrane with larger interlayer spacing and F-functioned channels, which exhibited an excellent water permeance of ∼219.7 L m−2 h−1 bar−1, which was 5.1 times higher than that of pristine GO membranes, while still maintained 99.9% ion rejection for wastewater treatment. Furthermore, the long-term stability of the F-GO membrane in nanofiltration performance was also experimentally obtained. Overall, our research demonstrates a simple way for achieving high permeances for the effective removal of high valence ions using GO-based membranes, and they may serve as the next promising materials for wastewater treatment. [ABSTRACT FROM AUTHOR]

Renal excretion is expected to be the major route for the elimination of biomedically applied nanoparticles from the body. Hence, understanding the nanomedicine–kidney interaction is crucially required, but it is still far from being understood. Herein, we explored the lateral dimension- (~70 nm and ~300 nm), dose- (1, 5, and 15 mg/kg in vivo and 0.1~250 μg/mL in vitro), and time-dependent (48 h and 7 d in vivo) deposition and injury of PEGylated graphene oxide sheets (GOs) in the kidney after i.v. injection in mice. We specially investigated the cytotoxic effects on three typical kidney cell types with which GO renal excretion is related: human renal glomerular endothelial cells (HRGECs) and human podocytes, and human proximal tubular epithelial cells (HK-2). By using in vivo fluorescence imaging and in situ Raman imaging and spectroscopic analysis, we revealed that GOs could gradually be eliminated from the kidneys, where the glomeruli and renal tubules are their target deposition sites, but only the high dose of GO injection induced obvious renal histological and ultrastructural changes. We showed that the high-dose GO-induced cytotoxicity included a cell viability decrease and cellular apoptosis increase. GO uptake by renal cells triggered cellular membrane damage (intracellular LDH release) and increased levels of oxidative stress (ROS level elevation and a decrease in the balance of the GSH/GSSG ratio) accompanied by a mitochondrial membrane potential decrease and up-regulation of the expression of pro-inflammatory cytokines TNF-α and IL-18, resulting in cellular apoptosis. GO treatments activated Keap1/Nrf2 signaling; however, the antioxidant function of Nrf2 could be inhibited by apoptotic engagement. GO-induced cytotoxicity was demonstrated to be associated with oxidative stress and an inflammation reaction. Generally, the l-GOs presented more pronounced cytotoxicity and more severe cellular injury than s-GOs did, demonstrating lateral size-dependent toxicity to the renal cells. More importantly, GO-induced cytotoxicity was independent of renal cell type. The results suggest that the dosage of GOs in biomedical applications should be considered and that more attention should be paid to the ability of a high dose of GO to cause renal deposition and potential nephrotoxicity. [ABSTRACT FROM AUTHOR]

We show the experimental achievement of dry GO membranes with interlayer spacings in the range from 7.09 Å to 8.72 Å, tuned and fixed by salts. We found that the interlayer spacings were dominated by the anions or the groups with negative charges in between the GO membranes. Density functional theory (DFT) calculations reveal that the highly efficient tuning of the interlayer spacing in dry GO membranes is due to ion‐π interactions on the graphene sheets, together with the steric effects of anions in between the GO sheets. The findings are helpful for extending their potential applications including chemical sensors, nanomaterial devices preparation, chemical catalysis and synthesis, and gas separation. [ABSTRACT FROM AUTHOR]

The effect of cationic concentration on controlling the interlayer spacings of graphene oxide (GO) membranes is systemically studied. It was found that a higher concentration leads to narrower interlayer spacings, and thus, ions in salt solutions were effectively rejected. This provides a new avenue for ion separation using graphene-based membranes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The pGO membrane- pH responsive and highly acidic environment adaptive GO membrane- was obtained by stacking PEI modified GO nanosheets. • The pGO membrane showed enlarged and positively charged nanochannels with increasing acidity in the surrounding solutions. • The pGO membrane exhibited high selectivity for Sr2+/monovalent salt ions with high permeability for monovalent ions. Separation of nuclides from radioactive wastewater is crucial for the safe disposal of nuclear wastes and the sustainable development of resources. However, it still poses great challenges due to the high acidity and high salty of complex composition in radioactive wastewater. Herein, a pH-responsive graphene oxide (GO) membrane, known as a pGO membrane, was developed for fast and efficient selective separation of Sr2+ nuclide ion from highly acidic radioactive wastewater containing multiple mixed salt ions. Different from traditional GO membranes, the interlayer spacings of pGO membranes can be adjusted and increased with increasing acidity in the surrounding solutions due to the presence of grafting molecule polyethylenimine(PEI) within the modified nanochannels of the pGO membrane. The resulting acidic environmentally adaptable membrane has enlarged and positively charged nanochannels in highly acidic solutions. This structure effectively blocks larger and highly charged hydrated Sr2+ nuclide ions while allowing smaller and lowly charged monovalent salt ions (such as Cs+, K+, Na+) to rapidly transport through the membrane. As a result, the pGO membrane exhibits high selectivity for Sr2+/monovalent salt ions with high permeability for monovalent ions. Overall, this work provides a novel sieving method for the separation of radionuclides in highly acidic solutions. [ABSTRACT FROM AUTHOR]

Graphene - based membranes have attracted considerable attentions in many fields of study such as desalination and water treatment due to their unique physical and chemical characteristics. However, graphene oxide (GO) membranes suffer from a severe permeability-selectivity trade-off, i.e., when high salt rejection rates are obtained, usually the extremely low water permeance (most <1 L m−2 h−1 bar−1) are presented, thus it is now far insufficient to meet the real-world applications. In this work, we demonstrated the feasibility of the small-flakes for reduced graphene oxide (S-rGO) membrane to create more ordered two-dimensional (2D) laminar channels for nanofiltration. The water permeances of S-rGO membrane for rejection Na 2 SO 4 and MgSO 4 solutions were 3.7 - and 3.9-fold higher than those of large-flakes rGO (L-rGO) membrane, while the rejections of S-rGO membrane still maintained as high as 87.0 ± 3.8% and 85.4 ± 2.5% for Na 2 SO 4 and MgSO 4 , respectively. Further, the long-term experiments of the S-rGO membrane demonstrated their high stability. Overall, this work sheds light on the preparing of high nanofiltration performance of GO-based membranes as well as the transport mechanism within 2D laminar channels, and advances the design of GO-based membranes for real world water purification, molecular/ionic sieving, and other environmental applications. [Display omitted] • The small flake reduced graphene oxide membrane (S-rGO membrane) has been developed for desalination. • The S-rGO membrane represented high salt rejection, high salt water permeance and high stability. • The outstanding membrane performance can be attributed to smaller interlayer spacings and shorter, less tortuous pathways. [ABSTRACT FROM AUTHOR]

Graphene-oxide (GO) membrane with notable ions sieving properties has attracted significant attention for many applications. However, because of the water swelling of GO membrane, the rejection of monovalent metal cations is generally low. In this work, we developed a fast and facile method to fabricate a kind of reduced GO membranes using the thermal treatment method at 160 °C for only one minute, which denoted as fast reduced GO membrane (FRGO). Surprising, the FRGO membrane represents high ion sieving ability and ultrahigh water/ions selectivity, compared with other reduced GO membranes with similar average interlayer spacings, and even superior to most of GO-based membranes reported in literature. Building on these findings, we provide a new light on fabricating of energy- and environment-related high desalination performance of GO-based membranes as well as a new insight into the transport mechanism within 2D laminar nanochannels. [ABSTRACT FROM AUTHOR]

Nanomaterials (NMs) as lung-targeted drug delivery vehicles have attracted great attentions. Recent studies indicated that elastic or deformable property of NMs could play a vital role in biomedical applications. Herein, polyvinylpyrrolidone (PVP) functionalized graphene oxide (GO-PVP) via a facile one-pot method and PEGylated GO (GO-PEG) nanosheets (NSs) were synthesized at room temperature. By using rare earth elemental labeling method, we quantitatively revealed that GO-PVP NSs were targeting retention in the lung that after 4 h intravenous injection, the lung/liver and lung/spleen ratios in GO-PVP treated mice were about 230-fold and 30-fold higher of those in GO-PEG treated mice, respectively, especially a considerable amount was retained in the lower respiratory tract including pulmonary interstitium and alveolar region as fibril-like shapes. The florescence imaging and in situ confocal Raman microscopy combining with laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) elemental imaging analysis further confirmed that a more amount of GO-PVP than GO-PEG retention in the pulmonary interstitium. Utilizing atomic force microscopy PeakForce quantitative nanomechanical mapping technique, the nanomechanical property investigation shows that GO-PVP NSs are softer, more adhesive and deformable than GO-PEG NSs. Further, the molecular dynamics simulations illustrate that GO-PVP has deformable structure due to the hydrogen-bond interaction at basal plane between PVP and GO that cause GO-PVP surface roughness and to possess low solvent accessible surface area (SASA), comparatively, the GO-PEG owns relatively firm structure and higher SASA. This study indicates that the well dispersion property and deformable structure of GO-PVP in the lung contribute to its filtration of the endothelial/epithelial barrier and retention in the interstitium and alveolar region. Importantly, the study inspires us to design elastic or deformable NMs in response to the lung disease especially those have occurred in the lower respiratory tract. [Display omitted] [ABSTRACT FROM AUTHOR]

• K+ can precisely control the interlayer spacings of GO membranes. • The controlled GO membranes showed highly efficiency for ions rejection. • The separation factor of controlled GO membranes for mono-/multi-valent ions is high. Ion sieving is of great importance in a variety of applications, including water purification, bio-medical engineering, resource utilization and environment protection. Despite previous efforts, the separation efficiency for mono-/multi valent ions is still far from satisfactory. Here, we use high concentration of KCl solution to control the interlayer spacings of graphene oxide (GO) membranes. Then, these KCl-controlled GO membranes can precisely sieve mono-/multi-valentions, especially for Na+/Mg2+ separation. The excellent performance of the membranes can be attributed to the narrower interlayer spacings of KCl-controlled GO membranes. [ABSTRACT FROM AUTHOR]

• An "ion-cage" strategy for stabilizing cations inbetween GO laminate is proposed. • The "ion-cage" GO membrane exhibited ultra-long structural stability. • The synergistic effect of Donan effect and size exclusion enhanced the performance. Multilayered graphene oxide (GO) membrane with sub-nanometer channels is an ideal candidate for desalination. However, excluding small ions using GO-based membranes in the pressured filtration processes remains a great challenge due to the tortuous transport paths of laminates and their water-swelling characteristic. In our previous work, we developed the cation-controlled theory to precisely regulate the interlayer spacing of GO membranes in aqueous solutions. In this work, we proposed an "ion-cage" strategy to enhance the stability (anti-swelling) of the K-controlled GO (icGO-K) membrane for achieving efficient desalination. The icGO-K membrane, coated with positively charged polyethyleneimine (PEI) on its upper and lower surfaces, immobilized intercalated cation K+ between the laminates by electrostatic repulsion to maintain the stability of the confined interlayer spacing. The icGO-K membrane demonstrated superior rejection of 95.3 %, 83.2 %, 81.8 %, and 70.7 % for MgCl 2 , MgSO 4 , NaCl, and Na 2 SO 4 while maintaining competitive permeance of ∼ 3.5 L m-2h−1 bar−1 in the desalination process. More importantly, the icGO-K membrane exhibited ultra-long desalination stability up to 720 h. The enhanced performance can be attributed to the synergistic effect of the confined interlayer spacing and surface electrostatic repulsion. Overall, this work provides attractive strategy to fabricate fine-tuning 2D laminate nanochannels for high efficiency of desalination application. [ABSTRACT FROM AUTHOR]

Due to the well-defined two-dimensional nanochannel nanostructures, graphene oxide (GO) membranes hold huge possibilities for sustainable brackish water desalination and wastewater purification. However, achieving effective nanofiltration performance and sufficient structural stability of GO membranes in aqueous environments remains a major obstacle. Herein, the TU-GO-KOH membrane - the GO membrane cross-linked by thiourea (TU) after KOH treatment, was prepared for achieving relatively high water permeance (∼14.2 L m−2 h−1) and high rejection (∼86.3 %) for NaCl rejection. These performances exceeded the nanofiltration performances of most GO–based membranes and commercial membranes reported in the literature. More importantly, the TU-GO-KOH membrane exhibited excellent separation stability over long-term (for 168 h) and under high pressures (up to 9 bar). Furthermore, even under ultra-sonication treatment and after long-term immersion in solutions with harsh pH values, the TU-GO-KOH membrane still maintained its own stability, which holds considerable promise for sustainable water treatment under harsh conditions. Additionally, the TU-GO-KOH membrane also showed enhanced mechanical properties. Overall, the superior desalination performance and notable stability of the TU-GO-KOH membrane make it a highly promising candidate for practical desalination and wastewater treatment. [Display omitted] • The robust TU-GO-KOH membrane was successfully constructed by cross-linked thiourea (TU) of GO membrane after KOH treatment. • The TU-GO-KOH membrane showed robust stability under high pressures, ultra-sonication, and even under harsh conditions. • The K+ can fix and control the interlayer spacing due to strong K+-π interactions. • The alkaline environment (KOH) enhanced the degree of cross-linking for the TU-GO membranes. [ABSTRACT FROM AUTHOR]

• Stable GO membrane was obtained by double cross-linking method. • High permeability and stability of GSM membrane was fabricated by MoS 2 nanosheets intercalation. • GSM membrane showed high rejection (>99%) and high permeability (112.5 L m−2 h−1 bar−1). • GSM membrane demonstrated excellent stability in water and even in acid and alkali solutions. Graphene oxide (GO)-based membrane has shown great potential in water purification due to its unique physicochemical properties and high permeability. However, it is a challenge to pursue highly permeable GO membranes without compromising stability. Here we employed sodium alginate (SA) together with Ca2+ as cross-linkers to double crosslink GO membrane to obtain stable GS membrane. Further, MoS 2 nanosheets were inserted between GO nanosheets to obtain GSM membrane with high permeability. The double cross-linked MoS 2 intercalation GO membrane, GSM-1:4, showed high removal of multiple dyes (>99%) and enhanced pure water permeance (112.5 L m−2 h−1 bar−1, 1.9 times and 5.8 times of the pure GO membrane and the double cross-linked GS-0.5 membrane, respectively). Meanwhile, the GSM-1:4 membrane demonstrated excellent stability in water and even in acid and alkali solutions. Our work provides new insights into the design of stable and highly efficient GO-based membranes with a two-dimensional layered structure for water treatment. [ABSTRACT FROM AUTHOR]