Outcomes of bilateral axillo-breast approach robotic parathyroidectomy versus open parathyroidectomy for primary hyperparathyroidism: a single-institution retrospective study.

Purpose: Bilateral axillo-breast approach robotic parathyroidectomy (BABA-RP) aims to remove overactive or enlarged parathyroid glands with no visible neck collar incision. In this study, we compared the safety and surgical outcomes of BABA-RP vs. those of an open surgery group to ascertain whether BABA-RP is a safe and feasible surgical approach for patients with primary hyperparathyroidism (pHPT). Methods: This single-institution retrospective cohort study included 74 patients with primary HPT who underwent open parathyroidectomy (n = 37) or BABA-RP (n = 37) at our institution between November 2014 and March 2023. Patient demographics, biochemical cure rates, operative time, blood loss rates, and complication rates were examined and compared. Results: The patients in the BABA-RP group were younger and had a longer mean operative time. Regarding complication events, 2 patients in the open surgery group and 1 patient in the BABA-RP group had transient hypoparathyroidism. All 74 patients achieved biochemical cure at <6 months, regardless of the approach used. Two patients in the BABA-RP group and 1 patient in the open surgery group had carcinoma on surgical pathology. All 3 patients with parathyroid carcinoma remained recurrence-free at 1-year follow-up. Conclusion: Compared with the open procedure, BABA-RP is a safe and feasible procedure that provides an excellent biochemical cure rate for patients with pHPT and has superior cosmetic benefits with equivalent surgical outcomes.

TSH receptor antibody as a predictor of difficult robotic thyroidectomy in patients with Graves' disease.

Thyroidectomy in Graves' disease can be challenging due to greater thyroid size and vascularity. While thyroid stimulating hormone receptor antibody (TRAb) level is associated with disease severity and thyroid vascularity, its impact on operative outcomes remains unclear. This study aimed to compare challenging factors for robotic thyroidectomy (RT) and open thyroidectomy (OT) in Graves' disease patients, including TRAb as a predictive factor for difficult thyroidectomy. This retrospective study included Graves' disease patients who underwent total thyroidectomy between September 2013 and January 2023. The clinical characteristics and operative outcomes were compared between patients who received OT and bilateral axillo-breast approach RT. Factors affecting operation time and estimated blood loss (EBL) were evaluated in both groups using regression analyses. A total of 85 patients received either OT (n = 48) or RT (n = 37). Median thyroid volumes in the OT and RT groups were 72.4 g and 57.6 g, respectively. Operation time was affected by thyroid volume in both groups. Additionally, higher thyroid hormone levels and bilateral central neck node dissection prolonged operation time in the RT group. EBL was marginally associated with thyroid volume in the OT group. However, in the RT group, TRAb level was independently associated with greater EBL (p = 0.04), while no significant association was found with thyroid volume. Predictive factors for difficult thyroidectomy differed by operation approaches. TRAb significantly predicted intraoperative bleeding in RT, while this association was absent in OT. Caution is warranted when performing RT on Graves' disease patients with high TRAb levels.

Analyzing circulating tumor cells and epithelial-mesenchymal transition status of papillary thyroid carcinoma patients following thyroidectomy: a prospective cohort study.

BACKGROUND: This study investigated the prevalence and subtype distribution of circulating tumor cells (CTCs) in patients with papillary thyroid cancer (PTC) before and after thyroidectomy to determine the potential of CTC count as a noninvasive marker of the efficacy of surgical treatment in PTC. MATERIALS AND METHODS: Between January 2021 and January 2022, 62 PTC patients who underwent thyroidectomy at Seoul National University Bundang Hospital were prospectively evaluated. Peripheral blood samples (7.5 ml) were collected from each patient for CTC analysis before surgery and at 2 weeks and 3 months after surgery. CTC count and the distribution of CTC subtypes, including epithelial, epithelial-mesenchymal, and mesenchymal phenotypes, were analyzed using the negative selection method and immunofluorescence staining. The relationship between CTC count and clinicopathological characteristics was analyzed before and after surgery. RESULTS: Before surgery, CTCs were detected in 87% (54/62) of patients; the mean CTC count was 8.0 and the median was 5.0 in 7.5 ml of peripheral blood. The mesenchymal or epithelial-mesenchymal phenotypes were predominant. After thyroidectomy, the mean and median CTC count values decreased to 5.3 and 2.5, respectively, at 2 weeks and to 4.3 and 3.0, respectively, at 3 months. This postoperative reduction in CTCs was more pronounced in patients with lymphatic invasion, lymph node metastasis, or BRAF V600E mutation. CONCLUSION: CTCs were detected in patients with PTC with a predominance of cells undergoing epithelial-mesenchymal transition. The CTC count decreased postoperatively, suggesting that liquid biopsy with CTC detection could be a valuable noninvasive tool for monitoring the efficacy of surgery in PTC.

Exploiting Organometallic Chemistry to Functionalize Small Cuprous Oxide Colloidal Nanocrystals.

The ligand chemistry of colloidal semiconductor nanocrystals mediates their solubility, band gap, and surface facets. Here, selective organometallic chemistry is used to prepare small, colloidal cuprous oxide nanocrystals and to control their surface chemistry by decorating them with metal complexes. The strategy is demonstrated using small (3-6 nm) cuprous oxide (Cu2O) colloidal nanocrystals (NC), soluble in organic solvents. Organometallic complexes are coordinated by reacting the surface Cu-OH bonds with organometallic reagents, M(C6F5)2, M = Zn(II) and Co(II), at room temperature. These reactions do not disrupt the Cu2O crystallinity or nanoparticle size; rather, they allow for the selective coordination of a specific metal complex at the surface. Subsequently, the surface-coordinated organometallic complex is reacted with three different carboxylic acids to deliver Cu-O-Zn(O2CR') complexes. Selective nanocrystal surface functionalization is established using spectroscopy (IR, 19F NMR), thermal gravimetric analyses (TGA), transmission electron microscopy (TEM, EELS), and X-ray photoelectron spectroscopy (XPS). Photoluminescence efficiency increases dramatically upon organometallic surface functionalization relative to that of the parent Cu2O NC, with the effect being most pronounced for Zn(II) decoration. The nanocrystal surfaces are selectively functionalized by both organic ligands and well-defined organometallic complexes; this synthetic strategy may be applicable to many other metal oxides, hydroxides, and semiconductors. In the future, it should allow NC properties to be designed for applications including catalysis, sensing, electronics, and quantum technologies.

Effect of thyroid-stimulating hormone suppression on quality of life in thyroid lobectomy patients: interim analysis of a multicenter, randomized controlled trial in low- to intermediate-risk thyroid cancer patients (MASTER study).

Purpose: Current clinical practices favor less or no thyroid-stimulating hormone (TSH) suppression for low- to intermediate-risk thyroid cancer patients who receive thyroid lobectomy. The association of TSH suppression on health-related quality of life (HR-QoL) in patients after thyroid lobectomy is not well studied. This study aimed to evaluate the effect of TSH suppression on patient HR-QoL after thyroid lobectomy. Methods: This study included patients enrolled in an ongoing, multicenter, randomized controlled study investigating the effects of TSH suppression. Patients were randomized to either the low-TSH group (TSH target range, 0.3-1.99 µIU/mL) or the high-TSH group (TSH target range, 2.0-7.99 µIU/mL). The HR-QoL, hyperthyroidism symptom, and depression symptom questionnaires performed preoperatively and 2 weeks and 3 months postoperatively were evaluated. Results: Total of 669 patients (low-TSH group, 340; high-TSH group, 329) were included. Although total HR-QoL score changes were not different between the 2 groups, the high-TSH group had a significantly higher score in the physical domain at postoperative 3 months (P = 0.046). The 2 groups did not have significant differences in hyperthyroidism and depression scores. Conclusion: In the short-term postoperative period, the physical HR-QoL scores in thyroid lobectomy patients were better when they did not receive TSH suppression. This study suggests the importance of considering HR-QoL when setting TSH suppression targets in thyroid lobectomy patients.

Observation of changes in quality of life for 5 years after thyroid surgery: an observational cross-sectional study in Korean population.

Purpose: As thyroid cancer patients are experiencing longer disease-free survival periods, evaluating their quality of life after surgery has become crucial. However, studies on this topic have primarily focused on Western populations, leaving a gap in understanding the Korean patient population's experiences and needs. This study aims to address this gap and provide insights into the quality of life of thyroid cancer patients in Korea. Methods: This cross-sectional study evaluated the quality of life of Korean thyroid cancer patients who underwent thyroid lobectomy or total thyroidectomy. Patients were surveyed using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC-QLQ-C30, ver. 3.0) during outpatient clinic visits from January to September 2015. The results were analyzed by comparing them to scores of the general population and based on the time elapsed since surgery. This approach allowed for a comprehensive evaluation of the quality-of-life outcomes in this patient population. Results: The study found that thyroidectomy had a notable impact on patients' role and cognitive functions. Patients also experienced worsened symptoms such as fatigue, dyspnea, and constipation, which improved over time and returned to normal levels. However, there were no significant changes in other functions and symptoms after surgery. Conclusion: The study's findings showed that thyroidectomy had a relatively minor impact on the functional and symptomatic well-being of patients. Therefore, the results suggest that thyroid surgery may be a safe and effective treatment option for thyroid cancer patients seeking to maintain a good quality of life.

Bilateral axillo-breast approach robotic thyroidectomy in pediatric patients with thyroid disease and cancer.

PURPOSE: Robotic thyroid surgeries have cosmetic advantages over open surgeries, which are especially important in pediatric patients due to social stigmas from neck scars. The present study describes outcomes in a series of children who underwent bilateral axillo-breast approach (BABA) robotic thyroidectomy. METHODS: Pediatric patients aged ≤18 years who underwent BABA robotic thyroidectomy between 2014 and 2022 were retrospectively reviewed. Their clinical characteristics and surgical outcomes were evaluated. Surgical completeness was determined by comparing the number of retrieved lymph nodes per compartment to previously reported lymph node quantification. RESULTS: This study included 26 pediatric patients of mean age 15.5 years (range, 5-18 years). Of these 26 patients, 21 (80.8%) had thyroid cancer, with 9 (42.9%) having aggressive tumor pathology. The mean operation time was 157.3 min. No patient needed open conversion. Five patients (19.2%) experienced complications including transient hypoparathyroidism (n = 5), permanent hypoparathyroidism (n = 2), and chyle leakage (n = 1), but none experienced vocal cord palsy. The mean numbers of retrieved lymph nodes at levels IIa, III, IV, Vb, and VI were 3.2, 4.1, 5.6, 1.0, and 9.7, respectively, numbers comparable with the known quantification except for level II, as IIb dissection was omitted in our series. CONCLUSION: BABA robotic thyroidectomy is safe and effective in pediatric patients with thyroid diseases. Most complications were minor and transient, with the operation time similar to robotic thyroidectomy in adults. Surgical completeness was also satisfactory. Robotic thyroidectomy can be considered a surgical option, regardless of patient age or diagnosis.

Matched Ligands for Small, Stable Colloidal Nanoparticles of Copper, Cuprous Oxide and Cuprous Sulfide.

This work applies organometallic routes to copper(0/I) nanoparticles and describes how to match ligand chemistries with different material compositions. The syntheses involve reacting an organo-copper precursor, mesitylcopper(I) [CuMes]z (z=4, 5), at low temperatures and in organic solvents, with hydrogen, air or hydrogen sulfide to deliver Cu, Cu2 O or Cu2 S nanoparticles. Use of sub-stoichiometric quantities of protonated ligand (pro-ligand; 0.1-0.2 equivalents vs. [CuMes]z ) allows saturation of surface coordination sites but avoids excess pro-ligand contaminating the nanoparticle solutions. The pro-ligands are nonanoic acid (HO2 CR1 ), 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (HO2 CR2 ) or di(thio)nonanoic acid, (HS2 CR1 ), and are matched to the metallic, oxide or sulfide nanoparticles. Ligand exchange reactions reveal that copper(0) nanoparticles may be coordinated by carboxylate or di(thio)carboxylate ligands, but Cu2 O is preferentially coordinated by carboxylate ligands and Cu2 S by di(thio)carboxylate ligands. This work highlights the opportunities for organometallic routes to well-defined nanoparticles and the need for appropriate ligand selection.

Effect of body habitus on surgical outcomes following bilateral axillo-breast approach robotic thyroidectomy: a retrospective cohort study.

INTRODUCTION: BMI has been shown to predict perioperative outcomes in patients undergoing surgery. Most studies assessing the role of body habitus in thyroid surgery have focused on open surgery, with few studies assessing patients undergoing robotic surgery. The present study evaluated the effects of BMI on surgical outcomes in patients undergoing bilateral axillo-breast approach (BABA) robotic thyroidectomy. MATERIALS AND METHODS: This study included patients who underwent BABA robotic thyroidectomy between January 2013 and September 2021 at Seoul National University Bundang Hospital. Patients were categorized into six groups based on the WHO classification of overweight and obesity. Clinicopathological characteristics, postoperative complications, and surgical outcomes were evaluated. RESULTS: A total of 1921 patients were included. Comparisons of the six BMI groups showed no statistically significant differences in postoperative stay, resection margin involvement, postoperative complications, and recurrence. Subgroup analysis showed that hypocalcemia rates differed among BMI groups in patients who underwent lobectomy, with underweight and class II obese patients being at the highest risk ( P =0.006). However, the actual number of complications was relatively small and similar among the groups. In patients who underwent total thyroidectomy and isthmectomy, BMI was not correlated with postoperative complications, including hypocalcemia, recurrent laryngeal nerve palsy, postoperative bleeding, and chyle leakage. CONCLUSION: Body habitus was not significantly associated with operative time and postoperative complications in patients undergoing BABA robotic thyroidectomy, indicating that this approach is safe and feasible in obese patients.

BRAFV600E and TERT promoter C228T mutations on ThyroSeq v3 analysis of delayed skin metastasis from papillary thyroid cancer: a case report and literature review.

BACKGROUND: Skin metastasis from papillary thyroid cancer (PTC) is a rare entity that can occur up to decades after treatment of the primary tumor. Here, we present a patient who developed skin metastasis 10 years after treatment of her primary tumor and describe the molecular findings of the metastatic lesion. CASE PRESENTATION: A 44-year-old female with a history of PTC who underwent a total thyroidectomy and radioactive iodine (RAI) treatment 10 years ago presented with a 1.3-cm skin lesion along the prior thyroidectomy scar. A biopsy revealed metastatic PTC, and the patient underwent surgical excision of the lesion. ThyroSeq molecular testing showed the copresence of BRAFV600E mutation and TERT promoter C228T mutation. The patient subsequently received one round of adjuvant RAI therapy. CONCLUSIONS: A high index of suspicion is warranted in patients with a history of PTC who develop a skin lesion, even several years after remission of the primary disease. In patients with high-risk mutations, such as BRAFV600E and TERT promoter C228T mutations, long-term surveillance of disease recurrence is particularly important.

Bilateral axillo-breast approach robotic total thyroidectomy in a 5-year-old patient with intractable Graves' disease.

Robotic thyroid surgeries in children are gaining popularity due to cosmetic advantages, but most previous studies include patients of school-age or older. We hereby introduce our case of a 5-year-old patient with Graves' disease to show key differences and similarities between pediatric and adult bilateral axillo-breast approach (BABA) robotic thyroidectomies. Despite the small body, no additional working space was needed and the flap creation was performed as similarly done in adults. The anatomy was not much different, except that the parathyroid tissues were easily identified due to low body fat, and the prominent thymus covered most of the level VI area. The patient did not experience postoperative complications such as hypoparathyroidism or vocal cord palsy. Postoperative wounds showed excellent results with minimal scars. BABA robotic thyroidectomy can be performed safely in pediatric patients and may be considered an alternative option for conventional open thyroidectomy in children.

Prevalence of Postoperatively Detected High-risk Features in 2- to 4-cm Papillary Thyroid Cancers.

CONTEXT: The 2015 American Thyroid Association guidelines proposed thyroid lobectomy as an acceptable option for 1- to 4-cm papillary thyroid cancers (PTC) without extrathyroidal extension (ETE) or lymph node (LN) metastasis. However, high-risk features are often detected postoperatively, even in tumors that are considered low risk on preoperative workup. A continued evaluation is necessary to determine the optimal treatment strategies. OBJECTIVE: We examined the frequency of preoperatively and postoperatively detected high-risk features in 2- to 4-cm PTCs to assess the appropriate surgical extent. METHODS: All patients who underwent a thyroid surgery between 2015 and 2020 with a final diagnosis of 2- to 4-cm PTC were selected. Demographics, preoperative findings, perioperative course, and surgical pathology were retrospectively analyzed. RESULTS: Of the entire study cohort (N = 424), 244 (57.5%) patients had at least 1 of the following high-risk features: gross ETE (18.6%), distant metastasis (1.2%), >3 LN involvement with extranodal extension (24.8%), any LN > 3 cm (0.5%), positive margin (13.2%), TERT mutation (2.6%), vascular invasion (10.8%), cN1 disease (28.5%), and > 5 LN involvement (30.4%). Two hundred patients had neither ETE nor LN metastasis on preoperative imaging, but 62/200 (31.0%) were found to have at least 1 of the aforementioned high-risk features on final pathology. Preoperative imaging had sensitivities of 75.9% and 44.4% for detecting gross ETE and LN metastasis, respectively. CONCLUSION: A significant portion of patients with 2- to 4-cm PTCs, including those who preoperatively met the criteria for lobectomy, were found to have high-risk features on final pathology. Careful patient selection and appropriate counseling are necessary when considering lobectomy for tumors greater than 2 cm.

The short video lecture for robotic bilateral axillo-breast approach to lateral neck lymph node dissection.

Lateral neck lymph node dissection (LND) along with total thyroidectomy is the standard treatment for thyroid cancer patients with metastases to the lateral neck lymph nodes. In general, lateral neck LND removes lymph nodes located at levels II to V ipsilateral to the thyroid cancer and preserves the spinal accessory nerve, internal jugular vein, and sternomastoid muscle during surgery. This video article was written to introduce the robotic bilateral axillo-breast approach for lateral neck LND and to describe the surgical method.

High-Resolution Mapping of Strain Partitioning and Relaxation in InGaN/GaN Nanowire Heterostructures.

Growing an Inx Ga1- x N/GaN (InGaN/GaN) multi-quantum well (MQW) heterostructure in nanowire (NW) form is expected to overcome limitations inherent in light-emitting diodes (LEDs) based on the conventional planar heterostructure. The epitaxial strain induced in InGaN/GaN MQW heterostructure can be relaxed through the sidewalls of NW, which is beneficial to LEDs because a much larger misfit strain with higher indium concentration can be accommodated with reduced piezoelectric polarization fields. The strain relaxation, however, renders highly complex strain distribution within the NW heterostructure. Here the authors show that complementary strain mapping using scanning transmission electron microscopy and dark-field inline holography can comprehend the strain distribution within the axial In0.3 Ga0.7 N/GaN MQW heterostructure embedded in GaN NW by providing the strain maps which can cover the entire NW and fine details near the sidewalls. With the quantitative evaluation by 3D finite element modelling, it is confirmed that the observed complex strain distribution is induced by the strain relaxation leading to the strain partitioning between InGaN quantum disk, GaN quantum well, and the surrounding epitaxial GaN shell. The authors further show that the strain maps provide the strain tensor components which are crucial for accurate assessment of the strain-induced piezoelectric fields in NW LEDs.

Prognostic significance of surgery-induced sarcopenia in the survival of gastric cancer patients: a sex-specific analysis.

BACKGROUND: Preoperative sarcopenia is associated with a poor long-term prognosis in patients with gastric cancer (GC). Most GC patients rapidly lose muscle mass after gastrectomy. This retrospective cohort study analysed the effect of postoperative muscle loss and surgery-induced sarcopenia on the long-term outcomes of patients with GC. METHODS: Preoperative and postoperative 1 year abdominal computed tomography scans were available for 1801 GC patients who underwent curative gastrectomy between January 2009 and December 2013 at Seoul National University Bundang Hospital. The patients were categorized into normal, presarcopenia, and sarcopenia groups according to the skeletal muscle index (SMI) measured on computed tomography scans. Patients who were not sarcopenic prior to gastrectomy but became sarcopenic after surgery were defined as the surgery-induced sarcopenia group. RESULTS: There were 1227 men and 574 women included in the study. The mean age of the patients was 59.5 ± 12.3 years. Multivariable Cox-regression analyses showed that preoperative SMI was not associated with overall survival (OS). However, postoperative sarcopenia was associated with significantly worse OS only in men [hazard ratio (HR), 1.75; 95% confidence interval (CI), 1.08-2.85]. SMI loss was an independent risk factor for OS in the entire cohort and in men (HR, 1.01; 95% CI, 1.00-1.02, for the entire cohort; HR, 1.02; 95% CI, 1.01-1.04, for men). The surgery-induced sarcopenia group was associated with significantly higher mortality (HR, 1.84; 95% CI, 1.16-2.90, for the cohort; HR, 2.73; 95% CI, 1.54-4.82, for men), although SMI loss and surgery-induced sarcopenia were not risk factors in women. Similar results were obtained for relapse-free survival. CONCLUSIONS: Postoperative muscle mass loss and surgery-induced sarcopenia are prognostic factors for survival in patients with GC. Impact of postoperative muscle mass loss and surgery-induced sarcopenia on survival outcomes is dependent on the sex.

Oncologic comparison between nonradical management and total mesorectal excision in good responders after chemoradiotherapy in patients with mid-to-low rectal cancer.

PURPOSE: This study was performed to compare the oncologic outcomes between nonradical management and total mesorectal excision in good responders after chemoradiotherapy. METHODS: We analyzed 75 patients, who underwent 14 watch-and-wait, 30 local excision, and 31 total mesorectal excision, in ycT0-1N0M0 based on magnetic resonance imaging after chemoradiotherapy for advanced mid-to-low rectal cancer in 3 referral hospitals. The nonradical management group underwent surveillance with additional sigmoidoscopy and rectal magnetic resonance imaging every 3-6 months within the first 2 years. RESULTS: Nonradical management group had more low-lying tumors (P < 0.001) and less lymph node metastasis based on magnetic resonance imaging (P = 0.004). However, cT stage, ycT, and ycN stage were not different between the 2 groups. With a median follow-up period of 64.7 months, the 5-year locoregional failure rate was higher in the nonradical management group than in the total mesorectal excision group (16.7% vs. 0%, P = 0.013). However, the 5-year overall survival and disease-free survival rates of the nonradical management and total mesorectal excision groups were not different (95.2% vs. 93.5%, P = 0.467; 76.4% vs. 83.6%, P = 0.665; respectively). CONCLUSION: This study shows that nonradical management for ycT0-1N0 mid-to-low rectal cancer may be an alternative treatment to total mesorectal excision under proper surveillance and management for oncologic events.

Comparison of Bioelectrical Impedance Analysis and Computed Tomography on Body Composition Changes Including Visceral Fat After Bariatric Surgery in Asian Patients with Obesity.

PURPOSE: The accuracy of bioelectrical impedance analysis (BIA) in patients with obesity has been controversial. This study aimed to validate the use of BIA in detecting body composition changes, especially for visceral fat, before and after bariatric surgery using computed tomography (CT) as a reference method. MATERIALS AND METHODS: This retrospective study included Korean patients with a BMI of ≥ 35, or ≥ 30 with metabolic comorbidities. All patients underwent bariatric surgery, and underwent BIA and CT evaluation before and 6 months after the operation. The skeletal muscle index (SMI) and visceral fat index (VFI), variables corrected for height, were compared between BIA and CT. RESULTS: Forty-eight patients (18 men, 30 women) demonstrated a mean weight loss of 27.5 kg. Significant decreases in both VFI and SMI were observed in both BIA and CT (all p<0.001), with greater VFI change compared to SMI (48.2% vs. 10.4% in CT, respectively). Both pre- and post-operative measurements of VFI and SMI were significantly correlated between BIA and CT (all p<0.05). However, the percent decrease was significantly correlated only with VFI (ρ=0.71, p<0.001). The Bland-Altman analysis showed that BIA underestimated VFI, with a greater degree of underestimation in subjects with higher VFI. CONCLUSION: Despite the underestimation of BIA in measuring visceral fat, BIA VFI was associated with CT VFI. The SMI values showed significant correlations before and after surgery, but not with the percent decrease. Our results suggest that BIA can be a reliable tool for measuring body composition, especially for visceral fat, after bariatric surgery.

Self-Assembly of Bowlic Supramolecules on Graphene Imaged at the Individual Molecular Level using Heavy Atom Tagging.

The self-assembly of bowlic supramolecules on graphene surface is studied with single molecular sensitivity. This is achieved by incorporating a heavy metal tag in the form of a single W atom into the tip of the molecular structure, which enables the direct imaging of molecular distribution using annular dark-field scanning transmission electron microscopy (ADF-STEM) along with graphene as an electron transparent support. The bowlic molecules have nonplanar geometry, and their orientations with respect to their graphene substrate and with each other result in various packing configurations. Statistical data on intermolecular distances is obtained from numerous measurements of the bright contrast from the single metal atom tags. The analysis shows that the bowlic molecules lie sideways on the graphene surface with favorable head-to-tail stacking, rather than sitting vertically with the bowl facing toward the graphene surface. In thicker film regions, nanoscale lamellar fringes are observed, demonstrating that large-scale aligned packing extends into 3D. Image simulations and various molecular packing schemes are discussed to help interpret the ADF-STEM images and the possible range of molecular interactions occurring. These results aid the understanding of nonplanar supramolecular assemblies on van der Waals surfaces for potential applications in molecular recognition by porous films.

Direct Imaging of Individual Molecular Binding to Clean Nanopore Edges in 2D Monolayer MoS2.

We use annular dark-field scanning transmission electron microscopy (ADF-STEM) to study how solution-deposited molecules bind to the edges and surface regions around nanopores in MoS2 monolayers. Nanopores with clean atomically flat edges and controllable mean diameter were generated by time-dependent large-area electron beam exposure during an in situ heating process, ready for subsequent molecular attachment. An organic molecule was designed to have a dithiolane end group that binds to Mo-terminated sites and a ligand structure that incorporates a single transition metal atom (Pt) marker for ADF-STEM detection. Pt atoms were used to track molecular binding around zigzag edges of MoS2 and to predict the orientations and conformations of molecules upon binding. We found that the molecules preferred to reside on the surface of the MoS2, pointing inward when attaching to the edge, rather than dangling out from the edge into free space, which is attributed to van der Waals interactions between the aromatic core of the molecule and the MoS2 basal planes. These results help us understand the way solution-deposited single molecules attach to free-standing edges of 2D crystals and the influence of van der Waals forces in guiding molecular binding.