Nanosphere lithography (NSL) is an inexpensive, inherently parallel, high-throughput, and materials-general nanofabrication technique capable of producing well-ordered 2D periodic particle arrays of nanoparticles. This paper focuses on the synthesis of size-tunable silver nanoparticle arrays by nanosphere lithography and their structural characterization by atomic force microscopy (AFM). The in-plane diameter, a, of Ag nanoparticles was tuned from 21 to 126 nm by systematic variation of the nanosphere diameter, D. Similarly, the out-of-plane height, b, was tuned from 4 to 47 nm by varying the mass thickness, d m, of the Ag overlayer. Experimental measurements of a, b, and interparticle spacing d ip of many individual nanoparticles as a function of D and d m were carried out using AFM. These studies show (i) b = d m, (ii) d ip accurately corresponds to predictions based on the nanosphere mask geometry, (iii) a, after correction for AFM tip convolution, is governed only by the mask geometry and the standard deviation, σD, of the nanosphere diameter, and (iv) line-of-sight deposition is strictly operative. Furthermore, we have established that nanosphere lithography can fabricate nanoparticles that contain only ca. 4 × 104 atoms and are in the size range of a surface-confined cluster.

This work presents a novel approach to fine-tuning the size, shape, and interparticle spacing of nanoparticles fabricated by nanosphere lithography (NSL). This approach, termed angle-resolved nanosphere lithography (AR NSL), is a variant of NSL that yields vastly different, and increasingly flexible, nanostructures. This is accomplished by controlling the angle, θ, between the surface normal of the sample assembly and the propagation vector of the material deposition beam. Comparison of experimental results to simulated nanoparticle array geometries generated using an analytical model show excellent qualitative agreement. Using AR NSL, we have demonstrated that it is possible to reduce in-plane nanoparticle dimensions by a factor of 4. This important result shows that it will be possible to achieve fabrication of nanoparticles with precision control of their dimensions in a size regime comparable with the industry standard electron beam lithography. AR NSL provides a massively parallel, rather than serial, nanoparticle fabrication method. One limitation of the AR NSL technique is the inability to pattern an entire substrate with a single nanoparticle geometry without control of the mask domain orientation. While the presence of multiple domains in any given colloidal crystal mask complicates the fabrication of large-area homogeneous nanoparticle arrays, this quality is, in fact, useful in laboratory scale experiments requiring a diverse set of nanostructure features on a single sample. The precision tuning of nanoparticle size, shape, and spacing that can be achieved in a massively parallel, materials/substrate general, and inexpensive fashion using AR NSL is likely to have significant impact on the fields of surface-enhanced spectroscopy, near field optical microscopy, nanoscopic object manipulation, and chemical/biological sensing.

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Background The rapid spread of COVID‐19 has placed tremendous strain on the American healthcare system. Few prior studies have evaluated the well‐being of or changes to training for American resident physicians during the COVID‐19 pandemic. We aim to study predictors of trainee well‐being and changes to clinical practice using an anonymous survey of American urology residents. Methods An anonymous, voluntary, 47‐question survey was sent to all ACGME‐accredited urology programmes in the United States. We executed a cross‐sectional analysis evaluating risk factors of perception of anxiety and depression both at work and home and educational outcomes. Multiple linear regressions models were used to estimate beta coefficients and 95% confidence intervals. Results Among ~1800 urology residents in the USA, 356 (20%) responded. Among these respondents, 24 had missing data leaving a sample size of 332. Important risk factors of mental health outcomes included perception of access to PPE, local COVID‐19 severity and perception of susceptible household members. Risk factors for declination of redeployment included current redeployment, having children and concerns regarding ability to reach case minimums. Risk factors for concern of achieving operative autonomy included cancellation of elective cases and higher level of training. Conclusions Several potential actions, which could be taken by urology residency programme directors and hospital administration, may optimise urology resident well‐being, morale, and education. These include advocating for adequate access to PPE, providing support at both the residency programme and institutional levels, instituting telehealth education programmes, and fostering a sense of shared responsibility of COVID‐19 patients.

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