How to delay the serial port write for 1second in c#

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C#

Hi,
In my code i have to handle the serial port write, which should be delayed for 1 second.
My code is as follows.

while (bytesRd < byteExpctd)
               {

                   bytesRd += serialPort.Read(Req, bytesRd, byteExpctd - bytesRd);
                   //serialPort.ReadTimeout = 80;
               }
               byteExpctd = (int)Req[1];
               while (bytesRd < byteExpctd)
               {

                   bytesRd += serialPort.Read(Req, bytesRd, byteExpctd - bytesRd);

               }

               if (Req[0] == 0x14 && Req[0] == 0x06)
               {
                   AckMsg[0] = 0x0B;
                   AckMsg[1] = 0x06;
                   AckMsg[2] = 0xA4;
                   AckMsg[3] = CheckSum(AckMsg);
                   serialPort.Write(AckMsg, 0, 5);
               }
               else
               {
                  // code for something
               }
               Thread.sleep(1000);
               RsltMsg[0] = 0x9F;
               RsltMsg[1] = 0x05;
               RsltMsg[2] = 0x19;
               RsltMsg[3] = CheckSum(RsltMsg);
               serialPort.Write(RsltMsg, 0, 3);

How to delay the serial port write for 1 second in c#? I have to introduce a delay of 1 minute between the first and second write. I tried with Thread.Sleep(), but it doesn't make any change. Is there any alternate solution to introduce the delay of 1 minute. I am using custom baud rate of 10,4K. Please help.