Synergistic Cation Solvation Reorganization and Fluorinated Interphase for High Reversibility and Utilization of Zinc Metal Anode.

Batteries based on zinc (Zn) chemistry offer a great opportunity for large-scale applications owing to their safety, cost-effectiveness, and environmental friendliness. However, the poor Zn reversibility and inhomogeneous electrodeposition have greatly impeded their practical implementation, stemming from water-related passivation/corrosion. Here, we present a multifunctional electrolyte comprising gamma-butyrolactone (GBL) and Zn(BF4)2·xH2O to resolve these intrinsic challenges. The systematic results confirm that water reactivity toward a Zn anode is minimized by forcing GBL solvents into the Zn2+ solvation shell and constructing a fluorinated interphase on the Zn anode surface via anion decomposition. Furthermore, NMR was selected as an auxiliary testing protocol to elevate and understand the role of electrolyte composition in building the interphase. The combined factors in synergy guarantee high Zn reversibility (average Coulombic efficiency is 99.74%), high areal capacity (55 mAh/cm2), and high Zn utilization (∼91%). Ultimately, these merits enable the Zn battery utilizing a VO2 cathode to operate smoothly over 5000 cycles with a low-capacity decay rate of ∼0.0083% per cycle and a 0.23 Ah VO2/Zn pouch cell to operate over 400 cycles with a capacity retention of 77.3%.

Impact of 6-month triptorelin formulation on predicted adult height and basal gonadotropin levels in patients with central precocious puberty.

Background: Triptorelin, a long-acting gonadotropin-releasing hormone (GnRH) agonist, is available in 1-, 3-, and 6-month formulations to treat central precocious puberty (CPP). The triptorelin pamoate 22.5-mg 6-month formulation recently approved for CPP offers greater convenience to children by reducing the injection frequency. However, worldwide research on using the 6-month formulation to treat CPP is scarce. This study aimed to determine the impact of the 6-month formulation on predicted adult height (PAH), changes in gonadotropin levels, and related variables. Methods: We included 42 patients (33 girls and nine boys) with idiopathic CPP treated with a 6-month triptorelin (6-mo TP) formulation for over 12 months. Auxological parameters, including chronological age, bone age, height (cm and standard deviation score [SDS]), weight (kg and SDS), target height (TH), and Tanner stage, were evaluated at baseline, and after 6, 12, and 18 months of treatment. Hormonal parameters, including serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol for girls or testosterone for boys, were analyzed concurrently. Results: The mean age at treatment initiation was 8.6 ± 0.83 (8.3 ± 0.62 for girls, 9.6 ± 0.68 for boys). The peak LH level following intravenous GnRH stimulation at diagnosis was 15.47 ± 9.94 IU/L. No progression of the modified Tanner stage was observed during treatment. Compared to baseline, LH, FSH, estradiol, and testosterone were significantly reduced. In particular, the basal LH levels were well suppressed to less than l.0 IU/L, and the LH/FSH ratio was less than 0.66. The bone age/chronological age ratio remained stable with a decreasing trend (1.15 at the start of treatment, 1.13 at 12 months, 1.11 at 18 months). PAH SDS increased during treatment (0.77 ± 0.79 at baseline, 0.87 ± 0.84 at the start of treatment, 1.01 ± 0.93 at six months, and 0.91 ± 0.79 at 12 months). No adverse effects were observed during treatment. Conclusion: The 6-mo TP suppressed the pituitary-gonadal axis stably and improved the PAH during treatment. Considering its convenience and effectiveness, a significant shift to long-acting formulations can be expected.

LiF Protective Layer on a Li Anode: Toward Improving the Performance of Li-O2 Batteries with a Redox Mediator.

The high charging overpotential and insulating/insoluble Li2O2 discharge products have seriously hindered the development of Li-O2 batteries. Here, we report a highly concentrated 5.0 M lithium nitrate (LiNO3) in N,N-dimethylacetamide (DMA) with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a redox mediator (RM) and with the LiF layer by adding N,N-dimethyltrifluoroacetamide (DMTFA) to the electrolyte, which reduces the charge voltage (3.6 V over 65 cycles) and allows stable cycling for 100 cycles without noticeable fading in capacity. The Li plating/stripping test and electrochemical impedance of the Li/Li symmetric cell results reveal that a Li/Li symmetric cell with DMTFA is stable due to the formation of a LiF protective layer on the Li metal, which suppresses the RM shuttle effect, improving the interface stability of Li and the electrolyte and also restraining the growth of dendrite during cell cycling. This work may provide a novel strategy for designing a protective layer for Li anodes in Li-O2 batteries when using an RM.

Intraocular Pressure Elevation during Lateral Body Posture in Side-sleeping Glaucoma Patients.

SIGNIFICANCE: In side-sleeping open-angle glaucoma (OAG) patients, eyes that showed progression exhibited a greater intraocular pressure (IOP) elevation when subjects were rested in the lateral decubitus (LD) posture on the ipsilateral side compared with those eyes that did not progress. PURPOSE: The purposes of this study were to investigate whether lying in the LD position for an extended period affects IOP in side-sleeping patients with OAG when rested on their own pillow and to compare posture-induced IOP variations between eyes with recent glaucomatous progression and those without. METHODS: Twenty-eight bilateral OAG patients who reported a preference for side sleeping were included. We measured IOP in both eyes, with the patient in the sitting and supine positions, 5 and 30 minutes after they had been in the right or left LD position (depending on their sleeping habits) and 5 minutes after they had returned to the supine position. While in the recumbent postures, the patients rested on their own pillows from home. The patients were divided into the correspondence and noncorrespondence subgroups, based on whether the laterality of the progressed eye corresponded with their habitual sleeping side. RESULTS: The IOP of the lower-sided eye increased further (+1.6 ± 1.8 mmHg; P < .001) when the LD posture was maintained for an additional 25 minutes. Such time-dependent IOP elevation in the dependent eye was greater in patients whose LD posture corresponded with glaucoma progression (+2.5 ± 1.7 mmHg) than in those who showed no correspondence or no glaucoma progression (+1.0 ± 1.6 mmHg; P = .03). CONCLUSIONS: Compared with nonprogressed eyes, progressed eyes exhibited a greater IOP elevation when the side-sleeping patients with OAG were rested in the LD posture on the ipsilateral side.

Enhanced Cycle Stability of Rechargeable Li-O2 Batteries by the Synergy Effect of a LiF Protective Layer on the Li and DMTFA Additive.

Li metal is an ideal anode for rechargeable Li-O2 batteries because of its large theoretical capacity (3860 mAh g-1). However, problems with the growth of dendrites and reaction with electrolytes and moisture during cycling have prevented its practical application. Herein, we report that the use of a 2 wt % N,N-dimethyltrifluoroacetamide (DMTFA) additive in a dimethyl sulfoxide (DMSO) electrolyte with a LiF layer on the Li anode allows for good cycling performance in Li-O2 batteries. Indeed, a Li-O2 cell with a multiwalled carbon nanotube (MWCNT) cathode, 1.0 M LiNO3/DMTFA + DMSO (2:98 v/v) electrolyte, and a LiF layer on the Li anode could be cycled 92 times at a current density of 1000 mA g-1 with a 1000 mAh g-1.

Comparison of Retinal Vessel Diameter Between Open-Angle Glaucoma Patients With Initial Parafoveal Scotoma and Peripheral Nasal Step.

PURPOSE: To compare retinal vessel diameters (RVDs) between open-angle glaucoma (OAG) patients with initial parafoveal scotoma (PFS) and those with initial peripheral nasal step (PNS). DESIGN: Retrospective, cross-sectional study. METHODS: We enrolled 151 eyes of 151 patients with OAG (83 with normal-tension glaucoma [NTG] and 68 with primary open-angle glaucoma [POAG]). The patients were categorized into the PFS and PNS groups according to the location of the initial visual field (VF) defect. Clinical characteristics and RVD indices-central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE)-were compared between the groups. Subgroup analyses were conducted in the NTG and POAG groups. RESULTS: Forty-six patients had PFS and 105 had PNS. The CRAE of the PFS group was significantly lower than that of the PNS group in all glaucoma patients (P = .001). However, neither the mean deviation in VF nor that in the average retinal nerve fiber layer thickness showed significant intergroup differences. In the NTG subgroup analysis, the CRAE of the PFS group was significantly lower than that of the PNS group (P = .013). Conversely, in the POAG subgroup analysis, the CRAE in the PFS group did not differ significantly from that in the PNS group (P = .123). CONCLUSIONS: Retinal arteriolar diameter was narrower in OAG patients with initial PFS than in those with initial PNS, especially in the NTG group. This suggests that the initial location of the VF defect may be associated with the vascular mechanism in patients with glaucoma.

Retinal vessel diameter in bilateral glaucoma suspects: comparison between the eye converted to glaucoma and the contralateral non-converted eye.

PURPOSE: To investigate retinal vessel diameter in patients classified as bilateral glaucoma suspects who showed unilateral glaucomatous conversion. METHODS: This retrospective study included 21 patients who had initially been diagnosed as bilateral glaucoma suspects but showed unilateral glaucomatous conversion during a follow-up period of more than 2 years. Conversion to glaucoma was determined either by documentation of a new retinal nerve fiber layer defect on red-free photography or a reproducible glaucomatous visual field defect. The central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were measured from fundus photographs taken at baseline and at the point of glaucoma conversion. RESULTS: The mean CRAE of the converted eyes was significantly lower than that of the non-converted eyes at baseline (164.9 ± 13.2 µm vs 175.2 ± 15.6 µm; p = 0.001), but no significant difference was observed in the mean CRVE (p = 0.108). The mean CRAE of the converted eyes was also lower than in the non-converted eyes at the point of glaucoma conversion (158.6 ± 13.5 µm vs 168.0 ± 17.2 µm; p = 0.011). CONCLUSION: In bilateral glaucoma suspects, there was a significant inter-eye difference in CRAE at baseline between eyes that converted to glaucoma and those that did not. These findings suggest that measurement of retinal arteriolar diameter may help clinicians when evaluating the risk of conversion in glaucoma suspects.

Carbon Cathodes in Rechargeable Lithium-Oxygen Batteries Based on Double-Lithium-Salt Electrolytes.

The use of carbon materials as air electrodes in lithium-oxygen (Li-O2 ) batteries is known to be advantageous owing to their good conductivity and because they offer sites suitable for the reversible electrode reactions. However, the exact influence of carbon materials on the electrochemical performance of Li-O2 batteries is not clear. In this study the electrochemical performance of four different types of carbon materials (multiwalled carbon nanotubes (MWCNTs), CMK-3, graphene nanosheets (GNSs), and Ketjen Black (KB)) as air electrodes is examined. We find that a Li-O2 cell based on an electrode of multiwalled carbon nanotubes (MWCNTs) demonstrates good rate performance and cycle stability, when using LiNO3 -LiTFSI/DMSO as electrolyte. Li-O2 cells based on such MWCNT electrodes, with a cut-off capacity of 1000 mAh g(-1) at 500 mA g(-1) , can undergo around 90 cycles without obvious losses of capacity. Even when the discharge depth is increased to 2000 mA h g(-1) , stable cycling is maintained for 45 cycles at a charge potential below 4.0 V.

Long-term Surgical Outcomes of 180-Degree Suture Trabeculotomy in Korean Patients With Primary Congenital Glaucoma.

PURPOSE: To investigate the surgical outcomes of 180-degree suture trabeculotomy in Korean patients with primary congenital glaucoma (PCG). PATIENTS AND METHODS: This retrospective study included 21 eyes of 17 children with PCG who underwent 180-degree suture trabeculotomy as a first surgical procedure. Surgical success was defined as (1) an intraocular pressure (IOP)<22 mm Hg with or without medication; (2) no additional intraocular surgery; and (3) no evidence of progressive optic disc cupping. The main outcome measure was the success rate of 180-degree suture trabeculotomy. Secondary outcome measures were IOP, number of glaucoma medications, and occurrence of complications. RESULTS: Of the 21 eyes included, 18 (85.7%) were classified as having achieved success at the final visit (mean last follow-up or failure time, 54.91±45.68 mo). Median age at surgery was 11.97 months with mean IOP 29.8±9.6 mm Hg, on average of 1.52 medications. The mean IOP at the final visit was 16.9±5.6 mm Hg on an average of 0.38 medications. The surgical success rate of 180-degree suture trabeculotomy at 1, 3, and 5 years was 95.0%, 87.7%, and 78.9%, respectively (Kaplan-Meier analysis). Three eyes underwent second operations and the mean time to failure was 29.39±19.75 months. Hyphema was observed in 10 eyes, but it cleared up within 7.6 days. CONCLUSION: The 180-degree suture trabeculotomy performed for PCG had a significant IOP-lowering effect and caused no remarkable complications.

Diagnostic Ability of Retinal Vessel Diameter Measurements in Open-Angle Glaucoma.

PURPOSE: To determine the diagnostic ability of retinal vessel diameter (RVD) measurements and the factors related to retinal vascular diameters in patients with open-angle glaucoma (OAG). METHODS: This retrospective observational study included 145 patients with OAG (63 with high-tension and 82 with low-tension glaucoma) and 60 healthy controls. The central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were measured using the IVAN software version 1.3. Receiver operating characteristic (ROC) curves were obtained for the average retinal nerve fiber layer (RNFL) thickness and RVD indices including CRAE, CRVE, and CRAE/CRVE ratio. Areas under the ROC curves (AUCs), 95% confidence intervals (CIs), and sensitivities at a fixed specificity (>90% and >80%) were calculated. Factors related to CRAE were analyzed by simple and multiple linear regression analyses. RESULTS: Among the RVD indices, the CRAE had the largest AUC for discriminating glaucomatous changes between eyes with glaucoma and those without (0.803; 95% CI, 0.742-0.855). The AUC of CRAE did not significantly differ from that of average RNFL thickness (P = 0.134). However, CRAE showed lower sensitivity than average RNFL thickness at a specificity greater than 90%. Factors significantly associated with CRAE in both simple and multiple linear regression analyses were age, spherical equivalent, average RNFL thickness, presence of diabetes mellitus, and a glaucoma diagnosis (all P ≤ 0.05). CONCLUSIONS: The diagnostic ability of CRAE for detecting OAG was good, which was not much worse than that of average RNFL thickness. This finding suggests the potential usefulness of RVD for glaucoma detection.

Optimal surgical timing in infantile exotropia.

OBJECTIVE: To evaluate age at surgery and duration of misalignment, which affect surgical outcomes of infantile exotropia in healthy children younger than 1 year. METHODS: The charts of 39 patients who have at least 1 year of follow-up period after surgery with a diagnosis of early-onset exotropia were reviewed retrospectively. Patients were divided into 2 groups (preoperative deviation [PD]): success (exodeviation ≤8 PD or esodeviation ≤5 PD at 1 year postoperatively without reoperation in the whole follow-up period) or failure (exodeviation >8 PD or esodeviation >5 PD at 1 year postoperatively, or reoperation for recurrence or overcorrection during the follow-up period). We evaluated the age at surgery and the duration of misalignment divided into 5 categories-before 6, 12, 18, 24, and 30 months-to suggest appropriate surgical timing affecting surgical outcome and compared between the 2 groups. RESULTS: Overall, 74% of the patients comprised the success group and 26% the failure group. There was no statistically significant difference in the age of alignment between 2 groups (p = 0.91). The mean duration of misalignment was 16.7 months in the success group and 20.1 months in the failure group, with no significant difference (p = 0.52). There were 4 patients (14%) with a misalignment duration of ≥24 months in the success group and 5 such patients (50%) in the failure group; the difference was statistically significant (p = 0.024). Therefore, with a duration of misalignment of up to 24 months as the reference level, the odds of having a successful outcome decreased significantly over 24 months, with the multiple logistic regression model yielding a risk estimate over 6-fold of failure (odds ratio 6.25; p = 0.024). CONCLUSIONS: The postoperative surgical outcome was influenced by the duration of the misalignment, rather than the age at surgery. Surgery within 24 months of misalignment favourably affected the percentage of patients who achieved successful outcome in the treatment of infantile exotropia.

Modified inferior oblique transposition considering the equator for primary inferior oblique overaction (IOOA) associated with dissociated vertical deviation (DVD).

PURPOSE: Inferior oblique anterior transposition (IOAT) should be done only in patients with inferior oblique overaction (IOOA) and dissociated vertical deviation (DVD) without fusional potential because the procedure can cause anti-elevation syndrome. This study reports the results of modified inferior oblique transposition onto the equator in 7 patients diagnosed with infantile exotropia or esotropia associated with IOOA and DVD. METHODS: We performed modified inferior oblique (IO) transposition onto or considering the equator on 7 patients who had infantile exotropia or esotropia associated with IOOA and DVD. Five patients had infantile exotropia, and the other two patients had infantile esotropia. Six patients had undergone bilateral rectus--Bilateral Lateral Rectus (BLR) or Bilateral Medial Rectus (BMR)--recession previously and one patient underwent BLR recession and IO transposition simultaneously. They had more than +1.5 IOOA with DVD in both eyes. IO was transposed vertically onto the equator in this study. The mean distance between the lateral border of the inferior rectus insertion and the equator was 5.6 mm (range: 4.5 to 6.5 mm). Three months after the operation, degree of IOOA and DVD in each eye was evaluated. RESULTS: IOOA and DVD were markedly reduced in all patients (+0.5 ∼+1 for IOOA postoperatively). Mild contralateral IOOA was noted but the motility disturbance was successfully corrected in all cases postoperatively. CONCLUSION: Bilateral IO transposition onto the equator could minimize antielevation and corrected IOOA and DVD successfully in patients with infantile exotropia or esotropia.

Change in the location of the equator and recessed muscles in young rabbit eyes.

PURPOSE: To study the changes in the location of the equator and the new insertion of extraocular muscle after recession surgery in a rabbit model. METHOD: An experimental study was performed in ten eyes of five rabbits. Eyes were divided into two groups according to the amount of recession. In right eyes, 5 mm superior recti (SR) muscle recession, approximately 2 mm posterior to the equator, was performed (5 mm recession group), while in the left eyes, 3 mm recession was performed to the location of the equator (3 mm recession group). We measured the distance of the equator from the limbus, as well as the distance between the superior rectus insertion and the equator. The preoperative measurements were compared with the results 2 months after the surgery. The change in location of the superior rectus and the equator was compared between the two eyes. RESULT: The recessed SR muscle did not show any significant change in location in both groups (p = 0.18 and 0.16 respectively). However, the location of the equator of rabbit eye showed movement of about 1 mm posterior to the initial location with the growth of the eyeballs (p = 0.04 and 0.03, respectively). CONCLUSION: The location of the equator moved posteriorly at 2 months postoperatively in young rabbit model while the insertion of the recessed SR did not show any significant movement.

3D asthenopia in horizontal deviation.

PURPOSE: This study was conducted to investigate the asthenopic symptoms in patients with exotropia and esotropia while watching stereoscopic 3D (S3D) television (TV). METHODS: A total 77 subjects who more than 9 years of age were enrolled in this study. We divided them into three groups; Thirty-four patients with exodeviation (Exo group), 11 patients with esodeviation (Eso group) and 32 volunteers with normal binocular vision (control group). The S3D images were shown to all patients with S3D high-definition TV for a period of 20 min. Best corrected visual acuity, refractive errors, angle of strabismus, stereopsis test and history of strabismus surgery, were evaluated. After watching S3D TV for 20 min, a survey of subjective symptoms was conducted with a questionnaire to evaluate the degree of S3D perception and asthenopic symptoms such as headache, dizziness and ocular fatigue while watching 3D TV. RESULTS: The mean amounts of deviation in the Exo group and Eso group were 11.2 PD and 7.73PD, respectively. Mean stereoacuity was 102.7 arc sec in the the Exo group and 1389.1 arc sec in the Eso group. In the control group, it was 41.9 arc sec. Twenty-nine patients in the Exo group showed excellent stereopsis (≤60 arc sec at near), but all 11 subjects of the Eso group showed 140 arc sec or worse and showed more decreased 3D perception than the Exo and the control group (p < 0.001, Kruskal-Wallis test). The Exo group reported more eye fatigue (p < 0.001, Kruskal-Wallis test) than the Eso and the control group. However, the scores of ocular fatigue in the patients who had undergone corrective surgery were less than in the patients who had not in the Exo group (p < 0.001, Kruskal-Wallis test) and the amount of exodeviation was not correlated with the asthenopic symptoms (dizziness, r = 0.034, p = 0.33; headache, r = 0.320, p = 0.119; eye fatigue, r = 0.135, p = 0.519, Spearman rank correlation test, respectively). CONCLUSION: Symptoms of 3D asthenopia were related to the presence of exodeviation but not to esodeviation. This may indicate that S3D symptoms are closely related to the convergence demand.

Change in efficiency of aspheric intraocular lenses based on pupil diameter.

PURPOSE: To measure the effect of spherical aberration correction by aspheric intraocular lenses (IOLs) based on pupil diameter, and to determine the minimum pupil diameter for each aspheric IOL. DESIGN: Retrospective cross-sectional study. METHODS: Eight-six patients (169 eyes) who were implanted with a HOYA AF-1 NY-60 (HOYA Corporation) or Tecnis ZCB00 1-piece IOL (Abbott Medical Optics Inc) were enrolled. Ocular, corneal, and internal spherical aberrations were measured at the 1-month postoperative visit using the Wavefront Analyzer KR-1W (Topcon). Minimum pupil diameter, which is required for each aspheric IOL to be effective, was calculated using a regression equation. RESULTS: The mean value of internal spherical aberration of the Tecnis ZCB00 group (-0.09 ± 0.094 µm) was lower than that of the HOYA NY-60 group (-0.05 ± 0.072 µm) (P = .005). The original negative spherical aberrations of the HOYA NY-60 (-0.18 µm) were measured at a pupil diameter of 5.6 mm, and for the Tecnis ZCB00 (-0.27 µm) at a pupil diameter of 6.1 mm. The aspheric IOL efficiency dropped to 0% when the pupil diameter was 3.47 mm for the Tecnis ZCB00 group and 3.71 mm for the HOYA NY-60 group. CONCLUSIONS: When the pupil diameters of patients are smaller than 3.4 mm for the Tecnis ZCB00 and 3.7 mm for the HOYA NY-60, the spherical aberration correction using these aspheric IOLs seems to be ineffective. Approximately 10% of the eyes showed smaller pupil size than the minimum effective diameter under mesopic conditions.

Surgical correction for lower lid epiblepharon using thermal contraction of the tarsus and lower lid retractor without lash rotating sutures.

PURPOSE: To evaluate the long-term efficacy of a new surgical technique for the correction of lower lid epiblepharon using thermal contraction of the tarsus and lower lid retractor without lash rotating sutures. METHODS: A retrospective study was conducted on 112 eyes of 56 patients who underwent surgical correction of lower lid epiblepharon with a modified Hotz operation (group A) or a new procedure (group B). The new technique requires that thermal contraction using bipolar cautery was applied to the inferior tarsus including the pretarsal orbicularis oculi muscle and lower lid retractor to create lash rotation without additional rotating sutures. The authors compared the results from these two techniques. RESULTS: 44 eyes of 22 patients (11 boys and 11 girls) were included in group A, the average age was 5.5 years (± 2.2), follow-up periods were 56.9 months (± 7.7). Undercorrections developed in four eyes (9.1%), and epiblepharon recurred in seven eyes (15.9%). In group B, 68 eyes of 34 (20 male and 14 female) patients were included, with an average age of 5.1 years (± 2.5), and a mean follow-up period of 39.7 months (± 9.5). Epiblepharon recurred in three eyes (4.4%), and no patients were undercorrected. The recurrence and undercorrection rates were significantly lower in group B (p=0.022 and p=0.047). CONCLUSION: The new surgical technique for the correction of lower lid epiblepharon using thermal contraction of the tarsus and lower lid retractor without lash rotating sutures was very useful and effective for the correction of epiblepharon, with good cosmetic results.

Li-air rechargeable battery based on metal-free graphene nanosheet catalysts.

Metal-free graphene nanosheets (GNSs) were examined for use as air electrodes in a Li-air battery with a hybrid electrolyte. At 0.5 mA cm(-1), the GNSs showed a high discharge voltage that was near that of the 20 wt % Pt/carbon black. This was ascribed to the presence of sp(3) bonding associated with edge and defect sites in GNSs. Moreover, heat-treated GNSs not only provided a similar catalytic activity in reducing oxygen in the air, but also showed a much more-stable cycling performance than GNSs when used in a rechargeable Li-air battery. This improvement resulted from removal of adsorbed functional groups and from crystallization of the GNS surface into a graphitic structure on heat treatment.