UX design for a responsive web app

I am looking for an experienced UX designer to create a responsive web app for our business. I am specifically looking for a designer to design the app using prototyping techniques. We have a specific platform in mind, so the designer should ideally have experience in building on this platform. The level of interaction desired is moderate. We are looking for an individual who is able to create an app that is user-friendly and visually pleasing. The ideal designer should have a proven track record of successful UX designs, be highly detail-oriented, and have excellent communication skills. We are open to different styles and approaches when it comes to the design of our app.