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1.
Surg Neurol Int ; 15: 98, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38628510

RESUMO

Background: Giant cavernous carotid artery aneurysms (>25 mm) are rare (3-5%), with some prone to spontaneous thrombosis (10-20% complete). We present a unique case of one of the largest aneurysms spontaneously thrombosing and calcifying. Case Description: A 57-year-old with persistent right-sided headaches had a substantial hyperdense mass in the right middle cranial fossa, eroding petrous bone. Magnetic resonance imaging and digital subtraction angiography revealed a giant cavernous segment fusiform aneurysm of the right internal carotid artery (ICA) with spontaneous thrombosis and distal ICA occlusion. Collateral circulation maintains the cerebral blood supply. Despite anatomical challenges, conservative management was chosen due to the patient's stability. Conclusion: This case highlights the complex interplay between thrombosed giant aneurysms and affected vessels, with unique features such as cross-flow, calcification, and bone erosion. We advocate conservative management for stable cases, supported by literature, emphasizing vigilant follow-up. This expands the spectrum of aneurysm presentations and encourages further research into their dynamics.

2.
World Neurosurg ; 184: e743-e753, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38342171

RESUMO

BACKGROUND: Papilledema's association with hydrocephalus (HCP)-linked larger vestibular schwannoma (VS) is established but cases lacking concurrent HCP require further investigation. METHODS: This retrospective comparative observational study, conducted from July 2018 to July 2023, examined 120 VS patients undergoing surgery. Patients were categorized into Group 1 (papilledema without HCP) and Group 2 (no papilledema or HCP), with comprehensive data analyzed. RESULTS: In this study, Group 1 (14 patients with papilledema) and Group 2 (106 patients without papilledema or HCP) were compared. Group 1 was younger (mean age 27.21 ± 11.73 years) than Group 2 (mean age 54.66 ± 11.44 years). Both groups had similar symptom durations and tumor detection times. Group 1 had increased vascularity (P = 0.001), elevated cisterna magna protein levels (P = 0.001), and a higher incidence of neurofibromatosis 2 (P = 0.003). They also experienced longer surgeries (P = 0.001) and more blood loss (P = 0.001), leading to extended postoperative complications. Group 2 showed improved postsurgery visual outcomes (P = 0.001), better Glasgow Outcome Scores (P = 0.001), enhanced facial nerve preservation (P = 0.002), and improved hearing on follow-up (P = 0.003). Logistic regression analysis highlighted prolonged surgery duration (P = 0.057) and papilledema (P = 0.0001) as significant factors influencing visual improvement. CONCLUSIONS: Patients with VS require preoperative fundoscopy evaluation due to potential visual loss and papilledema, even without HCP. Early treatment initiation enhances visual and hearing outcomes. Meticulous surgery is vital given the lesion's hypervascular nature and adherence to surrounding structures. Preoperative embolization may aid in preserving neurovascular structures. In developing countries with higher blindness rates, judicious noncontrast computed tomography brain evaluation is crucial for timely detection and treatment initiation of lesions like VS.


Assuntos
Hidrocefalia , Neuroma Acústico , Papiledema , Humanos , Adolescente , Adulto Jovem , Adulto , Pessoa de Meia-Idade , Idoso , Neuroma Acústico/complicações , Neuroma Acústico/diagnóstico por imagem , Neuroma Acústico/cirurgia , Papiledema/diagnóstico por imagem , Papiledema/etiologia , Estudos Retrospectivos , Hidrocefalia/etiologia , Hidrocefalia/cirurgia , Hidrocefalia/diagnóstico , Cegueira , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/etiologia , Progressão da Doença , Resultado do Tratamento
3.
Surg Neurol Int ; 14: 370, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37941621

RESUMO

Background: The medial posterior choroidal artery (MPCA) aneurysm is extremely uncommon. Thus yet, just a few cases have been reported. Due to the deep position, narrow lumen, fragile walls, and extensive tortuosity, both endovascular and microsurgical procedures are strictly limited. A case study of successful endovascular glue embolization of a left MPCA aneurysm and a literature review is included in this report. Case Description: A 17-year-old female arrived at our institution 2 days after suffering a major intraventricular hemorrhage with a minor subarachnoid hemorrhage. Digital subtraction angiography revealed a left MPCA aneurysm. The patient underwent a successful endovascular glue embolization and had a favorable functional outcome. Conclusion: Endovascular glue embolization yielded favorable clinical and angiographic results in MPCA aneurysms where microcatheter access and maneuverability are challenging.

4.
J Drug Target ; 31(10): 999-1012, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-37926975

RESUMO

Drug delivery systems (DDS) based on nanocarriers are designed to transport therapeutic agents to specific areas of the body where they are required to exhibit pharmacodynamic effect. These agents rely on an appropriate carrier to protect them from rapid degradation or clearance and enhance their concentration in target tissues. Spanlastics, an elastic, deformable surfactant-based nanovesicles have the potential to be used as a drug delivery vehicle for wide array of drug molecules. Spanlastics are formed by the self-association of non-ionic surfactants and edge activators in an aqueous phase and have gained attention as promising drug carriers due to their biodegradable, biocompatible, and non-immunogenic structure. In recent years, numerous scientific journals have published research articles exploring the potential of spanlastics to serve as a DDS for various types of drugs as they offer targeted delivery and regulated release of the drugs. Following brief introduction to spanlastics, their structure and methods of preparation, this review focuses on the delivery of various drugs using spanlastics as a carrier via various routes viz. topical, transdermal, ototopical, ocular, oral and nasal. Work carried out by various researchers by employing spanlastics as a carrier for enhancing therapeutic activity of different moieties has been discussed in detail.


Assuntos
Sistemas de Liberação de Medicamentos , Lipossomos , Lipossomos/química , Portadores de Fármacos/química , Administração Cutânea , Tensoativos/química
7.
Asian J Neurosurg ; 18(1): 157-164, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-37056889

RESUMO

Malignant peripheral nerve sheath tumor (MPNST) of the scalp is rare. These lesions are associated with neurofibromatosis type 1 (NF1), but patients had been reported without NF1 also. We tried to analyze the difference between the clinical course and outcome of the patient with MPNST having stigmata of NF1 and without it. We included five patients treated over 3 years between July 2018 and July 2021 with diffuse scalp MPNST. Two of these five patients with MPNST of the scalp had neurocutaneous stigmata of NF1. Three were female and two males with an average age of 38.40 ± 18.48 years-the youngest with NF1 being a 19-year-old female. We found dull aching pain as the most typical complaint in all patients and a repeated episode of generalized seizure in one patient. In these cases, two patients with NF1 have highly vascular tumors and attained large sizes greater than 30 cm. These two cases required preoperative digital subtraction angiography (DSA) and embolization with n-butyl acrylate. Total excision of the tumor was done in all patients with radiotherapy. Metastases within 1 year were noted in two patients with NF1, and one of these two succumbed to her illness. The rest of the three patients without NF1 are under follow-up with no evidence of disease with a maximum follow-up of 2 years. Large MPNST (size > 20 cm) are rare and reported to have been associated with and without NF1. Patients with scalp MPNST with NF1 can achieve larger size with fast progression of tumor size and higher chances of recurrence and metastases.

8.
Faraday Discuss ; 243(0): 307-320, 2023 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-37017214

RESUMO

Ga was identified earlier as one of the "overlooked" metals for catalyzing the electrochemical nitrogen reduction reaction (ENRR). We investigate here the electrocatalytic activity of Ga towards the nitrogen reduction reaction. We used a combination of molecular modelling and simulations using periodic density functional theory calculations (DFT), and experimental ENRR measurements. The ENRR was found to proceed via an associative mechanism where the first PCET to dinitrogen forming the surface adsorbed N2H* species is the overpotential limiting step. The bare Ga cathode has a high overpotential (>2 V (SHE)) for the ENRR. We also investigated the effect of a water-in-salt electrolyte (WISE) on the rate of ammonia formation. The addition of an Li salt lowers the overpotential to 1.88 V (SHE). DFT calculations revealed that the H-adatom was more favorably bound than the N-adatom, and the hydrogen evolution reaction (HER) is expected to dominate at high cathodic potentials. Experimental ENRR tests corroborate our results wherein no significant NH3 formation was detected. The low electrochemical activity of Ga is attributed to poor binding and activation of N2 which originates from an electropositive surface charge distribution.

9.
Surg Neurol Int ; 14: 4, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36751455

RESUMO

Backgound: Pituitary apoplexy is associated with stroke, head injury, and brain tumors. Still, its presentation due to the ruptured aneurysm is rare and its presentation with akinetic mutism has not been reported. Case Description: The patient in the present study is 21-year-old female who presented in our emergency department in an altered sensorium with Glasgow comma score (GCS) E2V1M1. She was intubated and resuscitated. Routine blood investigations, lipid profile, and hormonal studies were normal. Initial noncontrast computed tomography (NCCT) head revealed subarachnoid hemorrhage in the interhemispheric fissure and evidence of bleeding in the pituitary gland. Magnetic resonance imaging (MRI) brain was soon done, which showed an infarct and hemorrhage in the pituitary gland; there was an evidence of an infarct in the bilateral medial frontal gyrus, basal ganglia, and supplementary motor area. MR arteriography revealed an aneurysm at the left A1-anterior communicating artery (Acom) junction directed superomedially with diffuse spasm in a bilateral anterior cerebral artery. Pterional craniotomy was done with clipping of the aneurysm and evacuation of blood clots from the interhemispheric fissure and pituitary gland. Histopathology features suggestive of the non-functioning pituitary tumor with interspersed hemorrhagic necrosis. Intraarterial vasodilation with microcatheter injection was given, but vasospasm did not improve. Postoperatively, Levodopa was started. She used to track objects in front of her eye and started nodding her head in "yes and no fashion," with power in limbs improved to 3/5 at 6 months of follow-up. Conclusion: Pituitary apoplexy with ruptured A1-Acom junction aneurysm with nonfunctioning pituitary macroadenoma is rare, and its presentation with akinetic mutism has not been reported. As there is scarce literature suggesting an association between pituitary apoplexy and ruptured aneurysm, it is challenging to comment regarding its pathogenesis. Although akinetic mutism generally has a poor prognosis, it may respond to Levodopa with a better outcome.

10.
Childs Nerv Syst ; 39(4): 963-974, 2023 04.
Artigo em Inglês | MEDLINE | ID: mdl-36571597

RESUMO

OBJECTIVES: A few previous studies have reported the role of embolization with curative intent in the treatment of the early phase of a spontaneous cerebral hemorrhage in pediatric patients, and its efficacy needs to be compared with surgery at the same time risk factors for hemorrhage following early embolization in such patients need to be evaluated. METHODS: From a pool of 80 pediatric (< 18 years) who had undergone treatment for ruptured AVM with hemorrhage at our center between July 2018 and July 2022, we identified 36 patients with spontaneous bleeding due to AVM. Out of which, 20 were treated solely by embolization (group 1), while the remaining patients were treated surgically (with and without adjuvant embolization) (group 2). RESULT: Spetzler-Martin's grading of the lesion suggested seven lesions < 3 and 13 lesions ≥ 3 in the embolization group. Similarly, seven lesions were < 3 and nine ≥ 3 Spetzler-Martin grade in the surgery group. Incomplete embolization was associated with hemorrhage in two patients treated with curative intent and four patients treated with embolization as adjuvant in the surgery group (p = 0.01). On follow-up, 18 patients in the embolization group and 12 in the surgery group had Glasgow outcome scores ≥ 4 (p = 0.273). CONCLUSION: In the pediatric age group, incomplete embolization is the significant risk factor for hemorrhage in AVMs treated after a hemorrhagic stroke. Embolization with curative intent is as effective as surgery in treating such lesions as adjuvant embolization with careful patient selection.


Assuntos
Embolização Terapêutica , Malformações Arteriovenosas Intracranianas , Radiocirurgia , Humanos , Criança , Microcirurgia , Resultado do Tratamento , Estudos Retrospectivos , Malformações Arteriovenosas Intracranianas/complicações , Malformações Arteriovenosas Intracranianas/diagnóstico por imagem , Malformações Arteriovenosas Intracranianas/cirurgia , Hemorragia Cerebral/diagnóstico por imagem , Hemorragia Cerebral/etiologia , Hemorragia Cerebral/cirurgia
11.
Turk Neurosurg ; 33(5): 754-763, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36482852

RESUMO

AIM: To compare the outcomes of distal anterior cerebral artery (DACA) aneurysm treatment using endovascular therapy (EVT) and surgical clipping, and to assess their risk factors. MATERIAL AND METHODS: We retrospectively sampled and analyzed 31 patients treated for ruptured Distal anterior cerebral artery (DACA) aneurysms from a larger sample of 250 patients treated for ruptured aneurysms between July 2018 and July 2021. The outcomes of patients who underwent clipping and EVT were compared using chi-square tests. T-tests were used for univariate analysis and a logistic regression analysis was used to determine the risk factors affecting outcomes. RESULTS: Of the 31 patients, 20 were treated with clipping and 11 with EVT. Patients treated with EVT had a mean age of 35.45 ± 6.66. The mean age of the clipping group was 44.4 ± 6.94 years (p=0.002). Intraoperative rupture was significantly more common in the clipping group (p=0.025). There were no significant differences in the postoperative incidence of vasospasm or hydrocephalus (p=0.12). Modified Rankin Scale scores (p=0.017) and Glasgow Outcome Scale scores (p=0.02) both at discharge and 6-month follow-ups were significantly better in the EVT group than in the clipping group. Length of stay in the Intensive Care Unit (ICU) was 9.27 ± 2.6 days following EVT and 23.60 ± 6.29 following clipping (p=0.001). Age (p=0.0136), Hunt and Hess grade (p=0.02), and the occurrence of intraprocedural rupture (p=0.009) were found to significantly affect outcomes. CONCLUSION: The outcomes of EVT were better than those for clipping and required a shorter stay in the ICU and the hospital. This may be partially attributable to the dual-trained neurovascular surgeon who performed the procedures. Older age, poorer Hunt and Hess grades, and intraoperative aneurysm rupture adversely affected outcomes.


Assuntos
Aneurisma Roto , Embolização Terapêutica , Procedimentos Endovasculares , Aneurisma Intracraniano , Acidente Vascular Cerebral , Humanos , Adulto , Pessoa de Meia-Idade , Aneurisma Intracraniano/cirurgia , Estudos Retrospectivos , Procedimentos Endovasculares/métodos , Resultado do Tratamento , Embolização Terapêutica/métodos , Aneurisma Roto/cirurgia , Acidente Vascular Cerebral/terapia
12.
Colloids Surf B Biointerfaces ; 222: 113113, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36566688

RESUMO

Owing to their tolerance to antibiotics, bacterial biofilms continue to pose a threat to mankind and are leading cause for non-healing of burn wounds. Within the biofilm matrix, antibiotics become functionally inactive due to restricted penetration and enzymatic degradation leading to rise of antimicrobial resistance. The objective of present investigation was to develop and characterize levofloxacin (LFX) loaded clove oil nanoscale emulgel (LFX-NE gel) and evaluate its in vivo therapeutic efficacy in Pseudomonas aeruginosa biofilm infected burn wound in mice. The optimized emulgel was found to possess good texture profile and showed shear thinning behavior. In vitro release study demonstrated complete drug release in 8 h and emulgel was found to be stable for 3 months at 25 °C and 40 °C. In vivo study revealed biofilm dispersal, complete wound closure, re-epithelialization and collagen deposition by LFX-NE gel in comparison to various control groups. LFX-NE gel was able to clear the infection within 7 days of treatment and promote wound healing as well. Therefore, administration of LFX-incorporated NE gel could be a beneficial treatment strategy for P. aeruginosa biofilm-infected burn wounds.


Assuntos
Queimaduras , Infecções por Pseudomonas , Infecção dos Ferimentos , Camundongos , Animais , Levofloxacino/farmacologia , Pseudomonas aeruginosa , Óleo de Cravo/farmacologia , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Biofilmes , Infecção dos Ferimentos/tratamento farmacológico , Infecção dos Ferimentos/metabolismo , Infecção dos Ferimentos/microbiologia , Queimaduras/tratamento farmacológico , Queimaduras/microbiologia , Cicatrização , Infecções por Pseudomonas/tratamento farmacológico
13.
Indian J Otolaryngol Head Neck Surg ; 74(Suppl 2): 2386-2394, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36452620

RESUMO

Post treatment voice quality is an important consideration in choosing the management option for laryngeal cancer. We assessed voice quality after radiotherapy in patients of early squamous cell carcinoma of glottis comprehensively using Videolaryngostroboscopy (VLS), Grade, Roughness, Breathiness, Asthenia and Strain (GRBAS) scores and Voice Handicap Index (VHI)-10. Fifty four consenting patients of early squamous cell carcinoma of glottis (Tis, T1 and T2) awaiting definitive radiotherapy were recruited consecutively. Voice was evaluated by VLS, GRBAS scores and VHI-10 before radiotherapy as well as 3 months and 12 months after radiotherapy. There were 52 males and 2 females in the study. Hoarseness of voice was the commonest presenting symptom. Mean duration of symptoms was 2.45 months (± 0.80), ranging from 1 to 4 months. 35 (64.82%) were T1 while 19 (35.18%) were T2 lesions. They received 60-70 Gy of radiotherapy in 28-35 fractions. There was only one recurrence on follow up for 12 months. On VLS at 12 months post-RT the periodicity, phase symmetry, mucosal waves and amplitude were normal in 74.07%, 70.37%, 56.67% and 78.7% cases respectively. Complete glottic closure was obtained in 72.22%. The voice was 'acceptable' (Grade 1 or 2 on VLS parameters) in more than 90% cases. Mean total GRBAS score was 3.39 (± 2.67). Mean total VHI-10 was 6.7 (± 1.75). All indices were significantly better than pre RT levels. Good quality of voice can be expected after radiotherapy for early glottic cancer in majority of patients.

14.
Cureus ; 14(10): e30211, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36246087

RESUMO

INTRODUCTION: Septicemia is globally considered the most important cause of neonatal morbidity and fatality. Serum C-Reactive Protein (CRP) is an acute phase reactant, which is brought out in response to the inflammatory reaction. It is prophesied to drop down speedily after the coherent weeding out of microbial incitation due to the short half-life of CRP. CRP levels reflect the individual's association between microbial infection and defensive mechanisms.  Methods: This hospital-based cross-sectional study included 150 admitted patients with suspected sepsis in the Department of Pediatrics, Rajendra Institute Medical Sciences (RIMS), Ranchi, India, over a study period of one year (2020 to 2021). CRP was estimated on the day of admission and repeated after 72 hours, on the fifth day, and on the seventh day for serial values of CRP, and the findings were compared by making three groups. Further, the research participants were designated to three different groups according to the CRP estimation levels. RESULTS: Out of the 150 assumed neonatal septicemia patients, antibiotics were paused in 42 neonates (28%) within 72 hours. In group 2, 8% of neonates' antibiotics were stopped in five days, and a total of 102 neonates (68%) could be discharged on the seventh day of antibiotic therapy as their CRPs became negative on the third day and seventh day consecutively, along with negative blood culture reports. In group 3, antibiotics of 48 neonates (32%) were continued beyond seven days. CONCLUSION: CRP has a skyscraping specificity and negative predictive values (NPV); thus, by estimating serial CRPs, the antibiotic therapy duration can be determined, which further helps determine the period of hospitalization.

15.
Organometallics ; 41(14): 1829-1835, 2022 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-35910260

RESUMO

The choice of a solvent and the reaction conditions often defines the overall behavior of a homogeneous catalytic system by affecting the preferred reaction mechanism and thus the activity and selectivity of the catalytic process. Here, we explore the role of solvation in the mechanism of ketone reduction using a model representative of a bifunctional Mn-diamine catalyst through density functional theory calculations in a microsolvated environment by considering explicit solvent and fully solvated ab initio molecular dynamics simulations for the key elementary steps. Our computational analysis reveals the possibility of a Meerwein-Ponndorf-Verley (MPV) type mechanism in this system, which does not involve the participation of the N-H moiety and the formation of a transition-metal hydride species in ketone conversion. This path was not previously considered for Mn-based metal-ligand cooperative transfer hydrogenation homogeneous catalysis. The MPV mechanism is strongly facilitated by the solvent molecules present in the reaction environment and can potentially contribute to the catalytic performance of other related catalyst systems. Calculations indicate that, despite proceeding effectively in the second coordination sphere of the transition-metal center, the MPV reaction path retains the enantioselectivity preference induced by the presence of the small chiral N,N'-dimethyl-1,2-cyclohexanediamine ligand within the catalytic Mn(I) complex.

16.
Cureus ; 14(7): e27230, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35910696

RESUMO

INTRODUCTION: There is a growing focus on researching the management of children with COVID-19 admitted to hospital, especially among developing countries with new variants alongside concerns with the overuse of antibiotics. Patient care can be improved with guidelines, but concerns with the continued imprudent prescribing of antimicrobials, including antibiotics, antivirals, and antimalarials. OBJECTIVE: Consequently, a need to document the current management of children with COVID-19 across India. Key outcome measures included the percentage of prescribed antimicrobials, adherence to current guidelines, and mortality. METHODOLOGY: A point prevalence study using specially developed report forms among 30 hospitals in India. RESULTS: The majority of admitted children were aged between 11 and 18 years (70%) and boys (65.8%). Reasons for admission included respiratory distress, breathing difficulties, and prolonged fever. 75.3% were prescribed antibiotics typically empirically (68.3% overall), with most on the Watch list (76.7%). There were no differences in antibiotic prescribing whether hospitals followed guidelines or not. There was also appreciable prescribing of antimalarials (21.4% of children), antivirals (15.2%), and antiparasitic medicines (27.2%) despite limited evidence. The majority of children (92.2%) made a full recovery. CONCLUSION: It was encouraging to see low hospitalization rates. However, concerns about high empiric use of antibiotics and high use of antimalarials, antivirals, and antiparasitic medicines exist. These can be addressed by instigating appropriate stewardship programs.

17.
ACS Energy Lett ; 7(5): 1586-1593, 2022 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-35601628

RESUMO

Finding alternative ways to tailor the electronic properties of a catalyst to actively and selectively drive reactions of interest has been a growing research topic in the field of electrochemistry. In this Letter, we investigate the tuning of the surface electronic properties of electrocatalysts via polymer modification. We show that when a nickel oxide water oxidation catalyst is coated with polytetrafluoroethylene, stable Ni-CF x bonds are introduced at the nickel oxide/polymer interface, resulting in shifting of the reaction selectivity away from the oxygen evolution reaction and toward hydrogen peroxide formation. It is shown that the electron-withdrawing character of the surface fluorocarbon molecule leaves a slight positive charge on the water oxidation intermediates at the adjacent active nickel sites, making their bonds weaker. The concept of modifying the surface electronic properties of an electrocatalyst via stable polymer modification offers an additional route to tune multipathway reactions in polymer/electrocatalyst environments, like with ionomer-modified catalysts or with membrane electrode assemblies.

18.
Chem Sci ; 13(13): 3803-3808, 2022 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-35432905

RESUMO

The electrocatalytic CO2 reduction reaction (CO2RR) is one of the key technologies of the clean energy economy. Molecular-level understanding of the CO2RR process is instrumental for the better design of electrodes operable at low overpotentials with high current density. The catalytic mechanism underlying the turnover and selectivity of the CO2RR is modulated by the nature of the electrocatalyst, as well as the electrolyte liquid, and its ionic components that form the electrical double layer (EDL). Herein we demonstrate the critical non-innocent role of the EDL for the activation and conversion of CO2 at a high cathodic bias for electrocatalytic conversion over a silver surface as a representative low-cost model cathode. By using a multiscale modeling approach we demonstrate that under such conditions a dense EDL is formed, which hinders the diffusion of CO2 towards the Ag111 electrocatalyst surface. By combining DFT calculations and ab initio molecular dynamics simulations we identify favorable pathways for CO2 reduction directly over the EDL without the need for adsorption to the catalyst surface. The dense EDL promotes homogeneous phase reduction of CO2 via electron transfer from the surface to the electrolyte. Such an outer-sphere mechanism favors the formation of formate as the CO2RR product. The formate can undergo dehydration to CO via a transition state stabilized by solvated alkali cations in the EDL.

19.
Digit Discov ; 1(1): 8-25, 2022 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-35340336

RESUMO

Exploration of the local chemical space of molecular scaffolds by post-functionalization (PF) is a promising route to discover novel molecules with desired structure and function. PF with rationally chosen substituents based on known electronic and steric properties is a commonly used experimental and computational strategy in screening, design and optimization of catalytic scaffolds. Automated generation of reasonably accurate geometric representations of post-functionalized molecular scaffolds is highly desirable for data-driven applications. However, automated PF of transition metal (TM) complexes remains challenging. In this work a Python-based workflow, ChemSpaX, that is aimed at automating the PF of a given molecular scaffold with special emphasis on TM complexes, is introduced. In three representative applications of ChemSpaX by comparing with DFT and DFT-B calculations, we show that the generated structures have a reasonable quality for use in computational screening applications. Furthermore, we show that ChemSpaX generated geometries can be used in machine learning applications to accurately predict DFT computed HOMO-LUMO gaps for transition metal complexes. ChemSpaX is open-source and aims to bolster and democratize the efforts of the scientific community towards data-driven chemical discovery.

20.
Dalton Trans ; 51(8): 3019-3026, 2022 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-35079760

RESUMO

Homogeneous ruthenium catalysed methanol dehydrogenation could become a key reaction for hydrogen production in liquid fuel cells. In order to improve existing catalytic systems, mechanistic insight is paramount in directing future studies. Herein, we describe what computational mechanistic research has taught us so far about ruthenium catalysed dehydrogenation reactions. In general, two mechanistic pathways can be operative in these reactions: a metal-centered or a metal-ligand cooperative (Noyori-Morris type) minimum energy reaction pathway (MERP). Discerning between these mechanisms on the basis of computational studies has proven to be highly input dependent, and to circumvent pitfalls it is important to consider several factors, such as solvent effects, metal-ligand cooperativity, alternative geometries, and complex electronic structures of metal centres. This Frontiers article summarizes the reported computational research performed on ruthenium catalyzed dehydrogenation reactions performed in the past decade, and serves as a guide for future research.

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