Effect of Chemical Microenvironment in Spirothiopyran Monolayer Direct-Write Photoresists

Abstract

We study the effect of the microenvironment on writing chemical patterns into spirothiopyran monolayers over large areas in a single step with light. Surfaces functionalized with photoresponsive spirothiopyran are fabricated by chemically modifying amine-terminated monolayers. The merocyanine isomer selectively participates in a thiol-Michael addition reaction with maleimide-functionalized molecules, rendering these surfaces ideal for fast, mask-less direct writing. The local microenvironment of spirothiopyran is found to strongly influence the kinetics of photoswitching. The quantum yield of ring opening is found to be 17 times faster for spirothiopyran surrounded by a locally charged environment rich in guanidinium diluent molecules as compared to a closed-packed monolayer without diluents. Hydrophilic environments are also found to improve the kinetics of ring closing. Optimization of the diluent concentration leads to dramatic improvements in both contrast and yield of direct writing. This enables the monolayer to be used for maskless two-color photopatterning in which spatial control over patterning is obtained by varying the relative intensity of incident UV and green light. These experiments demonstrate the capacity of spirothiopyran monolayers to serve as a versatile toolbox for rapid, large-area surface functionalization.

Super-resolution interference lithography enabled by non-equilibrium kinetics of photochromic monolayers

“…The higher quantum yield for SP / MC ring opening in this model (32%), relative to the experimental value in solution (25%), is attributed to differences in the chemical microenvironment on the monolayer surface relative to the solution phase, in accord with our previous study on STP monolayer photokinetics. 26 Based on this model, it is clear that for any xed values of I 1 and I 2 , there is a photo-equilibrium formed between the SP and MC isomers. If no maleimide is present, a steady state concentration of the isomers is established.…”

“…We have previously demonstrated that the kinetics of the ring-opening and ring-closing reaction for spirothiopyran monolayers are extremely sensitive to the chemical microenvironment on the surface. 26 Here, super-resolution direct writing of maleimidefunctionalized molecules is performed using a STED-inspired scheme ( Fig. 1(b)).…”

“…Spirothiopyran functionalized monolayers were synthesized as per our previously reported procedure. 26 Briey, glass coverslips were cleaned by immersing in freshly prepared piranha solution (7 parts concentrated sulfuric and 3 parts 30% hydrogen peroxide) for 30 minutes. (CAUTION: piranha solution reacts violently with organic matter.)…”

“…Recently, we developed photo-switchable monolayers by covalently anchoring spirothiopyran to glass and explored the effect of monolayer composition on switching kinetics. 26 This is accomplished using a two-step process where hydrolysis resistant amine functionalized monolayers 27 are coupled to carboxylic acid functionalized spirothiopyran. The functional spirothiopyran (STP) derivatives in these surfaces retain their ability to reversibly photoswitch between the "closed" spirothiopyran (SP) and "open" merocyanine (MC) isomers ( Fig.…”

Synthesis of Carboxy ATTO 647N Using Redox Cycling for Xanthone Access

“…This unique characteristic, along with its photophysical properties, make it an ideal fluorophore for these peptide sequencing studies. Additionally, other groups have found this fluorophore to be useful in applications such as Förster resonance energy transfer (FRET) studies and single-molecule imaging, − enzyme monitoring and protein conformation, , lithography, neuron and protein analysis, , and DNA origami visualization …”