Fluorescence microscopy uniquely enables physical and biological research in micro- and nanofluidic systems. However, in channels with depths below 10 nm, the limited number of fluorophores results in fluorescence intensity below the detection limit of optical microscopes. To overcome this barrier, we applied Fabry-Pérot interference to enhance fluorescence intensity with a silicon nitride layer below the sub-10 nm channel. A silicon nitride layer of suitable thickness can selectively enhance both absorption and emission wavelengths, leading to a fluorescent signal that is enhanced 20-fold and readily imaged with traditional microscopes. To demonstrate this method, we studied the mass transport of a binary solution of ethanol and Rhodamin B in 8 nm nanochannels. The large molecular size of Rhodamin B (∼1.8 nm) relative to the channel depth results in both separation and reduced diffusivity, deviating from behavior at larger scales. This method extends the widely available suite of fluorescence analysis tools and infrastructure to unprecedented sub-10 nm scale with relevance to a wide variety of biomolecular interactions.
Background: The improper exploitation of water resources by humans has disrupted the natural balance of groundwater. Given the water resources restriction, it is crucial to manage these resources properly, recognize the current situation, and anticipate the harvesting or feeding effects. In this regard, simulators or models can act as valuable tools. Methods: In this research, we performed quantitative modeling of groundwater flow in the Quar-Maharlu plain, Fars Province, Iran using the PMWIN software. The model included three years’ calibration (2011-2014) for hydraulic conductivity coefficient and one year’s verification (2014-2015). To evaluate the model error in calibration and verification, the root mean square deviation (RMSD) was used. After simulating the aquifer to optimize the artificial recharge location by the flood spreading method, different scenarios were defined and examined by considering the natural and artificial factors. Results: The RMSD values for calibration were 1.55, 1.49, and 1.56 m for 2011, 2012, and 2013, respectively. The RMSD for verification of one year was 1.77 m, indicating the acceptable ability of the model to predict groundwater flow parameters. The stock variation for the whole aquifer was -8.88 mm3 in 2014. In the next step, the best recharging location was selected to create the maximum head increase (5.3cm) in the entire area of the plain. Conclusion: One of the effective ways to offset the negative balance is to strengthen the aquifer through artificial recharge.
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