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1.
World J Clin Cases ; 12(17): 3177-3182, 2024 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-38898872

RESUMO

BACKGROUND: Supernumerary phantom limb (SPL) sensation is the experience of additional limbs, either single or a pair of limbs. Unique to traumatic spinal cord injuries, we report effect of transcranial direct current stimulation (tDCS) on SPL pain in a patient with cervical cord injury. CASE SUMMARY: The subject was a 57-year-old man who was diagnosed with complete spinal cord injury (C6/C5, motor level; C5/C5, sensory level; AIS-A) approximately three months ago. After a period of 2 wk, we administered anodal tDCS over the motor cortex for 15 minutes at an intensity of 1.5 mA. Following that treatment, the patient experienced a decrease of SPL pain intensity and frequency, which lasted for 1 week after the end of treatment. CONCLUSION: Targeting the motor cortex through neuromodulation appears to be a promising option for the management of SPL pain.

2.
Clin Orthop Surg ; 16(3): 347-356, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38827766

RESUMO

Artificial intelligence (AI) has rapidly transformed various aspects of life, and the launch of the chatbot "ChatGPT" by OpenAI in November 2022 has garnered significant attention and user appreciation. ChatGPT utilizes natural language processing based on a "generative pre-trained transfer" (GPT) model, specifically the transformer architecture, to generate human-like responses to a wide range of questions and topics. Equipped with approximately 57 billion words and 175 billion parameters from online data, ChatGPT has potential applications in medicine and orthopedics. One of its key strengths is its personalized, easy-to-understand, and adaptive response, which allows it to learn continuously through user interaction. This article discusses how AI, especially ChatGPT, presents numerous opportunities in orthopedics, ranging from preoperative planning and surgical techniques to patient education and medical support. Although ChatGPT's user-friendly responses and adaptive capabilities are laudable, its limitations, including biased responses and ethical concerns, necessitate its cautious and responsible use. Surgeons and healthcare providers should leverage the strengths of the ChatGPT while recognizing its current limitations and verifying critical information through independent research and expert opinions. As AI technology continues to evolve, ChatGPT may become a valuable tool in orthopedic education and patient care, leading to improved outcomes and efficiency in healthcare delivery. The integration of AI into orthopedics offers substantial benefits but requires careful consideration and continuous improvement.


Assuntos
Inteligência Artificial , Procedimentos Ortopédicos , Humanos , Processamento de Linguagem Natural , Assistência ao Paciente
3.
Medicina (Kaunas) ; 60(5)2024 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-38793022

RESUMO

Background and Objectives: Endoscopic epidural neuroplasty (EEN) facilitates adhesiolysis through direct epiduroscopic visualization, offering more precise neural decompression than that exhibited by percutaneous epidural neuroplasty (PEN). We aimed to compare the effects of EEN and PEN for 6 months after treatment with lower back and radicular pain in patients. Methods: This retrospective study compared the visual analog scale (VAS) and Oswestry disability index (ODI) scores in patients with low back and radicular pain who underwent EEN or PEN with a steering catheter. The medical records of 107 patients were analyzed, with 73 and 34 undergoing EEN and PEN, respectively. Results: The VAS and ODI scores decreased at all time points after EEN and PEN. VAS and ODI scores decreased more in the EEN group than those in the PEN group at 1 day and 1- and 6-months post-procedure, indicating superior pain relief for both lower back and radicular pain through EEN. Conclusions: EEN is a superior treatment of pain control than PEN in lower back and radicular pain patients.


Assuntos
Dor Lombar , Humanos , Dor Lombar/cirurgia , Dor Lombar/terapia , Feminino , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Resultado do Tratamento , Seguimentos , Idoso , Adulto , Endoscopia/métodos , Medição da Dor/métodos , Espaço Epidural , Descompressão Cirúrgica/métodos
4.
Anesth Pain Med (Seoul) ; 19(2): 156-160, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38725171

RESUMO

BACKGROUND: Mounier-Kuhn syndrome (MKS) is a rare disorder characterized by abnormal dilation of the trachea and main bronchi. MKS can be easily missed on chest X-rays, making diagnosis difficult. Under general anesthesia, challenges such as airway leakage or collapse during mechanical ventilation may complicate the achievement of adequate tidal volumes. CASES: A 94-year-old woman requiring emergency hemiarthroplasty of the hip under general anesthesia was admitted. Preoperative chest X-rays revealed dilation of the trachea and main bronchi, but the patient exhibited no respiratory symptoms. We diagnosed her with MKS and opted for an 8.0-mm-inner-diameter reinforced tracheal tube. We positioned the cuff in the subglottic area, inflating it while monitoring for air leakage. Throughout the surgery, adequate tidal volume was maintained. CONCLUSIONS: Anesthesiologists must conduct a comprehensive evaluation of patients with MKS, including a review of chest radiographs, and establish a meticulous anesthesia plan prior to surgery.

5.
Clin Orthop Surg ; 16(2): 303-312, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38562639

RESUMO

Background: Glenoid position and inclination are important factors in protecting against scapular notching, which is the most common complication that directly affects the longevity of reverse shoulder arthroplasty (RSA). This study aimed to investigate the biomechanical characteristics of glenosphere orientation, comparing neutral tilt, inferior overhang with an eccentric glenosphere at the same placement of baseplate, and inferior tilt after 10° inferior reaming in the lower part of the glenoid in RSA. Methods: Nine cadaveric shoulders were tested with 5 combinations of customized glenoid components: a centric glenosphere was combined with a standard baseplate (group A); an eccentric glenosphere to provide 4-mm inferior overhang than the centric glenosphere was combined with a standard baseplate (group B); a centric glenosphere was combined with a wedge-shaped baseplate tilted inferiorly by 10° with the same center of rotation (group C); an eccentric glenosphere was attached to a wedge-shaped baseplate (group D); and 10° inferior reaming was performed on the lower part of the glenoid to apply 10° inferior tilt, with a centric glenosphere secured to the standard baseplate for simulation of clinical tilt (group E). Impingement-free angles for adduction, abduction, forward flexion, external rotation, and internal rotation were measured. The capability of the deltoid moment arm for abduction and forward flexion, deltoid length, and geometric analysis for adduction engagement were evaluated. Results: Compared with neutral tilt, inferior tilt at the same position showed no significant difference in impingement-free angle, moment arm capability, and deltoid length. However, group D resulted in better biomechanical properties than a central position, regardless of inferior tilt. Group E demonstrated a greater range of adduction, internal and external rotation, and higher abduction and forward flexion capability with distalization, compared to corresponding parameters for inferior tilt with a customized wedge-shaped baseplate. Conclusions: A 10° inferior tilt of the glenosphere, without changing the position of the baseplate, had no benefit in terms of the impingement-free angle and deltoid moment arm. However, an eccentric glenosphere had a significant advantage, regardless of inferior tilt. Inferior tilt through 10° inferior reaming showed better biomechanical results than neutral tilt due to the distalization effect.


Assuntos
Artroplastia do Ombro , Articulação do Ombro , Prótese de Ombro , Humanos , Artroplastia do Ombro/métodos , Articulação do Ombro/cirurgia , Ombro/cirurgia , Escápula , Amplitude de Movimento Articular , Fenômenos Biomecânicos
6.
Bioengineering (Basel) ; 11(4)2024 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-38671801

RESUMO

XRD diffraction and IR absorption were investigated for raw loess powder and heat-treated loess powder. Raw loess retains its useful minerals, but loses their beneficial properties when calcined at 850 °C and 1050 °C. To utilize the useful minerals, loess balls were made using a low-temperature wet-drying method. The radiant energy and transmittance were measured for the loess balls. Far-infrared ray (FIR) emitted from loess bio-balls is selectively absorbed as higher vibrational energy by water molecules. FIR can raise the body's core temperature, thereby improving blood flow through the body's thermoregulatory mechanism. In an exploratory study with 40 participants, when the set temperature of the loess ball mat was increased from 25 °C to 50 °C, blood flow increased by 39.01%, from 37.48 mL/min to 52.11 mL/min, in the left middle finger; in addition, it increased by 39.62%, from 37.15 mL/min to 51.87 mL/min, in the right middle finger. The FIR emitted from loess balls can be widely applied, in various forms, to diseases related to blood flow, such as cold hands and feet, diabetic foot, muscle pain, and menstrual pain.

7.
J Craniofac Surg ; 35(4): e354-e357, 2024 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-38587387

RESUMO

Scalp reconstruction has always been a challenging problem for even the most experienced surgeon to provide good aesthetic and functional results. This is mainly because the scalp is less mobile and tight, requiring a much larger dissection for the size of the original defect. We hypothesized that the omega variant perforator-based keystone island flap at the subgaleal plane provides a versatile and easily reproducible reconstructive option for scalp reconstruction after wide skin cancer excision. We reviewed all patients who underwent reconstruction with the keystone flap or its modification to repair scalp defects following wide resection of skin cancer in the scalp abutting calvarium from May 2021 to July 2023. We designed the flap width 50% wider than original keystone flap design first introduced by Dr. Behan. We reconstructed medium- to large-sized scalp defects ranging from 2×2 to 5×5 cm 2 using an omega variant perforator-based keystone island flap. All patients were satisfied with the aesthetic outcomes without complications. Keystone flaps are a versatile option for reconstructing the scalp after cancer resection. This strategy obviates the need for skin grafting, myocutaneous flap or free flap after cancer removal in the scalp.


Assuntos
Carcinoma Basocelular , Retalho Perfurante , Procedimentos de Cirurgia Plástica , Couro Cabeludo , Neoplasias Cutâneas , Humanos , Couro Cabeludo/cirurgia , Neoplasias Cutâneas/cirurgia , Neoplasias Cutâneas/patologia , Masculino , Feminino , Carcinoma Basocelular/cirurgia , Idoso , Pessoa de Meia-Idade , Procedimentos de Cirurgia Plástica/métodos , Crânio/cirurgia , Idoso de 80 Anos ou mais , Invasividade Neoplásica , Neoplasias de Cabeça e Pescoço/cirurgia , Adulto
8.
Antioxidants (Basel) ; 13(1)2024 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-38247510

RESUMO

Tendinopathy is a debilitating condition marked by degenerative changes in the tendons. Its complex pathophysiology involves intrinsic, extrinsic, and physiological factors. While its intrinsic and extrinsic factors have been extensively studied, the role of physiological factors, such as hypoxia and oxidative stress, remains largely unexplored. This review article delves into the contribution of hypoxia-associated genes and oxidative-stress-related factors to tendon degeneration, offering insights into potential therapeutic strategies. The unique aspect of this study lies in its pathway-based evidence, which sheds light on how these factors can be targeted to enhance overall tendon health.

9.
J Shoulder Elbow Surg ; 33(3): 678-685, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-37572747

RESUMO

BACKGROUND: This study compared the clinical outcomes of open subpectoral biceps tenodesis and arthroscopic suprapectoral biceps tenodesis for symptomatic biceps tenosynovitis. Although both techniques have pros and cons, no studies have compared clinical and functional outcomes during the recovery phase. Previous studies show that suprapectoral tenodesis has a higher probability of Popeye deformity and postoperative bicipital pain and stiffness, whereas subpectoral tenodesis has a higher risk of nerve complications and wound infections. This study aimed for clinical comparison between arthroscopic suprapectoral biceps tenodesis and open subpectoral biceps tenodesis. METHODS: This study is a retrospective review of institutional records of patients with biceps tendinitis who underwent open or arthroscopic biceps tenodesis. Surgical indications included biceps tenosynovitis, biceps partial tear, and biceps pulley lesion. Patients with prior shoulder surgery, preoperative shoulder stiffness, or full-thickness tear of rotator cuff were excluded. Tenodesis was considered when the pain recurs within 3 months despite conservative treatment including at least 2 triamcinolone injections on the biceps tendon sheath. Visual analog scale (VAS) score for pain, presence of the night pain, American Shoulder and Elbow Surgeons (ASES) score, Constant score, and range of motion were assessed preoperatively at 3, 6, 12, and 24 months postoperatively and the last follow-up. RESULTS: A total of 72 patients (33 with arthroscopic suprapectoral biceps tenodeses and 39 with open subpectoral biceps tenodeses) were included in analysis. At postoperative 6 months, lower VAS score (0.4 ± 0.8 vs. 1.7 ± 1.9, P < .001), and the presence of the night pain (2 [6%] vs. 14 [36%], P = .002), ASES score (89.6 ± 9.2 vs. 81.4 ± 14.6, P = .006), and Constant score (89.4 ± 5.6 vs. 82.0 ± 12.5, P = .003) compared with the subpectoral group. The mean number of postoperative steroid injections for pain control in the subpectoral group (0.51 ± 0.80) was significantly higher than that in the suprapectoral group (0.18 ± 0.40) (P = .031). However, postoperative clinical outcomes were restored similar between the 2 groups at 12 months and the last follow-up. DISCUSSION: Arthroscopic suprapectoral biceps tenodesis performed statistically better than the subpectoral biceps tenodesis for the VAS, ASES, night pain, and Constant score at postoperative 6 months. However, only night pain and the Constant score showed differences that exceeded minimum clinically important difference during the recovery phase. At postoperative 12 and 24 months, biceps tenodesis provided satisfactory clinical outcomes and pain relief regardless of the fixation technique and suture anchor location.


Assuntos
Tenodese , Tenossinovite , Humanos , Tenodese/métodos , Ombro/cirurgia , Tenossinovite/cirurgia , Artroscopia/métodos , Dor
10.
Arthroscopy ; 40(1): 58-67, 2024 01.
Artigo em Inglês | MEDLINE | ID: mdl-37355184

RESUMO

PURPOSE: To introduce a classification of posterior labral tear and describe clinical characteristics, magnetic resonance imaging (MRI)/magnetic resonance arthrography (MRA) findings, arthroscopic findings, and outcomes after arthroscopic repair for patients with posterior labral tears without glenohumeral instability. METHODS: Sixty patients with posterior labral tear who underwent arthroscopic repair were analyzed retrospectively. Patients with shoulder instability were excluded. Tear patterns were classified into 3 types; occult (type 1), incomplete (type 2), and complete (type 3) based on MRI/MRA studies. A visual analog scale score for pain, American Shoulder and Elbow Surgeons score, Single Assessment Numeric Evaluation score for satisfaction, and return to sports were evaluated at a minimum follow-up of 2 years. Computed tomography arthrography was performed at a year follow-up for assess labral healing. The diagnosis was confirmed in arthroscopy, and arthroscopic labral repair without capsular plication was performed. RESULTS: The mean patient age was 30.4 ± 6.9 years, and all patients were male. Forty-four patients (73.3%) were participating in sports. MRI/MRA studies identified 10 patients with type 1, 18 with type 2, and 32 with type 3 tears. Type 1 tear patients showed a significantly longer symptom duration than those with type 3 (32.5 ± 17.2 vs 18.2 ± 17.1 months; P = .015). In arthroscopic findings, 70% of type 1 tear was confirmed as incomplete or complete tears. The American Shoulder and Elbow Surgeons score improved from 79.6 ± 10.3 to 98.1 ± 3.7, and pain was relieved from 2.4 ± 0.7 to 0.2 ± 0.5 at the last follow-up visit with high labral healing rate (95%). Thirty-nine (88.6%) patients returned to sports at preinjury levels. CONCLUSIONS: In active young men with shoulder pain during daily activities or sports despite programmed conservative treatment, posterior labral tears should be considered even when MRI/MRA findings are ambiguous. Arthroscopic posterior labral repair without capsular plication provided satisfactory clinical outcomes and a high labral healing rate. LEVEL OF EVIDENCE: Level Ⅳ, case series.


Assuntos
Instabilidade Articular , Lacerações , Lesões do Ombro , Articulação do Ombro , Humanos , Masculino , Adulto Jovem , Adulto , Feminino , Articulação do Ombro/diagnóstico por imagem , Articulação do Ombro/cirurgia , Instabilidade Articular/diagnóstico por imagem , Instabilidade Articular/cirurgia , Estudos Retrospectivos , Lesões do Ombro/cirurgia , Ruptura , Dor de Ombro/cirurgia , Artroscopia/métodos
11.
ACS Nano ; 18(1): 1073-1083, 2024 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-38100089

RESUMO

The significance of metal-semiconductor interfaces and their impact on electronic device performance have gained increasing attention, with a particular focus on investigating the contact metal. However, another avenue of exploration involves substituting the contact metal at the metal-semiconductor interface of field-effect transistors with semiconducting layers to introduce additional functionalities to the devices. Here, a scalable approach for fabricating metal-oxide-semiconductor (channel)-semiconductor (interfacial layer) field-effect transistors is proposed by utilizing solution-processed semiconductors, specifically semiconducting single-walled carbon nanotubes and molybdenum disulfide, as the channel and interfacial semiconducting layers, respectively. The work function of the interfacial MoS2 is modulated by controlling the sulfur vacancy concentration through chemical treatment, which results in distinctive energy band alignments within a single device configuration. The resulting band alignments lead to multiple functionalities, including multivalued transistor characteristics and multibit nonvolatile memory (NVM) behavior. Moreover, leveraging the stable NVM properties, we demonstrate artificial synaptic devices with 88.9% accuracy of MNIST image recognition.

12.
Nat Commun ; 14(1): 4704, 2023 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-37543676

RESUMO

Direct partial oxidation of methane to liquid oxygenates has been regarded as a potential route to valorize methane. However, CH4 activation usually requires a high temperature and pressure, which lowers the feasibility of the reaction. Here, we propose an electro-assisted approach for the partial oxidation of methane, using in-situ cathodically generated reactive oxygen species, at ambient temperature and pressure. Upon using acid-treated carbon as the electrocatalyst, the electro-assisted system enables the partial oxidation of methane in an acidic electrolyte to produce oxygenated liquid products. We also demonstrate a high production rate of oxygenates (18.9 µmol h-1) with selective HCOOH production. Mechanistic analysis reveals that reactive oxygen species such as ∙OH and ∙OOH radicals are produced and activate CH4 and CH3OH. In addition, unstable CH3OOH generated from methane partial oxidation can be additionally reduced to CH3OH on the cathode, and so-produced CH3OH is further oxidized to HCOOH, allowing selective methane partial oxidation.

13.
Medicina (Kaunas) ; 59(7)2023 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-37512104

RESUMO

Background and Objective: The tongue mucosa often changes due to various local and systemic diseases or conditions. This study aimed to investigate whether deep learning can help detect abnormal regions on the dorsal tongue surface in patients and healthy adults. Materials and Methods: The study collected 175 clinical photographic images of the dorsal tongue surface, which were divided into 7782 cropped images classified into normal, abnormal, and non-tongue regions and trained using the VGG16 deep learning model. The 80 photographic images of the entire dorsal tongue surface were used for the segmentation of abnormal regions using point mapping segmentation. Results: The F1-scores of the abnormal and normal classes were 0.960 (precision: 0.935, recall: 0.986) and 0.968 (precision: 0.987, recall: 0.950), respectively, in the prediction of the VGG16 model. As a result of evaluation using point mapping segmentation, the average F1-scores were 0.727 (precision: 0.717, recall: 0.737) and 0.645 (precision: 0.650, recall: 0.641), the average intersection of union was 0.695 and 0.590, and the average precision was 0.940 and 0.890, respectively, for abnormal and normal classes. Conclusions: The deep learning algorithm used in this study can accurately determine abnormal areas on the dorsal tongue surface, which can assist in diagnosing specific diseases or conditions of the tongue mucosa.


Assuntos
Aprendizado Profundo , Adulto , Humanos , Algoritmos , Rememoração Mental , Mucosa Bucal
14.
Clin Shoulder Elb ; 26(4): 445-454, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37442776

RESUMO

The Latarjet procedure is a surgical procedure that can effectively restore glenohumeral stability, especially in patients with anterior shoulder instability and glenoid bone loss. Many studies have shown comparable clinical outcomes between patients undergoing the arthroscopic Latarjet procedure and those undergoing traditional open methods or other glenohumeral joint stabilization procedures. However, the arthroscopic Latarjet procedure is a challenging technique due to the unfamiliar portal placements, proximity of neurovascular structures, and serious postoperative complications. The arthroscopic Latarjet procedure has not yet been widely applied, and a clear understanding of the anatomical structure and the precise methods is required prior to operation performance. Satisfactory clinical outcomes can be achieved by thorough preoperative planning and proper implant fixation methods.

16.
J Clin Med ; 11(23)2022 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-36498718

RESUMO

Percutaneous plasma disc decompression (PPDD) is a minimally invasive treatment for discogenic low back pain and herniated disc-related symptoms. However, there are no known outcome predictive variables during the procedure. The purpose of this study was to evaluate and validate epidurography as an intra-procedure outcome predictor. We retrospectively enrolled 60 consecutive patients who did not respond to conventional treatments. In the next stage of treatment, PPDD was performed, and the epidurography was conducted before and after the PPDD. We analyzed the relationship between epidurographic improvement and the success rate. The Numerical Rating Scale and the Oswestry Disability Index were used to assess pain and functional capacity, respectively, before the procedure and 1 month after the procedure. The pain reduction and the success rate in the epidurographic improvement group were significantly higher than in the epidurographic non-improvement group. Both the Numerical Rating Scale and the Oswestry Disability Index scores were significantly reduced in both groups, but there was no significant difference in Oswestry Disability Index scores. This study's results showed that PPDD is an effective treatment method. We also suggested that epidurography may be a potential outcome predictor for ensuring successful outcomes and determining the endpoint of the procedure.

17.
Sensors (Basel) ; 22(24)2022 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-36560040

RESUMO

An electrical impedance spectroscopy (EIS) experiment was performed using a double-shell electrical model to investigate the feasibility of detecting physiological changes in lettuce leaves over 16 h. Four lettuce plants were used, and the impedance spectra of the leaves were measured five times per plant every hour at frequencies of 500 Hz and 300 kHz. Estimated R-C parameters were computed, and the results show that the lettuce leaves closely fit the double-shell model (DSM). The average resistance ratios of R1 = 10.66R4 and R1 = 3.34R2 show high resistance in the extracellular fluid (ECF). A rapid increase in resistance (R1, R2, and R4) and a decrease in capacitance (C3 and C5) during water uptake were observed. In contrast, a gradual decrease in resistance and an increase in capacitance were observed while the LED light was on. Comparative studies of leaf physiology and electrical value changes support the idea that EIS is a great technique for the early monitoring of plant growth for crop production.


Assuntos
Espectroscopia Dielétrica , Lactuca , Espectroscopia Dielétrica/métodos , Agricultura , Fazendas , Plantas , Folhas de Planta/fisiologia , Impedância Elétrica
18.
J Korean Soc Radiol ; 83(4): 938-944, 2022 Jul.
Artigo em Coreano | MEDLINE | ID: mdl-36238904

RESUMO

Spinal epidermoid cysts are extremely rare benign tumors and can be congenital or acquired. Acquired spinal epidermoid cysts are found in the lumbosacral region. To our knowledge, no case of epidermoid cyst related to spinal cord stimulator insertion has yet been reported. We report the MRI findings of a rare case of thoracic intradural epidermoid cyst acquired after spinal cord stimulator insertion in a 50-year-old female.

19.
Acc Chem Res ; 55(18): 2672-2684, 2022 09 20.
Artigo em Inglês | MEDLINE | ID: mdl-36067418

RESUMO

Electrocatalysis is a key driver in promoting the paradigm shift from the current fossil-fuel-based hydrocarbon economy to a renewable-energy-driven hydrogen economy. The success of electrocatalysis hinges primarily on achieving high catalytic selectivity along with maximum activity and sustained longevity. Many electrochemical reactions proceed through multiple pathways, requiring highly selective catalysts.Atomically dispersed metal catalysts have emerged as a new frontier in heterogeneous catalysis. In addition to the widely perceived advantages of maximized active site utilization and substantially reduced metal content, they have shown different catalytic selectivities in some electrocatalytic reactions compared to the traditional nanoparticle (NP)-based catalysts. Although there have been significant advances in their synthesis, the highly energetic nature of a single atomic site has made the preparation of atomically dispersed metal catalysts rely on empiricism rather than rational design. Consequently, the structural comprehension of a single atomic site and the understanding of its unusual electrocatalytic selectivity remain largely elusive.In this Account, we describe our endeavors toward developing general synthetic approaches for atomically dispersed metal catalysts for the discovery of new selective and active electrocatalysts and to understand their catalytic nature. We introduce synthetic approaches to produce a wide range of nonprecious- and precious-metal-based atomically dispersed catalysts and control their coordination environments. Metallomacrocyclic-compound-driven top-down and metal salt/heteroatom layer-based bottom-up strategies, coupled with a SiO2-protective-layer-assisted method, have been developed that can effectively generate single atomic sites while mitigating the formation of metallic NPs. The low-temperature gas-phase ligand exchange method can reversibly tune the coordination structure of the atomically dispersed metal sites. We have used the prepared atomically dispersed metal catalysts as model systems to investigate their electrocatalytic reactivity for renewable energy conversion and commodity chemical production reactions, in which high selectivity is important. The reactions of our interest include the following: (i) the oxygen reduction reaction, where O2 is reduced to either H2O or H2O2 via the four-electron or two electron pathway, respectively; (ii) the CO2 reduction reaction, which should suppress the hydrogen evolution reaction; and (iii) the chlorine evolution reaction, which competes with the oxygen evolution reaction. The type of metal center to which the reactant is directly bound is found to be the most important in determining the selectivity, which originates from the dramatic changes in the binding energy of each metal center with the reactants. The coordination structure surrounding the metal center also has a significant effect on the selectivity; its control can modulate the oxidation state of the metal center, thereby altering the binding strength with the reactants.We envisage that future advances in the synthesis of atomically dispersed metal catalysts, combined with the growing power of computational, spectroscopic, and microscopic methods, will bring their synthesis to the level of rational design. Elaborately designed catalysts can overcome the current limits of catalytic selectivity, which will help establish the field of atomically dispersed metal catalysts as an important branch of catalysis.


Assuntos
Dióxido de Carbono , Cloro , Catálise , Combustíveis Fósseis , Hidrogênio/química , Peróxido de Hidrogênio , Ligantes , Metais , Oxigênio , Energia Renovável , Dióxido de Silício
20.
JACS Au ; 2(8): 1811-1817, 2022 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-36032528

RESUMO

Os-based catalysts present remarkable catalytic activity; however, their use has been limited by the undesirable side reactions that generate highly toxic and volatile OsO4 even at room temperature. Herein, we demonstrate that the thermal stability of Os-based catalysts can be dramatically improved by downsizing Os nanoparticles (NPs) into atomically dispersed species. We observed that Os NPs were converted into OsO4 after calcination at 250 °C followed by sublimation, whereas single Os sites retained their structure after calcination. Temperature-programmed oxidation analysis confirmed that Os NPs started to undergo oxidation at 130 °C, whereas atomically dispersed Os preserved its state up to 300 °C. The CO oxidation activity of the atomically dispersed Os catalyst at 400 °C (100% conversion) was stably preserved over 30 h. By contrast, the activity of Os NP catalyst declined drastically. This study highlights the unique catalytic behavior of atomically dispersed catalysts, which is distinct from that of NP-based catalysts.

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