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1.
Molecules ; 28(15)2023 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-37570875

RESUMO

Cancer is a progressive disease of multi-factorial origin that has risen worldwide, probably due to changes in lifestyle, food intake, and environmental changes as some of the reasons. Skin cancer can be classified into melanomas from melanocytes and nonmelanoma skin cancer (NMSC) from the epidermally-derived cell. Together it constitutes about 95% of skin cancer. Basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (CSCC) are creditworthy of 99% of NMSC due to the limited accessibility of conventional formulations in skin cancer cells of having multiple obstacles in treatment reply to this therapeutic regime. Despite this, it often encounters erratic bioavailability and absorption to the target. Nanoparticles developed through nanotechnology platforms could be the better topical skin cancer therapy option. To improve the topical delivery, the nano-sized delivery system is appropriate as it fuses with the cutaneous layer and fluidized membrane; thus, the deeper penetration of therapeutics could be possible to reach the target spot. This review briefly outlooks the various nanoparticle preparations, i.e., liposomes, niosomes, ethosomes, transferosomes, transethosomes, nanoemulsions, and nanoparticles technologies tested into skin cancer and impede their progress tend to concentrate in the skin layers. Nanocarriers have proved that they can considerably boost medication bioavailability, lowering the frequency of dosage and reducing the toxicity associated with high doses of the medication.

2.
PLoS One ; 19(6): e0295850, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38935798

RESUMO

In the context of the United Nations Sustainable Development Goals (UN-SDGs), this study accentuates the role of the tourism and hospitality sector in promoting sustainability. The primary purpose is to unravel the relationship between corporate social responsibility (CSR) and energy-specific sustainable behavior of employees (ESBE), with particular emphasis on the mediating roles of green intrinsic motivation and personal environmental norms. Utilizing a three-wave data collection approach, we secured 325 valid responses from sector employees at various levels (manager-non managers) and applied Structural Equation Modeling through the SMART-PLS tool to assess the hypothesized relationships. The findings highlight a pronounced interconnection between CSR, ESBE, and the designated mediating variables. These results not only augment the academic literature by illustrating the psychological underpinnings bridging CSR to ESBE, but also equip the tourism and hospitality industry with actionable insights. Through informed CSR initiatives aligned with employee values, the sector can galvanize sustainable behaviors and create business models that resonate with the aspirations of the UN-SDGs, pointing the way to a more sustainable industry.


Assuntos
Motivação , Responsabilidade Social , Desenvolvimento Sustentável , Humanos , Conservação dos Recursos Naturais/métodos , Masculino , Feminino , Adulto , Turismo
3.
PLoS One ; 19(4): e0295853, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38625885

RESUMO

The COVID-19 pandemic has emerged as a significant event of the current century, introducing substantial transformations in economic and social activities worldwide. The primary objective of this study is to investigate the relationship between daily COVID-19 cases and Pakistan stock market (PSX) return volatility. To assess the relationship between daily COVID-19 cases and the PSX return volatility, we collected secondary data from the World Health Organization (WHO) and the PSX website, specifically focusing on the PSX 100 index, spanning from March 15, 2020, to March 31, 2021. We used the GARCH family models for measuring the volatility and the COVID-19 impact on the stock market performance. Our E-GARCH findings show that there is long-term persistence in the return volatility of the stock market of Pakistan in the period of the COVID-19 timeline because ARCH alpha (ω1) and GARCH beta (ω2) are significant. Moreover, is asymmetrical effect is found in the stock market of Pakistan during the COVID-19 period due to Gamma (ѱ) being significant for PSX. Our DCC-GARCH results show that the COVID-19 active cases have a long-term spillover impact on the Pakistan stock market. Therefore, the need of strong planning and alternative platform should be needed in the distress period to promote the stock market and investor should advised to make diversified international portfolio by investing in high and low volatility stock market to save their income. This study advocated the implications for investors to invest in low volatility stock especially during the period of pandemics to protect their return on investment. Moreover, policy makers and the regulators can make effective policies to maintain financial stability during pandemics that is very important for the country's economic development.


Assuntos
COVID-19 , Humanos , COVID-19/epidemiologia , Paquistão/epidemiologia , Pandemias , Pessoal Administrativo , Desenvolvimento Econômico
4.
RSC Adv ; 14(19): 13291-13305, 2024 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-38655486

RESUMO

Cycloplatination of symmetrical N,N',N''-triarylguanidines, (ArNH)2C[double bond, length as m-dash]NAr with cis-[Pt(TFA)2(S(O)Me2)2] in toluene afforded cis-[Pt(TAG)(TFA)(S(O)Me2)] (TAG = triarylguanidinate(1-)-κC,κN; TFA = OC(O)CF3; 6-9) in 75-82% yields. The reactions of 6-9 and the previously known cis-[Pt(TAG)X(S(O)Me2)] (X = Cl (1) and TFA (2-5)) with acetylacetone (acacH) or 2-picolinic acid (picH) in the presence of a base afforded [Pt(TAG)(acac)] (acac = acetylacetonate-κ2O,O'; 10-18) and [Pt(TAG)(pic)] (pic = 2-picolinate-κN,κO; 19) in high yields. The new complexes were characterised by analytical, IR and multinuclear NMR spectroscopies. Further, molecular structures of 11, 12, 13·0.5 toluene and 14-19 were determined by single crystal X-ray diffraction. Absorption spectra of 10-19 in solution and their emission spectra in crystalline form were measured. Platinacycles 10-19 are bluish green light emitter in the crystalline form, and emit in the λPL = 488-529 nm range (11 and 13-19) while 12 emits at λPL = 570 nm. Unlike other platinacycles, the emission band of 12 is broad, red shifted, and this pattern is ascribed to the presence of an intermolecular N-H⋯Pt interaction involving the endocyclic amino unit of the six-membered [Pt(TAG)] ring and the Pt(ii) atom in the adjacent molecule in an asymmetric unit of the crystal lattice. Lifetime measurements were carried out for all platinacycles in crystalline form, which revealed lifetime in the order of nanoseconds. The origin of absorption and emission properties of 11, 15, 18 and 19 were studied by TD-DFT calculations.

5.
J Pak Med Assoc ; 63(11): 1451-5, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24392544

RESUMO

OBJECTIVE: The study was undertaken to find the frequency of Generalised Anxiety Disorder (GAD) along with associated factors in an urban settlement of Karachi. METHOD: A cross-sectional study was conducted at Defence Housing Authority (DHA), a posh area of Karachi. The sample population consisted of residents of ages between 18 and 65. The sample of 420 was completed by randomly going to residences in the DHA area. Self-administered questionnaires were handed out after taking informed consent. General Anxiety Disorder (GAD) 7 scale was used to estimate the anxiety level. The data was entered and analysed using SPSS version 16.0. Pearson's chi-square was used as the primary statistical test. RESULTS: The mean anxiety score of the total individuals selected was 5.1 +/- 3.79. Males reported a mean score of 4.99 +/- 4.01 while females reported a mean score of 5.25 +/- 3.42. A score of 5 is considered as the threshold for anxiety and anything below 5 is considered as normal. Based on this benchmark, out of the total sample size of 420, 211 (50.2%) individuals reported some degree of anxiety. Employment and education status were found to be significantly associated (p = 0.01) with anxiety among the participants. CONCLUSION: Based on the results, the high prevalence of anxiety in one of the most developed areas of Karachi is alarming. For 50.2% of the respondents to have anxiety is high considering the sample chosen represented individuals that were educated and had a high standard of living. The major factors responsible for anxiety cited by respondents were chronic diseases and emotional harm.


Assuntos
Transtornos de Ansiedade/epidemiologia , Saúde da População Urbana , Adolescente , Adulto , Idoso , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Paquistão , Prevalência , Fatores de Risco , Autorrelato , Fatores Socioeconômicos , Adulto Jovem
6.
Drug Res (Stuttg) ; 73(4): 200-212, 2023 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-36736354

RESUMO

Skin provides an excellent barrier to molecular transport, as the stratum corneum is the most formidable barrier to the passage of most pharmaceuticals. Various attempts have been made to improve drug administration into the body through intact skin. Though very few routes are as attractive as the topical route, drug transport through the skin is challenging. To overcome the challenges, researchers have found a system in which the drug is encapsulated into the vesicle, penetrating deeper into the skin to hit the target site. Vesicular systems like transethosome, an ultra- deformable vesicle (UDV), tend to accumulate in the skin layers. Since transethosomes have small particle size and can easily alter the shape of vesicles compared to other vesicular systems, they can penetrate through the layers of skin. Hence, the drug encapsulated into transethosomes can easily reach the target site. Transethosomes consist of ethanol and phospholipids along with an edge activator. Ethanol and edge activator help to enhance the skin permeation of transethosomes. Various methods of preparation of transethosomes, comparison of transethosomes with other lipid vesicles, characterization of transethosomes, and application of transethosomes have been covered in this review. Transethosomes can deliver a different variety of drugs, such as anticancer, corticosteroids, proteins and peptides, analgesics.


Assuntos
Sistemas de Liberação de Medicamentos , Absorção Cutânea , Sistemas de Liberação de Medicamentos/métodos , Administração Cutânea , Lipossomos/química , Pele/metabolismo , Portadores de Fármacos/química
7.
Cureus ; 15(2): e35219, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36968940

RESUMO

Massive pulmonary embolism (PE) is an uncommon but severe complication of pregnancy or during the first few weeks after giving birth. Our intention was to thoroughly analyze the information available to its management methods. Significant bleeding of mother survival and early deliveries in fetal survivals were having hemorrhage and were having key outcomes. We found 127 severe PE cases that have had at least one form of treatment (at least 83% big; 23% with cardiac arrest). The 83 women who received thrombolysis had a 94% (95%) survival rate. Cardiac arrest in pregnancy is uncommon, although maintaining current competency can be challenging. While maternal mortality rates have decreased globally over the past 25 years, they have increased in the United States. The intricacy of the maternal mortality issue is a result of a number of clinical and socioeconomic problems such as unequal healthcare access, racial and ethnic disparities, maternal comorbidities, and bias in epidemiologic ascertainment. The importance of doctors being prepared to react to a potential maternal cardiac arrest in any situation where they are providing treatment for pregnant women is highlighted by the rise in maternal mortality. For the treatment of maternal cardiac arrest, an interdisciplinary team with expertise in both the maternal resuscitation procedure and the physiological changes that take place during pregnancy is necessary. Additionally offered are basic and advanced cardiac life support protocols. Techniques to remove obstacles like aortocaval compression that could impair the effectiveness of resuscitation should be used.

8.
Int J Pharm ; 631: 122506, 2023 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-36535455

RESUMO

The main aim of this study was to optimize the transethosomes of apigenin formulated by the thin film hydration method using surfactant Span 80. Response surface Box-Behnken design with three levels of three factors was used to design and optimize the formulations. The prepared transethosomal formulations were characterized for entrapment efficiency, vesicle size, and flux to obtain the optimized formulation batch. The optimized batch was further incorporated into the gel and characterized for the in-vitro, ex-vivo, and cytotoxic studies. The result showed the optimized transethosomes were smooth, nanosized, unilamellar, and spherical with an entrapment efficiency of 78.75 ± 3.14 %, a vesicle size of 108.75 ± 2.31 nm, and a flux of 4.10 ± 0.63 µg/cm2/h. In-vitro cumulative drug release of transethosomal gel of apigenin (TEL gel) and the conventional gel was 92.25 ± 3.5 % and 53.40 ± 3.10 %, respectively, after 24 h study. Ex-vivo permeation of TEL gel and conventional gel showed 86.20 ± 3.60 % and 51.20 ± 3.20 % permeation of apigenin at 24 h, respectively. A cytotoxic study confirmed that TEL gel significantly reduces cell viability compared to conventional gel. The results suggested that topical application of apigenin transethosomal gel may be a better treatment strategy for skin cancer because of the prolonged sustained release of the drug and the better permeability of apigenin through the skin.


Assuntos
Apigenina , Portadores de Fármacos , Portadores de Fármacos/metabolismo , Administração Cutânea , Pele/metabolismo , Absorção Cutânea , Sistemas de Liberação de Medicamentos/métodos , Tamanho da Partícula
9.
ACS Nano ; 17(3): 2399-2410, 2023 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-36661409

RESUMO

Perovskite nanocrystals are high-performance, solution-processed materials with a high photoluminescence quantum yield. Due to these exceptional properties, perovskites can serve as building blocks for metasurfaces and are of broad interest for photonic applications. Here, we use a simple grating configuration to direct and amplify the perovskite nanocrystals' original omnidirectional emission. Thus far, controlling these radiation properties was only possible over small areas and at a high expense, including the risks of material degradation. Using a soft lithographic printing process, we can now reliably structure perovskite nanocrystals from the organic solution into light-emitting metasurfaces with high contrast on a large area. We demonstrate the 13-fold amplified directional radiation with an angle-resolved Fourier spectroscopy, which is the highest observed amplification factor for the perovskite-based metasurfaces. Our self-assembly process allows for scalable fabrication of gratings with predefined periodicities and tunable optical properties. We further show the influence of solution concentration on structural geometry. By increasing the perovskite concentration 10-fold, we can produce waveguide structures with a grating coupler in one printing process. We analyze our approach with numerical modeling, considering the physiochemical properties to obtain the desired geometry. This strategy makes the tunable radiative properties of such perovskite-based metasurfaces usable for nonlinear light-emitting devices and directional light sources.

10.
Cureus ; 14(4): e24545, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35651407

RESUMO

Objective To determine if the presence of meconium-stained amniotic fluid (MSAF) by itself or in combination with abnormal fetal heart tracing (FHT) (category II and III) is associated with poor neonatal outcomes in full-term newborns. Design/methods This is a retrospective cohort study. Cases included singleton and full-term neonates with MSAF. Cases were compared to matched controls (clear amniotic fluids) for the outcomes. SPSS (IBM SPSS Statistics for Windows, Version 22.0, Armonk, NY, USA) and SAS 9.4 (SAS Institute Inc., Cary, NC, USA) were used for data analysis. Results From 5512 deliveries, 210 cases (MSAF group) and 210 matched controls were identified. Cases and controls were similar in most maternal characteristics. Abnormal FHT was present in 43.2% of cases compared to 17.6% of controls (p<0.001). Low Apgar scores (<7) at one and five minutes were more common in the MSAF group (p=0.03 and 0.007, respectively). The neonatal intensive care unit (NICU) admission rate was also higher in the MSAF group (p=0.002). However, the mean hospital stay was similar in both groups (p=0.44). Twenty-two (10.5%) cases required resuscitation at birth compared to six (2.9%) controls (p=0.003). After applying the logistic regression model to adjust for the FHT pattern and Apgar scores at one minute, the association of MSAF with resuscitation lost significance. The factors associated with resuscitation requirement at birth were Apgar score at one minute (adjusted odds ratios (aOR) 4.1; 95% CI 2.8-5.1, p<0.001) and abnormal FHTs (aOR, 0.03; 95% CI 0.004-0.257, p=0.001). Conclusions Neonates born with MSAF were more likely to have abnormal FHT and require resuscitation at birth. However, after adjusting for confounding factors, abnormal FHT and one-minute Apgar scores were the only variables predictive of resuscitation needs at birth.

11.
J Perinatol ; 42(2): 209-216, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34675370

RESUMO

OBJECTIVE: To evaluate vitamin D status in very low birth weight (VLBW) infants and response to vitamin D intake. STUDY DESIGN: In this prospective cohort study of VLBW infants, 25-hydroxyvitamin D [25(OH)D] was measured regularly starting at birth. Daily vitamin D intake was estimated from parenteral and enteral sources. RESULTS: Of the included 83 infants born between November 2016 and March 2018, 44 (53%) had 25(OH)D < 30 ng/mL at birth but achieved vitamin D sufficiency (VDS) by 3 weeks while receiving 120-400 IU/day. Twenty-three (27.7%) infants had at least one 25(OH)D level >100 ng/mL during the study period. Infants whose intake was > 600 IU/day had higher prevalence of vitamin D excess (VDE). CONCLUSION: In our study, low 25(OH)D was common in VLBW infants at birth. Vitamin D intake of 120-260 IU/day from parenteral and 200-400 IU/day from enteral route was appropriate for VLBW infants to achieve VDS. Doses > 600 IU/day increased risk of VDE.


Assuntos
Unidades de Terapia Intensiva Neonatal , Deficiência de Vitamina D , Humanos , Lactente , Recém-Nascido , Recém-Nascido de muito Baixo Peso , Estudos Prospectivos , Vitamina D , Deficiência de Vitamina D/epidemiologia , Vitaminas
12.
Cureus ; 14(10): e30202, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36381893

RESUMO

Food supplements may be consumed through diet and have been shown to modify skin functions, making them helpful in the management of skin aging. However, there are not many clinical trials that back up these assertions. The stratum corneum, which acts as the organism's contact with its environment, is the principal function of the epidermis of land vertebrates. Antioxidants are chemicals that slow down or prevent other molecules from oxidizing. In people's diets, their use has considerably expanded in recent years. Due to their benefits for health, nutrition, and therapy, natural antioxidants are increasingly being used in place of synthetic antioxidant components. A popular component thought to be an antioxidant is hydrolyzed collagen. With aging comes a steady loss of physiological integrity, capacity to handle stress from the inside out, and function. This is a byproduct of several intricate biological processes that are affected by diseases both local and systemic as well as constitutive and environmental variables. Systemic and constitutive (genetic) variables influence skin aging and its phenotypic manifestation. The biological process of skin aging is complicated and impacted by both external and endogenous causes. The primary contributor to skin cancer is sun exposure. Ultraviolet radiation from the sun can kill skin cells by directly absorbing DNA damage. The skin's hydration is a crucial factor that affects its mechanical and physical characteristics. This study looks at how the stratum corneum's molecular and macroscopic characteristics interact and change with skin wetness. Although there is little information written about them and even less is understood about them, moisturizers are a crucial component of a dermatologist's toolkit. There is a plethora of anticipated skin products on the market, but their true scientific function is yet unknown. These items play a well-known part in many skin problems, while occasionally being dismissed as simple cosmetics.

13.
Ann Thorac Med ; 17(1): 21-27, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35198045

RESUMO

OBJECTIVE: Sleep problems during the coronavirus disease 2019 (COVID-19) pandemic commonly affected general populations. Data on the effect of the COVID-19 pandemic on sleep quality in Saudi Arabia are scarce. Thus, the aim of our study was to evaluate sleep quality and assess the psychological burden of the pandemic in COVID-19 patients and the general population. METHODS: This was a multicenter, observational, cross-sectional survey. Participants with COVID-19 were recruited from different health-care centers in the western region during the lockdown period from May 13, 2020 to September 2, 2020. All participants completed a validated online survey. The control group comprised individuals from the general public who responded to the online survey through social media. Demographic data, COVID-19 status, and history of chronic diseases were collected. Sleep quality, depression, and insomnia were assessed using validated questionnaires. RESULTS: In total, 1091 participants were surveyed and 643 (58.9%) were positive for COVID-19. Poor sleep quality was reported in 66.1% of COVID-19 patients (mean score ± standard deviation [SD] 6.9 ± 4.0) and 72.8% of controls (mean score ± SD 7.6 ± 4.3). Insomnia affected 50.5% of COVID-19 patients (mean score ± SD 6.5 ± 5.5) and 58.5% of controls (mean score ± SD 7.6 ± 5.5). Depression was diagnosed in 39.5% of COVID-19 patients (mean score ± SD 4.7 ± 4.6) and 70.1% of controls (mean score ± SD 8.9 ± 6.7). CONCLUSIONS: The COVID-19 pandemic had a great impact on mental health and sleep quality in both COVID-19 patients and the general population but more pronounced in the general population.

14.
Cureus ; 13(10): e18491, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34754652

RESUMO

Infantile perianal pyramidal protrusion (IPPP) is an uncommon and underreported benign cutaneous lesion characterized by a protrusion from the anal orifice. It is also believed to be often mistaken for other conditions. The unawareness of this lesion may be responsible for underreporting and an excessive concern both in providers and in parents. Timely diagnosis and reassurance need to be emphasized in the provider community. We report an interesting case of IPPP on the first day of life, which was erroneously diagnosed as imperforate anus at her delivery.

15.
Artigo em Inglês | MEDLINE | ID: mdl-34501713

RESUMO

Customers have become very sensitive regarding the innovative evaluation of services. Due to competition in the hospitality industry, it is a challenge for hotel marketers to understand customers' behavior. There is scant research in the hotel industry of Pakistan and especially on boutique hotels. This research seeks to measure the relationship between substantive, communicative elements of the sustainable servicescape and behavioral intentions (word of mouth) in a boutique hotel setting. However, the mediating effect of the overall perceived image is examined between these constructs. Responses of boutique hotel visitors were collected from Lahore, Islamabad, Faisalabad, and Murree. Data were analyzed by using structural equation modeling (SEM). Results display that both substantive and communicative servicescape elements positively affect the perceived image of customers, which has a positive influence on behavioral intentions such as word of mouth (WOM). Theoretical and practical implications are also discussed.


Assuntos
Indústrias , Intenção , Comunicação , Criatividade , Inquéritos e Questionários
16.
Front Psychol ; 12: 762746, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-35222141

RESUMO

The purpose of this study is to find empirical evidence on whether work from home or residential emissions reduces office emissions. Based on existing research the study supports that there are short-term effects on office emissions, i.e., carbon emissions do not outshine the long-term effects. The shift from offices to working from home due to COVID-19 regulations meant more people operating from home as maintaining their position in the market was crucial. The potential research area is to understand how this would affect energy usage and carbon emissions. This study has used a before and after mixed approach to collect data from 301 working-from-home employees and 348 top managers who are responsible for monitoring the employees in a work from home setting. Convenience sampling helped collect responses in a timely manner as offices were not allowing visitors and collecting data in person was difficult, so online surveys were conducted. Work from home reduced usage of office equipment, transportation, pollution, etc. The air quality improved considerably but our findings show that the low emissions were only short-lived. This was not a long-term scenario as organizations kept practicing their operations even at home and the emissions stayed in the environment. Future suggestions and implications are also provided. The results give new insights to researchers in the field of sustainability and the environment.

17.
Sci Rep ; 10(1): 2615, 2020 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-32054972

RESUMO

Nonlinear optical properties, such as two-(or multi-) photon absorption (2PA), are of special interest for technologically important applications in fast optical switching, in vivo imaging and so on. Highly intense infrared ultrashort pulses probe deep into samples and reveal several underlying structural perturbations (inter-layer distortions, intra-layer crumpling) and also provide information about new excited states and their relaxation. Naturally self-assembled inorganic-organic multiple quantum wells (IO-MQWs) show utility from room-temperature exciton emission features (binding energies ~200-250 meV). These Mott type excitons are highly sensitive to the self-assembly process, inorganic network distortions, thickness and inter-layer distortions of these soft two-dimensional (2D) and weak van der Waal layered hybrids. We demonstrate strong room-temperature nonlinear excitation intensity dependent two-photon absorption induced exciton photoluminescence (2PA-PL) from these IO-MQWs, excited by infrared femtosecond laser pulses. Strongly confined excitons show distinctly different one- and two-photon excited photoluminescence energies: from free-excitons (2.41 eV) coupled to the perfectly aligned MQWs and from energy down-shifted excitons (2.33 eV) that originate from the locally crumpled layered architecture. High intensity femtosecond induced PL from one-photon absorption (1PA-PL) suggests saturation of absorption and exciton-exciton annihilation, with typical reduction in PL radiative relaxation times from 270 ps to 190 ps upon increasing excitation intensities. From a wide range of IR excitation tuning, the origin of 2PA-PL excitation is suggested to arise from exciton dark states which extend below the bandgap. Observed two-photon absorption coefficients (ß ~75 cm/GW) and two-photon excitation cross-sections (η2σ2 ~ 110GM), further support the evidence for 2PA excitation origin. Both 1PA- and 2PA-PL spatial mappings over large areas of single crystal platelets demonstrate the co-existence of both free and deep-level crumpled excitons with some traces of defect-induced trap state emission. We conclude that the two-photon absorption induced PL is highly sensitive to the self-assembly process of few to many mono layers, the crystal packing and deep level defects. This study paves a way to tailor the nonlinear properties of many 2D material classes. Our results thus open new avenues for exploring fundamental phenomena and novel optoelectronic applications using layered inorganic-organic and other metal organic frameworks.

18.
ACS Omega ; 4(1): 2275-2282, 2019 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-31459470

RESUMO

Heavily doped nanocrystals of host KLaF4 with rare earth (RE3+ = Er3+, Tm3+, and Yb3+) ions prepared by a simple one-step template-free wet-chemical route have been reported. Prepared KLaF4 nanocrystals reveal phase-pure cubic structures (lattice constant a = 5.931Å) with space group Fm3m. Precisely defined molar ratios of heavily dopant RE3+ ions allow us to achieve wide color upconversion (UC) emission tunability (blue, green to yellow-orange-red) and white light, without any morphology and structure changes. The enhanced red emission by a factor of ∼120 has been achieved in 20% Yb3+ and 5% Tm3+ ions in KLaF4:1% Er3+ nanocrystals, which is due to an efficient sensitizer-acceptor (Yb3+ to Er3+ and Tm3+ ions) energy transfer and interexchange energy process between acceptors. For the first time, the key role of sensitizer (Yb3+) for UC emission energy transfer to Er3+ and/or Tm3+ is experimentally demonstrated. The evidence of upconversion photoluminescence excitation spectra reveals a broad safe biological excitation window (690-1040 nm), which can be well demonstrated by low-cost NIR diode lasers/LEDs. The applicability of these cubic nanophosphors is demonstrated as light-emitting polymer composite coatings and blocks for LEDs and solar cell panels. These well-dispersed UC nanocrystals can also be found to have greater use in bioimaging and spectral studies.

19.
Antibiotics (Basel) ; 8(4)2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31653014

RESUMO

The aim of this study was to explore the phytochemical composition, heavy metals analysis and the antibacterial activity of six medicinal plants i.e., Terminalia chebula Retz (fruits), Aegle marmelos L., (fruits), Curcuma longa L., (rhizomes), Syzygium aromaticum L., (flower buds), Piper nigrum L., (seeds), Cinnamomum cassia L., (barks) and its two remedial recipes (recipe 1 and 2) used against diarrhea obtained from the local herbal practitioners (Hakeems). A preliminary phytochemical screening of the above-mentioned plants extract in methanol, chloroform, n-hexane and distilled water revealed the presence of various constituents such as alkaloids, flavonoids, tannins and saponins by using standard procedures. The quantitative phytochemical studies shows that alkaloids, flavonoid and saponins were in maximum amount in Terminalia chebula. The concentration of Cd, Ni, Pb, Fe, Cr, Cu and Zn were investigated by using an atomic absorption spectrometer. The obtained analysis shows that Cr, Fe and Pb were present in the highest concentration in medicinal plants and their recipes. The antibacterial activities of the crude extract found in the recipes of methanol, chloroform, n-hexane and distilled water were analyzed by using agar well disc diffusion assay and minimum inhibitory concentration (MIC) by broth dilution method against four bacterial strains, namely, E. coli, Salmonella, Shigella and Methicillin-resistant Staphylococcus aureus (MRSA), respectively. The maximum zones of inhibition in methanol, water, chloroform and n-hexane extracts were seen in recipe 2 against Shigella (22.16 ± 0.47 mm), recipe 2 against Shigella (20.33 ± 0.24 mm), recipe 1 against Shigella (20.30 ± 0.29 mm) and recipe 2 against E. coli (30.23 ± 0.12 mm), respectively. Furthermore, the recipe extracts are more active against the tested bacterial strains than the extracts from individual plants. Therefore, it is concluded that the use of herbal plants and their recipes are the major source of drugs in a traditional medicinal system to cure different diseases.

20.
ACS Omega ; 4(22): 19565-19572, 2019 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-31788586

RESUMO

Synthesis, crystal structure, and optical properties of two-dimensional (2D) layered structurally slightly different inorganic-organic (IO) hybrid semiconductors (R-C6H4C2H4NH3)2PbI4 (R = CH3, Cl) are presented. They are naturally self-assembled systems where two (RNH3)+ moieties are sandwiched between two infinitely extended 2D layers of the [PbI6]4- octahedral network and treated as natural IO multiple quantum wells. While the former compound crystallizes into an orthorhombic system in the Cmc21 space group, the latter crystallizes into a monoclinic system in the space group P21/c. As a thin film, they are well-oriented along the (l00) direction. Both single crystals and thin films show strong room-temperature Mott type exciton features that are highly sensitive to the self-assembly and crystal packing. Linear (one-photon) and nonlinear (two-photon) optical probing of single crystals for exciton photoluminescence imaging and spectral spatial mapping provide deep insight into the layered re-arrangement and structural crumpling due to organic conformation. The strongly confined excitons, within the lowest band gap of inorganic, show distinctly different one- and two-photon excited photoluminescence peaks: free excitons from perfectly aligned 2D self-assembly and energy down-shifted excitons originated from the locally crumpled layered arrangement. Their structural aspects are successfully presented with proper correlation that emphasize various differences in physical and optical properties associated between these novel IO hybrids.

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