| 1. |
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| 2. |
- Andrén, Oliver C. J., et al.
(författare)
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Antibiotic-Free Cationic Dendritic Hydrogels as Surgical-Site-Infection-Inhibiting Coatings
- 2019
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Ingår i: Advanced Healthcare Materials. - : Wiley. - 2192-2640 .- 2192-2659.
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Tidskriftsartikel (refereegranskat)abstract
- A non-toxic hydrolytically fast-degradable antibacterial hydrogel is herein presented to preemptively treat surgical site infections during the first crucial 24 h period without relying on conventional antibiotics. The approach capitalizes on a two-component system that form antibacterial hydrogels within 1 min and consist of i) an amine functional linear-dendritic hybrid based on linear poly(ethylene glycol) and dendritic 2,2-bis(hydroxymethyl)propionic acid, and ii) a di-N-hydroxysuccinimide functional poly(ethylene glycol) cross-linker. Broad spectrum antibacterial effect is achieved by multivalent representation of catatonically charged β-alanine on the dendritic periphery of the linear dendritic component. The hydrogels can be applied readily in an in vivo setting using a two-component syringe delivery system and the mechanical properties can accurately be tuned in the range equivalent to fat tissue and cartilage (G' = 0.5-8 kPa). The antibacterial effect is demonstrated both in vitro toward a range of relevant bacterial strains and in an in vivo mouse model of surgical site infection.
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| 3. |
- Blom, Karen Ann
(författare)
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Ordinary people, meaningful pasts – Negotiating narratives in public pedagogical spaces of family history research
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation examines three family history research experiences as public pedagogical spaces, analysing the narratives presented and participants’ negotiations with these. In the context of enhanced digitalisation and rapidly developing technologies, disturbances in the form of pandemics, hackers, and wars remind us of the instability of the present, raising existential questions and reinforcing the desire to anchor oneself in the past. Despite this growing interest, academic research focusing on family history is sparse. This dissertation project is unique in its focus on a Swedish context, the selection of three specific family history experiences as case studies, and its use of a public pedagogical perspective examining relational learning beyond formal institutions intrinsically woven within the fabric of society.This dissertation uses three case studies as reflections of more extensive experiences of the phenomenon of interest in family history and the past. These include the Swedish family history television series Allt för Sverige’s previous contestants’ narratives, the results from four genetic ancestry testing companies, and participants’ narratives from two Swedish non-formal family history research courses. Analysing these further within this compilation dissertation engages a conceptual framework consisting of Rüsen’s historical narrative typology, Hall’s decoding/encoding model, and Ellsworth’s use of Public Pedagogy as relational and facilitating transitional spaces for knowledge in the making. An emphasis on the process of pedagogy, rather than the product of knowledge, is prominent in this hermeneutic phenomenological study and reflects the concept of Bildung as the cultivation of the whole person.The findings reveal a more complex picture of family historians, history, and family history research experiences than what is often portrayed. Participants deem not only the effervescent or exceptional findings and activities valuable, but the everyday banal is perceived as significant and contributes to the development of understanding and meaning. Moreover, regardless of the physical site of the experience, the infused pedagogical intent is illustrated through participants’ interactions and negotiations. In a field surrounded by rock walls their ancestor built, discovering a relative had only five spoons in a testament, or examining a deep map to trace the movements of ancestors all provide opportunities to juxtapose, confirm, and/or challenge previous knowledge with new information and experiences, reiterating the extensive reach of public pedagogy.Despite narratives presenting conflicting depictions of the past, participants of this study demonstrate agency in their negotiations, resulting in enhanced empathy and enriched historical consciousness. By exploring these family history research experiences as pedagogical spaces, this dissertation provides a more nuanced understanding of the broader field of public pedagogy and contributes new insights from Swedish and participants’ perspectives to the growing body of research on family history. It highlights the potential and benefits of examining the small, seemingly insignificant, everyday items and events. Moreover, it contributes a more comprehensive illustration of the seepage/pervasiveness of public pedagogy as complex and relational.
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| 4. |
- Blom, Kerstin, et al.
(författare)
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Internet-vs. group-delivered cognitive behavior therapy for insomnia : A randomized controlled non-inferiority trial
- 2015
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Ingår i: Behaviour Research and Therapy. - : Elsevier. - 0005-7967 .- 1873-622X. ; 70, s. 47-55
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to compare guided Internet-delivered to group-delivered cognitive behavioral therapy (CBT) for insomnia. We conducted an 8-week randomized controlled non-inferiority trial with 6-months follow-up. Participants were forty-eight adults with insomnia, recruited via media. Interventions were guided Internet-delivered CBT (ICBT) and group-delivered CBT (GCBT) for insomnia. Primary outcome measure was the Insomnia Severity Index (ISI), secondary outcome measures were sleep diary data, depressive symptoms, response- and remission rates. Both treatment groups showed significant improvements and large effect sizes for ISI (Within Cohen's d: ICBT post = 1.8, 6-months follow-up = 2.1; GCBT post = 2.1, 6-months follow-up = 2.2). Confidence interval of the difference between groups posttreatment and at FU6 indicated non-inferiority of ICBT compared to GCBT. At post-treatment, two thirds of patients in both groups were considered responders (ISI-reduction > 7p). Using diagnostic criteria, 63% (ICBT) and 75% (GCBT) were in remission. Sleep diary data showed moderate to large effect sizes. We conclude that both guided Internet-CBT and group-CBT in this study were efficacious with regard to insomnia severity, sleep parameters and depressive symptoms. The results are in line with previous research, and strengthen the evidence for guided Internet-CBT for insomnia. Trial registration: The study protocol was approved by, and registered with, the regional ethics review board in Linkoping, Sweden, registration number 2010/385-31. (C) 2015 The Authors. Published by Elsevier Ltd.
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| 5. |
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| 6. |
- Blom, Tobias, et al.
(författare)
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An In-Situ Prepared Nano-Manipulator Tip for Electrical Characterization of Free Standing Graphene Like Sheets Inside a Focused Ion Beam/Scanning Electron Microscope
- 2011
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Ingår i: Journal of Nanoelectronics and Optoelectronics. - : American Scientific. - 1555-130X .- 1555-1318. ; 6:2, s. 162-168
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Tidskriftsartikel (refereegranskat)abstract
- Although contacting and moving atoms has been demonstrated using probe techniques, for many nano-objects, a fast and reproducible nano-probe technique is needed to acquire a large number of electrical measurements on nano-objects that are often similar but not the identical. Nano-manipulators have become a common tool in many scanning electron microscopes (SEM) and focussed ion beam devices (FIB). They can be rapidly and reproducibly moved from one nano-object to another. In this work we present a procedure to obtain reproducible electrical measurements of nano- to micron-sized objects by using a sharp, tungsten tip with well defined surface properties. The tip is a part of a manipulator and is sharpened in-situ by using the gallium ion beam inside a focused ion beam/scanning electron microscope (FIB/SEM). The contact resistance between a Au surface and the tip is 70 kΩ before the sharpening procedure and 10 Ω after sharpening. The leakage current of the total set-up of 10pA makes it possible to measure currents through a variety of nano-objects. This measurement technique is applied to measure the resistance of as grown, water treated and two HCl treated carbon nanosheets (CNS). These CNS vary in size and morphology. Using this nano-contacting set-up, we could obtain measurements of more than 400 different CNS. The obtained histograms allow us to observe a clear decrease of the resistance between original and 3 hour acid treated CNSs. We observe that longer periods of exposure of the CNS to the HCl do not further modify the resistance.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Blom, Tobias
(författare)
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Fabrication and Applications of a Focused Ion Beam Based Nanocontact Platform for Electrical Characterization of Molecules and Particles
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of new materials with novel properties plays an important role in improving our lives and welfare. Research in Nanotechnology can provide e.g. cheaper and smarter materials in applications such as energy storage and sensors. In order for this development to proceed, we need to be able to characterize the material properties at the nano-, and even the atomic scale. The ultimate goal is to be able to tailor them according to our needs. One of the great challenges concerning the characterization of nano-sized objects is how to achieve the physical contact to them. This thesis is focused on the contacting of nanoobjects with the aim of electrically characterizing them and subsequently understanding their electrical properties. The analyzed nanoobjects are carbon nanosheets, nanotetrapods, nanoparticles and molecular systems. Two contacting strategies were employed in this thesis. The first strategy involved the development of a focused ion beam (FIB) based nanocontact platform. The platform consists of gold nanoelectrodes, having nanogaps of 10-30 nm, on top of an insulating substrate. Gold nanoparticles, double-stranded DNA and cadmium telluride nanotetrapods have been trapped in the gaps by using dielectrophoresis. In certain studies, the gold electrodes have also been coated with conducting or non-conducting molecules, prior to the trapping of gold nanoparticles, in order to form molecular junctions. These junctions were subsequently electrically characterized to evaluate the conduction properties of these molecular systems. For the purpose of better controlling the attachment of molecules to the nanoelectrodes, a novel route to synthesize alkanedithiol coated gold nanoparticles was developed. The second contacting strategy was based on the versatility of the FIB instrument as a platform for in-situ manipulation and electrical characterization of non-functionalized and functionalized carbon nanosheets, where it was found that the functionalized samples had an increased conductivity by more than one order of magnitude. Both contacting strategies proved to be valuable for building knowledge around contacting and electrical characterization of nanoobjects
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Blom, Tobias, et al.
(författare)
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Fabrication and characterization of highly reproducible, high resistance nanogaps made by focused ion beam milling
- 2007
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 18:28, s. 285301-
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Tidskriftsartikel (refereegranskat)abstract
- Nanoelectrodes were fabricated combining photolithography, electron beam lithography and focused ion beam milling allowing for large scale integration and nanoengineering of the electrode properties. The structure determination by transmission and scanning electron microscopy showed a highly reproducible gap width. The atomic scale electrode structure was characterized using scanning and transmission electron microscopy. The nanogap resistances were found to be the highest hitherto reported for nanogaps, namely in the 300–1300 TΩ range. Gold nanoparticles were trapped by ac dielectrophoresis, and the electrodes were shown to be stable enough to endure empty gap voltages as high as 5 V as well as currents high enough to induce fusing of trapped nanoparticles.
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| 17. |
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| 18. |
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| 19. |
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| 20. |
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| 21. |
- Blom, Victoria, et al.
(författare)
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Lifestyle Habits and Mental Health in Light of the Two COVID-19 Pandemic Waves in Sweden, 2020
- 2021
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Ingår i: International Journal of Environmental Research and Public Health. - : MDPI AG. - 1660-4601 .- 1661-7827. ; 18:6
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Tidskriftsartikel (refereegranskat)abstract
- The COVID-19 pandemic has become a public health emergency of international concern, which may have affected lifestyle habits and mental health. Based on national health profile assessments, this study investigated perceived changes of lifestyle habits in response to the COVID-19 pandemic and associations between perceived lifestyle changes and mental health in Swedish working adults. Among 5599 individuals (50% women, 46.3 years), the majority reported no change (sitting 77%, daily physical activity 71%, exercise 69%, diet 87%, alcohol 90%, and smoking 97%) due to the pandemic. Changes were more pronounced during the first wave (April-June) compared to the second (October-December). Women, individuals <60 years, those with a university degree, white-collar workers, and those with unhealthy lifestyle habits at baseline had higher odds of changing lifestyle habits compared to their counterparts. Negative changes in lifestyle habits and more time in a mentally passive state sitting at home were associated with higher odds of mental ill-health (including health anxiety regarding one's own and relatives' health, generalized anxiety and depression symptoms, and concerns regarding employment and economy). The results emphasize the need to support healthy lifestyle habits to strengthen the resilience in vulnerable groups of individuals to future viral pandemics and prevent health inequalities in society.
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| 22. |
- Blom, Åsa, 1977-, et al.
(författare)
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Utomhuskonstruktioner i trä : några erfarenheter från byggnation i trä av flerbostadshus
- 2017
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Användandet av materialet trä i produkter är ett lån från naturen som förr eller senare genom nedbrytning av vedsubstansen ska återföras till det naturliga kretsloppet. Avseende användningen av solitt trä i produkter bestäms tidsperioden innan återföringen till naturen av produktens konstruktion och trämaterialet i sig självt i relation till den omgivande miljön samt användningen och hanteringen av produkten. En produkts förmåga att motstå, eller behålla sina egenskaper trots dessa yttre påfrestningar benämns dess beständighet.
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| 23. |
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| 24. |
- Ekblom Bak, Elin, 1981-, et al.
(författare)
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Cardiorespiratory fitness and lifestyle on severe COVID-19 risk in 279,455 adults: a case control study
- 2021
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Ingår i: International Journal of Behavioral Nutrition and Physical Activity. - : Springer Science and Business Media LLC. - 1479-5868. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- Background The impact of cardiorespiratory fitness (CRF) and other lifestyle-related factors on severe COVID-19 risk is understudied. The present study aims to investigate lifestyle-related and socioeconomic factors as possible predictors of COVID-19, with special focus on CRF, and to further study whether these factors may attenuate obesity- and hypertension-related risks, as well as mediate associations between socioeconomic factors and severe COVID-19 risk. Methods Out of initially 407,131 participants who participated in nationwide occupational health service screening between 1992 and 2020, n = 857 cases (70% men, mean age 49.9 years) of severe COVID-19 were identified. CRF was estimated using a sub-maximum cycle test, and other lifestyle variables were self-reported. Analyses were performed including both unmatched, n = 278,598, and sex-and age-matched, n = 3426, controls. Severe COVID-19 included hospitalization, intensive care or death due to COVID-19. Results Patients with more severe COVID-19 had significantly lower CRF, higher BMI, a greater presence of comorbidities and were more often daily smokers. In matched analyses, there was a graded decrease in odds for severe COVID-19 with each ml in CRF (OR = 0.98, 95% CI 0.970 to 0.998), and a two-fold increase in odds between the lowest and highest (< 32 vs. >= 46 ml center dot min(-1)center dot kg(-1)) CRF group. Higher BMI (per unit increase, OR = 1.09, 1.06 to 1.12), larger waist circumference (per cm, OR = 1.04, 1.02 to 1.06), daily smoking (OR = 0.60, 0.41 to 0.89) and high overall stress (OR = 1.36, 1.001 to 1.84) also remained significantly associated with severe COVID-19 risk. Obesity- and blood pressure-related risks were attenuated by adjustment for CRF and lifestyle variables. Mediation through CRF, BMI and smoking accounted for 9% to 54% of the associations between low education, low income and blue collar/low skilled occupations and severe COVID-19 risk. The results were consistent using either matched or unmatched controls. Conclusions Both lifestyle-related and socioeconomic factors were associated with risk of severe COVID-19. However, higher CRF attenuated the risk associated with obesity and high blood pressure, and mediated the risk associated with various socioeconomic factors. This emphasises the importance of interventions to maintain or increase CRF in the general population to strengthen the resilience to severe COVID-19, especially in high-risk individuals.
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| 25. |
- Fredin, Kristofer, et al.
(författare)
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Using a molten organic conducting material to infiltrate a nanoporous semiconductor film and its use in solid-state dye-sensitized solar cells
- 2009
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Ingår i: Synthetic metals. - : Elsevier BV. - 0379-6779 .- 1879-3290. ; 159:1-2, s. 166-170
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We describe a method to fill thin films of nanoporous TiO2 with solid organic hole-conducting materials and demonstrate the procedure specifically for use in the preparation of dye-sensitized solar cells. Cross-sections of the films were investigated by scanning electron microscopy and it was observed that a hot molten organic material fills pores that are 10 mu m below the surface of the film. We characterized the incident photon to current conversion efficiency properties of the solid TiO2/organic dye/organic hole-conductor heterojunctions and the spectra show that the dye is still active after the melting process.
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| 26. |
- Hajati, Y, et al.
(författare)
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Improved gas sensing activity in structurally defected bilayer graphene
- 2012
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 23:50, s. 50550-
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Tidskriftsartikel (refereegranskat)abstract
- Graphene is a two-dimensional material with a capability of gas sensing, which is here shown to be drastically improved by inducing gentle disorder in the lattice. We report that by using a focused ion beam technique, controlled disorder can be introduced into the graphene structure through Ga + ion irradiation. This disorder leads to an increase in the electrical response of graphene to NO 2 gas molecules by a factor of three in an ambient environment (air). Ab initio density functional calculations indicate that NO 2 molecules bind strongly to Stone–Wales defects, where they modify electronic states close to the Fermi level, which in turn influence the transport properties. The demonstrated gas sensor, utilizing structurally defected graphene, shows faster response, higher conductivity changes and thus higher sensitivity to NO 2 as compared to pristine graphene.
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| 27. |
- Holmlund, Tobias, et al.
(författare)
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Change in cardiorespiratory fitness on self-rated health : prospective cohort study in 98 718 Swedish adults.
- 2023
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Ingår i: Scandinavian Journal of Public Health. - : Sage Publications. - 1403-4948 .- 1651-1905. ; 51:4, s. 542-551
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To study how change in cardiorespiratory fitness over time is associated with the development of poor self-rated health in healthy Swedish adults, and whether this association varies with sex, age, body mass index and cardiorespiratory fitness at baseline. A secondary aim was to study the influence of other predictors of self-rated health. Methods: A total of 98,718 participants (45% women, mean age 42.2 years) with two assessments from occupational health service screenings between 1988 and 2019 (mean duration 4.3 years), with good self-rated health at baseline were included. Cardiorespiratory fitness was assessed as estimated maximal oxygen consumption using submaximal cycle testing. Change in cardiorespiratory fitness was expressed as percentage annual change. Poor self-rated health at follow-up was defined as percieving self-rated health as 'poor' or 'very poor'. Results: A large decrease in cardiorespiratory fitness (⩾-3%) was associated with a 34% higher risk of poor self-rated health compared to maintainers (-1 to +1%) after multi-adjustment including change in body mass index, back/neck pain, stress, exercise habits and sleep quality or sleep problems. The associations for decreasers were stronger with longer follow-up time (>10 years). Preserving, or changing to, risk level for body mass index, back/neck pain, stress, exercise and sleep quality/problems were associated with a higher risk of poor self-rated health. Conclusions: Preserving or increasing cardiorespiratory fitness is associated with a lower risk of poor self-rated health, independently of change in other health-related variables, which may act as a protection against future poor self-rated health. This is of high clinical value, and strategies for maintaining or improving cardiorespiratory fitness have the potential to influence both disease and mortality.
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| 28. |
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| 29. |
- Jafri, Hassan, et al.
(författare)
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Control of Conductivity in Graphene by Formation of Defects
- 2008
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Ingår i: AVS 55th International Symposium & Exhibition 2008, October 19-24, Boston, USA.
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Konferensbidrag (refereegranskat)abstract
- Due to their large surface areas, the conductivity of graphene and carbonnano-sheets depends strongly on their chemical environment. This is thebase for future environmental sensors containing graphene sheets. Here, abinitiocalculations propose a possibility of conductivity increase. In theexperiment, a 1-2 orders of magnitude increase of the conductivity isobserved experimentally on sub-nanometTe carbon nano-sheets by using anin-situ nano-manipulation set-up. The conductivity of the graphene sheetswas assessed from first-principle simulations. Insertion of defects in thegraphene sheets can lead to a strong increase of the conductivity of singlegraphene sheets. To study this result experimentally, we carried outconductivity measurements on sub-nanometre graphene nano-sheets that aredeposited on W -substrates by radio-frequency plasma-enhanced chemicalvapour deposition. This deposition process creates free-standingmicrometer-sized carbon nano-sheets with sub-nanometre thickness. Thesenano-sheets were exposed to an acid treatment. It has been shown recentlythat such acid treatment creates defects in these sheets. Using a nanomanipulatorinside a scanning electron microscope, we individuallycontacted the nano-sheets and measured their resistance as a function oftheir functionalization. From more than 1000 measurements we obtain a 1-2order of magnitude increase of conductivity in the functionalised carbonnano-sheets as compared to just water treated or untreated carbon nanosheets.This result corresponds well to the conductivity change obtainedfrom theory. This study makes it possible to create environmental sensorsbased on graphene like carbon nano-sheets.
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| 30. |
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| 31. |
- Jafri, Hassan M., et al.
(författare)
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Identification of vibrational signatures from short chains of interlinked molecule-nanoparticle junctions obtained by inelastic electron tunnelling spectroscopy
- 2013
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Ingår i: Nanoscale. - 2040-3364 .- 2040-3372. ; 5:11, s. 4673-4677
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Tidskriftsartikel (refereegranskat)abstract
- Short chains containing a series of metal- molecule-nanoparticle nanojunctions are a nano-materials system with the potential to give electrical signatures close to those from single molecule experiments while enabling to build portable devices on a chip. Inelastic electron tunnelling spectroscopy (IETS) measurements provide one of the most characteristic electrical signals of single and few molecules. In interlinked molecule-nanoparticle (NP) chains containing of typically 5-7 molecules in a chain, the spectrum is expected to be a superposition of the vibrational signature of individual molecules. We have established a stable and reproducible molecule-AuNP multi-junction by placing few 1,8-octanedithiol (ODT) molecules into a versatile and portable nanoparticle-nanoelectrode platform and measured for the first time vibrational molecular signatures complex and coupled few-molecule-NP junctions. From quantum transport calculations, we model the IETS spectra and identify vibrational modes as well as the number of molecules contributing to the electron transport in the measured spectra.
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| 32. |
- Jafri, Hassan, et al.
(författare)
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Systematic assessment of a nanoparticle bridge platform for molecular electronics measurements
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A combination of electron beam lithography, photolithography and focused ion beam milling was used to create a nanogap platform, which was bridged by gold nanoparticles (AuNPs) in order to make electrical measurements and assess the platform under ambient conditions. Initially bare electrodes were tested to determine the response of the platform and it was found that creating devices in ambient conditions requires careful cleaning processes and awareness of the contributions contaminants may make to measurements. Both octanethiol (OT) and Biphenyldithiol (BPDT) molecules were also tested by functionalizing the nanoelectrodes with the molecules prior to bridging the nanogap with the nanoparticles. Measurements on OT show that it is possible to make measurements on relatively small numbers of molecules, but that a large variation in response can be expected when one of the metal-molecule junctions is physisorbed, which was partially explained by attachment of OT molecules to different sites on the surface of the Au electrode using a density function theory calculation. On the other hand, when dealing with BPDT, high yields for device creation are very difficult to achieve when preparing the devices in ambient conditions. Significant hysteresis, or conductance switching, in the I-V curves of BPDT was also observed, which we attribute primarily to voltage induced changes at the interface between the molecule and the metal.
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| 33. |
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| 34. |
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| 35. |
- Jafri, S. Hassan M., et al.
(författare)
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Assessment of a nanoparticle bridge platform for molecular electronics measurements
- 2010
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 21:43, s. 435204-
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Tidskriftsartikel (refereegranskat)abstract
- A combination of electron beam lithography, photolithography and focused ion beam milling was used to create a nanogap platform, which was bridged by gold nanoparticles in order to make electrical measurements and assess the platform under ambient conditions. Non-functionalized electrodes were tested to determine the intrinsic response of the platform and it was found that creating devices in ambient conditions requires careful cleaning and awareness of the contributions contaminants may make to measurements. The platform was then used to make measurements on octanethiol (OT) and biphenyldithiol (BPDT) molecules by functionalizing the nanoelectrodes with the molecules prior to bridging the nanogap with nanoparticles. Measurements on OT show that it is possible to make measurements on relatively small numbers of molecules, but that a large variation in response can be expected when one of the metal-molecule junctions is physisorbed, which was partially explained by attachment of OT molecules to different sites on the surface of the Au electrode using a density functional theory calculation. On the other hand, when dealing with BPDT, high yields for device creation are very difficult to achieve under ambient conditions. Significant hysteresis in the I-V curves of BPDT was also observed, which was attributed primarily to voltage induced changes at the interface between the molecule and the metal.
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| 36. |
- Jafri, Syed Hassan Mujtaba, et al.
(författare)
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Conductivity engineering of graphene by defect formation
- 2010
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 43:4, s. 045404-
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Tidskriftsartikel (refereegranskat)abstract
- Transport measurements have revealed several exotic electronic properties of graphene. The possibility to influence the electronic structure and hence control the conductivity by adsorption or doping with adatoms is crucial in view of electronics applications. Here, we show that in contrast to expectation, the conductivity of graphene increases with increasing concentration of vacancy defects, by more than one order of magnitude. We obtain a pronounced enhancement of the conductivity after insertion of defects by both quantum mechanical transport calculations as well as experimental studies of carbon nano-sheets. Our finding is attributed to the defect induced mid-gap states, which create a region exhibiting metallic behaviour around the vacancy defects. The modification of the conductivity of graphene by the implementation of stable defects is crucial for the creation of electronic junctions in graphene-based electronics devices.
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| 37. |
- Jafri, S.Hassan M., et al.
(författare)
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Control of junction resistances in molecular electronic devices fabricated by FIB
- 2010
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Ingår i: 36th International Conference on Micro and Nano Engineering, MNE2010, Italy (2010).
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Konferensbidrag (refereegranskat)abstract
- Molecules provide an opportunity to fabricate electronic devices with much smaller basic unit in size i.e. 1-5 nm as compared to today’s silicon based electronics. Furthermore, molecules can be synthesized withalmost unlimited variation of their electronic structure. Theoretically, molecules in various configurations were demonstrated as rectifiers, transistors or memories, but experimentally it is still very difficult to obtaina stable and reproducible molecular based device [1]. A major hurdle to realize such devices is to make reliable electrical contacts to a single or a few molecules. Here, we show the first reproducible and systematic evaluation of a nanogap-nanoparticle bridge set-up that can be used as base for development of few molecule molecular electronics under ambient conditions. We have developed a nano-contact platform by top-down approach [2] with a gap size of 20-30nm using combined techniques of photolithography, electron beam lithography and focused ion beam milling (Fig 1). These gaps demonstrate excellent resistance in order of 1000 TΩ enabling us to carry out electrical characterization of highly resistive nanomaterials.However, compared to the size of molecules these gaps are quite big. In this study, we used metallic nanoparticles to bridge the gap and thus obtain electrical contacts with 1-2nm long molecules in the junction between the nanoelectrodes and the nanoparticles. The nanoparticles are assembled in the gap by a bottom-up approach using dielectrophrosis trapping process. Prior to introduction of molecules in such devices, we found that the trapping of gold nanoparticles (AuNP) in between clean nanoelectrodes without presence of molecules often gave resistance in order of mega-ohms to giga-ohms due to presence of a non conductive barrier. However, it was observed that cleaning protocols of both the gold contacts and nanoparticles in solution lead to resistance of less than a few hundreds of ohms (Fig 2). Molecules were introduced both by functionalizing the electrode gap and the the nanoparticles and the results of both functionalisation protocols are compared. By optimizing the electrode cleaning as well as the functionalisation of the metallic surfaces, we obtain reproducible electrical measurements. We fabricated such devices either by depositing a Self Assembled Monolayer (SAM) of molecules on the nano-contacts and bridging the gap by AuNP or by bridging the clean nano-contacts with molecule-coated-AuNP (Fig 3). Here we utilized a model molecules octanethiol (OT), octanedithiol and biphenyldithiol in fabrication of devices and study of metal molecule junction resistance. IV characterization of OT molecules (Fig 4) showed linear response where current levels varied between picoamps and femtoamps with an applied voltage of 1-3V. OT in this setup had one physisorbed contact with gold, which resulted in much less wave function mixing at the molecule-metal interface, and consequently decreased the transmission probability at the molecule-electrode interface. As a result, in the evaluation of more than 50 devices, a considerable variation of resistance between different devices due to the lack of covalent binding, the variation in number of trapped AuNPs, incomplete coverage of OT on the uneven surface of nanoelectrodes and variation in contact surface geometry. Density functional theory is used to understand the origin of the resistance fluctuation. We were able to estimate the average resistance per octanethiol molecule for such device in order of 175GΩ, in good agreement with other published results. Our results with the measurements on OT in such devices demonstrate that it is possible to fabricate stable electronic devices having relatively small numbers of molecules with reliable metal molecule junction by combing top-down and bottom-up approaches. By functionalizing the nanoparticles, we obtained a strong decrease of the resistance spread of such devices from 3 orders of magnitude to about 1 order of magnitude, making this technology a potential approach for molecular devices operating at ambient conditions.
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| 38. |
- Jafri, S Hassan M, et al.
(författare)
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Control of junction resistances in molecular electronic devices fabricated by FIB
- 2011
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Ingår i: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 88:8, s. 2629-2631
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Tidskriftsartikel (refereegranskat)abstract
- A major hurdle to realize molecular electronic devices (MEDs) is to make reliable electrical contacts to a single or a few molecules. Our nano-contact platform with a gap size of less than 25 nm with resistances above 1000 TΩ was built using combined techniques of photolithography, electron beam lithography and focused ion beam milling. In this study, we have used gold nanoparticles (AuNPs) to bridge the nanoelectrode gaps by dielectrophoretic trapping and thus obtain electrical contacts. The electrodes and/or the nanoparticles were functionalised with 1–2 nm long alkane-thiol molecules so that the electronic structure of these molecules determines the properties of the electrical junction. Molecules were introduced both by functionalising the nanogap and the nanoparticles and the results of both functionalisation protocols are compared. Here, we show the nanogap–nanoparticle bridge set-up containing metal–molecule junctions that can be used as a base for the development of molecular electronics containing only a few molecules under ambient conditions. Current–voltage (I–V) characterization of alkanethiol/gold junction showed non-linear response where mean geometric resistance of four different junctions could be tuned from 20 GΩ to 20 TΩ. The results from the measurements on 1-alkanethiol in such devices is a first step to demonstrate that this platform has the potential to obtain stable electronic devices having relatively small numbers of molecules with reliable metal molecule junction by combing top-down and bottom-up approaches.
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| 40. |
- Jafri, S. Hassan M., et al.
(författare)
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Nano-fabrication of molecular electronic junctions by targeted modification of metal-molecule bonds
- 2015
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Reproducibility, stability and the coupling between electrical and molecular properties are central challenges in the field of molecular electronics. The field not only needs devices that fulfill these criteria but they also need to be up-scalable to application size. In this work, few-molecule based electronics devices with reproducible electrical characteristics are demonstrated. Our previously reported 5 nm gold nanoparticles (AuNP) coated with omega-triphenylmethyl (trityl) protected 1,8-octanedithiol molecules are trapped in between sub-20 nm gap spacing gold nanoelectrodes forming AuNP-molecule network. When the trityl groups are removed, reproducible devices and stable Au-thiol junctions are established on both ends of the alkane segment. The resistance of more than 50 devices is reduced by orders of magnitude as well as a reduction of the spread in the resistance histogram is observed. By density functional theory calculations the orders of magnitude decrease in resistance can be explained and supported by TEM observations thus indicating that the resistance changes and strongly improved resistance spread are related to the establishment of reproducible and stable metal-molecule bonds. The same experimental sequence is carried out using 1,6-hexanedithiol functionalized AuNPs. The average resistances as a function of molecular length, demonstrated herein, are comparable to the one found in single molecule devices.
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- Jafri, Syed Hassan Mujtaba, et al.
(författare)
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Stability optimisation of molecular electronic devices based on nanoelectrode-nanoparticle bridge platform in air and different storage liquids
- 2014
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Ingår i: Journal of nanoparticle research. - : Springer Science and Business Media LLC. - 1388-0764 .- 1572-896X. ; 16:12, s. 2811-
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Tidskriftsartikel (refereegranskat)abstract
- The long-term stability of metal nanoparticle-molecule junctions in molecular electronic devices based on nanoelectrodes (NEL) is a major challenge in the effort to bring related molecular electronic devices to application. To optimize the reproducibility of molecular electronic nanodevices, the time-dependent modification of such junctions as exposed to different media needs to be known. Here, we have studied (1) the stability of Au-NEL and (2) the electrical stability of molecule-Au nanoparticle (AuNP) junctions themselves with the molecule being 1,8-octanedithiol (ODT). Both the NELs only and the junctions were exposed to air and liquids such as deionized water, tetrahydrofuran, toluene and tetramethylethylenediamine (TMEDA) over a period of 1 month. The nanogaps remained stable in width when stored in either deionized water or toluene, whereas the current through 1,8-octanedithiol-NP junctions remained most stable when stored in TMEDA as compared to other solvents. Although it is difficult to follow the chemical processes in such devices in the 10-nm range with analytical methods, the behavior can be interpreted from known interactions of solvent molecules with electrodes and ODT.
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| 46. |
- Kallings, Lena, 1969-, et al.
(författare)
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Workplace sitting is associated with self-reported general health and back/neck pain : a cross-sectional analysis in 44,978 employees.
- 2021
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Ingår i: BMC Public Health. - : BioMed Central. - 1471-2458. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Total sitting time is associated with a higher risk for cardio metabolic disease and mortality, while breaks in prolonged sitting attenuate these effects. However, less is known about associations of different specific domains and breaks of sitting on general health, back/neck pain and if physical activity could influence these associations. The aim was to investigate how workplace sitting and frequency of breaking up workplace sitting is associated with self-reported general health and self-reported back/neck pain.METHODS: 44,978 participants (42% women) from the Swedish working population, who participated in a nationwide occupational health service screening 2014-2019, were included in this cross-sectional study. Self-reported sitting duration and frequency of breaks from sitting at work, general health, back/neck pain, exercise, leisure time sitting, diet, smoking, stress and body mass index were assessed. Occupation was classified as requiring higher education qualifications or not. Logistic regression modelling was used to assess the association between workplace sitting/frequency of breaks in workplace sitting and poor general health and back/neck pain, respectively.RESULTS: Compared to sitting all the time at work, sitting ≤75% of the time showed significantly lower risks for poor general health (OR range 0.50-0.65), and sitting between 25 and 75% of the time showed significantly lower risks (OR 0.82-0.87) for often reported back/neck pain. For participants reporting sitting half of their working time or more, breaking up workplace sitting occasionally or more often showed significantly lower OR than seldom breaking up workplace sitting; OR ranged 0.40-0.50 for poor health and 0.74-0.81 for back/neck pain.CONCLUSIONS: Sitting almost all the time at work and not taking breaks is associated with an increased risk for self-reported poor general health and back/neck pain. People sitting almost all their time at work are recommended to take breaks from prolonged sitting, exercise regularly and decrease their leisure time sitting to reduce the risk for poor health.
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