Amyotrophic lateral sclerosis (ALS) associated with TAR DNA-binding protein 43 (TDP-43) aggregation has been considered as a lethal and progressive motor neuron disease. Recent studies have shown that both C-terminal TDP-43 (C-TDP-43) aggregates and oligomers were neurotoxic and pathologic agents in ALS and frontotemporal lobar degeneration (FTLD). However, misfolding protein has long been considered as an undruggable target by applying conventional inhibitors, agonists, or antagonists. To provide this unmet medical need, we aim to degrade these misfolding proteins by designing a series of proteolysis targeting chimeras (PROTACs) against C-TDP-43.C. elegans by motility assay and confocal microscopy. The impact of TDP-43 PROTAC on C-TDP-43 oligomeric intermediates was monitored by fluorescence lifetime imaging microscopy and size exclusion chromatography in the Neuro-2a cells co-expressing eGFP-C-TDP-43 and mCherry-C-TDP-43.By applying filter trap assay, western blotting, and microscopy imaging, the degradation efficiency of C-TDP-43 aggregates was studied in Neuro-2a cells overexpressing eGFP-C-TDP-43 or mCherry-C-TDP-43. The cell viability was characterized by alarmarBlue assay. The beneficial and disaggregating effects of TDP-43 PROTAC were examined with the YFP-C-TDP-43 transgenic 2 decreased C-TDP-43 aggregates and relieved C-TDP-43-induced cytotoxicity in Neuro-2a cells without affecting endogenous TDP-43. We showed that PROTAC 2 bound to C-TDP-43 aggregates and E3 ligase to initiate ubiquitination and proteolytic degradation. By applying advanced microscopy, it was further shown that PROTAC 2 decreased the compactness and population of C-TDP-43 oligomers. In addition to cellular model, PROTAC 2 also improved the motility of transgenic C. elegans by reducing the C-TDP-43 aggregates in the nervous system.Four PROTACs with different linker lengths were synthesized and characterized. Among these chimeras, PROTAC 2 against both C-TDP-43 aggregates and oligomers to reduce their neurotoxicity, which shed light on the potential drug development for ALS as well as other neurodegenerative diseases.Our study demonstrated the dual-targeting capacity of the newly-designed PROTAC The online version contains supplementary material available at 10.1186/s12929-023-00921-7. With the increase in the aging population, the misfolded proteinaceous agents associated with neurodegenerative diseases have drawn increasing attention , 2. The Recently, proteolysis targeting chimeras (PROTACs) have received increasing attention due to their potential abilities to induce targeted protein degradation including the neurodegenerative disease associated proteins –17. StruNowadays, PROTACs have been developed to degrade a wide range of proteins, such as androgen receptor , bromodo1–4  also rescued the C-TDP-43-mediated motility defects in nematode C. elegans.To provide a proof-of-concept examination, we developed “TDP-43 PROTAC” as a novel therapeutic strategy for reducing the C-TDP-43 cytotoxicity in ALS and other TDP-43 proteinopathy Fig. A. A TDP-2Cl2) was distilled from CaH2, and tetrahydrofuran (THF) was distilled from sodium. All nonaqueous reactions were performed in oven-dried glassware under a slightly positive pressure of argon unless otherwise noted. Reactions were magnetically stirred and monitored by thin-layer chromatography on silica gel using phosphomolybdic acid (PMA), p-anisaldehyde, KMnO4, ninhydrin or iodine vapor as visualizing agent. Flash chromatography was performed on silica gel of 60–200 μm particle size. Yields are reported for spectroscopically pure compounds. Melting points were recorded on a Yanaco micro apparatus or Electrothermal MEL-TEMP 1101D apparatus in open capillaries and are not corrected. Infrared (IR) spectra were recorded on Thermo Scientific Nicolet is-5 FT-IR spectrometer. Nuclear magnetic resonance (NMR) spectra were obtained on Bruker AVIII 500 (500 MHz) and Bruker AVIII 400 (400 MHz) spectrometers. Chemical shifts are given in δ values relative to tetramethylsilane . Internal standards were CHCl3 (δH = 7.24), CDCl3 , CD2HOD (δH = 3.31), CD3OD (δC = 49.15), (H3C)2SO , or (CHD2)2SO . The splitting patterns are reported as s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), dd (double of doublets), td (triple of doublets) and br (broad). Coupling constants (J) are given in Hz. Electrospray ionization high-resolution mass spectra (ESI-HRMS) were recorded on a Bruker Daltonics BioTOF III high-resolution mass spectrometer. UV–Vis absorption spectra were recorded on a PerkinElmer Lambda 35 spectrometer. Fluorescence spectra were recorded on an AMINCO-Bowman Series 2 luminescence spectrometer.All the reagents and solvents were reagent grade and used as purchased without further purification unless indicated otherwise. All solvents were anhydrous grade unless indicated otherwise. Dichloromethane . All compounds are > 95% pure by HPLC analysis.New compounds were characterized by their physical and spectroscopic properties  in anhydrous acetonitrile (75 mL) at 65 °C for 1.5 h to give 2-bromo-6-methoxybenzo[d]thiazole (5) thiazol-2-yl)-N,N-dimethylaniline (7) thiazol-2-yl)-N,N-dimethylaniline compound (S2a) . C19H21N5O2S; yellow solid; mp 96.0–97.0 °C.To a solution of compound ulfonate   in THF (3 mL) was stirred with PPh3  and H2O  at room temperature for 24 h. The mixture was concentrated under reduced pressure, and purified by flash chromatography on a silica gel column with elution of CH2Cl2/MeOH (10:1) to give the amino compound 9a . C19H23N3O2S; yellow solid; mp 66.5–67.5 °C; TLC (CH2Cl2/MeOH = 7:1) Rf = 0.13; IR νmax (neat) 3358, 3190, 2919, 2849, 1659, 1653, 1634, 1470, 1423, 1264, 828 cm–1; 1H NMR  δ 7.83 , 7.80 , 7.26 , 7.00 , 6.65 , 4.10 , 3.77 , 3.52 , 2.95 , 2.83 , 1.91 ; 13C NMR  δ 166.4, 156.0, 151.7, 148.9, 135.6, 128.3 (2 ×), 122.5, 121.3, 115.2, 111.5 (2 ×), 105.2, 73.3, 69.3, 67.9, 41.5, 39.9 (2 ×). ESI-HRMS calcd for C19H24N3O2S: 358.1584, found: m/z 358.1570 [M + H]+.A solution of azido compound 2O  in AcOH (3 mL) was heated under reflux for 12 h. The mixture was concentrated under reduced pressure, and purified by flash chromatography on a silica gel column with elution of CH2Cl2/MeOH (100:1) to give 2--4-fluoroisoindoline-1,3-dione (10) +.A mixture of compound 1, the substitution reaction of 10  with 9b  gave a crude product, which was purified by flash chromatography on a silica gel column with elution of EtOAc/CH2Cl2 (1:1) to give the desired compound 2 . The purity of compound 2 was 97.0% as shown by HPLC on a silica column , elution: EtOAc/hexane = 3:1 at a flow rate of 3.0 mL/min, tR = 17.9 min. C34H35N5O7S; yellow solid; mp 128.0–129.0 °C; TLC (EtOAc/ CH2Cl2 = 1:1) Rf = 0.5; IR νmax (neat) 3357, 3197, 2920, 2849, 1653, 1632, 1471 cm–1; 1H NMR  δ 8.35 , 7.88 , 7.82 , 7.41 , 7.29 , 7.01–6.99 , 6.84 , 6.71 , 6.44 , 4.85 , 4.15 , 3.86 , 3.78–3.64 , 3.40 , 3.01 , 2.87–2.59 , 2.09–2.00 ; 13C NMR  δ 171.1, 169.2, 168.4, 167.6, 166.6, 156.2, 151.9, 149.0, 146.7, 136.0, 135.6, 132.4, 128.5 (2 ×), 122.6, 121.5, 116.7, 115.4, 111.7 (2 ×), 111.6, 110.2, 105.4, 70.9, 70.7, 69.8, 69.5, 68.1, 48.8, 42.3, 40.14 (2 ×), 31.3, 22.7. ESI-HRMS calcd for C34H36N5O7S: 658.2330, found: m/z 658.2307 [M + H]+.By a procedure similar to that for compound 1, the substitution reaction of 10  with 9c  gave a crude product, which was purified by flash chromatography on a silica gel column with elution of EtOAc/CH2Cl2 (1:1) to give the desired compound 3 . The purity of compound 3 was 95.1% as shown by HPLC on a silica column , elution: EtOAc/hexane = 9:1 at a flow rate of 3.0 mL/min, tR = 15.9 min. C36H39N5O8S; yellow solid; mp 87.5–89.0 °C; TLC (EtOAc/CH2Cl2 = 1:1) Rf = 0.38; IR νmax (neat) 3358, 3197, 2919, 2849, 1661, 1645, 1622, 1471, 1407 cm–1; 1H NMR  δ 8.55 , 7.86 , 7.81 , 7.39 , 7.27 , 7.05–6.96 , 6.82 , 6.68 , 6.42 , 4.86 , 4.13 , 3.84 , 3.72–3.67 , 3.67–3.59 , 3.38 , 2.99 , 2.80–2.60 , 2.04 ; 13C NMR  δ 171.2, 169.2, 168.5, 167.5, 166.5, 156.2, 151.9, 148.6, 146.7, 135.9, 135.4, 132.4, 128.5 (2 ×), 122.5, 121.2, 116.7, 115.4, 111.7 (2 ×), 111.5, 110.1, 105.4, 70.7, 70.6 (3 ×), 69.6, 69.4, 68.1, 48.8, 42.3, 40.1 (2 ×), 31.3, 22.6. ESI-HRMS calcd for C36H40N5O8S: 702.2592, found: m/z 702.2589 [M + H]+.By a procedure similar to that for compound 1, the substitution reaction of 10  with 9d  gave a crude product, which was purified by flash chromatography on a silica gel column with elution of EtOAc/CH2Cl2(2:1) to give the desired compound 4 . The purity of compound 4 was 99.3% as shown by HPLC on a silica column , elution: EtOAc/MeOH = 99:1 at a flow rate of 3.0 mL/min, tR = 11.3 min. C38H43N5O9S; yellow solid; mp 77.5–79.0 °C; TLC (EtOAc/ CH2Cl2 = 2:1) Rf = 0.38; IR νmax (neat) 3356, 3197, 2921, 2851, 1653, 1634, 1470, 1456, 1368, 742, 701 cm–1; 1H NMR  δ 8.66 , 7.85 , 7.80 , 7.40 , 7.27 , 7.05–6.96 , 6.83 , 6.68 , 6.42 , 4.85 , 4.14 , 3.84 , 3.73–3.67 , 3.67–3.57 , 3.38 , 2.99 , 2.85–2.60 , 2.07–1.97 ; 13C NMR  δ 171.3, 169.1, 168.5, 167.5, 166.5, 156.1, 151.8, 148.7, 146.7, 135.9, 135.5, 132.4, 128.4 (2 ×), 122.5, 121.3, 116.7, 115.4, 111.7 (2 ×), 111.5, 110.1, 105.3, 70.8, 70.6, 70.5 (2 ×), 70.4 (2 ×), 69.6, 69.3, 68.0, 48.7, 42.2, 40.1 (2 ×), 31.3, 22.6. ESI-HRMS calcd for C38H44N5O9S: 746.2854, found: m/z 746.2888 [M + H]+.By a procedure similar to that for compound S-transferase (GST) antibody labelled with europium cryptate which binds GST-tagged human cereblon/DDB1 protein. This assay can be used to detect competitive ligand that replaces the binding of thalidomide to human cereblon/DDB1 protein. GST-tagged human cereblon and DDB1 protein was co-expressed by using baculovirus expression system. The GST-tagged protein complex was purified by using Glutathione Sepharose (Cytiva LifeSciences) and the purity of the recombinant protein was confirmed by SDS-PAGE. The competitive binding of a given compound was measured by incubating various concentrations of compounds with 100 nM cereblon/DDB1 in a buffer containing 50 mM Tris at pH 7.5 and 200 mM NaCl. Final concentration of DMSO was kept at 2.5%. Subsequently, the reaction was added 20 μL of 10 nM XL-665-labelled-thalidomide and 100 nM europium cryptate-labelled GST antibody. All assays were performed in 384-well plates (Geiner Bio-One) and the signals were measured using a Pherastar (BMG) plate reader with excitation at 337 nm and emission at 665 nm/620 nm for detection. The ratio of the acceptor  and the donor  emission signals were used for calculation of EC50 values by using a nonlinear fit model (GraphPad Prism Software). Data was presented as means ± standard deviation (n = 3).A cereblon TR-FRET binding assay was developed by using XL-665-labelled thalidomide (Perkin Elmer) and a specific glutathione 208–414, C-TDP-43) were constructed into pEGFP-C3 vector , Academia Sinica). To get the mCherry-C-TDP-43 and FLAG-C-TDP-43 plasmid, C-TDP-43 was subcloned from pEGFP-TDP-43208–414 construct into pcDNA3.1-mCherry and pCMV-tag2B vector, respectively. Either eGFP, mCherry, and FLAG was fused N-terminally of TDP-43208–414. The pEGFP-C3 and pcDNA3.1-mCherry plasmid were used as control plasmids for FLIM-FRET experiments.The cDNA encoding N-terminal truncated TDP-43  at 37 °C in a humidified incubator containing 5% CO2.Neuro-2a cell is the mouse neuroblastoma cell line from Dr. Yijuang Chern . Neuro-2a cells were cultured in Dulbecco’s modified Eagle’s medium  containing 2 × 10g at 4 °C for 40 min . The supernatant (RIPA-soluble fraction) was carefully collected and the pellet of C-TDP-43 aggregates was further washed with RIPA buffer. During the washing step, the pellet was resuspended by 200 μL RIPA buffer and centrifuged at 70,000 g at 4 °C for 10 min. After centrifugation, the supernatant was carefully removed. Then, the washing step was repeated to remove most of the remaining RIPA-soluble protein. Lastly, 50 μL 1% sarkosyl buffer (1 g sarkosyl in 50 mL PBS buffer) was added into the pellet tube, followed by intense pipetting to resuspend the pellet (sarkosyl-soluble fraction). Both the RIPA-soluble and insoluble samples were further processed for detection by using western blot.This method demonstrated how to collect the RIPA-insoluble C-TDP-43 aggregates for SDS-PAGE analysis. RIPA buffer-lysed C-TDP-43 expressing Neuro-2a cells were centrifuged at 70,0004 cells/well and incubated overnight. The attached Neuro-2a cells were then transfected with the eGFP-C-TDP-43 plasmid (1.1 μg) using TurboFect™ transfection reagent (Invitrogen) according to manufacturer’s recommendations. After 2 h transfection, Neuro-2a cells were further treated with or without 5 μM PROTAC (compounds 1–4). The cell viability indicator, AlamarBlue (Invitrogen), was added after 42 h of incubation, and the mixture was incubated for another 6 h . Two-hundred μL conditioned medium was transferred to a 96-well plate, and cell viability was determined by the increased fluorescence intensity .Neuro-2a cells were seeded in a 24-well plate at a concentration of 8 × 105 cells/well and incubated overnight. Then, Neuro-2a cells were transfected with the eGFP-C-TDP-43 plasmid (2.2 μg) using Turbofect transfection reagent (Invitrogen) and treated with or without 5 μM PROTAC molecules after 2 h transfection. After incubation for another 22 h, the transfected cells were harvested by RIPA buffer containing protease inhibitor (Roche) and sonicated on ice for 10 s. Extracts were centrifuged at 14,000 rpm for 10 min at 4 °C, followed by measurement of protein concentration using a bicinchoninic acid (BCA) assay. For filter trap assay, 300 μL sample  were passed through 0.2 μm cellulose acetate (CA) membranes  membranes using a 48-well slot-blot apparatus. Aggregated eGFP-C-TDP-43 protein retained on CA membranes was determined by immunoblotting with TDP-43  antibody . Amersham™ protein® Nitrocellulose (NC) membranes  were applied to slot blot assay for soluble protein lysate analysis (endogenous TDP-43 and loading control).Neuro-2a cells were seeded in a 6-well plate at a concentration of 2 × 106 (blank control) or 2 × 106 (mCherry-C-TDP-43 overexpression) cells/mL. After overnight incubation, Neuro-2a cells were transfected with the mCherry-C-TDP-43 plasmid (10 μg) using Lipofectamine® 3000 (Invitrogen) and incubated for another 24 h. The transfected cells were then harvested with RIPA buffer containing complete protease inhibitor (Roche) and sonicated on ice . Next, PROTAC 2 at various concentrations  was added to each extract . The mixtures (PROTAC 2 + cell lysate) were gently shaken at 4 °C for 2 h. After that, the mixtures were fractionated and the RIPA-insoluble fraction were resuspended with RIPA buffer and loaded on CA membrane by applying filter trap assay. The fluorescent PROTAC 2 retained on C-TDP-43 aggregates was detected by Typhoon9410 Variable Mode Imager  .Neuro-2a cells were seeded in 10 cm dishes at a concentration of 1 × 106 cells in sterile 35 mm µ-Dish ] were transfected with mCherry-C-TDP-43 (1.1 µg) by TurboFect transfection reagent (Invitrogen). For quantifying the C-TDP-43 aggregates in the presence or absence of PROTAC 2 or MG132, mCherry-C-TDP-43 transfected cells were treated with PROTAC 2 (5 µM) after 2 h of transfection. For the group intended to block proteasome activity, MG132 (2 μM) was pre-treated 1 h before adding PROTAC 2. After total 24 h incubation, the Neuro-2a cells were fixed  and subsequently imaged with NIKON TiE microscope. Epifluorescence images were illuminated with an ultrahigh pressure mercury lamp (130 W) for UV excitation or using a 488 nm laser light source. Filters were used to collect fluorescence emission including excited eGFP  and mCherry  cubes. Cellular images were captured with an Andor iXon3 888 back-illuminated high-sensitivity EMCCD camera. Images were edited and cropped using Nikon NIS element software.Neuro-2a cells . The eGFP-C-TDP-43 excitation sources came from 488 nm (5 mW) sub-nanosecond modulated pulsed laser at the fundamental frequency of 20 MHz was controlled by ISS VistaVision software. The photon counts of eGFP were collected by GaAs photomultiplier tube (PMT) detector with EM1 filter (530/43 nm bandpass filter). To precisely obtain the lifetime value, the calibration of the system was operated by measuring fluorescein, a fluorophore with a single exponential lifetime around 4 ns in ddH2O, every time before the measurement.To study the EFRET maps and per-pixel distribution histogram (the population of each pixel corresponding to the EFRET maps)  Fig. B.2 would not form crosstalk with the eGFP donor .To fairly judge the E6 cells/dish) and treated after 2 h with PROTAC 2 (5 µM) or both PROTAC 2 (5 µM) and MG132 (2 µM). After 48 h incubation, the transfected cells were harvested in 1000 μL of ice-cold RIPA buffer containing protease inhibitor cocktail (Roche) and sonicated on ice for 1 min. Extracts were centrifuged at 14,000 rpm for 10 min at 4 °C and the protein concentrations were determined using BCA assay. Samples containing 300 μg of total proteins in a volume of 500 μL were filtered with a 0.22 μm filter (Millipore) and fractionated on a Superdex 200 10/300 column  at a flow rate of 0.3 mL/min. Each fraction (1 mL volume/fraction) was collected and subjected to western blot and slot blot analysis.Neuro-2a cells harboring eGFP-C-TDP-43 (10 µg) were seeded in 10 cm dishes ] and IW62 [Psnb-1::YFP(iwIs25)], respectively . The strains of nematodes were maintained with standard procedure and grown at 20 °C [2HPO4, 871 mL 0.05 M KH2PO4, 5.85 g NaCl) for overnight. For drug treatments, PROTAC 2 or/and DMSO were solely or along with MG132 applied to fresh NGM plates prior to installing the synchronized C. elegans. The body bends of the corresponding treatment in a duration of 30 s of the various strains were documented through SMZ800N stereomicroscope equipped with a CCD camera (Nikon). A body bend was counted as the head of one-day adult C. elegans travels across the mid-body in 1 × PBS buffer. Then, the bending videos of C. elegans were analyzed by ImageJ with the wrMTrck plugin [2 on C-TDP-43 accumulation in L4 worms, the confocal images were captured with LSM 780 (Zeiss).The YFP-C-TDP-43 and YFP transgenic strains of at 20 °C . For lark plugin . For monStatistical comparison of multiple independent groups was conducted by one-way ANOVA with Tukey or Dunnett post-hoc test. Two-way ANOVA with False Discovery Rate post-hoc test was used to determine the effect of two nominal predictor variables on a continuous outcome variable. Statistical comparison of two independent groups was done by two-tailed unpaired t-tests. Significance was accepted at p < 0.05. ns is not significant. All the statistical figures and analysis were done by GraphPad Prism9 software.7 phenylboronic acid (6) underwent Suzuki coupling reaction by the catalysis of Pd(dppf)Cl2 to form anisole 7 as the core structure of TDP-43 binder [7 was treated with BBr3 at 0 °C to obtain the 6-hydroxy substituted BTA (8). As an example, BTA 8 was subjected to alkylation with a PEG linker N3CH2CH2(OCH2CH2)OMs in the presence of K2CO3, followed by reduction of the azido group to amino group, to afford compound 9a. The conjugation of 9a with a pomalidomide analog 10, which bears a fluorine atom at the 4-position of the isoindoline ring, was conducted in 1-methyl-2-pyrrolidone (NMP) [1 (JMF4605). Other PROTAC molecules 2–4  having different PEG units were similarly synthesized (Supplementary Scheme S1 and S2). The successful conjugation reaction should not be performed under alkaline conditions in order to retain the imide groups in the pomalidomide structure.Bearing the linker optimization issue in mind, we synthesized PROTACs 3 binder . Anisolene (NMP) , an apro1–4 can induce C-TDP-43 aggregates degradation by expressing eGFP-TDP-43208–414 (hereafter referred as eGFP-C-TDP-43) in Neuro-2a cells  membrane  markedly reduced the eGFP-C-TDP-43 aggregates  and other PROTAC-treated groups did not significantly affect endogenous TDP-43 protein level compared to mock . PROTACs with shorter linker (PROTAC 1 and 2) showed neglectable cytotoxicity compared to mock group of Neuro-2a cells   [2 treatment. According to the western blot results, GSPT1 level remains stable irrespective of PROTAC 2 treatment at various concentrations  , we also , we als1–4 to CRBN with an in vitro time-resolved fluorescence resonance energy transfer (TR-FRET) assay  with the EC50 values in the range of 0.6–2.6 μM . We also examined whether PROTAC 2 can bind to C-TDP-43 aggregates by in vitro protein binding assay  colocalized with mCherry-C-TDP-43 aggregates . Both RIPA-soluble and insoluble fractions were further analyzed by SDS-PAGE with immunoblotting.Both ubiquitin–proteasome system (UPS) and autophagy pathway may account for the clearance of misfolded TDP-43 . General2 reduced the amount of insoluble C-TDP-43  (72%) compared to PROTAC 2 (33%) and the mock (59%)  was applied to monitor the population of C-TDP-43 oligomer. Since FLIM-FRET reflects the energy transfer through dipole–dipole coupling of a fluorescent donor and acceptor [In addition to TDP-43 aggregates, cumulative studies have also disclosed the pathological role of oligomeric TDP-43 in neurodegenerative diseases . As PROTacceptor , we furt2  lifetime fitting analysis (frame model) to obtain the efficiency of FRET (EFRET) maps and per-pixel distribution histograms from the FLIM image  in Neuro-2a cells  value in the cytosol   had similar expression yield . According to the FD lifetime fitting data of Additional file 2 significantly decreased the EFRET of the C-TDP-43 oligomeric intermediates from 48.92% to 40.11%  to the soluble ones (oligomers + monomers). By setting the threshold of the photon counts, we defined the 2FP-C-TDP-43 species which emitted high photon counts (red pixels) as “aggregated C-TDP-43”  transgenic C. elegans strains, which ectopically express either YFP alone or the YFP fused with a 25 kDa C-terminal fragment of human TDP-43 in the pan-neuron system [2, we recorded the cytosolic aggregates and kept tracing the thrashing frequency of YFP-C-TDP-43 C. elegans in the presence or absence of PROTAC 2.Progressive behavior impairment is the hallmark of ALS pathology . Other taluation . Herein,n system  . Furthermore, we utilized YFP control strain to confirm the degradation specificity of PROTAC 2. As shown in Additional file 2. Conclusively, PROTAC 2 only decreased the cytosolic aggregates in YFP-C-TDP-43 strain  as a CRBN binder, a benzothiazole-aniline (BTA) as a binder of C-TDP-43 protein in β-sheet structures, and a tetraethyleneglycol (TEG) linker to promote formation of the POM–TEG–BTA tertiary complex and thus enable degradation of C-TDP-43 aggregates via ubiquitin proteasome system. Compared to the positively charged thioflavin T (ThT), the electrically neutral BTA may have better cell permeability [S13) having aliphatic linkers (Supplementary Scheme S3) and a lenalidomide–BTA compound S18 that is connected by a triazole-containing linker (Supplementary Scheme S4). However, these compounds rendered low water solubility as the hydrophobicity of linkers increased, and their use as PROTACs was not further examined.PROTAC technology is known for inducing targeted-protein degradation and has been utilized in the field of cancer, immunity, and virus studies –17. Receeability  and higheability  to amylo1) significantly lost its TDP-43-degrading capability . Taken together, optimizing the length of linker is essential for the development of PROTACs in order to gain the potent efficacy and drug safety.During the PROTACs design and evaluation process, we found the length of linker was correlated with the degradation ability and cytotoxicity. Generally, the linker should be long enough to avoid steric hindrance between the target protein and E3 ligase, while the linker cannot be too long to cause futile transfer of ubiquitins . Zorba aity Fig. B. It wase.g. GSPT1) have just been identified [2 did not induce GSPT1 off-targeting degradation , unpredictable side effect of PROTAC may sometimes occur by occupying endogenous E3 ligase , 78. Anoentified ; howeverAlthough PROTACs appear to have many advantageous features for potential therapeutic uses, there are still many obstacles to be overcome, such as pharmacokinetics in the human body and blood–brain-barrier (BBB) penetration for treatment of CNS diseases. Lipinski’s rule of five (Ro5)  has been2 significant reduced C-TDP-43 aggregates, the beneficial effect on C-TDP-43 cytotoxicity in Neuro-2a and motor neuron defects in C. elegans were relatively minor. This disparity between degradation efficiency and beneficial results may arise from the loss of function of TDP-43 [2 treatment. Furthermore, while PROTAC 2 has been reported to degrade the misfolding protein aggregates, we provided new evidence to demonstrate PROTAC 2 could decrease both the amount and the compactness of cytosolic oligomers synchronously. As progressive transition of aggregation reflects the intrinsic energy states in aberrant amyloid protein [FRET of C-TDP-43 oligomeric intermediate in the aforementioned experiment suggested PROTAC 2 could also decrease the intrinsic energy state and interfere with the conformation of C-TDP-43 oligomers. The similar case has been reported in the other amyloid protein binding peptides (i.e. peptides against mutant Huntingtin protein). [It is also worthy to note that though PROTAC f TDP-43 . Increasf TDP-43 . Conclus protein , reductirotein). 2 is the first case which can effectively degrade C-TDP-43 oligomers in addition to its protein aggregates, which provides an alternatively therapeutic strategy against TDP-43 proteinopathy in ALS. To further examine the detailed therapeutic effects of PROTAC 2, the advanced studies of other animal models, including rodents with the mutant TDP-43 aggregates [As far as we know, PROTAC gregates , 89, wou2 (JMF4560) significantly reduced C-TDP-43 aggregates and alleviated C-TDP-43-induced toxicity through the proteasomal degradation (Fig. C. elegans, we also observed that PROTAC 2 was capable of reducing C-TDP-43 aggregates in the nervous system and exhibited beneficial effect on its motility (Fig. 2 could reduce the compactness of C-TDP-43 oligomeric intermediates and decrease their population. By demonstrating the efficiency of our newly-designed PROTACs on the degradation of C-TDP-43 aggregates and oligomers, we wish to develop these small molecules as new drugs against misfolding proteins in neurodegenerative diseases.Herein, we demonstrated that PROTAC 2 JMF450 signifi2 JMF450 signifiAdditional file 1. Figures S1–S9, synthetic schemes S1–S4, synthetic procedures and characterization of compounds, 1H and 13C NMR, absorption, and fluorescence spectra, and HPLC diagrams.Additional file 2. Video of YFP transgenic C. elegans during motility assay.Additional file 3. Video of YFP-C-TDP-43 transgenic C. elegans during motility assay.Additional file 4. Video of YFP-C-TDP-43 transgenic C. elegans upon PROTAC 2 treatment during motility assay.


Hospital-onset (HO) carbapenem-resistant Enterobacterales (CRE) infections are increasing; recently, the Centers for Disease Control and Prevention (CDC) reported a 35% increase during the COVID-19 pandemic. We evaluated the impact of HO CRE blood stream infections (BSI) on outcomes compared to community-onset (CO) CRE BSI.Patients prospectively enrolled in CRACKLE-2 from 56 hospitals in 10 countries between April 30, 2016 to November 30, 2019 with a qualifying CRE bloodstream culture were eligible. Infections were defined per CDC guidelines as CO when the culture was obtained immediately prior to admission or through the first three days of hospitalization, and HO when the culture was obtained on or after the fourth day of admission. Categorical variables were tested using a chi-square test; continuous variable distributions were compared using Wilcoxon rank sum and Kruskal Wallis tests, as appropriate. The primary outcome was desirability of outcome ranking (DOOR) 30 days after index culture. Difference in 30-day mortality was calculated with 95% confidence intervals (CI).Figure 1. The probability of a better DOOR outcome in a randomly selected patient with CO BSI compared to a patient with HO BSI is 60.6% (95% CI: 56.8-64.3%). Mortality at 30-days was 11.6% higher in HO BSI than CO BSI . A Kaplan-Meier curve of all-cause 30-day mortality is in Figure 2Among 891 patients with CRE BSI (Table 1), 65% of BSIs were hospital-onset (582/891). Compared to those with CO CRE, patients with HO CRE were younger , had lower Charlson comorbidity score , and more often had Pitt bacteremia sore ≥4, indicative of critical illness, . ICU admission prior to first culture was associated with HO BSI . Distribution of DOOR outcome at 30 days is shown in Desirability of outcome ranking at 30-days. Events evaluated included 1) deleterious effects, including absence of clinical response, prolonged hospitalization (>30 days following first positive culture), or readmission within 30 days; 2) any adverse events including renal failure or C. difficile infection; and 3) mortality at 30 days. Two subjects  missing 30-day DOOR due to missing disposition information are not included in the figure.Two subjects  are excluded from the figure due to missing mortality outcome information. One subject in the hospital onset group died on day 30 and is still considered at risk in the figure.HO CRE BSIs are associated with worse outcomes than CO CRE BSIs; this unique population warrants special attention. As CRE often contain mobile genetic elements that facilitate horizontal transfer, close monitoring of HO CRE rates and optimizing hospital infection prevention methods are critical to prevent added morbidity and mortality.Yohei Doi, MD, PHD, bioMerieux: Advisor/Consultant|FujiFilm: Advisor/Consultant|Gilead: Advisor/Consultant|Gilead: Honoraria|GSK: Advisor/Consultant|Meiji Seika Pharma: Advisor/Consultant|Moderna: Advisor/Consultant|Moderna: Honoraria|MSD: Advisor/Consultant|MSD: Honoraria|Shionogi: Advisor/Consultant|Shionogi: Grant/Research Support|Shionogi: Honoraria Michael J. Satlin, MD, AbbVie: IDMC member|Biomerieux: Grant/Research Support|Merck: Grant/Research Support|SNIPRBiome: Grant/Research Support Vance G. Fowler, MD, MHS, Amphliphi Biosciences, Integrated Biotherapeutics; C3J, Armata, Valanbio; Akagera, Aridis, Roche, Astra Zeneca: Advisor/Consultant|Genentech, Regeneron, Deep Blue, Basilea, Janssen;: Grant/Research Support|Infectious Diseases Society of America: Honoraria|MedImmune, Allergan, Pfizer, Advanced Liquid Logics, Theravance, Novartis, Merck; Medical Biosurfaces; Locus; Affinergy; Contrafect; Karius;: Grant/Research Support|Novartis, Debiopharm, Genentech, Achaogen, Affinium, Medicines Co., MedImmune, Bayer, Basilea, Affinergy, Janssen, Contrafect, Regeneron, Destiny,: Advisor/Consultant|Sepsis diagnostic: Patent pending|UpToDate: Royalties|Valanbio and ArcBio: Stock Options David van Duin, MD, PhD, Entasis: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Grant/Research Support|Pfizer: Advisor/Consultant|Pfizer: Honoraria|Qpex: Advisor/Consultant|Roche: Advisor/Consultant|Shionogi: Advisor/Consultant|Shionogi: Grant/Research Support|Union: Advisor/Consultant|Utility: Advisor/Consultant


The tensile yield strength of epoxy/graphene composites could be either enhanced or weakened by GBs under a tensile load parallel to the graphene sheet. The underlying mechanisms may be attributed to multi-factor coupling, including the tensile strength of the reinforcements, the interfacial interaction energy, and the inflection degree of reinforcements. A balance exists among these effect factors, resulting in the diversity in the tensile yield strength of epoxy/graphene composites. The compressive yield strength for epoxy/graphene composites is higher than their counterpart in tension. The tensile/compressive yield strength for the same configuration presents diversity in different directions. Both an excellent interfacial interaction and the appropriate inflection degree of wrinkles for GB configurations restrict the translational and rotational movements of epoxy chains during volume expansion, which eventually improves the overall gT. Understanding the reinforcing mechanism for graphene with GBs from the atomistic level provides new physical insights to material design for epoxy-based composites containing defective reinforcements.This work presents a molecular dynamics (MD) simulation study on the effect of grain boundaries (GBs) on the mechanical properties of epoxy/graphene composites. Ten types of GB models were constructed and comparisons were made for epoxy/graphene composites containing graphene with GBs. The results showed that the tensile and compressive behaviors, the glass transition temperature ( Epoxy with a cross-linked network structure is the most promising high-performance thermosetting polymer for multifunctional composites due to its excellent mechanical properties, good chemical stability, and durability. These characteristics make epoxy widely used in aerospace, coating, adhesives, electronics, automotive, and biotechnology fields ,3,4,5,6.Extensive experimental and computational studies were carried out on epoxy/graphene systems, highlighting significant improvements in their mechanical and thermal properties with the incorporation of graphene into epoxy ,20,21,22Although a significant amount of research has been performed to study the effect of graphene as reinforcement on the mechanical and thermal properties of epoxy, the reports are mostly focused on the effect of pristine and functionalized graphene. In fact, due to the limitations of synthetic techniques, the crystal growth of large-size graphene during the chemical vapor deposition (CVD) method leads to the formation of geometrical defects such as vacancies, dislocations, and grain boundaries (GBs) ,27. The Although these research works have made progress on the effect of GBs on the mechanical properties of graphene, there is a lack of research related to the effect of GBs on the mechanical and thermal properties of polymer/graphene composites. Verma et al.  evaluategT) of bi-crystalline graphene-reinforced epoxy composites. The stress–strain response, yield strength, elastic moduli (including Young’s modulus and compressive modulus), interfacial interaction energy, and gT of epoxy composites reinforced by pristine graphene and graphene with GBs are also estimated. The mechanism associated with the GB parameters on the mechanical properties and the thermal stability properties is proposed as well. Therefore, this work provides a theoretical basis for the industrialization of nano-reinforced graphene composites.In this work, using the MD method, we investigated in detail the effect of 10 types of GBs on the tensile/compressive behaviors and the glass transition temperature (n = 0). The atomistic models for the DGEBA and TETA segments are shown in L, mL) and  of the left and right crystalline domains. The constructions of GBs along the ZZ and AM directions are shown in The polymer matrix was composed of di-glycidyl ether of bisphenol A (DGEBA) as the resin matrix and triethylenetetramine (TETA) as the hardener. To reduce the computational cost, the polymerization degree of the initial DGEBA prior to cross-linking was set to 0  package . The ato−1, followed by another 100 ps equilibration under an isothermal-isobaric (NPT) ensemble at 300 K and 1 atm. Then, a series of cross-linked reactions were performed using a cross-linking algorithm [During the analysis, models with cross-linking degrees of around 84% were considered. The initial uncross-linked models were minimized using the conjugate gradient method with an energy convergence criterion of 0.0001 kcal mollgorithm ,41. No algorithm  and 100%−1. The tensile and compressive deformation processes were performed under an NPT  ensemble with an integration time step of 1 fs. The atomic stress was calculated using the virial theorem [After the initial cross-linked models were established, the mechanical properties of the epoxy/graphene composites were investigated by uniaxial tension and compression deformation using MD simulations. Three independent samples for each individual epoxy/graphene model were utilized for statistical analysis to quantify the errors. The final value of the mechanical properties was the average of three independent results and the error bars were determined by standard deviation. Before deformation, the initial cross-linked structures were minimized with the help of the conjugate gradient algorithm. Subsequently, the systems were relaxed with multi-step equilibration processes with an isothermal-isochoric (NVT) ensemble at 300 K for 1 ns, NPT  ensemble for 1ns, and an additional NVT (T = 300 K) ensemble for 1ns. The integration time step during the equilibration process was set to 0.25 fs. The root–mean–square displacement (RMSD) was examined to confirm the full equilibrium state. After the equilibration process, a constant uniaxial strain was applied along the x, y, or z directions at a strain rate of 0.0005 ps theorem ,34,43: and perpendicular to the graphene sheets were performed for all epoxy/graphene composites to investigate the effect of GBs on the mechanical properties of epoxy/graphene composites. Because it can directly influence the GB normal strength for graphene sheets, the stress component perpendicular to GBs can better reflect the effect of GBs on the properties of graphene . Thus, tTo further investigate the mechanism of GBs affecting the tensile mechanical properties of epoxy/graphene composites, the effect of the misorientation angle, the tensile strength of graphene sheets, the interaction energy, and the inflection angle on the tensile yield strength of epoxy/graphene composites with a tensile direction parallel to the graphene sheet were analyzed. In order to further comprehend the factors affecting the yield strength of epoxy/graphene composites, the interaction energy between the epoxy matrix and graphene with GBs was calculated using the following expression ,51.(2)ΔAs shown in In a word, the tensile yield strength of epoxy/graphene composites is affected by multi-factors simultaneously, including the tensile strength of the reinforcement, the interaction energy, and the structure of the reinforcement. The physics behind the enhancement in the mechanical properties of composites reinforced with graphene is complicated; a balance exists among these factors leading to a great difference in the tensile yield strength of all the GBs configurations.To further investigate the effect of GBs on the mechanical properties of epoxy/graphene composites, uniaxial compression along parallel and perpendicular directions to the interface was performed for different configurations of epoxy/graphene composites. The composite compression responses for pristine graphene and graphene with GB-reinforced epoxy composites are plotted in A uniaxial compressive simulation for the ZZ and AM configurations was performed with a compressive load parallel to the interface and perpendicular to the GB lines, as illustrated in From gT was calculated for all models. Note that it is a key thermal property affecting the mechanical properties, chemorheology, and internal stresses of thermosetting polymers [To understand the effect of GBs on the thermal stability of epoxy/graphene composites, polymers ,54,55.gT of all epoxy/graphene composites was determined by measuring the density of the composites while the NPT equilibration temperature levels gradually decreased from 600 to 300 K in increments of 20 K. During the cooling process, the structures were equilibrated for 500 ps under NPT ensemble (P = 1 atm) at each temperature with a density tolerance of 0.02 g/cm3. After fitting the data with a straight line, the value of gT could be obtained by searching for the intersection point of the density–temperature curves. In addition, the epoxy composite goes through a transition from a rubbery state, which is identified with a large slope, to a glassy state, which is identified with a small slope, during the cooling process [The  process .gT calculated by density-temperature curves are tabulated in gT of pristine graphene-reinforced epoxy composite is about 422.8 K, which is in good agreement with the value of 418.0 K from previous results [gT of epoxy composites. The gT of Epoxy/ZZ 8.9 and Epoxy/ZZ 9.4 are shown to be 456.2 K and 462.1 K, which are about a 7.9% and 9.3% improvement compared with that of epoxy/ZZ GRP, respectively. From gT of the other AM configurations is higher than that of Epoxy/AM GRP. The gT of Epoxy/AM 13.2 and Epoxy/AM 15.2 are shown to be 455.9 K and 455.6 K, which are about 33.1 K and 32.8 K higher than that of Epoxy/AM GRP, respectively. results . AdditiogT in pristine graphene and graphene containing GB reinforced epoxy composites is mainly related to the excellent interfacial interaction and the inflection degree of the wrinkles in graphene sheets. The strong interfacial interaction between the epoxy matrix and reinforcement can help to restrict the translational and rotational movements of epoxy chains during volume expansion. Moreover, the wrinkle structure of graphene with GBs increases the surface roughness, which is also conducive to blocking the slippage of epoxy chains. It also allows the composites to be heated evenly, avoiding heat concentration in the materials. However, the heavy wrinkle structure weakens the interfacial interaction energy to a certain degree, which creates a complex balance in influencing the gT of the epoxy/graphene composites. The gT of Epoxy/AM 27.8 is lower than that of epoxy/AM GRP, which is mainly due to its relatively weak interfacial interaction  and the low inflection angle of the graphene sheet (about 15°). The higher gT of Epoxy/ZZ 9.4 is related to its relatively strong interfacial interaction  and the appropriate inflection angle of the graphene sheet (about 41°). The improvement in gT indicates that the epoxy/graphene composites need a higher temperature to change from a glassy state to a rubbery state and that the strength of epoxy/graphene composites can remain stable at a higher temperature.The improvement of gT of epoxy/graphene composites are significantly affected by GBs. When the tensile load is parallel to the graphene sheet and perpendicular to the GB lines, the existence of GBs can either enhance or weaken the tensile yield strength of epoxy/graphene composites. The Epoxy/ZZ 9.4 and Epoxy/AM 21.8 configurations present stronger tensile yield strengths, which are considered to be superlative configurations. Multiple factors affect the tensile yield strength of epoxy/graphene composites, including the tensile strength of the reinforcement, the interfacial interaction energy, and the inflection degree of reinforcement. There is a complex balance of these influencing factors which leads to the difference in the tensile yield strength of all the GB configurations. The compressive yield strength for all GB configurations is stronger than the tensile yield strength, and diversity exists for the tensile (compressive) yield strength due to different loading directions. Graphene-containing GB-reinforced epoxy composites obtain a higher gT compared with pristine graphene-reinforced epoxy. The enhancement mechanism can be attributed to the excellent interfacial interaction and appropriate inflection degree of wrinkles in the graphene sheets with GBs. This work will shed light, from the molecular level, on the material design for epoxy composites containing defective reinforcements for practical applications.In summary, the effect of pristine graphene and graphene with GBs on the mechanical properties of epoxy composites was investigated using MD simulations. The results show that the yield strength, elastic moduli (Young’s modulus and compressive modulus), and


The trend of the RSE values is in good agreement with the experimentally evaluated thermal tolerance of a series of mechanoresponsive RMs based on the bisarylcyanoacetate motif. Furthermore, the singly occupied molecular orbital (SOMO) levels clearly exhibit a negative correlation with σp within a series of RMs that are based on the same skeleton, paving the way toward the development of RMs that can be handled under ambient conditions without peroxidation.Radical-type mechanophores (RMs) are attractive molecules that undergo homolytic scission of their central C–C bond to afford radical species upon exposure to heat or mechanical stimuli. However, the lack of a rational design concept limits the development of RMs with pre-determined properties. Herein, we report a rational design strategy of RMs with high thermal tolerance while maintaining mechanoresponsiveness. A combined experimental and theoretical analysis revealed that the high thermal tolerance of these RMs is related to the radical-stabilization energy (RSE) as well as the Hammett and modified Swain–Lupton constants at the  Radical-type mechanophores (RMs) are attractive molecules that undergo homolytic scission of their central C–C bond to afford radical species upon exposure to heat or mechanical stimuli. Radical-type mechanophores (RMs), which undergo mechanical-stimuli-induced homolytic scission of their central C–C bonds to afford radical species, have been used to study micro-to-macroscale mechanical stimuli, strengthened materials based on sacrificial bonds, or subsequent polymer propagation.13–23The development of mechanoresponsive materials (MRMs) that exhibit a variety of macroscale functionalities, including coloring, fluorescence, self-healing, and self-strengthening, upon exposure to mechanical stimuli has been a research hotspot in materials science during the past few decades.18,24 In contrast, the central C–C bond of difluorenylsuccinonitrile (DFSN), which exhibits the highest thermal tolerance among hitherto reported RMs, does not dissociate up to 100 °C.22 The extraordinary thermal tolerance of DFSN inspired us to apply the radical-polymerization methodology to develop highly mechanoresponsive or shape-memory materials.15,25,26 However, despite the clear importance of decreasing the propensity of the central C–C bond to subdue to thermal scission while preserving its ability to scission upon exposure to mechanical impact, the relationship between both phenomena is still unclear, which limits the scope of RM-based materials.The nature of the central C–C bond of RMs exerts a great impact on the functionality of the resulting polymeric materials. For example, the central C–C bonds of diarylbibenzofuranone (DABBF) and tetraarylsuccinonitrile (TASN) readily dissociate even at ambient temperature, which makes it possible to endow the polymeric material with self-healing properties.i.e., the radical-stabilization energy (RSE) (27–31 as well as the Hammett and modified Swain–Lupton constants at the para-position (σp)  27–31 as ion (σp) .32 The Reactions . We simueactions . Meanwhitic part .σp in a series of representative radical molecules including derivatives of arylbenzofuranone (ABF), arylbenzothiophenone (ABT), arylindolinone (AI), diarylacetonitrile (DAAN), cyanofluorene (CF), aryldicyanomethane (ADCM), arylcyanoacetate (ACA), and arylmalonate (AM). Dimers of ABF, ABT, AI, DAAN, and CF radicals are radical-type mechanophores previously developed in our group.18,22,24,33,34 In order to elucidate the electron-donating or -withdrawing nature of these radicals, not only ADCMs, which are well-known stable radicals under ambient conditions that possess two electron-withdrawing cyano groups,35–45 but also ACAs and AMs were investigated as ADCM analogues.46,47 The relationship between RSE and σp is plotted in σp range. The RSE value clearly increases with increasing σp value in the region of σp < 0, where the electron-donating nature of the functional groups increases with decreasing σp value. In contrast, the RSE values did not show significant changes and almost saturated in the region of σp > 0, where the electron-withdrawing nature of the functional groups increases with increasing σp value. These trends were theoretically reproduced irrespective of the computational methodology used , with a series of functional groups at the para-position as novel RMs  levels52–54 and slow C–C bond cleavage under ambient conditions (vide infra). We conducted variable-temperature electron paramagnetic resonance (EPR) spectroscopic measurements to determine the bond dissociation ratio (BDR) of the central C–C bond of the RMs and their dissociation constant (Kd) at 100 °C (Table S1Kd (ln Kd) are plotted as a function of increasing RSE and σp values of the BiACAs. As expected, the BDR and ln Kd values decrease with increasing RSE and σp values. Specifically, BDR and ln Kd values of 158 × 10−3% and −16.7, respectively, were obtained for BiACA-1 , 12.1 × 10−3% and −21.6 for BiACA-2 , 1.37 × 10−3% and −26.3 for BiACA-3 , 0.41 × 10−3% and −27.3 for BiACA-4 , and 0.20 × 10−3% and −28.7 for BiACA-5 . Furthermore, BiACA-5 exhibited one of the highest levels of thermal tolerance among our previously reported RMs. These results indicate that the thermal tolerance of RMs can be correlated with the RSE values and, therefore, with the substituent effect associated with the σp value.To prove this hypothesis experimentally, we synthesized ACA dimers, ovel RMs . In cont Table S1. In Fig.55,56 According to this postulate, the energy barrier between reactants, i.e., RMs, and products, i.e., radicals generated from RMs, is amenable to the thermodynamic stability of the products. Thus, RMs that bear electron-withdrawing groups, which showed shallow RSE values and, in turn, low thermodynamic stability, exhibit a higher energy barrier for thermal dissociation into the corresponding radical products, indicating higher thermal tolerance. Although DFT is a powerful tool to evaluate the dissociation of the central C–C bond and the TS in RMs, the rotation of the central C–C bond, which leads to complicated rotamers, hinders the interpretability of the results. The present approach provides a simple method for the prediction of the thermal tolerance of RMs without complicated TS searches.The relationship between RSE/thermodynamic stability and the thermal tolerance of RMs can be explained by the Hammond–Leffler postulate , which dvia the atom transfer radical polymerization (ATRP) of methyl methacrylate using a bifunctional initiator consisting of the BiACA-4 skeleton   is 246 times higher than that obtained at 100 °C (0.41 × 10−3%), indicating that the mechanical stimulus (grinding) greatly enhances the C–C bond dissociation. These results indicate that the thermal tolerance of an RM can be increased without significantly deactivating its mechanochemical reactivity.To investigate the mechanochemical reactivity of BiACAs, a poly(methyl methacrylate) (PMMA) derivative, PMMA-BiACA-4-PMMA, was synthesized skeleton . The Br hy (GPC) . A compa58–68Fmax) of BiACAs vs. σp. The Fmax value increases in the region σp < 0 and was almost saturated in the region σp > 0, similar to the case of the plots of RSE vs. σp  calculations, which allow theoretically evaluating the mechanochemical reactivity .58–68FigE vs. σp  and 2. T54 In this study, the SOMO levels clearly show a negative correlation with the σp values within the series of radicals that share the same skeleton, reflecting the substituent effect at the para-position  skeletons with different electron density. Furthermore, not only the thermal but also the oxygen tolerance could be related to the SOMO level, and the oxygen tolerance can thus be tuned according to this parameter. Our results provide a systematic guideline for the design of RMs with various functionalities while maintaining good thermal tolerance.In conclusion, we have demonstrated a rational designing strategy of RMs with high thermal tolerance. According to the relationship between the RSE and 2207403). The NMR and EPR spectra and the results of DFT calculation and CoGEF studies are provided in the ESI.†The data generated in this study are available in the main text or the ESI.H. S., K. M. and H. O. conceptualized this work. H. S. designed the experiments and carried out DFT calculations. Y. L. performed experiments include ESR measurement. All authors wrote the manuscript. Y. L. and H. S. prepared the ESI.†There are no conflicts to declare.SC-014-D3SC02991C-s001SC-014-D3SC02991C-s002


Two-dimensional metals stabilized at the interface between graphene and SiC are attracting considerable interest thanks to their intriguing physical properties, providing promising material platforms for quantum technologies. However, the nanoscale picture of the ultrathin metals within the interface that represents their ultimate two-dimensional limit has not been well captured. In this work, we explore the atomic structures and electronic properties of atomically thin indium intercalated at the epitaxial graphene/SiC interface by means of cryogenic scanning tunneling microscopy. Two types of surfaces with distinctive crystalline characteristics are found: (i) a triangular indium arrangement epitaxially matching the (√3 × √3)R30° cell of the SiC substrate and (ii) a featureless surface of more complex atomic structures. Local tunneling spectroscopy reveals a varying n-type doping in the graphene capping layer induced by the intercalated indium and an occupied electronic state at ∼−1.1 eV that is attributed to the electronic structure of the newly formed interface. Tip-induced surface manipulation is used to alter the interfacial landscape; indium atoms are locally de-intercalated below graphene. This enables the quantitative measurement of the intercalation thickness revealing mono and bi-atomic layer indium within the interface and offers the capability to tune the number of metal layers such that a monolayer is converted irreversibly to a bilayer indium. Our findings demonstrate a scanning probe-based method for in-depth investigation of ultrathin metal at the atomic level, holding importance from both fundamental and technical viewpoints. The STM tip is used to visualize and to engineer the intercalated indium at the interface between graphene and SiC substrate with atomic precision. Together with 2D van der Waals (vdW) materials8,9 2D metals are considered as compelling material platforms for quantum and optoelectronic technologies10,11 as well as for the investigation of new physical effects.12Crystalline, atomically thin metals stabilized at the interface between epitaxial graphene (EG) and a silicon carbide (SiC) substrate exhibit remarkable physical properties owing to their distinct dimensionality and dominant quantum size effects.3 for metal atoms to spontaneously squeeze themselves under graphene and form large-scale ordered ultrathin crystals typically in a range between one and a few atomic layers.3,7 A graphene top layer stabilizes the 2D metals at the interface and protects them effectively against environmental degradation. Sandwiched between EG and the SiC substrate, ultrathin metal serves as part of the vdW heterostructure which is immediately available for advanced experimental investigations and future applications.3,13 Upon intercalation, metal at the EG/SiC interface tends to match epitaxially with the uppermost atomic layers of the SiC substrate, forming a highly ordered triangular lattice as demonstrated for Ga,3,7 Au,5,14 Ag,6 Sn,15,16 and Cu17 through a wide range of investigation techniques including low-energy electron diffraction (LEED), low-energy electron microscopy (LEEM), angle-resolved photoemission spectroscopy (ARPES), cross-sectional scanning transmission electron microscopy (STEM), first principles density functional theory (DFT) and scanning tunneling microscopy (STM). In order to understand and exploit the rich physics of these interfacial 2D metals, it is significantly important to understand their microscopic details as well as their interaction within the EG/SiC interface at the atomic level.The high energy of the EG/SiC interface provides a strong thermodynamic driving force18 (√7 × √3) In on Si (111) exhibits a nearly free electron 2D electron gas (2DEG) system19 or superconductivity behaviors;20 and ultrathin In confined at the EG/SiC interface shows an extraordinary nonlinear optical response.7 First, bias-dependent imaging is used to identify the atomic structure of In below graphene which is only sensitive to a specific bias voltage range. A differential tunneling spectrum (dI/dV) is used to probe the electronic structures of the EG/In/SiC interface revealing the electronic doping of graphene induced by the charge transfer from the intercalated metal and an occupied state arising from the newly formed interface. Second, tip-induced surface manipulation using a relatively large bias voltage pulse is applied between the sample and the tip to enable de-intercalation of the In atoms below graphene, thus facilitating an accurate measurement of the metal thicknesses inside the EG/SiC interface, and to further tune the atomic layer numbers of the In. Our results demonstrate microscopic evidence on the structural and electronic properties of the confined metal and feasibility to control the interfacial landscape with atomic precision using solely the STM tip.Here, we reveal the atomic and electronic structures, the intercalation thickness and the interfacial engineering of the 2D indium using a cryogenic STM system. Indium is a group 13 metal in which its 2D form has not been well studied, nevertheless exhibiting various intriguing physics. For example, triangular monolayer indium on SiC (0001) displays non-trivial topological band inversion induced by spin–orbit coupling;2.2.1via silicon sublimation at 1800 °C, following our previous works.3 Here, we utilize partial-buffer EG, where we grow sub-monolayer EG (∼90% coverage), yielding regions where the graphene buffer layer (GBL) is exposed, to enable intercalation of In without the need for the oxygen-plasma treatment. The GBL consists of a graphene-like honeycomb structure in which one third of the carbon atoms in this layer are covalently bound to the Si atoms of the SiC substrate.21 Thus, this layer does not display the typical Dirac cone in its band structure as for graphene. This sample preparation provides a route to reduce surface roughness following intercalation, thereby enabling STM measurements of the surface following In intercalation. Atomically thin In is achieved via the confinement heteroepitaxy (CHet) in a horizontal tube furnace fitted with a 1 inch outer diameter quartz tube. Indium pellets are placed in an alumina crucible ∼5 mm below an EG/SiC substrate, and CHet is performed at 800 °C in a 500 Torr Ar environment (Ar flow of 50 sccm) for 30 minutes.EG is first formed from SiC 2.2−10 mbar) at a sample temperature of ∼5 K. Differential conductance dI/dV  was measured by using a lock-in technique amplifier with a peak-to-peak bias modulation of 5–10 mV and a modulation frequency of 675 Hz. Prior to all measurements, the STM tip is carefully calibrated by performing conductance spectra in the field emission regime (FER) on graphene/SiC using a high positive bias voltage (ranging from 2 V to 10 V) applied between the tip and the sample  operating under UHV  and GBL in which the (6√3 × 6√3)R30° superstructure of the underlying SiC substrate is visible. The (6√3 × 6√3)R30° reconstructed structure in the GBL is formed by the 1/3 monolayer of Si adatoms on top of the SiC substrate and can easily be observed by STM images with high corrugation21,22,25 and in case of monolayer or bilayer EG/SiC without intercalation, this superstructure is also evidenced.26–29 Previous studies22,23 have reported the intercalation of In at the EG/SiC interface using the initially grown GBL in which the metal intercalation tends to start at the GBL areas, resulting in monoatomic and bilayer In domains. However, some parts of the initially grown sub-monolayer EG  and GBL areas are not intercalated, resulting a quite complex surface consisting of three different types of topography: (i) monolayer In, (ii) bilayer In and (iii) the un-intercalated GBL or monolayer EG. However, in our case, evidence of un-intercalated monolayer EG or GBL is not observed. This may be because of the fact that our STM is only able to probe nanosized areas, and thus misses the topographic information on the larger scale at the micron size or more, even though we have approached the STM tip on about twenty locations. Nevertheless, the dominant topographic characteristics shown in i.e. different bias voltages). Only a few step edges of larger apparent height (∼3 Å) are observed  and high (red curve) intercalated regions. Around the Fermi level, both spectra reveal the linear dispersion of the π and π* bands of the graphene top layer. This again confirms that the initially grown GBL and sub-monolayer EG surface have been transformed into mono and bilayer graphene, respectively due to the intercalation since the GBL does not exhibit a linear band structure as it lacks the π states in the vicinity of the Fermi level.25,34–36 This also indicates that the graphene structure is essentially unperturbed and stacks with the SiC substrate as a quasi-free-standing layer mediated by the In atoms to form an EG/In/SiC heterostructure. A closer inspection around the Fermi level can be viewed in the magnified dI/dV spectra shown in 17,37 Au,5,34 Ag,6 Li,38 and Pb39 which is attributed to the charge transfer from the intercalated metal to the graphene capping layer. However, the doping effect shown here indicates an interesting behavior which varies apparently due to different In thicknesses (that is ∼1.2 Å). As pointed out by Baringhaus et al.40 for Ge intercalation under EG/SiC, the graphene boundary edge between low and high intercalated regions having different carrier densities can be considered like a p–n junction. The origin of the doping difference observed in our system might be explained according to the DFT prediction41 which demonstrates that the n-doping of a graphene layer sitting directly above metals is increased when the metal–graphene separation reduces from 3.3 Å or less. In order to avoid any mistake in identifying the Dirac point, it is worth noting that the gap-like feature centered at ±67 meV around the Fermi level as highlighted by the shaded rectangle in 42 Apart from the linear band dispersion of graphene, a noticeable occupied state at ∼−1.1 eV (marked by the red triangle) in the red spectrum of I/dV spectra in the bias voltage range between −3 V and +3 V and did not identify any other state in both regions. Since the occupied state at −1.1 eV has not been observed for the GBL or pristine graphene on SiC without intercalation,35,39 this state should be attributed to the electronic structure emerging from the newly formed interface. It is unclear if this occupied state arises from the main electronic contribution of the In itself as it might develop its own band structure or associated by a complicated electronic coupling between In layers and the SiC substrate or graphene at the interface. This nevertheless exhibits a very interesting electronic structure for the ultrathin In. In order to precisely describe this newly emerging state, further theoretical calculation is needed.Two-dimensional indium forms its own electronic state at the interface and modifies the electronic structure of graphene capping layers 43 (7 × 7) reconstruction of Si (111) below monolayer graphene44 and SiC interface structure below monolayer graphene.45,46 Accordingly, when the two atomically indistinguishable surface regions shown in Height variation in the STM image is correlated with two distinct atomic phases of indium. A challenge for identification of the intercalated structures at the EG/SiC interface is that metal layers are covered by graphene preventing direct access to the confined atoms underneath. In the STM technique, the tip is sensitive to the density of states located several atomic layers below a surface that has been used to directly identify the buried atomic structures, for example, Si vacancies and domain boundaries in yttrium silicide surface,26 We image this area at different bias voltages and observe that the atomic structure of the 2D In is only visible in the bias range between 1.5 V and 2.2 V. At larger negative and positive voltages, the STM images appear very unstable without special features. Previous studies3,5,6,14–17 have demonstrated various metal elements intercalated at the EG/SiC interface in which the first intercalated metal layer tends to match (1 × 1) epitaxially to the SiC substrate such that each metal atom is bound directly to the topmost Si atom of the SiC substrate. The unit cell of 6H-SiC (0001) is known to be 3.08 Å46,47 which is considerably smaller than that of the intercalated In (5.4 Å) found here. Thus, such a (1 × 1) match cannot be considered for this In network in the low region. Indeed, we found that the In unit cell (5.4 Å) coincides with the (√3 × √3)R30° cell of the underlying SiC (that is √3 × 3.08 = 5.33 Å). Therefore, in order to match the two lattice planes, each In atom must bind to either Si atom, carbon atom (T4 site) or hollow (H3 site) of the SiC topmost layer. Among these sites, the T4 site is proved to be energetically more favorable than the H3 and the hollow sites in various epitaxial 2D systems formed on the SiC (0001), for example, in case of Si adatoms chemisorbed and formed the (√3 × √3)R30° reconstruction on the SiC surface48,49 and recent observations for In intercalated at the EG/SiC interface.22,23 Notably, the atomic characteristics of the intercalated In atoms in our case are very similar to that of Sn atoms adsorbed on the SiC (0001) substrate without the graphene capping layer.50,51 In this system, each Sn atom is found located at the T4 positions and energetically bound to its three adjacent Si atoms on the SiC substrate. Such observations lead us to conclude that the well-ordered In structure found in the low intercalated region is commensurate strictly with the (√3 × √3)R30° superlattice at T4 positions on the SiC substrate as illustrated in 18 it is still unclear under which circumstances the (√3 × √3)R30° triangular network of In is formed. Nevertheless, the ordered structure of ultrathin In provides strong evidence that the intercalated 2D In significantly interacts with the SiC substrate within the interface. In turn, the topmost atomic layers of the SiC substrate can be considered as a considerably important epitaxial template for 2D metal to be formed. It is also noted that the In lattice in this region has the same crystallographic orientations with the graphene top layer which implies that graphene coverlayer is only lifted up due to the intercalation and maintains its registry with the underlying SiC substrate. This behavior is consistent with the previous DFT calculation3 which revealed that adding the graphene to the intercalated In/SiC only affects the band filling without modifying the stability of the intercalated metal.Lower intercalated regions exhibit an ordered indium atomic array that epitaxially matches the (√3 × √3)R30° cell of the underlying SiC. The details of the low region are further shown in 21,27,29,52 However, since the graphene layer is lifted and becomes a quasi-free-standing layer due to the In intercalation, this supercell should have a different origin. In more detail, Forti et al.17 have demonstrated in case of Cu intercalated at the EG/SiC interface that the Cu atoms in a monolayer match epitaxially with the SiC substrate such that a (2 × 2) Cu cell (lattice constant of 2.66 Å) is commensurate with the (√3 × √3)R30° cell of the SiC substrate. In such an atomic arrangement, the (13 × 13) supercell emerges from the superposition induced by the two atomic planes between monolayer graphene and monolayer 2D metal. Within this cell, the underlying metal atoms register with the graphene network either directly below the hollow center of the graphene hexagon or below the A or B sublattice atom resulting in a superlattice varying potential. Since the In intercalated layer matches in a (1 × 1) ratio with the (√3 × √3)R30° superlattice of the SiC substrate , the potential modulation periodicity induced by the atomic registry between In and graphene is similar to that between Cu and graphene. In addition, this superstructure is also present in other intercalated metal systems at the EG/SiC interface such as Au5,14 and Cu37 showing consistency with our observation.Coexisting with the atomic structure of the In layer, a large superstructure arising as a result of the lattice mismatch between the monolayer graphene and the underlying In lattice is visible as faint corrugation lines indicated by a cyan rhombus in 50 Third, a bright atomic-like chain is also observed in some areas as indicated by the red square in A range of defect types exists in the low intercalated layer, enabling visualization of the ultrathin nature of 2D In. As can be seen in the STM images of 22 At this stage of analysis, we tentatively attribute these point defects to monovacancies of the intercalated In layers. However, in order to precisely conclude that these are vacancies in the In layer, further investigation should be considered. In addition, it is worth noting that the bright triangular defects coexisting with the atomic resolution of graphene are clearly displayed at 1 V or lower bias voltages as shown in 53,54 which results from local charge transfer between the defect and the three adjacent carbon atoms in the graphene lattice.55–57 These defects are attributed to be either monovacancies or foreign atoms substituted monovacancies in the graphene lattice.55Bias-dependent imaging is unable to verify the structure of “thick” indium intercalated regions which is hypothesized to be composed of more than one metallic layer preventing individual atoms to be resolved. In I/dV) spectroscopy is further used to elucidate the electronic signatures of the defects in 2D indium. I/dV spectra obtained with the tip placed above six defects marked from 1 to 6 in I/dV spectra. As clearly seen, the defects vary slightly in sizes and contrast. This implies that they do not sit on the equivalent lattice sites of the topmost In layer if one assumes that this layer is formed with a periodic structure. The dI/dV spectra taken on the defect 4 and 6 do not show any pronounced peak and have different contrasts in the STM images, notably those shown in Differential  and the applied bias voltages (4 V and 5 V). As a result, after the first pulse of 4 V, the first dark hole with a size of ∼5 nm and a depth of ∼1.4 Å is formed as can clearly be seen in the STM image in 25,35,45,58 This is an important indication that the area inside the hole is composed of graphene sitting directly above the 6√3 × 6√3 reconstructed SiC substrate without the intercalated metal (hereafter denoted as 6 × 6 graphene). We refer to this observation as the “de-intercalation” of the underlying In induced by the tip voltage pulse. This also reflects that following the de-intercalation, the topmost EG layer remains intact and stacks directly with the SiC substrate followed by the restoration of the underlying GBL. However, to understand the exact mechanism of how the GBL is recovered under the top EG layer, further investigation is required.Tip-induced surface manipulation enables direct visualization and engineering of In layers at the EG/SiC interface . This is because in our case the newly formed pristine graphene area is very small after the voltage pulse, the surrounding area is still intercalated by In atoms, and thus, we expect a different electronic coupling between graphene and the SiC substrate. We again exclude that this de-intercalated area is composed of the GBL because in this case, no linear band dispersion typical for graphene should be observed.45 Note that the Dirac point shift in this spectrum is irrelevant with the shift induced by In atoms in the low and high intercalated regions that has been discussed in I/dV spectra measured on such locations on both low and high intercalated regions .20,30 Thus, we now attribute the higher intercalated region to be composed of an In bi-atomic layer and infer the lower intercalated region as a monoatomic layer. Indeed, first-principles DFT calculations from Orimoto et al.32 pointed out that upon intercalation of a Cu monolayer at the GBL/SiC interface, the graphene capping layer is lifted by 2 Å which apparently supports our observation. The thickness of the In monolayer (2.13 ± 0.25 Å) in the low regions is higher than half that of the bilayer (high) region (that is 3.38 : 2 = 1.69 Å). This suggests interesting heterostructural strain-induced behaviors in both low and high intercalated regions. As demonstrated in previous STEM and DFT studies,7 the bonding characters in an EG/metal/SiC heterostructure for bilayer Ga and In evolves from covalent at the SiC/metal interface (with interspacing between SiC and the first Ga layer of 2.19 Å) to metallic between the first Ga layer and the second Ga layer (with a larger interspacing of 2.36 Å) and to nonbonded vdW-like at metal/graphene interface. Assuming that our first and second In layers stack with the SiC substrate and EG under similar conditions, one could expect that the apparent height of the bilayer region here must have a thickness at least larger than two times that of the low regions (that is 4.26 Å). Since the thickness of the In bilayer region is measured to be 3.38 Å, it suggests that the interaction of the interfacial In layers with graphene capping layers in the high region is stronger than that in the monolayer (low) region.Tip-induced interface manipulation is a powerful method to directly visualize and investigate the properties of 2D metals below the graphene capping layer. Upon de-intercalation, the metal thicknesses in the low and high intercalated regions can easily be explored by measuring the height of the atomic steps between the intercalated and de-intercalated (6 × 6 graphene) regions. As can be seen in 3 suggests that the strong metal–SiC covalent bonds play an essential role in providing a strong thermodynamic driving force for an In bilayer to be formed as the most stable atomic phase at the EG/SiC interface.Apart from the de-intercalation ability of metal layers below graphene, the tip-induced manipulation demonstrated here is a versatile tool to control the number of intercalated layers with atomic precision, through which the remarkable dynamic behavior of the interfacial In atoms is revealed. As already mentioned above, upon the tip voltage pulses, some areas around the tip location in the low intercalated region appear with a higher apparent height. In This finding is reinforced by the fact that when we carried out tip voltage pulse in the high intercalated region, the 2D In is only de-intercalated. No newly formed structures with a thickness other than a bilayer are found. In fact, we found that the monolayer In is very easily perturbed by changes in the tip conditions such as applied bias voltages, bias polarity or tunneling current while the bilayer region appears more stable. Therefore, the tip-induced manipulation not only de-intercalates the In material but can also be used as a versatile tool to engineer the intercalated layers at the EG/SiC interface.4.In conclusions, this work presents an experimental demonstration of the detailed structures of 2D indium stabilized at the EG/SiC interface using cryogenic STM. Two atomic phases corresponding to monoatomic and bilayer In structures stabilized under graphene are revealed. On the In monolayer, a triangular lattice matching epitaxially with the (√3 × √3)R30° periodicity of the underlying SiC substrate is identified. In contrast, no clear indication of the atomic arrangement is probed for the In bilayer. This observation clearly demonstrates the significant importance of the SiC substrate as an epitaxial template for 2D crystalline In to be formed. We have successfully used tip-induced manipulation as a versatile tool to either de-intercalate or reconstruct the intercalated materials while the graphene top layer remains unaltered. This allows microscopic insight into the ultrathin In at the EG/SiC interface with respect to intercalation thickness, good control over the number of metal layers and thermodynamic stability of In at the interface. Our results contribute to exploring the atomic and electronic structure of the confined metal, strongly emphasizing on tip-induced manipulation as a first demonstration for the intercalated metal at the EG/SiC interface.V. D. Pham designed, performed all the STM experiments, analysed the data and wrote the manuscript. J. A. Robinson and C. Dong designed and prepared the intercalation samples. All authors contributed critical revisions and gave final approval of the manuscript.There are no conflicts to declare.NA-005-D3NA00630A-s001


In recent years, the global population has increased significantly, resulting in elevated levels of pollution in waterways. Organic pollutants are a major source of water pollution in various parts of the world, with phenolic compounds being the most common hazardous pollutant. These compounds are released from industrial effluents, such as palm oil milling effluent (POME), and cause several environmental issues. Adsorption is known to be an efficient method for mitigating water contaminants, with the ability to eliminate phenolic contaminants even at low concentrations. Carbon-based materials have been reported to be effective composite adsorbents for phenol removal due to their excellent surface features and impressive sorption capability. However, the development of novel sorbents with higher specific sorption capabilities and faster contaminant removal rates is necessary. Graphene possesses exceptionally attractive chemical, thermal, mechanical, and optical properties, including higher chemical stability, thermal conductivity, current density, optical transmittance, and surface area. The unique features of graphene and its derivatives have gained significant attention in the application of sorbents for water decontamination. Recently, the emergence of graphene-based adsorbents with large surface areas and active surfaces has been proposed as a potential alternative to conventional sorbents. The aim of this article is to discuss novel synthesis approaches for producing graphene-based nanomaterials for the adsorptive uptake of organic pollutants from water, with a special focus on phenols associated with POME. Furthermore, this article explores adsorptive properties, experimental parameters for nanomaterial synthesis, isotherms and kinetic models, mechanisms of nanomaterial formation, and the ability of graphene-based materials as adsorbents of specific contaminants. The world’s main vegetable oils are derived from palm, soybean, coconut, olive, peanut, sunflower, cottonseed, and rapeseed . Palm oiSeveral techniques are available for POME treatment; however, not all are suitable as they have varying treatment efficiencies and costs . POME trIn recent times, nanotechnology has been widely employed in several applications, including wastewater treatment, as nanomaterials have been proven to be highly effective in eliminating inorganic and organic pollutants from wastewater effluents compared to conventional adsorbents due to their low toxicity and small size ,20,21. AThe utilization of nanosized GO as an adsorbent can affect the extent of oxidation via interactions and the presence of hydrogen bonds due to its complex structure . ResearcThe discharge of toxins from anthropogenic activities into the environment has resulted in one of the major challenges of this century, which is the scarcity of clean water. Phenol is frequently found in industrial wastewater generated by sectors such as oil, gas, medicine, and pesticide production. As it can be harmful, numerous environmental protection agencies have instituted stringent concentration limits for phenol in wastewater to safeguard human health and preserve ecological equilibrium . In ASEAPhenol, a white, crystalline, and volatile aromatic chemical compound, is widely found in wastewater from several industries, including oil, gas, medicines, and pesticides, and even at low concentrations, it can affect the taste and odor of water . Phenol Numerous studies have shown that phenol is becoming a concern due to its persistence in the environment . An uninAdsorption and advanced oxidative processes (AOPs) have been demonstrated as viable, practical, and environmentally friendly alternatives for removing phenol from water among the advanced remediation technologies. In recent years, tertiary treatments have been successfully used to increase phenol absorption and meet stringent water quality requirements. Advanced oxidation technologies and adsorption are reported as highly viable approaches among these tertiary methods. Adsorption is an advantageous technique for phenol removal due to its simplicity in construction and use, cost-effectiveness, and ability to handle low-concentration fluids . In addisp2 hybridized orbitals. As a result, graphene holds tremendous promise for various applications, such as field-effect transistors (FETs), gas and biomolecule sensors, transparent conductive films (TCFs), and graphene batteries, due to its outstanding properties. Furthermore, when carbon atoms are arranged in layers, graphene oxide (GO) is formed, which features oxygen-containing functional groups, such as =O, -OH, -O-, and -COOH, connected to the sides and edges of the plane [Graphene is a material that has been widely studied over the last few decades and has been dubbed the “material of the future” due to its exceptional properties. Graphene has a unique honeycomb lattice structure in a two-dimensional plane, where each carbon atom is bonded to three other carbon atoms through he plane . GO can 11H4O5 (corresponding to a C/O ratio of 2.2) [With the presence of multiple oxygen functional groups on its surface sites, GO can serve as a precursor for synthesizing various graphene derivative products, such as fluoro-graphene, bromo-graphene, and graphene. In addition, it is possible to synthesize graphene by thermally or chemically reducing GO. It can be noted that GO can also be applied to advanced applications, which include delivery of medicine, thermal conductivity, and materials for architecture. However, there are certain challenges with GO, such as toxicity and issues during mass production, that must be fixed and investigated in detail to utilize them for commercial applications. Thus, novel techniques for environment-friendly, inexpensive, and mass production of GOs are crucial. British chemist B. C. Brodie made the first effort to fabricate GO in 1859 while experimenting on the reactivity of flake graphite ,51. ThisFurther, Staudenmaier and co-workers altered Brodie’s procedure (ST-GO—graphene Staudenmaier’s oxide) by altering the introduction method of the chlorate and the addition of sulfuric acid to the mixture. In this method, potassium chlorate was gradually added to the mixture to reduce the risk of explosive byproducts and the evolution of heat. Furthermore, reaction time was reduced to increase the acidity of the environment, and the resultant GO closely resembles BR-GO in terms of its characteristics. Back in 1937, Hofmann synthesized graphene oxide (HO-GO) with a reduced oxygen content (C/O ratio of 2.5) by mixing non-fuming nitric acid and potassium chlorate. Jankovský et al. (2017) reported that nitric acid levels have a substantial impact on the degree of oxidation in the graphene-based product .2O2) to neutralize the excess potassium permanganate. The final product produced by the Hummers method has a C/O ratio comparable to BR-GO (2.25). However, the method is not environmentally friendly due to the presence of NOx during the reaction. Recently, Perumal et al. (2022) summarized the extracts of plants from different taxonomy groups for the novel synthesis of graphene via a green reduction approach. The authors mentioned that several plant species and major plant parts from each plant have exclusive potential to form GO and reduced GO [The Hummers method, also known as the permanganate procedure, is the most commonly used and efficient method for synthesizing GO to date, as developed by Hummers and Offeman in 1958. This method involves adding an excess of potassium permanganate, a low volume of sulfuric acid, and excess sodium nitrate to the reaction mixture, with a reaction time ranging from 8 to 12 h. This technique is safer than other traditional methods as it avoids the production of explosive chlorine oxide. The procedure is completed by adding a diluted solution of hydrogen peroxide (Hduced GO . However6Sn5) nanoparticles with reduced graphene oxide via a chemical reduction approach. The GO was synthesized via modified Hummers’ method using graphite, whereas bi-metal-GO nanocomposite was formed via chemical reduction method as shown in It is noteworthy that graphene oxides possess certain limitations, such as sturdiness and the inability to blend with other materials to form composites or alloys, especially for environmental applications . Thus, rRecently, Ullah et al. (2021) prepared size-controlled aluminum-doped graphene via a chemical vapor deposition (CVD) approach. In this study, the graphene was prepared with the help of low (23 Pa) pressure on the surface of a copper foil as a growth substrate in a horizontal tube furnace. The results showed that the CVD approach is beneficial for the preparation of high-quality aluminum-doped monolayer graphene with large areas of aluminum doped on the graphene lattice . In geneThe removal of phenol via adsorption has received attention in the past decade. In particular, the utilization of graphene-based adsorbents for the decontamination of these organic pollutants is gaining significant attention among researchers. The treatment of phenol using graphene-based composites has been reported in various studies, as summarized and presented in 2SO4 and HPO4 (named GO1) as well as H2SO4, H3PO4, and HNO3 (named GO2) for the treatment of phenol in water. The influence of various parameters, including initial phenol concentration, temperature, and pH, on the adsorption process was also studied. The authors reported the modeling of the equilibrium adsorption data and compared it with conventional models, such as Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich adsorption isotherm models. It was noted that ultraviolet (UV) ray irradiation had a favorable influence on the adsorption process while increasing their adsorption capacity. It can be noted that the maximum adsorption capacities for GO1 and GO2 were 0.77 and 20.2 mg/g, respectively. It has been reported that the adsorption capacity reached its peak at pH 2 in the absence of UV radiation, whereas pH 6 was identified as optimal in the presence of UV irradiation. The adsorption rate increased with an increment in the initial phenol concentration, and an equilibrium point was reached where there was a drop in adsorption, after which it remained constant. The phenol concentration increment has resulted in increased pollutant uptake until equilibrium is attained, where the adsorption is reduced and has maintained a constant value. The maximum adsorptive capability of GO1 and GO2 has been elevated from 70.43 to 90.82% and 86.75 to 95.95% after UV exposure, respectively [3O4/PRd) for the adsorption of phenol in a batch process from a hydrous solution. The maximum adsorptive capability of GO composite was 191.0 mg/g at 15 min of equilibrium time. The adsorption behavior of phenol by the GO-Fe3O4/PRd adsorbent was described by Freundlich and Langmuir isotherm models with a pseudo-second-order kinetic model. The authors also revealed that the uptake of phenol by GO-Fe3O4/PRd was spontaneous, endothermic, and feasible [Recently, Al-Ghouti et al. (2022) reported the preparation of GO via two methods, such as the addition of Hfeasible .Bibi et al. (2022) developed GO modified with polyacrylic acid (GO-PAA) as a composite for the removal of phenol from real and synthesized effluents. The author utilized a variety of techniques, such as scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX), as well as Fourier transform-infrared (FTIR) and Brunauer-Emmet-Teller reaction (BET) techniques, to examine the GO and GO-PAA samples’ morphology, surface area, and surface chemistry, respectively. The adsorption parameters, such as temperature, pH, and initial phenol content, were also evaluated. The best adsorption was identified at a pH of 2 and a temperature of 25 °C. The results showed that the modification of the GO-PAA surface can lead to the aggregation of C=O groups, which eventually increases the adsorption ability of unmodified GO. The study also revealed that Langmuir’s isotherm model was best suited to describe the adsorption process of the GO sample, and the thermodynamics studies proved the exothermic and spontaneous nature of phenol adsorption processes. It was observed that the GO-PAA sample was able to remove 75% of the phenol from synthetic wastewater and 18% from real wastewater, respectively, at an optimal pH of 2 and a temperature of 25 °C . Further3O4 composite via a one-pot process for phenol uptake in batch adsorption. The composite exhibited a huge surface area and copious amino groups, and the maximum adsorptive capability, evaluated from the Langmuir model under optimum conditions, was 224.21 mg/g, with equilibrium reached in 60 min. The adsorption mechanism involved π-π interactions, hydrogen bonding, and electrostatic interactions between PVAm and phenols, and the composite was loaded with phenols that could be easily recycled using NaOH solution. Thus, the PVAm-GO-(o-MWCNTs)-Fe3O4 composite was an effective adsorbent for phenolic compound removal [3O4 hybrid material using sonication-assisted co-precipitation techniques to treat phenol. The adsorption kinetics showed that the phenol uptake efficacy was 68% in aqueous systems, with an outstanding adsorptive capability of ∼79 mg g−1 and an initial adsorption rate of 5.7 mg g−1 min−1. The process was initially governed by the boundary, then by surface diffusion, and finally via pore diffusion, as indicated by the kinetic models. According to the Langmuir isotherm, equilibrium isotherms showed that the adsorption was a spontaneous physisorption process with a maximum adsorption capacity of 658 mg/g [Zhou et al. (2020) synthesized a three-dimensional amino-poly(vinylamine) (PVAm)-functionalized GO-(o-MWCNTs)-Fe removal . In anot658 mg/g . Manna e658 mg/g . All theVerbena officinalis to reduce their toxicity towards the environment. The resultant GOs were encapsulated in sodium alginate via cross-linking to utilize the system for phenol treatment in olive mill wastewater. The study showed that these green synthesized GOs in sodium alginate were identified to possess 3.68 g/L of adsorbent dosage at a temperature of 25 °C and a pH of 4 with 135 min of adsorption time. In addition, the study also revealed that the GO system possesses 994 mg/g of phenol adsorption capacity for 4000 mg/L of initial concentration [The limitations of micro- and macro-sized graphene materials have led to the emergence of graphene nanomaterials and nanocomposites for the treatment of phenols via adsorption. Maio et al. (2020) prepared three-dimensional templates with graphene oxide-decorated polycaprolactone (PCL) via a one-pot process. In this study, the PCL solutions were coated on GO nanoparticles in ethanol through jet-wet electrospray or electrospinning on the surface of a stirred liquid collector. The phenol removal analysis showed that the GO-PCL nanoparticles possess a sorption equilibrium of 6 h via a pseudo-second-order model in fresh water with excellent robustness and recyclability . Even thntration . However2/h/bar, which is higher than individual graphene oxide membranes. The results revealed that the membrane can remove >75.8% of p-nitrophenol during a dead-end ultrafiltration process from wastewater [Othman et al. 2019) prepared novel copper-iron oxide nanoparticles that are supported on the surface of the reduced GO via a facile low-temperature approach. The synthesis has led to the decoration of copper-iron oxide nanoparticles on the surface of reduced GO sheets. The study showed that the composite possesses enhanced photocatalytic activity for phenol degradation. The results showed that the GO system can completely remove phenol from the contaminated water within 15 min at room temperature under photocatalytic conditions, as shown in stewater . All the019 prepaThe development of efficient, environmentally friendly, and cost-effective GO-based nanomaterials for micropollutant adsorption has gained considerable interest among researchers, industrial sectors, and policymakers . HoweverIn conclusion, the studies conducted on GO-based nanocomposites as adsorbents for phenol removal applications have demonstrated their high efficiency and effectiveness. These nanocomposites offer several advantages, including a high surface area, excellent mechanical strength, and unique chemical and physical properties, which contribute to their superior adsorption capacity for phenol and other organic contaminants. Furthermore, kinetic studies have shown that GO-based nanocomposites typically exhibit a pseudo-second-order reaction for phenol adsorption processes, indicating their ability to rapidly and efficiently remove phenol from wastewater. Moreover, the capacity of various GO-based composites with different modification types for adsorbing phenols has been extensively reported, showcasing their versatility and applicability in diverse wastewater treatment applications. It is noteworthy that the recovery of nanomaterials is the most significant aspect of their application in environmental applications. Recent research has highlighted the importance of developing efficient methods for the recovery and reusability of nanocomposites. Although specific percentages for nanomaterial recovery depend on the process, it is a critical area of focus for future investigations. Incorporating sustainable and environmentally friendly approaches to recover and recycle these materials will enhance the overall sustainability and cost-effectiveness of phenol removal processes. In summary, GO-based nanocomposites offer a sustainable and effective solution for the treatment of phenol-contaminated wastewater, providing a cost-effective and eco-friendly approach for pollutant removal. Further research efforts should aim to develop novel and efficient materials while also focusing on the recovery and reusability of nanomaterials to optimize their overall environmental impact and resource utilization.