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1.
BMC Public Health ; 23(1): 2339, 2023 11 25.
Article in English | MEDLINE | ID: mdl-38007477

ABSTRACT

BACKGROUND: Households of children with tuberculosis (TB) experience financial and social hardships, but TB-specific social protection initiatives primarily focus on adults. METHODS: We conducted a single-arm, pilot study of multi-component supportive benefits for children with pulmonary TB in Kampala, Uganda. At diagnosis, participants received in-kind coverage of direct medical costs, a cash transfer, and patient navigation. Caregivers were surveyed before diagnosis and 2 months into TB treatment on social and financial challenges related to their child's illness, including estimated costs, loss of income and dissaving practices. RESULTS: We included 368 children from 321 households. Pre-diagnosis, 80.1% of caregivers reported that their child's illness negatively impacted household finances, 44.1% of caregivers missed work, and 24% engaged in dissaving practices. Catastrophic costs (> 20% annual income) were experienced by 18.4% (95% CI 13.7-24.0) of households. School disruption was common (25.6%), and 28% of caregivers were concerned their child was falling behind in development. Two months post-diagnosis, 12 households (4.8%) reported being negatively affected by their child's TB disease (difference -75.2%, 95% CI -81.2 to -69.2, p < 0.001), with limited ongoing loss of income (1.6%) or dissavings practices (0.8%). Catastrophic costs occurred in one household (0.4%) at 2 months post-diagnosis. CONCLUSIONS: Households face financial and social challenges prior to a child's TB diagnosis, and child-sensitive social protection support may mitigate ongoing burden.


Subject(s)
Tuberculosis , Adult , Humans , Child , Pilot Projects , Uganda/epidemiology , Tuberculosis/diagnosis , Tuberculosis/epidemiology , Tuberculosis/prevention & control , Income , Public Policy
2.
IEEE Sens J ; 22(4): 2984-2992, 2022 Feb 15.
Article in English | MEDLINE | ID: mdl-36157103

ABSTRACT

Rapid screening of tuberculosis by evaluation of associated volatile organic biomarkers in breath is a promising technology that is significantly faster and more convenient than traditional sputum culture tests. Methyl nicotinate (MN) and methyl p-anisate (MPA) have been isolated as potential biomarkers for mycobacterium tuberculosis and have been found in the breath of patients with active pulmonary tuberculosis. A novel approach to detection of these biomarkers in liquid droplets (e.g. from breath condensate) using inexpensive screen-printed electrodes is presented. Previous modelling studies suggest that these biomarkers complex with certain transition metals of particular valence state. This interaction can be exploited by mixing the biomarker sample into an electroactive solution (EAS) containing the functional metal ion and observing the change electrochemically. The study focuses on low biomarker concentrations, determined to be clinically relevant based on preliminary GC-MS studies of the levels found in patient breath. It was found that both the cyclic voltammogram and square wave voltammogram of copper(II) change significantly when as little as 0.1 mM MN is added to the solution, with analysis times of less than 2 min. Copper(II) exhibits three separate peaks during square wave voltammetry. The location and area of each peak are affected differently as the concentration of MN increases, suggesting a reaction with specific oxidation states of the metal. In this way, a "fingerprint" method can be used to identify biomarkers once their known interaction is established.

3.
J Pediatric Infect Dis Soc ; 11(7): 316-321, 2022 Jul 21.
Article in English | MEDLINE | ID: mdl-35451001

ABSTRACT

BACKGROUND: C-reactive protein (CRP) has shown promise as a triage tool for pulmonary tuberculosis (TB) in adults living with the human immunodeficiency virus. We performed the first assessment of CRP for TB triage in children. METHODS: Symptomatic children less than 15 years old were prospectively enrolled in Kampala, Uganda. We completed a standard TB evaluation and measured CRP using a point-of-care assay. We determined the sensitivity and specificity of CRP to identify pulmonary TB in children using 10 mg/L and 5 mg/L cut-off points and generated a receiver operating characteristic (ROC) curve to determine alternative cut-offs that could approach the target accuracy for a triage test (≥90% sensitivity and ≥70% specificity). RESULTS: We included 332 children (median age 3 years old, interquartile range [IQR]: 1-6). The median CRP level was low at 3.0 mg/L (IQR: 2.5-26.6) but was higher in children with Confirmed TB than in children with Unlikely TB (9.5 mg/L vs. 2.9 mg/L, P-value = .03). At a 10 mg/L cut-off, CRP sensitivity was 50.0% (95% confidence interval [CI], 37.0-63.0) among Confirmed TB cases and specificity was 63.3% (95% CI, 54.7-71.3) among children with Unlikely TB. Sensitivity increased to 56.5% (95% CI, 43.3-69.0) at the 5 mg/L cut-off, but specificity decreased to 54.0% (95% CI, 45.3-62.4). The area under the ROC curve was 0.59 (95% CI, 0.51-0.67), and the highest sensitivity achieved was 66.1% at a specificity of 46.8%. CONCLUSIONS: CRP levels were low in children with pulmonary TB, and CRP was unable to achieve the accuracy targets for a TB triage test.


Subject(s)
C-Reactive Protein , Tuberculosis, Pulmonary , Adolescent , C-Reactive Protein/analysis , Child , Child, Preschool , Humans , Sensitivity and Specificity , Triage , Tuberculosis, Pulmonary/diagnosis , Uganda
4.
Langmuir ; 37(11): 3281-3287, 2021 03 23.
Article in English | MEDLINE | ID: mdl-33719459

ABSTRACT

Plasmon-enhanced photocatalysis has the potential to reduce activation energies and decrease temperature requirements, which increases catalyst stability and lowers process operating costs. The near-field enhancement that occurs at junctions between plasmonic nanoparticle clusters (i.e., hot spots) has been well-studied for sensing applications (e.g., Raman scattering). However, experimental insight into the effect of nanoparticle cluster hot spots on plasmon-enhanced photocatalysis is lacking. We demonstrate that catalytic activity is increased when clusters of gold nanoparticles (AuNPs) are formed relative to isolated particles using the same catalyst loading. Through experimental controls, we conclude that this catalytic enhancement is most likely due to the formation of plasmonic hot spots. Clusters of AuNPs were formed by adding L-cysteine to an AuNP dispersion, and a 20 ± 12% enhancement in the photocatalytic dye degradation rate was observed using a Fenton process. While this report may be a modest enhancement relative to the spectacular near-field electromagnetic field enhancements predicted by simulation at the nanoparticle junction, this finding supports the recent work of Srimanta et al. that plasmonic hot spots contribute to catalytic rate enchantments. It is anticipated that further self-assembly strategies to optimize interparticle orientations and cluster size distributions will improve the enhancement due to the formation of hot spots, and careful control will be required. For example, excess L-cysteine addition revealed extensive aggregation and subsequent rate reductions.

5.
J Pediatric Infect Dis Soc ; 10(5): 586-592, 2021 May 28.
Article in English | MEDLINE | ID: mdl-33416072

ABSTRACT

BACKGROUND: Xpert MTB/RIF Ultra (Xpert Ultra) has improved the sensitivity to detect pulmonary tuberculosis (TB) in adults. However, there have been limited prospective evaluations of its diagnostic accuracy in children. METHODS: We enrolled children undergoing assessment for pulmonary TB in Kampala, Uganda, over a 12-month period. Children received a complete TB evaluation and were classified as Confirmed, Unconfirmed, or Unlikely TB. We calculated the sensitivity and specificity of Xpert Ultra among children with Confirmed vs Unlikely TB. We also determined the diagnostic accuracy with clinical, microbiological, and extended microbiological reference standards (MRSs). RESULTS: Of the 213 children included, 23 (10.8%) had Confirmed TB, 88 (41.3%) had Unconfirmed TB, and 102 (47.9%) had Unlikely TB. The median age was 3.9 years, 13% were HIV-positive, and 61.5% were underweight. Xpert Ultra sensitivity was 69.6% (95% confidence interval [CI]: 47.1-86.8) among children with Confirmed TB and decreased to 23.4% (95% CI: 15.9-32.4) with the clinical reference standard. Specificity was 100% (95% CI: 96.4-100) among children with Unlikely TB and decreased to 94.7% (95% CI: 90.5-97.4) with a MRS. Sensitivity was 52.9% (95% CI: 35.1-70.2) and specificity 95.5% (95% CI: 91.4-98.1) with the extended MRS. Of the 26 positive Xpert Ultra results, 6 (23.1%) were "Trace-positive," with most (5/6) occurring in children with Unconfirmed TB. CONCLUSIONS: Xpert Ultra is a useful tool for diagnosing pulmonary TB in children, but there remains a need for more sensitive tests to detect culture-negative TB.


Subject(s)
Mycobacterium tuberculosis , Tuberculosis, Pulmonary , Child , Child, Preschool , Humans , Male , Prospective Studies , Sensitivity and Specificity , Sputum , Tuberculosis, Pulmonary/diagnosis , Uganda
6.
Sci Rep ; 10(1): 8050, 2020 May 15.
Article in English | MEDLINE | ID: mdl-32415134

ABSTRACT

The presence of Magnéli phases in titanium oxide nanotubes (NTs) can open up frontiers in many applications owing to their electrical and optical properties. Synthesis of NTs with Magnéli phases have posed a challenge due to the degradation and loss of morphology in NTs upon high-temperature treatments (>600 °C) in a reducing environment. This study reports on the synthesis of anodically formed NTs containing Magnéli phases through a double annealing route: oxygen (O2) annealing followed by annealing in 2% hydrogen with a nitrogen balance (2%H2-N2). The nucleation, growth, and transformation of anodized amorphous NTs into crystalline phases was investigated. The NTs obtained through this route were highly ordered and composed of mixed phases of anatase, rutile, and the Magnéli phase (Ti4O7). Experimental results from scanning electron microscopy (SEM), X-ray diffraction (XRD), scanning transmission electron microscopy (S/TEM), and Raman spectroscopy were combined with first principle calculations to develop an understanding of the sequential phase transformations during annealing. A predictive model was developed using density functional theory (DFT) to potentially predict the titanium oxides formed and their stability with reference to the mole fraction of oxygen. The change in the density of states (DOS), band structure, optical properties, and stability of phases are also discussed using DFT simulations. The combination of experimental characterization and modelling helped to understand the nucleation of anatase and rutile and the reorganization of these phases to form Magnéli phases on the anodized amorphous NTs through annealing treatment.

7.
Sensors (Basel) ; 18(5)2018 May 10.
Article in English | MEDLINE | ID: mdl-29747467

ABSTRACT

The availability of clean drinking water is a significant problem worldwide. Many technologies exist for purifying drinking water, however, many of these methods require chemicals or use simple methods, such as boiling and filtering, which may or may not be effective in removing waterborne pathogens. Present methods for detecting pathogens in point-of-use (POU) sterilized water are typically time prohibitive or have limited ability differentiating between active and inactive cells. This work describes a rapid electrochemical sensor to differentially detect the presence of active Escherichia coli (E. coli) O157:H7 in samples that have been partially or completely sterilized using a new POU electrocatalytic water purification technology based on superradicals generated by defect laden titania (TiO2) nanotubes. The sensor was also used to detect pathogens sterilized by UV-C radiation for a comparison of different modes of cell death. The sensor utilizes immunomagnetic bead separation to isolate active bacteria by forming a sandwich assay comprised of antibody functionalized secondary magnetic beads, E. coli O157:H7, and polyguanine (polyG) oligonucleotide functionalized secondary polystyrene beads as an electrochemical tag. The assay is formed by the attachment of antibodies to active receptors on the membrane of E. coli, allowing the sensor to differentially detect viable cells. Ultravioloet (UV)-C radiation and an electrocatalytic reactor (ER) with integrated defect-laden titania nanotubes were used to examine the sensors’ performance in detecting sterilized cells under different modes of cell death. Plate counts and flow cytometry were used to quantify disinfection efficacy and cell damage. It was found that the ER treatments shredded the bacteria into multiple fragments, while UV-C treatments inactivated the bacteria but left the cell membrane mostly intact.

8.
Foodborne Pathog Dis ; 15(1): 16-25, 2018 01.
Article in English | MEDLINE | ID: mdl-29106297

ABSTRACT

In response to the potential hazards associated with the globalization of the food industry, research has been focused on the development of new sensing techniques to provide the means of contamination detection at any stage in the food supply chain. The demand for on-site detection is growing as pre-emptive sensing of pathogens could eliminate foodborne-related outbreaks and associated healthcare costs. Reduction in food waste is also a driver for point-of-use (POU) sensing, from both an economic and environmental standpoint. The following review discusses the latest advancements in platforms that have the greatest potential for inexpensive, real-time detection, and identification of foodborne pathogens. Specific focus has been placed on the development techniques, which utilize micro- and nanoscale technology. Sample preparation-free techniques are also discussed, as the growing demand to enable POU sensing at any stage in the food supply chain will be a major driver toward the advancements of these nondestructive methods.


Subject(s)
Biosensing Techniques/instrumentation , Food Analysis/instrumentation , Food Contamination/analysis , Foodborne Diseases/microbiology , Nanotechnology , Electrochemical Techniques , Equipment Design , Host-Pathogen Interactions , Humans
9.
Environ Pollut ; 237: 731-739, 2018 Jun.
Article in English | MEDLINE | ID: mdl-29129431

ABSTRACT

This study reports a one-pot and eco-friendly method for the synthesis of spherical ibuprofen derived silver nanoparticles (IBU-AgNPs) in aqueous media using ibuprofen analgesics drug as capping as well as reducing agent. Formation of AgNPs occurred within a few min (less than 5 min) at room temperature without resorting to any harsh conditions and hazardous organic solvents. Synthesized AgNPs were characterized with common analytical techniques. Transmission electron microscope (TEM) images confirmed the formation of spherical particles having a size distribution in the range of 12.5 ± 1.5 nm. Employment of IBU analgesic aided the control of better size distribution and prevented agglomeration of particles. Such AgNPs solution was highly stable for more than two months when stored at ambient temperature. The IBU-AgNPs solution showed excellent ultra-rapid catalytic activity for the complete degradation of toxic 4-nitrophenol (4-NPh) into non-toxic 4-aminophenol (4-APh) within 40 s. AgNPs were recovered with the help of water insoluble-room temperature ionic liquid and reused with enhanced catalytic potential. This method provides a novel, rapid and economical alternative for the treatment of toxic organic pollutants to maintain water quality and environmental safety against water pollution. It is extendable for the control of other reducible contaminants in water as well. Furthermore, this catalytic activity for an effective degradation of organic toxins is expected to play a crucial role for achieving the Sustainable Development Goal 6 set by United Nations.


Subject(s)
Ibuprofen/chemistry , Ionic Liquids/chemistry , Metal Nanoparticles/chemistry , Nitrophenols/chemistry , Silver/chemistry , Catalysis , Ions , Models, Chemical
10.
Gels ; 4(4)2018 Oct 19.
Article in English | MEDLINE | ID: mdl-30674860

ABSTRACT

There is a strong commercial need for inexpensive point-of-use sensors for monitoring disease biomarkers or environmental contaminants in drinking water. Point-of-use sensors that employ smart polymer hydrogels as recognition elements can be tailored to detect almost any target analyte, but often suffer from long response times. Hence, we describe here a fabrication process that can be used to manufacture low-cost point-of-use hydrogel-based microfluidics sensors with short response times. In this process, mask-templated UV photopolymerization is used to produce arrays of smart hydrogel pillars inside sub-millimeter channels located upon microfluidics devices. When these pillars contact aqueous solutions containing a target analyte, they swell or shrink, thereby changing the resistance of the microfluidic channel to ionic current flow when a small bias voltage is applied to the system. Hence resistance measurements can be used to transduce hydrogel swelling changes into electrical signals. The only instrumentation required is a simple portable potentiostat that can be operated using a smartphone or a laptop, thus making the system suitable for point of use. Rapid hydrogel response rate is achieved by fabricating arrays of smart hydrogels that have large surface area-to-volume ratios.

11.
Sensors (Basel) ; 17(8)2017 Aug 04.
Article in English | MEDLINE | ID: mdl-28777343

ABSTRACT

Screening of colorectal cancer is crucial for early stage diagnosis and treatment. Detection of volatile organic compounds (VOCs) of the metabolome present in exhaled breath is a promising approach to screen colorectal cancer (CRC). Various forms of volatile organic compounds (VOCs) that show the definitive signature for the different diseases including cancers are present in exhale breathe. Among all the reported CRC VOCs, cyclohexane, methylcyclohexane, 1,3-dimethyl- benzene and decanal are identified as the prominent ones that can be used as the signature for CRC screening. In the present investigation, detection of the four prominent VOCs related to CRC is explored using functionalized titania nanotubular arrays (TNAs)-based sensor. These signature biomarkers are shown to be detected using nickel-functionalized TNA as an electrochemical sensor. The sensing mechanism is based on the electrochemical interaction of nickel-functionalized nanotubes with signature biomarkers. A detailed mechanism of the sensor response is also presented.


Subject(s)
Colorectal Neoplasms , Breath Tests , Early Detection of Cancer , Humans , Nanotubes , Titanium , Volatile Organic Compounds
12.
J Environ Sci (China) ; 44: 38-44, 2016 Jun.
Article in English | MEDLINE | ID: mdl-27266300

ABSTRACT

A field enhanced flow reactor using bias assisted photocatalysis was developed for bacterial disinfection in lab-synthesized and natural waters. The reactor provided complete inactivation of contaminated waters with flow rates of 50mL/min. The device consisted of titanium dioxide nanotube arrays, with an externally applied bias of up to 6V. Light intensity, applied voltage, background electrolytes and bacteria concentration were all found to impact the device performance. Complete inactivation of Escherichia coli W3110 (~8×10(3)CFU/mL) occurred in 15sec in the reactor irradiated at 25mW/cm(2) with an applied voltage of 4V in a 100ppm NaCl solution. Real world testing was conducted using source water from Emigration Creek in Salt Lake City, Utah. Disinfection of natural creek water proved more challenging, providing complete bacterial inactivation after 25sec at 6V. A reduction in bactericidal efficacy was attributed to the presence of inorganic and organic species, as well as the increase in robustness of natural bacteria.


Subject(s)
Disinfection/instrumentation , Photochemical Processes , Water Microbiology , Water Purification/instrumentation , Nanotubes , Titanium , Water Purification/methods
13.
Nanotechnology ; 26(26): 265401, 2015 Jul 03.
Article in English | MEDLINE | ID: mdl-26057179

ABSTRACT

The effect of annealing atmosphere on the supercapacitance behavior of iron oxide nanotube (Fe-NT) electrodes has been explored and reported here. Iron oxide nanotubes were synthesized on a pure iron substrate through an electrochemical anodization process in an ethylene glycol solution containing 3% H2O and 0.5 wt.% NH4F. Subsequently, the annealing of the nanotubes was carried out at 500 °C for 2 h in various gas atmospheres such as air, oxygen (O2), nitrogen (N2), and argon (Ar). The morphology and crystal phases evolved after the annealing processes were examined via field emission scanning electron microscopy, x-ray diffraction, Raman spectroscopy, and x-ray photoelectron spectroscopy. The electrochemical capacitance properties of the annealed Fe-NT electrodes were evaluated by conducting cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy tests in the Li2SO4 electrolyte. Based on these experiments, it was found that the capacitance of the Fe-NT electrodes annealed in air and O2 atmospheres shows mixed behavior comprising both the electric double layer and pseudocapacitance. However, annealing in N2 and Ar environments resulted in well-defined redox peaks in the CV profiles of the Fe-NT electrodes, which are therefore attributed to the relatively higher pseudonature of the capacitance in these electrodes. Based on the galvanostatic charge-discharge studies, the specific capacitance achieved in the Fe-NT electrode after annealing in Ar was about 300 mF cm(-2), which was about twice the value obtained for N2-annealed Fe-NTs and three times higher than those annealed in air and O2. The experiments also demonstrated excellent cycle stability for the Fe-NT electrodes with 83%-85% capacitance retention, even after many charge-discharge cycles, irrespective of the gas atmospheres used during annealing. The increase in the specific capacitance was discussed in terms of increased oxygen vacancies as a result of the enhanced transformation of the hematite (α-Fe2O3) phase to the magnetite (Fe3O4) phase for the electrodes annealed in the N2 and Ar atmospheres.

14.
Talanta ; 118: 304-11, 2014 Jan.
Article in English | MEDLINE | ID: mdl-24274301

ABSTRACT

The present study focuses on understanding of the principle of interaction of explosive molecule triacetonetriperoxide (TATP) with metal sensitized TiO2 nanotube composite material through theoretical modeling. This effort has also been extended in developing a laboratory scale sensor set up to detect TATP based on comprehensive computational modeling outcome and subsequent experimentation. Sensing mechanism depends on the nature of metal, where the TATP interaction with metal functionalized TiO2 prompts a change in conductivity of the sensor platform. Therefore, a metal with higher affinity towards TATP would enhance the conductance, thereby promoting the efficiency of the sensor platform. DFT methodology has been used to identify metal with high affinity to TATP. It was found that Co(2+) metal ion shows significantly higher affinity towards TATP, selected from an array of metal ions with different valency, from monovalent to tetravalent. The preliminary experimental data also suggests that Co(2+) ion detects TATP by inducing a change in conductivity of the sensor substrate.


Subject(s)
Biosensing Techniques/methods , Explosive Agents/analysis , Heterocyclic Compounds, 1-Ring/analysis , Models, Theoretical , Nanostructures/chemistry , Peroxides/analysis , Titanium/chemistry , Cobalt/chemistry
15.
Integr Biol (Camb) ; 5(4): 692-702, 2013 Apr.
Article in English | MEDLINE | ID: mdl-23407661

ABSTRACT

Traditional cell-screening techniques such as FACS and MACS are better suited for large numbers of cells isolated from bulk tissue and cannot easily screen stem or progenitor cells from minute populations found in their physiological niches. Furthermore, these techniques rely upon irreversible antibody binding, potentially altering cell properties, including gene expression and regenerative capacity. To address these challenges, we have developed a novel, label-free stem-cell analysis and sorting platform capable of quantifying cell-surface marker expression of single functional organ stem cells directly isolated from their micro-anatomical niche. Using our unique platform, we have discovered a remarkable heterogeneity in both the regenerative capacity and expression of CXCR4, ß1-integrin, Sca-1, M-cadherin, Syndecan-4, and Notch-1 in freshly isolated muscle stem (satellite) cells residing on different, single myofibers and have identified a small population of Sca-1(+)/Myf5(+) myogenic satellite cells. Our results demonstrate the utility of our single-cell platform for uncovering and functionally characterizing stem-cell heterogeneity in the organ microniche.


Subject(s)
Cell Separation/instrumentation , Microfluidic Analytical Techniques/instrumentation , Muscle Fibers, Skeletal/cytology , Muscle Fibers, Skeletal/physiology , Receptors, Cell Surface/metabolism , Satellite Cells, Skeletal Muscle/cytology , Satellite Cells, Skeletal Muscle/physiology , Animals , Cell Differentiation , Cells, Cultured , Dielectric Spectroscopy/instrumentation , Equipment Design , Equipment Failure Analysis , Flow Cytometry/instrumentation , Mice
16.
ACS Appl Mater Interfaces ; 5(5): 1688-97, 2013 Mar 13.
Article in English | MEDLINE | ID: mdl-23414084

ABSTRACT

Bismuth oxide (Bi2O3) decorated titania nanotube array (T-NT) composite materials were synthesized by a simple, yet versatile electrodeposition method. The effects of deposition current density and time on morphology evolution of the bismuth oxide phase were analyzed. It was found that an optimum deposition condition in terms of current density and time could be reached to achieve uniform and equiaxed crystal morphology of the deposited oxide phase. The morphology, shape, size distribution, and crystal structure of the bismuth oxide phase were evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopic techniques. The electrochemical capacitance of the T-NT/Bi2O3 composites was studied by conducting cyclic voltammetry and galvanostatic charge-discharge experiments. These studies indicated that the capacitance behavior of the composite material was dependent on the morphology and distribution of the bismuth oxide phase. The capacitance was greatly enhanced for the composite having equiaxed and uniformly distributed bismuth oxide particles. The maximum interfacial capacitance achieved in this study was approximately 430 mF cm(-2). Galvanostatic charge-discharge experiments conducted on the composite materials suggested stable capacitance behavior together with excellent capacitance retention even after 500 cycles of continuous charge-discharge operation.

17.
ACS Appl Mater Interfaces ; 4(11): 5883-90, 2012 Nov.
Article in English | MEDLINE | ID: mdl-23078074

ABSTRACT

Self-assembled arrays of titania nanotubes are synthesized via electrochemical anodization of Ti foils under the presence of UV-vis irradiation. Compared to control samples (anodized without light), the light-assisted anodized samples exhibit larger diameters as well as thicker nanotube walls, whereas the length of the nanotubes remains the same under otherwise similar synthesis conditions. Enhanced photoelectrochemical performance with light-assisted anodized samples under simulated AM 1.5 irradiation is observed by an increase in photocurrent density of 45-73% at 1.23 V (RHE). The enhanced photoelectrochemical performance is correlated to improved charge separation analyzed by Mott-Schottky. A mechanism on the photoeffect during anodization is presented. The morphology and improved properties obtained from the synthesis methodology may also find application in other fields such as sensing and catalysis.


Subject(s)
Crystallization/methods , Electrodes , Electroplating/methods , Nanotubes/chemistry , Nanotubes/ultrastructure , Titanium/chemistry , Titanium/radiation effects , Light , Materials Testing , Molecular Conformation/radiation effects , Nanotubes/radiation effects , Particle Size , Surface Properties/radiation effects
18.
Nanotechnology ; 23(38): 385601, 2012 Sep 28.
Article in English | MEDLINE | ID: mdl-22948670

ABSTRACT

Growth of TiO(2) nanotubes on thin Ti film deposited on Si wafers with site-specific and patterned growth using a photolithography technique is demonstrated for the first time. Ti films were deposited via e-beam evaporation to a thickness of 350-1000 nm. The use of a fluorinated organic electrolyte at room temperature produced the growth of nanotubes with varying applied voltages of 10-60 V (DC) which remained stable after annealing at 500 °C. It was found that variation of the thickness of the deposited Ti film could be used to control the length of the nanotubes regardless of longer anodization time/voltage. Growth of the nanotubes on a SiO(2) barrier layer over a Si wafer, along with site-specific and patterned growth, enables potential application of TiO(2) nanotubes in NEMS/MEMS-type devices.


Subject(s)
Crystallization/methods , Membranes, Artificial , Nanostructures/chemistry , Nanostructures/ultrastructure , Silicon/chemistry , Titanium/chemistry , Gases/chemistry , Macromolecular Substances/chemistry , Materials Testing , Molecular Conformation , Particle Size , Surface Properties
19.
Nanoscale Res Lett ; 7: 388, 2012 Jul 12.
Article in English | MEDLINE | ID: mdl-22788778

ABSTRACT

In this paper, we present the synthesis of self-organized TiO2 nanotube arrays formed by anodization of thin Ti film deposited on Si wafers by direct current (D.C.) sputtering. Organic electrolyte was used to demonstrate the growth of stable nanotubes at room temperature with voltages varying from 10 to 60 V (D.C.). The tubes were about 1.4 times longer than the thickness of the sputtered Ti film, showing little undesired dissolution of the metal in the electrolyte during anodization. By varying the thickness of the deposited Ti film, the length of the nanotubes could be controlled precisely irrespective of longer anodization time and/or anodization voltage. Scanning electron microscopy, atomic force microscopy, diffuse-reflectance UV-vis spectroscopy, and X-ray diffraction were used to characterize the thin film nanotubes. The tubes exhibited good adhesion to the wafer and did not peel off after annealing in air at 350 °C to form anatase TiO2. With TiO2 nanotubes on planar/stable Si substrates, one can envision their integration with the current micro-fabrication technique large-scale fabrication of TiO2 nanotube-based devices.

20.
Electrophoresis ; 30(9): 1470-81, 2009 May.
Article in English | MEDLINE | ID: mdl-19425002

ABSTRACT

We present a rapidly fabricated micro-capillary electrophoresis chip that utilizes surface-tension-driven flow for sample injection and extraction of DNA. Surface-tension-driven flow (i.e. passive pumping) [G. M. Walker et al., Lab. Chip. 2002, 2, 131-134] injects a fixed volume of sample that can be predicted mathematically. Passive pumping eliminates the need for tubing, valves, syringe pumps, and other equipment typically needed for interfacing with microelectrophoresis chips. This method requires a standard micropipette to load samples before separation, and remove the resulting bands after analysis. The device was made using liquid phase photopolymerization to rapidly fabricate the chip without the need of special equipment typically associated with the construction of microelectrophoresis chips (e.g. cleanroom) [A. K. Agarwal et al., J. Micromech. Microeng. 2006, 16, 332-340; S. K. Mohanty et al., Electrophoresis 2006, 27, 3772-3778]. Batch fabrication time for the device presented here was 1.5 h including channel coating time to suppress electroosmotic flow. Devices were constructed out of poly-isobornyl acrylate and glass. A standard microscope with a UV source was used for sample detection. Separations were demonstrated using Promega BenchTop 100 bp ladder in hydroxyl ethyl cellulose (HEC) and oligonucleotides of 91 and 118 bp were used to characterize sample injection and extraction of DNA bands. The end result was an inexpensive micro-capillary electrophoresis device that uses tools (e.g. micropipette, electrophoretic power supplies, and microscopes) already present in most labs for sample manipulation and detection, making it more accessible for potential end users.


Subject(s)
Electrophoresis, Capillary , Miniaturization/instrumentation , DNA/isolation & purification , Electrophoresis, Capillary/economics , Electrophoresis, Capillary/instrumentation , Equipment Design , Microscopy, Ultraviolet , Photochemistry , Surface Tension
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